From DNA to Silly Putty: The diverse world of polymers - Jan Mattingly

347,434 views ・ 2013-12-10

TED-Ed


Please double-click on the English subtitles below to play the video.

00:06
What do silk,
0
6826
1204
00:08
DNA,
1
8030
677
00:08
wood,
2
8707
763
00:09
balloons,
3
9470
828
00:10
and Silly Putty all have in common?
4
10298
2632
00:12
They're polymers.
5
12930
1789
00:14
Polymers are such a big part of our lives
6
14719
2433
00:17
that it's virtually impossible
7
17152
1456
00:18
to imagine a world without them,
8
18608
2224
00:20
but what the heck are they?
9
20832
1584
00:22
Polymers are large molecules
10
22416
1810
00:24
made of small units called monomers
11
24226
2664
00:26
linked together like the railroad cars from a train.
12
26890
2883
00:29
Poly means many,
13
29773
1529
00:31
and mono means one,
14
31302
1498
00:32
and mers or mero means parts.
15
32800
2883
00:35
Many polymers are made by repeating
16
35683
2170
00:37
the same small monomer over and over again
17
37853
2836
00:40
while others are made from two monomers
18
40689
1792
00:42
linked in a pattern.
19
42481
1923
00:44
All living things are made of polymers.
20
44404
2528
00:46
Some of the organic molecules in organisms
21
46932
2527
00:49
are small and simple,
22
49459
1329
00:50
having only one of a few functional groups.
23
50788
3155
00:54
Others, especially those that play structural roles
24
54467
2905
00:57
or store genetic information,
25
57372
1699
00:59
are macromolecules.
26
59071
1767
01:00
In many cases, these macromolecules are polymers.
27
60838
3416
01:04
For example, complex carbohydrates
28
64254
2382
01:06
are polymers of simple sugars,
29
66636
2154
01:08
proteins are polymers of amino acids,
30
68790
2304
01:11
and nucleic acids, DNA and RNA,
31
71094
2664
01:13
which contain our genetic information,
32
73758
1960
01:15
are polymers of nucleotides.
33
75718
2531
01:18
Trees and plants are made
34
78249
1297
01:19
of the polymer cellulose.
35
79546
1969
01:21
It's the tough stuff you find in bark and stems.
36
81515
2970
01:24
Feathers,
37
84485
692
01:25
fur,
38
85177
549
01:25
hair,
39
85726
537
01:26
and fingernails
40
86263
873
01:27
are made up of the protein keratin,
41
87136
2047
01:29
also a polymer.
42
89183
1590
01:30
It doesn't stop there.
43
90773
1650
01:32
Did you know that the exoskeletons
44
92423
1500
01:33
of the largest phylum in the animal kingdom,
45
93923
2508
01:36
the arthropods,
46
96431
1017
01:37
are made of the polymer chitin?
47
97448
1880
01:39
Polymers also form the basis
48
99928
1732
01:41
for synthetic fibers, rubbers, and plastics.
49
101660
3031
01:44
All synthetic polymers are derived from petroleum oil
50
104691
3385
01:48
and manufactured through chemical reactions.
51
108076
3200
01:51
The two most common types of reactions
52
111276
2166
01:53
used to make polymers
53
113442
1268
01:54
are addition reactions
54
114710
1229
01:55
and condensation reactions.
55
115939
2204
01:58
In addition reactions,
56
118143
1322
01:59
monomers simply add together to form the polymer.
57
119465
3088
02:02
The process starts with a free radical,
58
122553
2055
02:04
a species with an unpaired electron.
59
124608
3049
02:07
The free radical attacks
60
127657
1304
02:08
and breaks the bonds to form new bonds.
61
128961
2563
02:11
This process repeats over and over
62
131524
2082
02:13
to create a long-chained polymer.
63
133606
1997
02:15
In condensation reactions,
64
135603
1669
02:17
a small molecule, such as water,
65
137272
1829
02:19
is produced with each chain-extending reaction.
66
139101
3306
02:22
The first synthetic polymers
67
142407
1526
02:23
were created by accident
68
143933
1453
02:25
as by-products of various chemical reactions.
69
145386
2721
02:28
Thinking they were useless,
70
148107
1243
02:29
chemists mostly discarded them.
71
149350
2277
02:31
Finally, one named Leo Baekeland
72
151627
2283
02:33
decided maybe his useless by-product
73
153910
1884
02:35
wasn't so useless after all.
74
155794
2292
02:38
His work resulted in a plastic
75
158086
1629
02:39
that could be permanently squished into a shape
76
159715
2463
02:42
using pressure and high temperatures.
77
162178
2343
02:44
Since the name of this plastic,
78
164521
1651
02:46
polyoxybenzylmethylenglycolanhydride,
79
166172
3896
02:50
wasn't very catchy,
80
170068
1285
02:51
advertisers called it Bakelite.
81
171353
2241
02:54
Bakelite was made into telephones,
82
174502
1966
02:56
children's toys,
83
176468
887
02:57
and insulators for electrical devices.
84
177355
2633
02:59
With its development in 1907,
85
179988
2116
03:02
the plastics industry exploded.
86
182104
2504
03:04
One other familiar polymer, Silly Putty,
87
184608
2013
03:06
was also invented by accident.
88
186621
2153
03:08
During World War II,
89
188774
1085
03:09
the United States was in desperate need
90
189859
1742
03:11
of synthetic rubber to support the military.
91
191601
2589
03:14
A team of chemists at General Electric
92
194190
1917
03:16
attempted to create one
93
196107
1519
03:17
but ended up with a gooey, soft putty.
94
197626
2550
03:20
It wasn't a good rubber substitute,
95
200176
2016
03:22
but it did have one strange quality:
96
202192
2269
03:24
it appeared to be extremely bouncy.
97
204461
2648
03:27
Silly Putty was born!
98
207109
1606
03:28
Synthetic polymers have changed the world.
99
208715
2211
03:30
Think about it.
100
210926
1092
03:32
Could you imagine getting through a single day
101
212018
1841
03:33
without using plastic?
102
213859
1694
03:35
But polymers aren't all good.
103
215553
1967
03:37
Styrofoam, for example, is made mainly of styrene,
104
217520
3338
03:40
which has been identified as a possible carcinogen
105
220858
2165
03:43
by the Environmental Protection Agency.
106
223023
2582
03:45
As Styrofoam products are being made,
107
225605
2130
03:47
or as they slowly deteriorate in landfills or the ocean,
108
227735
3290
03:51
they can release toxic styrene
109
231025
1665
03:52
into the environment.
110
232690
1669
03:54
In addition, plastics that are created
111
234359
1658
03:56
by addition polymerization reactions,
112
236017
2277
03:58
like Styrofoam,
113
238294
1058
03:59
plastic bags,
114
239352
858
04:00
and PVC,
115
240210
1002
04:01
are built to be durable and food-safe,
116
241212
2204
04:03
but that means that they don't break down
117
243416
1540
04:04
in the environment.
118
244956
1410
04:06
Millions of tons of plastics
119
246366
1753
04:08
are dumped into landfills every year.
120
248119
2102
04:10
This plastic doesn't biodegrade,
121
250221
2241
04:12
it just breaks down
122
252462
1062
04:13
into smaller and smaller pieces,
123
253524
2036
04:15
affecting marine life
124
255560
1169
04:16
and eventually making their way back to humans.
125
256729
3005
04:19
Polymers can be soft or hard,
126
259734
1990
04:21
squishy or solid,
127
261724
1213
04:22
fragile or strong.
128
262937
2105
04:25
The huge variation between
129
265042
2284
04:27
means they can form
130
267326
914
04:28
an incredibly diverse array of substances,
131
268240
2365
04:30
from DNA
132
270605
829
04:31
to nylon stockings.
133
271434
1974
04:33
Polymers are so useful
134
273408
1616
04:35
that we've grown to depend on them every day.
135
275024
2469
04:37
But some are littering
136
277493
1187
04:38
our oceans, cities, and waterways
137
278680
2383
04:41
with effects on our health
138
281063
1209
04:42
that we're only beginning to understand.
139
282272
2283
About this website

This site will introduce you to YouTube videos that are useful for learning English. You will see English lessons taught by top-notch teachers from around the world. Double-click on the English subtitles displayed on each video page to play the video from there. The subtitles scroll in sync with the video playback. If you have any comments or requests, please contact us using this contact form.

https://forms.gle/WvT1wiN1qDtmnspy7