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Unit 1 What are polymers?

What are polymers? For one thing, they are complex and giant molecules and are different from low molecular weight compounds like, say, common salt.

什么是高聚物？首先，他们是合成物和大分子，而且不同于低分子化合物，譬如说普通的盐。

To contrast the difference, the molecular weight of common salt is only 58.5, while that of a polymer can be as high as several hundred thousand, even more than thousand thousands.

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。

These big molecules or ‘macro-molecules’ are made up of much smaller molecules, can be of one or more chemical compounds.

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。

To illustrate, imagine that a set of rings has the same size and is made of the same material. When these things are interlinked, the chain formed can be considered as representing a polymer from molecules of the same compound.

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化合物组成的高聚物。

Alternatively, individual rings could be of different sizes and materials, and interlinked to represent a polymer from molecules of different compounds.

另一方面，环可以大小不同、材料不同, 相连接后形成具有不同化合物组成的聚合物。

This interlinking of many units has given the polymer its name, poly meaning ‘many’ and mer meaning ‘part’ (in Greek).

聚合物的名称来自于许多单元相连接，poly意味着“多、聚、重复”，mer意味着“链节、基体”（希腊语中）。

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.

例如：气态化合物丁二烯的分子量为54，连接4000次可得到分子量大约为200000的聚丁二烯（合成橡胶）高聚物。

The low molecular weight compounds from which the polymers form are known as monomers. The picture is simply as follows:

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) 丁二烯 ＋丁二烯＋?＋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 (54×4 000≈)200 000 molecular weight. 能够知道分子量仅为54的小分子物质（单体）如何逐渐形成分子量为200000的大分子（高聚物）。

It is essentially the “giantness” of the size of the polymer molecule that makes its behavior (different from that of a commonly known chemical compound such as

benzene.)

实质上正是由于聚合物的巨大分子尺寸才使其性能不同于像苯这样的一般化合物（的性能）

Solid benzene, for instance, melts to become liquid benzene at 5.5℃ and , on further heating, boils into gaseous benzene.

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。

As against this well-defined behavior of a simple chemical compound, a polymer like polyethylene does not melt sharply at one particular temperature into clean liquid. 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。

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) .

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，它会转变成不同气体，但它不再是聚乙烯（如图1.1）

Another striking difference with respect to the behavior of a polymer and that of a low molecular weight compound concerns the dissolution process. 聚合物行为和低分子量化合物另一不同的行为为溶解过程。

Let us take, for example, sodium chloride and add it slowly to fixed quantity of water. The salt, which represents a low molecular weight compound, dissolves in water up to a 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.

例如，将氯化钠慢慢地添加到定量的水中。盐作为一种低分子量化合物，在水中溶解直到某一点（叫饱和点），但进一步添加, 盐不进入溶液中却沉到底部而保持原有的固体状态

The viscosity of the saturated salt solution is not very much different from that of water. 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.

饱和盐溶液的粘度与水的粘度接近.但是，如果我们用聚合物，如聚乙烯醇添加到定量水中，聚合物不是马上进入到溶液中。

The globules of polyvinyl alcohol first absorb water, swell and get distorted in shape and after a long time go into solution.

聚乙烯醇颗粒首先吸水溶胀，发生变形，经过很长时间后，（聚乙烯醇分子）进入到溶液中。

Also, we can add a very large quantity of the polymer to the same quantity of water without the saturation point ever being reached.

同样地，我们可以将大量的聚合物加入到同样量的水中，不存在饱和点。

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.

将越来越多的聚合物加入水中，认为聚合物溶解的时间明显地增加，最终呈现柔软像面团一样粘稠的混合物。

Another peculiarity is that, in water, polyvinyl alcohol never retains its original

powdery nature [as the excess sodium chloride does] [in a saturated salt solution].

另一个特点是，在水中聚乙烯醇不会像过量的氯化钠在饱和盐溶液中那样能保持其初始的粉末状态。

In conclusion, we can say that (1) the long time taken by polyvinyl alcohol for dissolution, (2) the absence of a saturation point, and (3) 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. 总之，我们可以讲（1）聚乙烯醇的溶解需要很长时间，（2）不存在饱和点，（3）粘度的增加是聚合物溶于溶液中的典型特性，这些特性主要归因于聚合物大分子的尺寸。

The behavior of a low molecular weight compound and that of a polymer on dissolution are illustrated in Fig.1.2.

Unit 2 Chain Polymerization

Many olefinic and vinyl unsaturated compounds are able to form chain-like macromolecules through elimination of the double bond, a phenomenon first recognized by Staudinger. Diolefins polymerize in the same manner, however, only one of the two double bonds is eliminated.

Staudinger首先发现许多烯烃和不饱和烯烃通过打开双键可以形成链式大分子。二烯烃以同样的方式聚合，但仅消除两个双键中的一个。

Such reactions occur through the initial addition of a monomer molecule to an initiator radical or an initiator ion, by which the active state is transferred from the initiator to the added monomer.

这类反应是通过单体分子首先加成到引发剂自由基或引发剂离子上而进行的，靠这些反应活性中心由引发剂转移到被加成的单体上。

In the same way by means of a chain reaction, one monomer molecule after the other is added (2000~20000 monomers per second) until the active state is terminated through a different type of reaction.

单体分子通过链式反应以同样的方式一个接一个地加上（每秒2000～20000个单体）直到活性中心通过不同的反应方式终止。

The polymerization is a chain reaction in two ways: because of the reaction kinetic and because as a reaction product one obtains a chain molecule. The length of the chain molecule is proportional to the kinetic chain length.

聚合反应成为链式反应的两种原因：反应动力学和作为链式反应产物分子。链分子的长度与动力学链长成正比。

One can summarize the process as follow (R. is equal to the initiator radical): 链式反应可以概括为以下过程（R·相当与引发剂自由基）：略

One thus obtains polyvinylchloride from vinylchloride, or polystyrene from styrene, or polyethylene from ethylene, etc.

因而通过上述过程由氯乙烯得到聚氯乙烯，或由苯乙烯获得聚苯乙烯，或乙烯获得聚乙烯，等等。

The length of the chain molecules, measured by means of the degree of polymerization, can be varied over a large range through selection of suitable reaction

conditions.

分子链长通过聚合度测量，可以通过选择适宜的反应条件大为改变

Usually, with commercially prepared and utilized polymers, the degree of polymerization lies in the range of 1000 to 5000, but in many cases it can be below 500 and over 10000.

商业制备和使用的聚合物，聚合度通常在1000～5000范围内，但在许多情况下可低于500或高于10000。

This should not be interpreted to mean that all molecules of a certain polymeric material consist of 500, or 1000, or 5000 monomer units. In almost all cases, the polymeric material consists of a mixture of polymer molecules of different degrees of polymerization.

这不应该把聚合物材料所有的分子理解为由500，或1000，或5000个单体单元组成。在几乎所有的情况下，聚合物材料由不同聚合度的聚合物分子的混合物组成。 Polymerization, a chain reaction, occurs according to the same mechanism as the well-known chlorine-hydrogen reaction and the decomposition of phosegene.

链式聚合反应的机理与众所周知的氯（气）-氢（气）反应和光气的分解机理相同。 The initiation reaction, which is the activation process of the double bond, can be brought about by heating, irradiation, ultrasonics, or initiators. The initiation of the chain reaction can be observed most clearly with radical or ionic initiators.

通过双键活化的引发剂反应，可以通过热、辐射、超声波或引发剂产生。可以很清楚地进行研究用自由基型或离子型引发剂引发的链式反应。

These are energy-rich compounds which can add suitable unsaturated compounds (monomers) and maintain the activated radical or ionic state so that further monomer molecules can be added in the same manner.

这些是高能态的化合物，它们能够加成不饱和化合物（单体）并保持自由基或离子活性中心 以致单体可以以同样的方式进一步加成。

For the individual steps of the growth reaction one needs only a relatively small activation energy and therefore through a single activation step (the actual initiation reaction) a large number of olefin molecules are converted, as is implied by the term “chain reaction”.

对于增长反应的各个步骤，每一步仅需要相当少的活化能，因此通过一步简单的活化反应（即引发反应）即可将许多烯类单体分子转化成聚合物，这正如连锁反应这个术语的内涵那样。

Because very small amounts of the initiator bring about the formation of a large amount of polymeric material (1:1000 to 1:1000), it is possible to regard polymerization from a superficial point of view as a catalytic reaction.

因为少量的引发剂引发形成大量的聚合物原料（1：1000～1：10000），从表面上看聚合反应被看成是催化反应。

For this reason, the initiators used in polymerization reactions are often designated as polymerization catalysts, even though, in the strictest sense, they are not true catalysts because the polymerization initiator enters into the reaction as a real partner and can be found chemically bound in the reaction product ,i.e. ,the polymer.

由于这个原因，通常把聚合反应的引发剂看作是聚合反应的引发剂。但因为聚合反

应的催化剂进入到反应内部而成为一部分，同时可以在反应产物，既聚合物的末端发现催化剂，所以严格地讲它们不是真正意义上的催化剂，

In addition to the ionic and radical initiators there are now metal complex initiators (which can be obtained, for example, by the reaction of titanium tetrachloride or titanium trichloride with aluminum alkyls), which play an important role in polymerization reactions (Ziegler catalysts) ,The mechanism of their catalytic action is not yet completely clear.

除离子引发剂和自由基引发剂外，还有金属络合物引发剂（可以通过四氯化钛或三氯化钛与烷基铝的反应得到）。它们在聚合反应中起到了重要作用（齐格纳引发剂）。它们催化活动的机理还不是十分清楚。

UNIT 3 Step-Growth polymerization

Many different chemical reactions may be used to synthesize polymeric materials by step-growth polymerization. These include esterification, amidation, the formation of urethanes, aromatic substitution, etc.

通过逐步聚合可用许多不同的化学反应来合成聚合材料。这些反应包括酯化、酰胺化、氨基甲酸酯、芳香族取代物的形成等。

Polymerization proceeds by the reactions between two different functional groups, e.g., hydroxyl and carboxyl groups, or isocyanate and hydroxyl groups.

通过在两种不同的官能团，如，羟基和羧基，或异氰酸酯和羟基之间可发生聚合反应。

All step-growth polymerization fall into two groups depending on the type of monomer(s) employed. The first involves two different polyfunctional monomers in which each monomer possesses only one type of functional group. 所有的逐步聚合反应根据所使用单体的类型可分为两类。第一类涉及两种不同的官能团单体，每一种单体仅具有一种官能团。

A polyfunctional monomer is one with two or more functional groups per molecule. The second involves a single monomer containing both types of functional groups. 一种多官能团单体每个分子有两个或多个官能团。第二类涉及含有两类官能团的单个单体。

The synthesis of polyamides illustrates both groups of polymerization reactions. Thus, polyamides can be obtained from the reaction of diamines with diacids or from the reaction of amino acids with themselves. 聚酰胺的合成说明了两类聚合反应。因此聚酰胺可以由二元胺和二元酸的反应或氨基酸之间的反应得到。

The two groups of reactions can be represented in a general manner by the equations as follows

两种官能团之间的反应一般来说可以通过下列反应式表示

Reaction (3.1) illustrates the former, while (3.2) is of the latter type. 反应（3.1）说明前一种形式，而反应（3.2）具有后一种形式。

Polyesterification, whether between diol and dibasic acid or intermolecularly between hydroxy acid molecules, is an example of a step-growth polymerization process.