WEBVTT 00:00:00.000 --> 00:00:02.410 The following content is provided under a Creative 00:00:02.410 --> 00:00:03.830 Commons license. 00:00:03.830 --> 00:00:06.840 Your support will help MIT OpenCourseWare continue to 00:00:06.840 --> 00:00:10.530 offer high-quality educational resources for free. 00:00:10.530 --> 00:00:13.400 To make a donation, or view additional materials from 00:00:13.400 --> 00:00:17.190 hundreds of MIT courses, visit MIT OpenCourseWare at 00:00:17.190 --> 00:00:18.440 ocw.mit.edu. 00:00:21.090 --> 00:00:22.620 PROFESSOR: We had a staff meeting yesterday, and we 00:00:22.620 --> 00:00:25.540 decided that what we're going to do is, we'll start with 00:00:25.540 --> 00:00:27.080 defects and solids. 00:00:27.080 --> 00:00:31.620 We didn't examine you on it with the last celebration. 00:00:31.620 --> 00:00:34.510 So we'll pick it up with defects, and we'll go through 00:00:34.510 --> 00:00:38.210 to the end of solutions, acid-bases. 00:00:38.210 --> 00:00:41.980 So the stuff that we covered on Monday, the nomenclature of 00:00:41.980 --> 00:00:43.540 organics, we're going to leave out. 00:00:43.540 --> 00:00:47.750 Because you don't have enough time with the recitations to 00:00:47.750 --> 00:00:50.420 really dig into that, and I think it's-- 00:00:50.420 --> 00:00:53.770 with the test being on a Monday this time, and not on a 00:00:53.770 --> 00:00:58.710 Wednesday, the schedule is little bit of out of balance 00:00:58.710 --> 00:01:00.800 from the way I'd like it to be. 00:01:00.800 --> 00:01:04.170 But I thought having the third celebration the Wednesday 00:01:04.170 --> 00:01:08.700 before Thanksgiving was not wise. 00:01:08.700 --> 00:01:12.580 I know that a number of you are going to be in transit 00:01:12.580 --> 00:01:14.240 that on Wednesday. 00:01:14.240 --> 00:01:17.990 But let me remind you that Wednesday, we will have a 00:01:17.990 --> 00:01:19.040 full-blown lecture. 00:01:19.040 --> 00:01:23.250 I'm going without any slow down. 00:01:23.250 --> 00:01:26.660 So next Wednesday, we will start biochemistry. 00:01:26.660 --> 00:01:29.770 So those of you who are not here, please make sure that 00:01:29.770 --> 00:01:30.840 you have viewed the lecture. 00:01:30.840 --> 00:01:33.660 Because when you return on Monday, you will have no idea 00:01:33.660 --> 00:01:34.900 what's going on. 00:01:34.900 --> 00:01:38.370 And it'd be a good idea not to blow biochemistry, because on 00:01:38.370 --> 00:01:39.400 the final exam-- 00:01:39.400 --> 00:01:42.590 if you fail the final, it's not good. 00:01:42.590 --> 00:01:44.440 It's really not good. 00:01:44.440 --> 00:01:49.270 So just to be clear, we're going to start with defects 00:01:49.270 --> 00:01:53.260 and solids, and go through, and end with acids, bases, and 00:01:53.260 --> 00:01:55.060 solution chemistry. 00:01:55.060 --> 00:01:56.310 OK. 00:01:56.310 --> 00:02:00.380 So today I want to start to get some mileage out of what 00:02:00.380 --> 00:02:02.460 we learned on Monday. 00:02:02.460 --> 00:02:06.890 I want to talk today about one of the applications of organic 00:02:06.890 --> 00:02:09.530 chemistry, and that's polymers. 00:02:09.530 --> 00:02:13.430 So we're going to take two lectures on polymers, and then 00:02:13.430 --> 00:02:16.260 we'll feed into biochemistry, and you'll see a very natural 00:02:16.260 --> 00:02:18.830 progression from what we're doing now into the 00:02:18.830 --> 00:02:20.360 biochemistry. 00:02:20.360 --> 00:02:24.490 So let's begin with a little bit of reflection on what 00:02:24.490 --> 00:02:25.910 we've done so far. 00:02:25.910 --> 00:02:30.330 Up until now, we've looked at various solid structures. 00:02:30.330 --> 00:02:33.220 We've started with single atoms. We looked at crystals, 00:02:33.220 --> 00:02:35.560 disordered crystals, and so on. 00:02:35.560 --> 00:02:38.510 We've looked at compounds, and we've even 00:02:38.510 --> 00:02:41.300 looked at small change. 00:02:41.300 --> 00:02:44.350 We looked at alkanes, straight chain 00:02:44.350 --> 00:02:46.860 alkanes, branched alkanes. 00:02:46.860 --> 00:02:49.260 And we've looked at network solids. 00:02:49.260 --> 00:02:50.540 Here is a regular network. 00:02:50.540 --> 00:02:54.140 This is the structure of graphite, for example. 00:02:54.140 --> 00:02:55.760 Nice, ordered crystalline structure. 00:02:55.760 --> 00:02:59.640 Diamond grows in three dimensions without abatement. 00:02:59.640 --> 00:03:01.480 We've looked at disordered networks, 00:03:01.480 --> 00:03:03.440 such as silicate glasses. 00:03:03.440 --> 00:03:05.450 So that's what we've looked at up until now. 00:03:05.450 --> 00:03:07.700 What I want to talk about today is polymers. 00:03:07.700 --> 00:03:10.440 Polymers are macromolecules. 00:03:10.440 --> 00:03:13.000 These are long chain molecules. 00:03:13.000 --> 00:03:17.550 By long, we're talking about thousands and thousands of 00:03:17.550 --> 00:03:18.860 repeat units. 00:03:18.860 --> 00:03:24.260 And this is the distinguishing feature between macromolecules 00:03:24.260 --> 00:03:26.040 that are found in the body, versus 00:03:26.040 --> 00:03:29.780 macromolecules that are man-made. 00:03:29.780 --> 00:03:31.990 Mother Nature is a polymer engineer. 00:03:31.990 --> 00:03:35.510 We are a macromolecular organism. 00:03:35.510 --> 00:03:37.140 This is all polymer. 00:03:37.140 --> 00:03:37.860 It's all polymer. 00:03:37.860 --> 00:03:40.755 The changes in shape is all elasticity in a polymer. 00:03:40.755 --> 00:03:45.870 And inside, of course, I've got a ceramic skeleton, which 00:03:45.870 --> 00:03:47.630 keeps the frame in place. 00:03:47.630 --> 00:03:49.660 But this is all polymers. 00:03:49.660 --> 00:03:54.520 But the difference here is, this is not a repeat unit. 00:03:54.520 --> 00:03:56.960 Whereas when we have a man-made structure, it's the 00:03:56.960 --> 00:04:01.320 same repeating chemical structure. 00:04:01.320 --> 00:04:04.170 And the other thing I want to say at the beginning is their 00:04:04.170 --> 00:04:05.160 importance in commerce. 00:04:05.160 --> 00:04:07.160 Polymers are found everywhere today. 00:04:07.160 --> 00:04:09.900 Trash bags, auto parts. 00:04:09.900 --> 00:04:12.460 And in culture, they're absolutely 00:04:12.460 --> 00:04:13.880 essential to culture. 00:04:13.880 --> 00:04:14.870 Let's think about it. 00:04:14.870 --> 00:04:20.250 When you play that DVD, that DVD is information 00:04:20.250 --> 00:04:22.220 embedded in a polymer. 00:04:22.220 --> 00:04:24.010 The magnetic drags. 00:04:24.010 --> 00:04:25.180 What are magnetic drags? 00:04:25.180 --> 00:04:29.310 These are polymers that have been coated with gammaferic 00:04:29.310 --> 00:04:31.690 oxide or some other magnetic material. 00:04:31.690 --> 00:04:34.605 Without polymers we couldn't have the modern era. 00:04:34.605 --> 00:04:38.310 And if you go back before the DVD, with the CD, before that 00:04:38.310 --> 00:04:40.400 was magnetic tape and cassette, and 00:04:40.400 --> 00:04:41.760 before that was this. 00:04:41.760 --> 00:04:43.270 You might see some of these around. 00:04:43.270 --> 00:04:47.180 This is an old way of presenting musical 00:04:47.180 --> 00:04:47.820 information. 00:04:47.820 --> 00:04:52.160 This is the phonograph record, photograph recording. 00:04:52.160 --> 00:04:57.570 And this is information that is scribed into a platter, and 00:04:57.570 --> 00:04:59.330 it's made of polyvinyl chloride. 00:04:59.330 --> 00:05:02.210 That's why you hear the term vinyl. 00:05:02.210 --> 00:05:07.440 Why is Virgin, the big Virgin enterprise, called Virgin? 00:05:07.440 --> 00:05:10.670 Because Virgin Records, when they made their platters, they 00:05:10.670 --> 00:05:14.460 started with virgin vinyl, not recycled polymer. 00:05:14.460 --> 00:05:18.280 And so their platters would lie flat on the turntable. 00:05:18.280 --> 00:05:20.150 Whereas some of them you buy, you put them 00:05:20.150 --> 00:05:21.290 down, and they warp. 00:05:21.290 --> 00:05:23.900 It's OK, because the needle would still track, but it 00:05:23.900 --> 00:05:25.570 looked kind of-- 00:05:25.570 --> 00:05:27.120 playing like this. 00:05:27.120 --> 00:05:28.640 And it's too bad that we've lost this. 00:05:28.640 --> 00:05:32.590 Because this gives rise to the real estate possibility for 00:05:32.590 --> 00:05:35.310 artwork, and liner notes, and so on, that you don't get when 00:05:35.310 --> 00:05:37.970 you download something for $0.99. 00:05:37.970 --> 00:05:38.750 OK? 00:05:38.750 --> 00:05:43.570 So an electromechanical device moves along here, and jiggles 00:05:43.570 --> 00:05:46.840 in the grooves, and those mechanical wigglings get 00:05:46.840 --> 00:05:52.790 converted into energy that ultimately gets fed through 00:05:52.790 --> 00:05:54.340 the loudspeakers. 00:05:54.340 --> 00:05:56.900 And now let's talk about visual information. 00:05:56.900 --> 00:06:01.590 Daguerre invented halide photography in the early 00:06:01.590 --> 00:06:04.890 1800s, but we didn't get motion pictures. 00:06:04.890 --> 00:06:09.470 Cinematography had to wait for the advent of polymers, 00:06:09.470 --> 00:06:13.020 because only when we could make material that would come 00:06:13.020 --> 00:06:18.850 out miles long on which we could coat with halide 00:06:18.850 --> 00:06:24.470 photosensitive emulsion, could we imagine images flashing 00:06:24.470 --> 00:06:27.380 past us faster than the persistence of vision. 00:06:27.380 --> 00:06:28.980 You need-- what's the persistence of vision? 00:06:28.980 --> 00:06:30.970 Around a twentieth of a second. 00:06:30.970 --> 00:06:33.690 Motion pictures are 24 frames a second. 00:06:33.690 --> 00:06:37.400 So you couldn't have glass plates on which you've got 00:06:37.400 --> 00:06:41.170 halide film zipping past at 24 frames a 00:06:41.170 --> 00:06:43.470 second for 90 minutes. 00:06:43.470 --> 00:06:47.110 So only with the advent of polymers did we have the birth 00:06:47.110 --> 00:06:48.920 of cinematography. 00:06:48.920 --> 00:06:52.070 So what I'm talking about here changed the world. 00:06:52.070 --> 00:06:56.610 It changed the world, and gives birth to the fantastic 00:06:56.610 --> 00:06:58.740 access that we have to information. 00:06:58.740 --> 00:07:01.870 And now, of course, as things move digitally, and they 00:07:01.870 --> 00:07:04.050 dematerialize, you're going to see a shift away. 00:07:04.050 --> 00:07:07.490 But all this stuff was enabled by the 00:07:07.490 --> 00:07:10.700 advent of polymer chemistry. 00:07:10.700 --> 00:07:14.870 So with that as a motivator, let's dive in. 00:07:14.870 --> 00:07:15.910 This is good stuff. 00:07:15.910 --> 00:07:17.010 It's really, really good. 00:07:17.010 --> 00:07:18.180 So now the payback comes. 00:07:18.180 --> 00:07:20.570 You know, all those little lessons about, where's the 00:07:20.570 --> 00:07:23.580 electron, where's the orbital, you know, who wants to learn 00:07:23.580 --> 00:07:24.070 that stuff. 00:07:24.070 --> 00:07:24.840 You have to learn it! 00:07:24.840 --> 00:07:26.900 If you're going to write the great novel, you've got to 00:07:26.900 --> 00:07:30.870 learn how to spell. 00:07:30.870 --> 00:07:32.470 All right. 00:07:32.470 --> 00:07:33.830 So let's go. 00:07:33.830 --> 00:07:36.040 So the polymer, it comes from the Greek poly, 00:07:36.040 --> 00:07:37.770 meaning may, right? 00:07:37.770 --> 00:07:42.990 Poly is many And the mer, the mer is this repeat 00:07:42.990 --> 00:07:45.620 unit, if you like. 00:07:45.620 --> 00:07:47.700 Many units, many units. 00:07:47.700 --> 00:07:50.000 So let's take a simple example. 00:07:50.000 --> 00:07:52.740 Last day we studied polyethylene. 00:07:55.760 --> 00:07:58.300 So polyethylene looks like this. 00:07:58.300 --> 00:08:01.090 Double bond, one, two, three, four, four hydrogens. 00:08:01.090 --> 00:08:02.705 So this is just ethylene. 00:08:06.380 --> 00:08:09.560 And what I can do with ethylene, is I can react it. 00:08:09.560 --> 00:08:11.650 Ethylene's a gas, room temperature. 00:08:11.650 --> 00:08:17.230 Put it into a reactor and expose it to an initiator. 00:08:17.230 --> 00:08:18.830 And the initiator is a radical. 00:08:18.830 --> 00:08:19.700 You know what the radical. 00:08:19.700 --> 00:08:22.240 It's something that's got this unpaired electron. 00:08:22.240 --> 00:08:23.710 It's very active. 00:08:23.710 --> 00:08:29.240 And the radical sees a unit of ethylene, which I'm going to 00:08:29.240 --> 00:08:30.670 write like this. 00:08:30.670 --> 00:08:33.710 We don't need to put the 120 degrees now. 00:08:33.710 --> 00:08:38.020 And what the ethylene does, is this radical attacks this 00:08:38.020 --> 00:08:40.830 double bond and figures, well, it's better to have two single 00:08:40.830 --> 00:08:41.970 bonds than one double bond. 00:08:41.970 --> 00:08:44.030 Reacts the double bond, breaks it, and 00:08:44.030 --> 00:08:46.250 then forms the following. 00:08:46.250 --> 00:08:52.920 The radical now bonds to the ethylene, breaks that double 00:08:52.920 --> 00:08:57.690 bond, and transfers the unpaired electron to the end. 00:08:57.690 --> 00:09:01.810 But now this thing is itself a radical, and it's swimming in 00:09:01.810 --> 00:09:03.180 a gas of ethylene. 00:09:03.180 --> 00:09:10.150 So now a second C2H4 comes up against this, and it's turned 00:09:10.150 --> 00:09:15.850 into the following, are now C C C C C, one, two, three, 00:09:15.850 --> 00:09:17.580 four, one, two, three, four. 00:09:17.580 --> 00:09:18.480 And so on. 00:09:18.480 --> 00:09:21.740 And this can go without limit, until we shut down the 00:09:21.740 --> 00:09:25.560 reactor, or we introduce something that terminates, 00:09:25.560 --> 00:09:27.690 that will cap this. 00:09:27.690 --> 00:09:28.220 All right? 00:09:28.220 --> 00:09:30.090 So this is the beginning of it. 00:09:30.090 --> 00:09:32.920 And what you see is attachment, attachment, 00:09:32.920 --> 00:09:35.060 attachment, breaking of double bonds. 00:09:35.060 --> 00:09:36.870 And so we have a repeat unit here. 00:09:36.870 --> 00:09:40.920 This repeat unit, the mer unit, is this ethylene unit, 00:09:40.920 --> 00:09:46.390 and it can go to a value of n that is very, very high. 00:09:46.390 --> 00:09:49.490 What kind of numbers can we expect to get? 00:09:49.490 --> 00:09:53.900 We can have numbers here where n takes values-- 00:09:53.900 --> 00:09:56.100 and these aren't hard and fast, but just to give you 00:09:56.100 --> 00:09:57.020 some idea-- 00:09:57.020 --> 00:10:01.640 you could have a, you know the oxymoron jumbo shrimp. 00:10:01.640 --> 00:10:04.420 You could have a short chain polymer. 00:10:04.420 --> 00:10:06.590 A short chain, long chain. 00:10:06.590 --> 00:10:07.980 You know? 00:10:07.980 --> 00:10:09.290 Boy, you're really dead today. 00:10:09.290 --> 00:10:10.010 What's the matter with you? 00:10:10.010 --> 00:10:10.960 Sleep deprived? 00:10:10.960 --> 00:10:12.240 You've-- 00:10:12.240 --> 00:10:12.510 All right. 00:10:12.510 --> 00:10:15.890 So n can go up to about 10,000. 00:10:15.890 --> 00:10:19.920 Now what's the atomic mass of this, just as representative? 00:10:19.920 --> 00:10:24.140 This is 2 times 12 is 24, 25, or 26, 27, 28. 00:10:24.140 --> 00:10:30.060 28's roughly 30, so 30 times 10,000, you've got 300,000. 00:10:30.060 --> 00:10:34.670 That's 300,000 grams per mole. 00:10:34.670 --> 00:10:37.620 This means you can have molecular weights on the order 00:10:37.620 --> 00:10:44.480 of a million grams per mole for one molecule. 00:10:44.480 --> 00:10:46.760 And by the way, the polymer people, they come from a 00:10:46.760 --> 00:10:49.150 different branch of science. 00:10:49.150 --> 00:10:50.820 So they don't use this grams per mole. 00:10:50.820 --> 00:10:55.740 Instead of grams per mole, they like to use the word, the 00:10:55.740 --> 00:10:58.030 dalton, as a unit of measure. 00:10:58.030 --> 00:11:00.650 So you might see in the pollymer literature, you'll 00:11:00.650 --> 00:11:05.340 see the polymer with so many kDa, kilodaltons, thousands of 00:11:05.340 --> 00:11:06.920 grams per mole. 00:11:06.920 --> 00:11:08.740 That's the nomenclature you will see. 00:11:08.740 --> 00:11:11.060 OK. 00:11:11.060 --> 00:11:14.610 Now, what are the properties of these things going to be? 00:11:14.610 --> 00:11:17.675 Oh wait, I'm going to show you something. 00:11:17.675 --> 00:11:18.820 To give you a sense. 00:11:18.820 --> 00:11:20.570 You need to be awakened. 00:11:20.570 --> 00:11:23.550 So let me give you a sense of just how long 00:11:23.550 --> 00:11:24.940 these molecules are. 00:11:24.940 --> 00:11:27.520 So I'm going to give you a little mechanical model here. 00:11:27.520 --> 00:11:29.230 I'm going to put up here so we get some-- 00:11:29.230 --> 00:11:31.655 So what I've got here is just a pull chain. 00:11:31.655 --> 00:11:35.110 If you go in the basement, you might see these pull chains. 00:11:35.110 --> 00:11:39.690 They're just made of brass, little brass balls, and then 00:11:39.690 --> 00:11:41.920 they've got links between them. 00:11:41.920 --> 00:11:44.850 And when you cut them-- you buy them by the foot at the 00:11:44.850 --> 00:11:46.030 hardware store. 00:11:46.030 --> 00:11:51.230 You put it on a light, you can turn the light on and off by 00:11:51.230 --> 00:11:52.820 toggling up and down. 00:11:52.820 --> 00:11:57.760 So I'm going to say, let's say this distance here represents 00:11:57.760 --> 00:12:00.800 the distance between mer units. 00:12:00.800 --> 00:12:03.280 This distance could be between 2 mer units. 00:12:03.280 --> 00:12:06.670 And I figured, let's see, I've got 40 feet here, 00:12:06.670 --> 00:12:07.610 and I did the math. 00:12:07.610 --> 00:12:11.220 So this thing here, with the 40 foot pull chain, has a 00:12:11.220 --> 00:12:13.510 polymerization index-- 00:12:13.510 --> 00:12:15.700 let's call this the polymerization index. 00:12:23.150 --> 00:12:26.330 So my polymerization index, I calculated it for this thing. 00:12:26.330 --> 00:12:29.610 It's on the order of about 3,000. 00:12:29.610 --> 00:12:30.920 So that's pretty good. 00:12:30.920 --> 00:12:33.020 It's right in the middle of this. 00:12:33.020 --> 00:12:34.190 It's actually-- 00:12:34.190 --> 00:12:38.250 this qualifies as a bona fide polymer. 00:12:38.250 --> 00:12:41.880 So let's take a look at what happens here. 00:12:55.260 --> 00:12:57.150 This is one molecule. 00:13:01.590 --> 00:13:04.420 So what do you know about 00:13:04.420 --> 00:13:06.070 interactions between molecules? 00:13:06.070 --> 00:13:09.180 Now, in the liquid state, what's this going to be? 00:13:09.180 --> 00:13:12.640 Is it going to be fluid, or is it going to be viscous? 00:13:12.640 --> 00:13:13.480 It's going to be viscous. 00:13:13.480 --> 00:13:17.580 Look, this is one molecule, and it entangles with itself. 00:13:17.580 --> 00:13:21.450 Now, to make a liquid, I have thousands of these things 00:13:21.450 --> 00:13:24.200 swimming around, above their crystallization-- 00:13:24.200 --> 00:13:26.410 oh, crystallization temperature. 00:13:26.410 --> 00:13:27.420 Freudian slip. 00:13:27.420 --> 00:13:29.790 Above their solidification temperature. 00:13:29.790 --> 00:13:32.180 When they solidify, are they going to 00:13:32.180 --> 00:13:33.760 form an ordered solid? 00:13:33.760 --> 00:13:35.775 One of these at each lattice site? 00:13:39.600 --> 00:13:41.040 Probably not. 00:13:41.040 --> 00:13:43.820 They're probably going to form disordered solids. 00:13:43.820 --> 00:13:46.800 So most of the polymers that we encounter are probably 00:13:46.800 --> 00:13:48.260 going to be disordered. 00:13:54.610 --> 00:13:59.920 How is this held together when it forms a solid? 00:13:59.920 --> 00:14:01.290 It's polyethylene. 00:14:01.290 --> 00:14:03.100 Well, what's your menu? 00:14:03.100 --> 00:14:05.120 Is it ionic bonding? 00:14:05.120 --> 00:14:07.810 Is it metallic bonding? 00:14:07.810 --> 00:14:09.700 Is it hydrogen bonding? 00:14:09.700 --> 00:14:12.400 How is it held together? 00:14:12.400 --> 00:14:14.070 Weak van der Waals. 00:14:14.070 --> 00:14:15.380 Weak van der Waals bonds. 00:14:15.380 --> 00:14:16.705 But look at the surface area. 00:14:19.410 --> 00:14:23.560 So this is what it looks like. 00:14:23.560 --> 00:14:26.290 See, and it entangles, is even entangles with my clothing. 00:14:26.290 --> 00:14:27.790 It just grabs onto everything. 00:14:27.790 --> 00:14:28.620 All right. 00:14:28.620 --> 00:14:30.820 Actually, why don't we-- 00:14:30.820 --> 00:14:33.665 David, let's cut to the screen. 00:14:37.646 --> 00:14:39.840 So here we are. 00:14:39.840 --> 00:14:41.420 This is it. 00:14:41.420 --> 00:14:42.950 This is the polymer. 00:14:42.950 --> 00:14:47.380 And every once in a while, a polymer will do 00:14:47.380 --> 00:14:49.460 something like this. 00:14:49.460 --> 00:14:52.410 It'll say, you know, I still, even though I'm in this big 00:14:52.410 --> 00:14:56.350 long chain molecule I still want to try to order. 00:14:56.350 --> 00:15:00.470 Because I read in 3091 that ordering lowers the free 00:15:00.470 --> 00:15:03.500 energy of the system... 00:15:03.500 --> 00:15:06.180 So what it does, it starts doing this. 00:15:06.180 --> 00:15:08.970 And can you see when it starts doing this, that it 00:15:08.970 --> 00:15:11.720 starts to take on-- 00:15:11.720 --> 00:15:15.520 if you walked into the room just now, and this were 00:15:15.520 --> 00:15:18.950 blowing up really high, you might see just this little 00:15:18.950 --> 00:15:21.250 snippet and say, wow. 00:15:21.250 --> 00:15:24.920 This thing is starting to look like a cubic array isn't it? 00:15:29.000 --> 00:15:31.040 This is a really good model. 00:15:31.040 --> 00:15:32.720 It's a really good model, because this 00:15:32.720 --> 00:15:35.470 is what really happens. 00:15:35.470 --> 00:15:39.730 And so that decreases the energy of the system. 00:15:39.730 --> 00:15:41.040 The bonds are greater there. 00:15:41.040 --> 00:15:44.540 So what's that going to do to the mechanical properties? 00:15:44.540 --> 00:15:45.890 Going to strengthen it, yeah. 00:15:45.890 --> 00:15:47.690 It's going to make things stiffer. 00:15:47.690 --> 00:15:51.050 Instead of being this soft, squishy polymer, it's going to 00:15:51.050 --> 00:15:52.240 have some stiffness to it. 00:15:52.240 --> 00:15:53.730 And you've come up across that stuff. 00:15:53.730 --> 00:15:58.250 The most notable one being the CD case. 00:15:58.250 --> 00:16:00.400 The people that make those, I'd like to bring them here 00:16:00.400 --> 00:16:03.570 and sit them down and teach them some polymer science. 00:16:03.570 --> 00:16:04.790 Those things are so brittle. 00:16:04.790 --> 00:16:05.580 They crack, right? 00:16:05.580 --> 00:16:07.380 There's only two classes of jewel cases. 00:16:07.380 --> 00:16:09.450 Those that are cracked, and those that will crack. 00:16:12.330 --> 00:16:15.020 Because these people don't know what they're doing. 00:16:15.020 --> 00:16:15.350 OK. 00:16:15.350 --> 00:16:20.370 So now let's have some time here to codify 00:16:20.370 --> 00:16:21.980 what we've just see. 00:16:21.980 --> 00:16:25.050 So first of all, we suspect that they're going to be solid 00:16:25.050 --> 00:16:28.210 at room temperature. 00:16:28.210 --> 00:16:29.080 Dominantly. 00:16:29.080 --> 00:16:32.200 We can engineer them to be liquid, but dominantly solid 00:16:32.200 --> 00:16:33.430 at room temperature. 00:16:33.430 --> 00:16:38.305 And van der Waals bonds abundant. 00:16:44.100 --> 00:16:44.430 OK. 00:16:44.430 --> 00:16:47.516 And the liquid, as a liquid, we expect viscous liquid. 00:16:55.580 --> 00:16:56.550 Good. 00:16:56.550 --> 00:16:57.450 Got that down. 00:16:57.450 --> 00:17:00.430 What else to have to know? 00:17:00.430 --> 00:17:02.260 Let's do calculation here. 00:17:02.260 --> 00:17:05.800 So I did one here where I said, what's this distance? 00:17:05.800 --> 00:17:08.300 We saw last day that this distance, carbon-carbon, 00:17:08.300 --> 00:17:10.720 remember, we're looking at single bond, double bond. 00:17:10.720 --> 00:17:14.000 A single bond carbon-carbon is about 1.5 angstroms. So this 00:17:14.000 --> 00:17:18.480 is 1.5 angstroms. The distance between successive mer units 00:17:18.480 --> 00:17:23.820 is about 3 angstroms. And so if you take something 3 00:17:23.820 --> 00:17:28.940 angstroms, and you make it this number of mer units, I 00:17:28.940 --> 00:17:35.940 came up with a polymerization index of 3571 when this thing 00:17:35.940 --> 00:17:38.790 weighs 10,010 kilodaltons. 00:17:38.790 --> 00:17:45.040 And so then that means that you'd end up with a length, 00:17:45.040 --> 00:17:56.690 molecular length is on the order of 10,714 angstroms, 00:17:56.690 --> 00:18:00.800 which is on the order of 1 micrometer, which then makes 00:18:00.800 --> 00:18:05.410 it greater than the wavelength of visible light. 00:18:05.410 --> 00:18:11.340 So this is really a different type of matter. 00:18:11.340 --> 00:18:12.190 And we can go there. 00:18:12.190 --> 00:18:17.470 We've talked about viscous, so I'm going to remind you of two 00:18:17.470 --> 00:18:18.710 observations here. 00:18:18.710 --> 00:18:22.550 Viscous liquids, amorphous solids. 00:18:22.550 --> 00:18:25.090 If you put those two ideas together, what 00:18:25.090 --> 00:18:27.090 else can we call upon? 00:18:27.090 --> 00:18:28.410 We can go back to this. 00:18:35.180 --> 00:18:36.870 Yeah. 00:18:36.870 --> 00:18:38.120 Remember this? 00:18:40.470 --> 00:18:41.520 What's this? 00:18:41.520 --> 00:18:45.510 This is super-cool liquid, super-cool viscous liquid. 00:18:45.510 --> 00:18:48.720 This is the solidification temperature, which in the case 00:18:48.720 --> 00:18:53.030 of liquid to amorphous solid is the glass transition 00:18:53.030 --> 00:18:54.320 temperature. 00:18:54.320 --> 00:18:58.180 And here we have the excess volume, right? 00:18:58.180 --> 00:19:00.220 This is the volume, and then there's some crystalline 00:19:00.220 --> 00:19:01.780 volume, and so on. 00:19:01.780 --> 00:19:02.240 Right? 00:19:02.240 --> 00:19:06.860 I can cool at a second rate, and I get this. 00:19:06.860 --> 00:19:12.930 So this is slow cool, this is fast cool. 00:19:12.930 --> 00:19:14.970 We have a Tg up here. 00:19:14.970 --> 00:19:20.030 Tgf I'll call Tg fast, and Tgs, Tg slow. 00:19:20.030 --> 00:19:21.780 So that'll give me a different volume. 00:19:21.780 --> 00:19:25.490 So this is volume fast and volume slow. 00:19:25.490 --> 00:19:26.100 All right? 00:19:26.100 --> 00:19:30.650 And since I know that density is equal to mass over volume, 00:19:30.650 --> 00:19:34.340 so therefore v fast is greater than-- 00:19:34.340 --> 00:19:38.540 I observe v fast is greater than v slow, so therefore 00:19:38.540 --> 00:19:48.290 density of the fast cool must be less than the density of 00:19:48.290 --> 00:19:51.030 the slow cool. 00:19:51.030 --> 00:19:52.460 Now I'm going to put some names on here. 00:19:52.460 --> 00:19:54.850 I'm going to call this the cooling curves for 00:19:54.850 --> 00:19:56.560 polyethylene. 00:19:56.560 --> 00:19:59.030 These are the cooling curves for polyethylene. 00:19:59.030 --> 00:20:01.620 So this, down here, gives me-- 00:20:01.620 --> 00:20:06.340 this is now high-density polyethylene, and up here is 00:20:06.340 --> 00:20:08.620 low-density polyethylene. 00:20:08.620 --> 00:20:10.230 Same thing, just different processing. 00:20:13.520 --> 00:20:16.740 So faster cooling quenches in more free volume. 00:20:16.740 --> 00:20:24.250 And since volume is a measure of disorder, right? 00:20:24.250 --> 00:20:28.040 What's the difference between great disorder and 00:20:28.040 --> 00:20:30.720 not-so-great disorder? 00:20:30.720 --> 00:20:34.540 David, again cut to the projector, please? 00:20:34.540 --> 00:20:37.520 Forgive me, the document camera? 00:20:37.520 --> 00:20:40.680 So the difference between high disorder and 00:20:40.680 --> 00:20:43.350 low disorder is this. 00:20:43.350 --> 00:20:46.100 This is the order, here. 00:20:46.100 --> 00:20:49.710 So what that tells me is that in high-density polyethylene, 00:20:49.710 --> 00:20:54.190 there is a greater percentage of zones like this. 00:20:54.190 --> 00:20:56.710 And we just reasoned that this is going to give stiffness and 00:20:56.710 --> 00:21:00.950 so on, and sure enough, for the low-density polyethylene, 00:21:00.950 --> 00:21:05.170 low-density polyethylene is used in things like food wrap, 00:21:05.170 --> 00:21:08.460 things like stretch and seal, where you can pull because you 00:21:08.460 --> 00:21:12.510 can move those macromolecules relative to one another 00:21:12.510 --> 00:21:16.160 without fracturing the material to stretch it over. 00:21:16.160 --> 00:21:21.420 Whereas the high-density polyethylene is used in such 00:21:21.420 --> 00:21:25.140 things as milk jugs, where you want a 00:21:25.140 --> 00:21:26.860 little bit of stiffness. 00:21:26.860 --> 00:21:31.490 Polyethylene milk jugs are still kind of floppy, but 00:21:31.490 --> 00:21:33.380 there's a little bit of stiffness to it. 00:21:33.380 --> 00:21:36.590 The other thing is, because the low-density polyethylene 00:21:36.590 --> 00:21:42.310 is dominantly amorphous, with almost none of this second 00:21:42.310 --> 00:21:46.190 zone here, it's transparent to visible light. 00:21:46.190 --> 00:21:48.350 But now, let's think about what's going on here. 00:21:48.350 --> 00:21:50.960 Where I've got this chain, and then all of a 00:21:50.960 --> 00:21:53.712 sudden I get to this. 00:21:53.712 --> 00:21:55.240 All right? 00:21:55.240 --> 00:21:58.030 So this is clear and colorless. 00:21:58.030 --> 00:21:58.320 Right? 00:21:58.320 --> 00:22:00.240 It's a high band gap material. 00:22:00.240 --> 00:22:02.190 There's no free electrons. 00:22:02.190 --> 00:22:04.730 It's going to be transparent to invisible light. 00:22:04.730 --> 00:22:07.940 So this is transparent to visible light all along. 00:22:07.940 --> 00:22:13.890 But can you see that because I have this zone of ordering, 00:22:13.890 --> 00:22:18.280 the density of matter here is different, and so therefore, 00:22:18.280 --> 00:22:25.960 when a photon comes in, the index of refraction-- 00:22:25.960 --> 00:22:27.610 now, you know, this is one of those days where n is 00:22:27.610 --> 00:22:28.190 going to come up. 00:22:28.190 --> 00:22:31.120 So here n is the polymerization index. 00:22:31.120 --> 00:22:33.010 Here it's index of refraction. 00:22:33.010 --> 00:22:34.630 So maybe we'll use a different color. 00:22:34.630 --> 00:22:35.450 How about that. 00:22:35.450 --> 00:22:36.200 All right? 00:22:36.200 --> 00:22:39.880 So the green n is index of refraction. 00:22:39.880 --> 00:22:46.630 So the index of refraction in the amorphous zone, is 00:22:46.630 --> 00:22:50.330 different from the index of refraction in the partially 00:22:50.330 --> 00:22:52.680 crystalline zone. 00:22:52.680 --> 00:22:57.410 So index of refraction varies from zone to zone. 00:22:57.410 --> 00:23:00.880 Even though each zone is clear and colorless, can you see 00:23:00.880 --> 00:23:04.640 that this boundary between the ordered and in the disordered 00:23:04.640 --> 00:23:07.100 zone acts like an interface? 00:23:07.100 --> 00:23:09.120 And what happens when you have an interface with a different 00:23:09.120 --> 00:23:10.350 index of refraction? 00:23:10.350 --> 00:23:11.450 It scatters light. 00:23:11.450 --> 00:23:15.220 And as a result, the milk jugs, they appear white. 00:23:15.220 --> 00:23:16.940 You can't see through them, even though they're 00:23:16.940 --> 00:23:21.170 constituted of the same continuous material. 00:23:21.170 --> 00:23:24.770 But there's these density fluctuations, because this is 00:23:24.770 --> 00:23:26.830 a higher density than this. 00:23:26.830 --> 00:23:30.210 So you can rationalize all of this stuff. 00:23:32.790 --> 00:23:33.110 OK. 00:23:33.110 --> 00:23:35.370 So this is what we would call partial 00:23:35.370 --> 00:23:37.750 crystallization in this zone. 00:23:45.080 --> 00:23:48.290 And that gives rise to the changes. 00:23:48.290 --> 00:23:50.100 Now, how would we distinguish these? 00:23:50.100 --> 00:23:53.890 What technique would I use to see if I've got order in this 00:23:53.890 --> 00:23:56.860 polymer, that I don't know anything about? 00:23:56.860 --> 00:23:59.530 How do I interrogate atomic order? 00:23:59.530 --> 00:24:02.550 What technique would I use? 00:24:02.550 --> 00:24:03.740 X-ray defraction. 00:24:03.740 --> 00:24:05.260 Thank you. 00:24:05.260 --> 00:24:06.780 Back to the slides, please, David. 00:24:11.900 --> 00:24:14.480 I'll find you the piece. 00:24:14.480 --> 00:24:18.940 This is called polyethylene, but remember last day, the 00:24:18.940 --> 00:24:22.680 IUPAC notation for this is ethyne, so 00:24:22.680 --> 00:24:24.140 this becomes polythene. 00:24:24.140 --> 00:24:28.100 And in the UK, it's known as polythene, and there's a 00:24:28.100 --> 00:24:31.850 Beatles song, Polythene Pam. 00:24:31.850 --> 00:24:32.590 The only reason-- 00:24:32.590 --> 00:24:33.950 I put up here for two reasons. 00:24:33.950 --> 00:24:36.840 One is, it has something to do with polymers. 00:24:36.840 --> 00:24:39.400 At least they knew something about polymers. 00:24:39.400 --> 00:24:42.560 It's apparently, they must have been in a drug haze at 00:24:42.560 --> 00:24:44.460 this period in their careers. 00:24:44.460 --> 00:24:47.440 This is absolutely terrible. 00:24:47.440 --> 00:24:49.970 Some of your parents probably adore the Beatles. 00:24:49.970 --> 00:24:53.140 If you want to provoke a conversation at Thanksgiving, 00:24:53.140 --> 00:24:56.000 pull out this one and ask them to talk about the lyrics here. 00:24:56.000 --> 00:24:57.030 But this is just garbage. 00:24:57.030 --> 00:24:57.650 This is garbage! 00:24:57.650 --> 00:24:59.730 This should be trash bag, is what it should be. 00:24:59.730 --> 00:25:02.470 But evidently, this woman used to show up at parties dressed 00:25:02.470 --> 00:25:05.080 only in a polythene bag, a see-through polythene 00:25:05.080 --> 00:25:06.260 bag, I might add. 00:25:06.260 --> 00:25:08.520 So this is a paean to her. 00:25:08.520 --> 00:25:10.650 Anyways, it's bad. 00:25:10.650 --> 00:25:12.580 Yeah, yeah, yeah. 00:25:12.580 --> 00:25:12.850 Anyway. 00:25:12.850 --> 00:25:13.930 So here we are. 00:25:13.930 --> 00:25:18.150 This indicates chrystalline polyethylene. 00:25:18.150 --> 00:25:20.740 Here you can see the C2H4 unit. 00:25:20.740 --> 00:25:26.530 And it's attempting to try to occupy, as these beads line up 00:25:26.530 --> 00:25:31.280 here, they're trying to set up a faux lattice. 00:25:31.280 --> 00:25:33.470 And this is what you might see. 00:25:33.470 --> 00:25:36.060 And towards the end of the lecture, I'll show you a 00:25:36.060 --> 00:25:38.830 transmission electron micrograph where you can see 00:25:38.830 --> 00:25:43.530 this by dying it with different colors. 00:25:43.530 --> 00:25:43.820 OK. 00:25:43.820 --> 00:25:45.360 So now here's some x-ray defraction. 00:25:45.360 --> 00:25:49.000 So this is crystalline, where they zoomed in on one of these 00:25:49.000 --> 00:25:52.160 zones, and they've just gotten the defraction 00:25:52.160 --> 00:25:53.490 pattern from that zone. 00:25:53.490 --> 00:25:55.430 And you see Bragg peaks. 00:25:55.430 --> 00:25:57.400 And then this is in the amorphous region. 00:25:57.400 --> 00:25:58.500 it's not featureless. 00:25:58.500 --> 00:25:59.810 There's one broad peak. 00:25:59.810 --> 00:26:02.100 Why one broad peak? 00:26:02.100 --> 00:26:04.500 Because even though there's no long-range order, you have 00:26:04.500 --> 00:26:05.280 short-range order. 00:26:05.280 --> 00:26:07.570 You know that you've got a carbon on either side, you've 00:26:07.570 --> 00:26:08.710 got hydrogens and so on. 00:26:08.710 --> 00:26:11.880 So that short range order gives you the broad peak. 00:26:11.880 --> 00:26:13.410 But look at C here. 00:26:13.410 --> 00:26:15.130 Isn't this interesting? 00:26:15.130 --> 00:26:22.720 That if you have a polymer that has both some order and a 00:26:22.720 --> 00:26:26.400 lot of disorder, if you take the x-ray defraction pattern 00:26:26.400 --> 00:26:32.410 more broadly, more globally, you get the additive spectrum. 00:26:32.410 --> 00:26:36.940 So you can see that this is amorphous, but there are some 00:26:36.940 --> 00:26:39.950 zones of crystallinity. 00:26:39.950 --> 00:26:44.610 And that's the additivity power of x-ray defraction that 00:26:44.610 --> 00:26:46.650 allows us to interrogate. 00:26:46.650 --> 00:26:51.130 So now let's talk in a little more fine structure about 00:26:51.130 --> 00:26:52.820 molecular architecture. 00:26:52.820 --> 00:26:57.115 So tailoring molecular architecture. 00:27:01.700 --> 00:27:02.590 And why are we doing this? 00:27:02.590 --> 00:27:05.050 Because we want to engineer these materials for desirable 00:27:05.050 --> 00:27:05.660 properties. 00:27:05.660 --> 00:27:10.010 Like CD cases that break after about one or two uses, OK? 00:27:10.010 --> 00:27:12.990 Of polymers. 00:27:12.990 --> 00:27:15.100 Actually, there's probably a business opportunity there. 00:27:15.100 --> 00:27:16.870 You start a company where you make jewel cases 00:27:16.870 --> 00:27:18.830 that actually work. 00:27:18.830 --> 00:27:20.890 People might be willing to pay, you know, a penny more 00:27:20.890 --> 00:27:22.340 for something that works. 00:27:22.340 --> 00:27:22.740 All right. 00:27:22.740 --> 00:27:24.280 So how do we change this? 00:27:24.280 --> 00:27:28.060 What I'm going to show is a whole bunch of cartoons of 00:27:28.060 --> 00:27:28.710 architecture. 00:27:28.710 --> 00:27:30.200 But how do we control this? 00:27:30.200 --> 00:27:31.970 It's processing. 00:27:31.970 --> 00:27:33.590 It's processing. 00:27:33.590 --> 00:27:37.100 Processing and in the synthesis algorithm. 00:27:37.100 --> 00:27:39.310 I'm assuming I already have polyethylene, so how am I 00:27:39.310 --> 00:27:40.460 going to tailor it? 00:27:40.460 --> 00:27:41.830 It's in the processing. 00:27:41.830 --> 00:27:45.300 And so what I can do, is I've got a number of 00:27:45.300 --> 00:27:48.920 levers I can move. 00:27:48.920 --> 00:27:53.240 One is the composition of the polymer, and the second one 00:27:53.240 --> 00:27:56.810 is, I can use catalysis. 00:27:56.810 --> 00:27:59.940 I already hinted at that last day in talking about gasoline. 00:27:59.940 --> 00:28:03.500 How do you start with petroleum and get octane and 00:28:03.500 --> 00:28:05.280 not heptane and so on? 00:28:05.280 --> 00:28:11.040 By playing with cataylsis, we can direct certain forms. You 00:28:11.040 --> 00:28:15.220 can actually preferably synthesize a certain 00:28:15.220 --> 00:28:17.920 architecture by using catalysts. 00:28:17.920 --> 00:28:19.680 So let's look at these variables. 00:28:19.680 --> 00:28:22.600 First one is composition, obviously. 00:28:22.600 --> 00:28:25.640 If you change the composition of something, you can very 00:28:25.640 --> 00:28:27.950 much expect to change its properties. 00:28:27.950 --> 00:28:30.490 So what do we have here? 00:28:30.490 --> 00:28:32.080 We can-- 00:28:32.080 --> 00:28:36.960 here's a simple example I can start here with. 00:28:36.960 --> 00:28:38.210 This is ethylene. 00:28:40.490 --> 00:28:47.890 Or I can put a chlorine here, so this now 00:28:47.890 --> 00:28:50.420 becomes chloride, right? 00:28:50.420 --> 00:28:53.020 This will become, what's the radical, is vinyl, so this is 00:28:53.020 --> 00:28:56.800 vinyl chloride. 00:28:56.800 --> 00:28:59.810 So if I polymerize this, this becomes polyethylene. 00:28:59.810 --> 00:29:01.470 If I polymerize this, this becomes 00:29:01.470 --> 00:29:03.940 polyvinyl chloride, PVC. 00:29:03.940 --> 00:29:08.470 Which is why you heard the fellows from Blue Man Group at 00:29:08.470 --> 00:29:13.130 the beginning banging on PVC tubing to make their music. 00:29:13.130 --> 00:29:13.410 All right. 00:29:13.410 --> 00:29:18.270 So I use a pure, in other words, only one mer. 00:29:18.270 --> 00:29:20.050 It's pure polyethylene. 00:29:20.050 --> 00:29:21.460 This it's called a homopolymer. 00:29:26.210 --> 00:29:31.830 Only one mer type in use. 00:29:31.830 --> 00:29:35.950 If I want to make the polymer analogy of an alloy-- 00:29:35.950 --> 00:29:40.040 in ally metals, alloy has more than one metal mixed in, or a 00:29:40.040 --> 00:29:42.340 metal can even have nonmetals mixed in. 00:29:42.340 --> 00:29:46.085 Then the polymer term is called copolymer. 00:29:46.085 --> 00:29:48.640 I'll call this a copolymer. 00:29:48.640 --> 00:29:55.730 And a copolymer has greater than one mer type. 00:29:55.730 --> 00:29:59.700 So for example here, this could just be polyethylene. 00:29:59.700 --> 00:30:04.800 Whereas here, an example would be polyethylene, and then the 00:30:04.800 --> 00:30:10.100 notation is hyphen lowercase c hyphen, which is an indication 00:30:10.100 --> 00:30:13.040 of the fact that you're making a copolymer. 00:30:13.040 --> 00:30:17.420 And this copolymer has mer units of ethylene, and mer 00:30:17.420 --> 00:30:19.430 units of vinyl chloride. 00:30:19.430 --> 00:30:22.630 So this is a copolymer of polyethylene 00:30:22.630 --> 00:30:24.430 and polyvinyl chloride. 00:30:24.430 --> 00:30:27.960 And then we can start looking at the various ways of 00:30:27.960 --> 00:30:29.380 arranging these. 00:30:29.380 --> 00:30:32.590 So we can start with, for example, we can have a 00:30:32.590 --> 00:30:45.680 sequence of random mer types. 00:30:45.680 --> 00:30:48.960 So as you're going down the chain, you get either an 00:30:48.960 --> 00:30:53.120 ethylene, or a vinyl chloride. 00:30:53.120 --> 00:30:58.050 So this is called a random copolymer, and it's designated 00:30:58.050 --> 00:31:01.400 polyethylene-r-polyvinyl chloride. 00:31:01.400 --> 00:31:05.560 And actually, I think I've got a cartoon showing this. 00:31:05.560 --> 00:31:06.250 Yeah. 00:31:06.250 --> 00:31:10.600 So A and B are different mer types. 00:31:10.600 --> 00:31:13.150 And so a random copolymer just has A, B, B, 00:31:13.150 --> 00:31:15.330 A, A, A, B, A, whatever. 00:31:15.330 --> 00:31:18.770 And this is controlled in the synthesis process. 00:31:18.770 --> 00:31:24.200 So I can take the same mix of A and B, in other words, the 00:31:24.200 --> 00:31:26.980 same two mer types, but mix them in 00:31:26.980 --> 00:31:28.390 an alternating sequence. 00:31:28.390 --> 00:31:29.730 So they're very regular. 00:31:29.730 --> 00:31:35.040 It's 1 mer of ethylene, and then one mer of vinyl 00:31:35.040 --> 00:31:37.540 chloride, alternating all the way down the backbone. 00:31:37.540 --> 00:31:40.760 So this gives you a regular copolymer, and it's designated 00:31:40.760 --> 00:31:42.140 A for alternating, because we've 00:31:42.140 --> 00:31:45.030 already used R for random. 00:31:45.030 --> 00:31:48.580 So instead of a sequence of random, we have a sequence of 00:31:48.580 --> 00:31:54.210 alternating mer types. 00:31:54.210 --> 00:31:55.500 So that would be, in this case, 00:31:55.500 --> 00:31:59.165 polyethylene alternating PVC. 00:31:59.165 --> 00:32:00.940 So that's two of them. 00:32:00.940 --> 00:32:05.320 And then you see the block copolymer shown. 00:32:05.320 --> 00:32:13.520 And in that case, the mers grouped into-- 00:32:13.520 --> 00:32:15.860 they call them blocks, even though it's a line. 00:32:15.860 --> 00:32:17.790 You know, maybe it's like walking down the street. 00:32:17.790 --> 00:32:19.480 I've walked down one block. 00:32:19.480 --> 00:32:23.950 So this is one block, and then there's the next block. 00:32:23.950 --> 00:32:26.720 They're grouped into blocks. 00:32:26.720 --> 00:32:32.750 So in that case, we have the block copolymer, lowercase b, 00:32:32.750 --> 00:32:35.030 and then PVC. 00:32:35.030 --> 00:32:38.470 And what you see there is a run. 00:32:38.470 --> 00:32:39.720 A run of-- 00:32:42.370 --> 00:32:45.260 So all of the A's are grouped, and then we 00:32:45.260 --> 00:32:47.090 have all of the B's. 00:32:47.090 --> 00:32:50.310 And this is actually an artist's misconception. 00:32:50.310 --> 00:32:54.060 In point of fact, most block copolymers that you find, this 00:32:54.060 --> 00:32:56.180 is the stuff they use for the soles of your 00:32:56.180 --> 00:32:57.110 sneakers and so on. 00:32:57.110 --> 00:32:58.650 They're block copolymers. 00:32:58.650 --> 00:33:00.730 They're usually just a diblock. 00:33:00.730 --> 00:33:03.620 There's usually just two different mer types. 00:33:03.620 --> 00:33:07.320 One half of the macromolecule is one mer type, the other 00:33:07.320 --> 00:33:10.770 half of the macromolecule is the other mer type. 00:33:10.770 --> 00:33:14.250 Sometimes you might find a triblock, where you might find 00:33:14.250 --> 00:33:16.690 block A, block B, and then another block A. 00:33:16.690 --> 00:33:20.210 But this is a pentablock and he's even got ellipses here as 00:33:20.210 --> 00:33:21.350 though this thing keeps going. 00:33:21.350 --> 00:33:23.230 There's no commercial product that looks like that. 00:33:23.230 --> 00:33:26.430 It's usually a diblock, occasionally a triblock. 00:33:26.430 --> 00:33:27.060 OK? 00:33:27.060 --> 00:33:30.500 And then the last thing you can do, as is shown up here, 00:33:30.500 --> 00:33:33.270 is what is known as the graft. 00:33:33.270 --> 00:33:37.280 And in the graft, the thing that distinguishes the graft 00:33:37.280 --> 00:33:39.750 is mers grouped into blocks. 00:33:39.750 --> 00:33:50.310 In this case, a long side chain of other mer. 00:33:50.310 --> 00:33:53.470 So that's different from side group that we saw last day. 00:33:53.470 --> 00:33:55.570 These are long macromolecular chains. 00:33:55.570 --> 00:33:59.130 So you see here the primary backbone is A, and then you 00:33:59.130 --> 00:34:02.890 have this very, very long macromolecular chain of B. 00:34:02.890 --> 00:34:07.625 And this is called the graft copolymer. 00:34:07.625 --> 00:34:10.730 So that would be polyethylene, could be the backbone, and 00:34:10.730 --> 00:34:14.180 then long side chains of polyvinyl chloride. 00:34:14.180 --> 00:34:18.070 And all of these have their different architectures. 00:34:18.070 --> 00:34:20.310 And I think I have an example here of one. 00:34:20.310 --> 00:34:22.540 This one, I think I mentioned last day, when we were looking 00:34:22.540 --> 00:34:25.920 at the butadiene. 00:34:25.920 --> 00:34:28.520 So this is hard-sided luggage. 00:34:28.520 --> 00:34:30.850 And if you go to grandma's house, and she hasn't gotten 00:34:30.850 --> 00:34:34.390 into the digital age, and isn't an old hipster with a 00:34:34.390 --> 00:34:38.800 cell phone, she's still got the old hard plastic 00:34:38.800 --> 00:34:40.680 telephone, it's made of this stuff. 00:34:40.680 --> 00:34:44.830 ABS, which is acrylonitrile butadiene styrene. 00:34:44.830 --> 00:34:48.880 And the backbone is butadiene, and then you have-- 00:34:48.880 --> 00:34:50.400 OK, so here's the backbone. 00:34:50.400 --> 00:34:53.130 It's long butadiene, which we saw last day. 00:34:53.130 --> 00:34:55.970 And then you've got side chains of two types. 00:34:55.970 --> 00:34:58.740 And this is just indicating A, A, but this is a 00:34:58.740 --> 00:34:59.750 macromolecule. 00:34:59.750 --> 00:35:03.210 This might be 3,000 units long, whereas this is 10,000 00:35:03.210 --> 00:35:04.110 units long. 00:35:04.110 --> 00:35:06.390 And this might be 2,000 units long. 00:35:06.390 --> 00:35:09.590 So you have side chains of acrylonitrile and side chains 00:35:09.590 --> 00:35:11.650 of polystyrene. 00:35:11.650 --> 00:35:14.650 And that's the hard plastic. 00:35:14.650 --> 00:35:18.300 It's coming back, because people want luggage that 00:35:18.300 --> 00:35:21.980 doesn't destroy their contents anymore. 00:35:21.980 --> 00:35:23.760 So that's coming back. 00:35:23.760 --> 00:35:24.040 OK. 00:35:24.040 --> 00:35:27.940 So this is what we can do in terms of composition. 00:35:27.940 --> 00:35:31.570 Let's look at, also, the side group arrangement. 00:35:31.570 --> 00:35:33.840 And this is called tacticity. 00:35:33.840 --> 00:35:38.290 Tacticity, which is the equivalent of what we saw last 00:35:38.290 --> 00:35:39.600 day as stereo isomerism. 00:35:44.640 --> 00:35:50.730 Remember, I showed you the cis and trans on the butadiene. 00:35:50.730 --> 00:35:56.230 On the cis, you've got, in one case, you've got whatever the 00:35:56.230 --> 00:35:57.120 functional group is. 00:35:57.120 --> 00:36:01.370 I'm going to put A, A, B, B. 00:36:01.370 --> 00:36:05.660 And then so this is the cis version, or I can do a trans 00:36:05.660 --> 00:36:09.630 version, which is instead, I'll put in A up here 00:36:09.630 --> 00:36:10.900 and an A down here. 00:36:10.900 --> 00:36:13.450 I'll put a B up here and a B down here. 00:36:13.450 --> 00:36:15.090 So this is a trans version. 00:36:15.090 --> 00:36:18.410 So imagine the analogy for polymers. 00:36:18.410 --> 00:36:19.380 So let's look at that. 00:36:19.380 --> 00:36:22.160 It's easier to see it, and then we can just document it. 00:36:22.160 --> 00:36:25.430 So here's three different polymers, all right? 00:36:25.430 --> 00:36:28.780 So I'm going to start with the lowest one. 00:36:28.780 --> 00:36:32.460 This is called isotactic, because this is vinylchloride. 00:36:32.460 --> 00:36:35.890 There's vinyl chloride by itself. 00:36:35.890 --> 00:36:38.160 There's the vinyl radical from ethylene. 00:36:38.160 --> 00:36:39.930 And then we tack on chlorine. 00:36:39.930 --> 00:36:42.580 And now when we polymerize, we're going to break this 00:36:42.580 --> 00:36:45.920 double bond in order to link this carbon to the neighbor. 00:36:45.920 --> 00:36:48.350 So now the backbone only has single bonds, right? 00:36:48.350 --> 00:36:50.830 You start with the double bonded precursor, and now 00:36:50.830 --> 00:36:52.950 you've got this chain of single bonds. 00:36:52.950 --> 00:36:53.220 Right? 00:36:53.220 --> 00:36:54.390 But look at the chlorine. 00:36:54.390 --> 00:36:57.460 The chlorine could either be below, or it could be above. 00:36:57.460 --> 00:36:58.720 Well, in this case, the chlorine is 00:36:58.720 --> 00:37:00.410 always below the chain. 00:37:00.410 --> 00:37:03.680 So this is called isotactic polyvinyl chloride. 00:37:03.680 --> 00:37:06.830 Now this one, you know, they're trying to mix two 00:37:06.830 --> 00:37:07.540 things at once. 00:37:07.540 --> 00:37:09.980 I would have shown this with vinyl chloride in 00:37:09.980 --> 00:37:11.090 all three, but OK. 00:37:11.090 --> 00:37:13.830 So imagine now, in this case it's syndiotactic. 00:37:13.830 --> 00:37:17.090 This happens to be polystyrene, because this is 00:37:17.090 --> 00:37:21.840 vinyl benzine, or what's the other way to 00:37:21.840 --> 00:37:25.360 call it, phenyl ethylene. 00:37:25.360 --> 00:37:26.410 You can have either way. 00:37:26.410 --> 00:37:26.680 All right? 00:37:26.680 --> 00:37:30.830 So you can say you're putting a phenyl group onto vinyl, or 00:37:30.830 --> 00:37:33.850 you're putting onto the ethylene, or vice versa. 00:37:33.850 --> 00:37:36.930 But the radical, this thing here is called styrene, and 00:37:36.930 --> 00:37:39.040 we're going to break that double bond and away we go. 00:37:39.040 --> 00:37:43.720 So this is the benzine ring, and it alternates from above 00:37:43.720 --> 00:37:44.840 the chain to below the chain. 00:37:44.840 --> 00:37:46.610 Above the chain to below the chain. 00:37:46.610 --> 00:37:49.010 So in this, this is called syndiotactic. 00:37:49.010 --> 00:37:52.040 And the top one is a polypropylene, so you start 00:37:52.040 --> 00:37:55.250 with propylene, that has the double bond here. 00:37:55.250 --> 00:37:59.020 It's got three carbons and the methyl group coming out, and 00:37:59.020 --> 00:38:02.940 so you break that double bond and make the chain. 00:38:02.940 --> 00:38:05.600 And it seems to be on a random basis where that 00:38:05.600 --> 00:38:06.540 methyl group appears. 00:38:06.540 --> 00:38:08.750 Sometimes above the chain, sometimes below the chain. 00:38:08.750 --> 00:38:13.830 So those are three different ways of arranging, so three 00:38:13.830 --> 00:38:15.060 different tacticities. 00:38:15.060 --> 00:38:25.710 So we've got isotactic, we've got syndiotactic, and we've 00:38:25.710 --> 00:38:28.620 got atactic. 00:38:28.620 --> 00:38:31.370 So the way to remember them, isotactic obviously means, 00:38:31.370 --> 00:38:33.590 everything's on the same side. 00:38:33.590 --> 00:38:35.500 And when I'm talking about the same side, what is it? 00:38:35.500 --> 00:38:38.580 Same side of the backbone. 00:38:38.580 --> 00:38:41.390 And we're talking about the position of 00:38:41.390 --> 00:38:43.380 functional groups, right? 00:38:43.380 --> 00:38:44.560 That's what this is all about. 00:38:44.560 --> 00:38:46.440 The positioning of functional groups. 00:38:56.830 --> 00:38:59.450 In other words, a methyl, or a benzine, or what have you. 00:38:59.450 --> 00:39:01.230 So same side of backbone. 00:39:01.230 --> 00:39:06.050 Atactic is random, and then by elimination, this one must 00:39:06.050 --> 00:39:09.970 mean alternating, above and below. 00:39:09.970 --> 00:39:11.870 On opposite sides of the chain. 00:39:11.870 --> 00:39:14.580 And these have different propensities for 00:39:14.580 --> 00:39:15.470 crystallization. 00:39:15.470 --> 00:39:16.960 Which of these three-- 00:39:16.960 --> 00:39:20.650 imagine that all three of them were polyvinyl chloride. 00:39:20.650 --> 00:39:24.770 Which of the three, atactic, syndiotactic, isotactic, would 00:39:24.770 --> 00:39:29.010 be most favorable from the standpoint of partial 00:39:29.010 --> 00:39:32.730 crystallization, to loop back and forth? 00:39:32.730 --> 00:39:37.870 The one that's most regular, so the isotactic one has. 00:39:37.870 --> 00:39:40.060 OK. 00:39:40.060 --> 00:39:41.220 Third one. 00:39:41.220 --> 00:39:44.930 Third one is the backbone configuration. 00:39:53.280 --> 00:39:56.290 This is the configuration of the main chain, all right? 00:39:56.290 --> 00:39:59.276 And this is called conformality. 00:39:59.276 --> 00:40:03.510 You see, they have different words for everything that came 00:40:03.510 --> 00:40:04.850 from a different heritage. 00:40:04.850 --> 00:40:09.040 So to me, it answers the question, how 00:40:09.040 --> 00:40:10.503 distended is the chain? 00:40:14.850 --> 00:40:18.690 And we saw this last day, when we looked at what happens when 00:40:18.690 --> 00:40:23.050 we start with something like this, where we have staggered 00:40:23.050 --> 00:40:27.440 or eclipsed, remember, orientation of 00:40:27.440 --> 00:40:29.480 the hydrogens here. 00:40:29.480 --> 00:40:32.860 In the case of staggered, we get the lower. 00:40:32.860 --> 00:40:35.640 Both of these are straight chains, because if you start 00:40:35.640 --> 00:40:38.180 at one end, you move monotonically all the way down 00:40:38.180 --> 00:40:40.010 the chain to the other end. 00:40:40.010 --> 00:40:41.640 There's no branching here. 00:40:41.640 --> 00:40:47.250 But one of them, the lower one, has staggering of that 00:40:47.250 --> 00:40:49.660 carbon-carbon bond, with the result, things 00:40:49.660 --> 00:40:51.190 form this giant loop. 00:40:51.190 --> 00:40:54.550 So in polymers, imagine this, instead of being 36 units 00:40:54.550 --> 00:40:57.490 long, imagine it being 3,600 units long. 00:40:57.490 --> 00:40:59.390 So now you can have things to do this. 00:41:02.115 --> 00:41:04.540 You can even take a little break here and 00:41:04.540 --> 00:41:06.500 crystallize and so on. 00:41:06.500 --> 00:41:13.980 So how do I distinguish that from something that does this? 00:41:13.980 --> 00:41:15.600 So how distended is the chain? 00:41:15.600 --> 00:41:20.020 This one here is as distended as it can be, and others can 00:41:20.020 --> 00:41:21.480 be much more coiled. 00:41:21.480 --> 00:41:23.430 So this one is called linear chain. 00:41:29.300 --> 00:41:30.500 This is branch chain. 00:41:30.500 --> 00:41:32.460 Now, this is not graft. 00:41:32.460 --> 00:41:34.960 Don't confuse this with the graft copolymer. 00:41:34.960 --> 00:41:38.920 Graft copolymer means, I have one mer down the backbone, and 00:41:38.920 --> 00:41:41.300 a second mer off to the side. 00:41:41.300 --> 00:41:42.490 That's a graft copolymer. 00:41:42.490 --> 00:41:43.640 This is a homopolymer. 00:41:43.640 --> 00:41:46.630 A homopolymer that has different branches. 00:41:46.630 --> 00:41:50.030 So all of these, let's put this here to remind us. 00:41:50.030 --> 00:41:53.710 These are homopolymer cartoons. 00:41:53.710 --> 00:41:55.520 Homopolymers that haven't changed anything. 00:41:55.520 --> 00:41:56.890 So this is something that actually 00:41:56.890 --> 00:41:58.500 has different branches. 00:41:58.500 --> 00:42:04.180 So this is branched chain, branch chain architecture. 00:42:04.180 --> 00:42:06.170 Good. 00:42:06.170 --> 00:42:10.790 So which one of these is going to be harder to crystallize. 00:42:10.790 --> 00:42:12.760 Which one is-- well, obviously, I've given it away, 00:42:12.760 --> 00:42:15.470 I put that little piece of crystallinity in there. 00:42:15.470 --> 00:42:19.130 Can you see that when these two solidify, that the one on 00:42:19.130 --> 00:42:21.380 the right, because it's got these branched chains with the 00:42:21.380 --> 00:42:22.980 covalent bonds sticking out. 00:42:22.980 --> 00:42:24.320 It's not going to pack as well. 00:42:24.320 --> 00:42:27.120 And if it doesn't pack as well, it's going to have a 00:42:27.120 --> 00:42:28.250 higher free volume. 00:42:28.250 --> 00:42:30.430 If it's got a higher free volume, it's got a higher 00:42:30.430 --> 00:42:31.330 degree of disorder. 00:42:31.330 --> 00:42:33.970 So the branched chains have a greater 00:42:33.970 --> 00:42:36.000 propensity for disorder. 00:42:36.000 --> 00:42:38.710 So let's put that down. 00:42:38.710 --> 00:42:42.020 Branched chain, harder to crystallize. 00:42:46.490 --> 00:42:51.080 And crystallize, it's not a giant crystal or polycrystal. 00:42:51.080 --> 00:42:54.030 We're talking about the degree to which we can get that 00:42:54.030 --> 00:42:55.200 amount of ordering. 00:42:55.200 --> 00:42:59.330 And then the last one I want to show you is, here's three 00:42:59.330 --> 00:43:00.820 different chains. 00:43:00.820 --> 00:43:04.042 1, 2, and 3. 00:43:04.042 --> 00:43:08.560 And what we're going to do is we're going to cross-link. 00:43:08.560 --> 00:43:11.080 We're going to form bridges. 00:43:11.080 --> 00:43:12.660 These are covalent bridges. 00:43:15.770 --> 00:43:17.290 These are not hydrogen bonds. 00:43:17.290 --> 00:43:19.180 These are not weak van der Walls bonds. 00:43:19.180 --> 00:43:22.830 These are strong covalent bonds, all the way along here, 00:43:22.830 --> 00:43:26.100 linking backbone to backbone. 00:43:26.100 --> 00:43:27.420 So this is cross-linked. 00:43:34.750 --> 00:43:37.080 And what do you think the mechanical properties of this 00:43:37.080 --> 00:43:38.270 are going to be? 00:43:38.270 --> 00:43:42.320 If I want extend this, like stretch and seal, I can pull 00:43:42.320 --> 00:43:46.150 chain number three relative to chain number one quite easily, 00:43:46.150 --> 00:43:52.630 until this covalent bond has bent over as far as it can, 00:43:52.630 --> 00:43:54.070 and then what happens? 00:43:54.070 --> 00:43:56.160 I can't pull it anymore. 00:43:56.160 --> 00:43:58.660 And what happens when I let it go? 00:43:58.660 --> 00:43:59.910 It springs back. 00:43:59.910 --> 00:44:02.570 So this imparts elasticity. 00:44:02.570 --> 00:44:05.850 This makes the polymer rubbery. 00:44:05.850 --> 00:44:08.230 Cross-linked polymers are rubbery. 00:44:08.230 --> 00:44:10.040 But you know, the polymer people, they 00:44:10.040 --> 00:44:11.770 want elevated words. 00:44:11.770 --> 00:44:14.030 If you say to a polymer person, oh, so you've made a 00:44:14.030 --> 00:44:15.430 rubber, they cringe. 00:44:15.430 --> 00:44:16.490 They want to have a fancy word. 00:44:16.490 --> 00:44:19.040 They call this an elastimer. 00:44:19.040 --> 00:44:22.060 It's got the word mer in it, so they're happy, and it's 00:44:22.060 --> 00:44:24.110 elastic, so it's an elastimer. 00:44:24.110 --> 00:44:25.450 Rubbery. 00:44:25.450 --> 00:44:27.600 So how are we going to make these cross-links? 00:44:27.600 --> 00:44:30.080 What are we going to have to look for as an architectural 00:44:30.080 --> 00:44:33.150 feature to make cross-links? 00:44:33.150 --> 00:44:34.662 We look at the backbone. 00:44:34.662 --> 00:44:38.680 If we've got a backbone going like this, all these 00:44:38.680 --> 00:44:40.900 carbon-carbon bonds, and down here I've got 00:44:40.900 --> 00:44:42.390 carbon-carbon bonds. 00:44:45.100 --> 00:44:49.210 If I break one of these bonds in order to go up in this 00:44:49.210 --> 00:44:52.220 direction, I've broken the chain. 00:44:52.220 --> 00:44:55.790 So how am I going to have the bonding capability to form a 00:44:55.790 --> 00:44:59.420 covalent bridge between chains without breaking the very 00:44:59.420 --> 00:45:01.400 chain I'm trying to link? 00:45:01.400 --> 00:45:05.810 What feature am I going to have to have in the chain? 00:45:05.810 --> 00:45:08.820 I need, after polymerization, to still 00:45:08.820 --> 00:45:11.090 have some double bonds. 00:45:11.090 --> 00:45:14.300 And if I've got still double bonds in the backbone after 00:45:14.300 --> 00:45:15.760 polymerization-- 00:45:15.760 --> 00:45:17.460 and now would I do that? 00:45:17.460 --> 00:45:20.510 I have to have a double bond to break in the first place. 00:45:20.510 --> 00:45:24.050 So what would happen if I started with a unit that had 00:45:24.050 --> 00:45:25.420 two double bonds in it? 00:45:25.420 --> 00:45:28.450 That way, I give up one double bond in order to make the 00:45:28.450 --> 00:45:30.600 chain, and I still have a second double bond. 00:45:30.600 --> 00:45:36.120 That's why the rubber has butadiene. 00:45:36.120 --> 00:45:39.130 The diene has two double bonds, after polymerization, 00:45:39.130 --> 00:45:42.410 still has one double bond, and now what I can do is break 00:45:42.410 --> 00:45:46.210 this double bond and this double bond, and link them. 00:45:46.210 --> 00:45:47.190 But if I link them, they're going to 00:45:47.190 --> 00:45:48.930 be too close together. 00:45:48.930 --> 00:45:50.260 They're going to be scrunched in. 00:45:50.260 --> 00:45:52.560 I want to have some play, here. 00:45:52.560 --> 00:45:53.650 I want to make this rubbery. 00:45:53.650 --> 00:45:54.810 So what do I do? 00:45:54.810 --> 00:45:56.290 I put a spacer in here. 00:45:56.290 --> 00:45:57.760 What do I use as a spacer? 00:45:57.760 --> 00:45:58.655 An atom. 00:45:58.655 --> 00:46:00.670 And what kind of an atom do I need? 00:46:00.670 --> 00:46:03.890 I need an atom that's capable of making one, 00:46:03.890 --> 00:46:05.910 two covalent bonds. 00:46:05.910 --> 00:46:07.620 What am I going to choose? 00:46:07.620 --> 00:46:11.660 What atom do you know likes to make linkages? 00:46:15.950 --> 00:46:19.140 How did we make silicate? 00:46:19.140 --> 00:46:21.390 What's the linker in silicate? 00:46:21.390 --> 00:46:22.280 Oxygen. 00:46:22.280 --> 00:46:25.280 You could use oxygen, but I want to make this thing even 00:46:25.280 --> 00:46:28.105 farther apart, and a little bit, you know, oxygen's small 00:46:28.105 --> 00:46:29.300 and it's got too much strength. 00:46:29.300 --> 00:46:31.810 If I want to make it weaker, but something that behaved 00:46:31.810 --> 00:46:35.080 like oxygen, sulfur, I'd go down one row in 00:46:35.080 --> 00:46:36.270 the periodic table. 00:46:36.270 --> 00:46:37.460 So I'd put a sulfur in here. 00:46:37.460 --> 00:46:40.880 And if I wanted to do a really good job, I'll put a sulfur 00:46:40.880 --> 00:46:43.620 here, since I got a double bond from both sides, I'll put 00:46:43.620 --> 00:46:47.010 two sulfurs, and make a disulfide linkage, and now 00:46:47.010 --> 00:46:49.810 I've got the making of rubber. 00:46:49.810 --> 00:46:51.060 Disulfide linkage. 00:46:55.080 --> 00:46:57.680 And again, the feature, I have to start with the backbone 00:46:57.680 --> 00:47:00.800 that has a covalent bond at the end. 00:47:00.800 --> 00:47:03.120 OK. 00:47:03.120 --> 00:47:08.170 Well, let me tell you a little bit about the birth of rubber. 00:47:08.170 --> 00:47:09.325 It started here in Massachusetts. 00:47:09.325 --> 00:47:13.500 It started just across the river, in Roxbury. 00:47:13.500 --> 00:47:16.720 Nathaniel Hayward discovered that rubber treated with 00:47:16.720 --> 00:47:19.090 sulfur was not sticky. 00:47:19.090 --> 00:47:20.570 If you take natural rubber-- 00:47:20.570 --> 00:47:22.330 you ever work with natural rubber? 00:47:22.330 --> 00:47:23.130 It's very sticky. 00:47:23.130 --> 00:47:24.790 You can't do anything with it. 00:47:24.790 --> 00:47:28.740 And Hayward reasoned that by playing with the sulfur, he 00:47:28.740 --> 00:47:30.700 could-- he didn't understand the molecular architecture. 00:47:30.700 --> 00:47:34.430 But he learned that by playing with sulfur, and introducing 00:47:34.430 --> 00:47:38.090 sulfur to the rubber, he lost the stickiness and he got an 00:47:38.090 --> 00:47:40.470 enhanced elasticity. 00:47:40.470 --> 00:47:46.530 So Charles Goodyear came to Boston from Ohio to meet with 00:47:46.530 --> 00:47:52.150 Hayward, and he learned about disulfide linkage and so on. 00:47:52.150 --> 00:47:54.490 Took the idea back to Ohio. 00:47:54.490 --> 00:47:57.580 And one day in the laboratory, he was trying to prepare a 00:47:57.580 --> 00:48:00.690 batch of sulfonated rubber. 00:48:00.690 --> 00:48:03.240 And it was a laboratory accident. 00:48:03.240 --> 00:48:06.610 He knocked over the vessel containing this sulfonated 00:48:06.610 --> 00:48:09.810 rubber, and it landed on a hot stove. 00:48:09.810 --> 00:48:12.640 Things were powered by fire. 00:48:12.640 --> 00:48:15.600 Landed on a hot stove, and then by heating it, he gave 00:48:15.600 --> 00:48:18.510 birth to the process of vulcanization. 00:48:18.510 --> 00:48:22.490 And hence was born the American rubber tire industry, 00:48:22.490 --> 00:48:26.280 by that accident, starting with the trip to Roxbury to 00:48:26.280 --> 00:48:27.580 learn about this. 00:48:27.580 --> 00:48:30.550 And you could have done it all with what you learned today. 00:48:30.550 --> 00:48:33.280 You're just about 150 years too late. 00:48:33.280 --> 00:48:33.860 OK. 00:48:33.860 --> 00:48:35.960 I will see you on Friday.