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1、A 高分子化学和高分子物理UNIT 1 What are Polymer?第一单元什么是高聚物？What are polymers? For one thing, they are complex and giant molecules and are different from low molecular weight compounds like, say, commonsalt. To contrast the difference, the molecular weight of common salt is only 58.5, while that of a polymer ca
2、n be as high as several hundred thousand, even more than thousand thousands. These big molecules or macro-molecules are made up of much smaller molecules, can be of one or more chemical compounds. To illustrate, imagine that a set of rings has the same size and is made of the same material. Whenthes
3、e things are interlinked, the chain formed can be considered as representing a polymer from molecules of the same compound. Alternatively, individual rings could be of different sizes and materials, and interlinked to represent a polymer from molecules of different compounds. 什么是高聚物？首先，他们是合成物和大分子，而且
4、不同于低分子化合物，譬如说普通的 盐。 与低分子化合物不同的是， 普通盐的分子量仅仅是58.5 ， 而高聚物的分子量高于105，甚至大于106。这些大分子或“高分子”由许多小分子组成。小分子相互结合形成大分子，大分子能够是一种或多种化合物。 举例说明， 想象一组大小相同并由相同的材料制成的环。当这些环相互连接起来，可以把形成的链看成是具有同种分子量化合物组成的高聚物。另 一方面，独特的环可以大小不同、材料不同，相连接后形成具有不同分子量化合物组成的 聚合物。 This interlinking of many units has given the polymer its name, poly
5、 meaning manyand mer meaning part (in Greek). As an example, a gaseous compound called butadiene, with a molecular weight of 54, combines nearly 4000 times and gives a polymer known as polybutadiene (a synthetic rubber) with about 200 000molecular weight. The low molecular weight compounds from whic
6、h the polymers form are known as monomers. The picture is simply as follows: 许多单元相连接给予了聚合物一个名称， poly 意味着“多、聚、重复” ， mer 意味着“链节、基体” (希腊语中) 。例如：称为丁二烯的气态化合物，分子量为54，化合将近4000次，得到分子量大约为200000 被称作聚丁二烯(合成橡胶)的高聚物。形成高聚物的低分子化合物称为单体。下面简单地描述一下形成过程：butadiene + butadiene +?+ butadiene- - polybutadiene(4 000 time)丁二
7、烯 二丁二烯+十 丁二烯 聚丁二烯( 4000 次)One can thus see how a substance (monomer) with as small a molecule weight as 54 grow to become a giant molecule (polymer) of (54 x 4 000 )200 000 molecular weight.It is essentially the giantness of the size of the polymer molecule that makes its behavior different from tha
8、t of a commonly known chemical compound such as benzene. Solid benzene, for instance, melts to become liquid benzene at 5.5 and , on further heating, boils into gaseous benzene. As against this well-defined behavior of a simple chemical compound, a polymer like polyethylene does not melt sharply at
9、one particular temperature into clean liquid. Instead, it becomes increasingly softer and, ultimately, turns into a very viscous, tacky molten mass. Further heating of this hot, viscous, molten polymer does convert it into various gases but it is no longer polyethylene. （Fig. 1.1） .因而能够看到分子量仅为54 的小分
10、子物质（单体）如何逐渐形成分子量为 200000 的大分子（高聚物） 。实质上，正是由于聚合物的巨大的分子尺寸才使其性能不同于象苯这样的一般化合物。例如，固态苯，在 5.5 熔融成液态苯，进一步加热，煮沸成气态苯。与这类简单化合物明确的行为相比， 像聚乙烯这样的聚合物不能在某一特定的温度快速地熔融成纯净的液体。而聚合物变得越来越软，最终，变成十分粘稠的聚合物熔融体。将这种热而粘稠的聚合物熔融体进一步加热， 不会转变成各种气体， 但它不再是聚乙烯 （如图 1.1 ） 。 固态苯 液态苯 气态苯加热， 5.5 加热， 80 固体聚乙烯 熔化的聚乙烯 各种分解产物-但不是聚乙烯加热加热图 1.1 低
11、分子量化合物（苯）和聚合物（聚乙烯）受热后的不同行为Another striking difference with respect to the behavior of a polymer and that of a low molecular weight compound concerns the dissolution process. Let us take, for example, sodium chloride and add it slowly to s fixed quantity of water. The salt, which represents a low mol
12、ecular weight compound, dissolves in water up tos point （called saturation point） but, thereafter, any further quantity added does not go into solution but settles at the bottom and just remains there as solid.The viscosity of the saturated salt solution is not very much different from that of water
13、. But if we take a polymer instead, say, polyvinyl alcohol, and add it to a fixed quantity of water, the polymer does not go into solution immediately.The globules of polyvinyl alcohol first absorb water, swell and get distorted inshape and after a long time go into solution. Also, we can add a very
14、 large quantity of the polymer to the same quantity of water without the saturation point ever being reached. As more and more quantity of polymer is added to water, the time taken for the dissolution of the polymer obviously increases and the mix ultimately assumes a soft, dough-like consistency. A
15、nother peculiarity is that, in water, polyvinyl alcohol never retains its original powdery nature as the excess sodium chloride does in a saturated salt solution. In conclusion, we can say that （1） the long time taken by polyvinyl alcohol for dissolution, （2） the absence of asaturation point, and （3
16、） the increase in the viscosity are all characteristics of a typical polymer being dissolved in a solvent and these characteristics are attributed mainly to the large molecular size of the polymer. The behavior of a low molecular weight compound and that of a polymer on dissolution are illustrated in Fig.1.2.发现另一种不同的聚合物行为和低分子量化合物行为是关于溶解过程。例如，让我们研究一下，将氯化钠慢慢地添加到固定量的水中。盐，代表一种低分子量化合物，在水中达到点（叫饱和点）溶解，但，此
