聚酯化反应是逐步聚合反应过程的一个例子。反应可能在二元酸和二元醇之间或羟基酸分子间进行。
The esterification reaction occurs anywhere in the monomer matrix where two monomer molecules collide, and once the ester has formed, it, too, can react further by virtue of its still-reactive hydroxyl or carboxyl groups.
酯化反应出现在单体本体中两个单体分子相碰撞的位置，且酯一旦形成，依靠酯上仍有活性的羟基或羧基还可以进一步进行反应。
The net effect of this is that monomer molecules are consumed rapidly without any large increase in molecular weight.
酯化的结果是单体分子很快地被消耗掉，而分子量却没有多少增加。
Fig. 3.1 illustrates this phenomenon. Assume, for example, that each square in Fig. 3.1a represents a molecule of hydroxy acid. After the initial dimmer molecules from (b), half the monomer molecules have been consumed and the average degree of polymerization (DP) of polymeric species is 2.
图3.1说明了这个现象。假定图3.1中的每一个方格代表一个羟基酸分子。产生二聚体分子后（b），一半的单体分子消耗了，这时平均聚合度（DP）是2。
As trimer and more dimer molecules form (c), more than 80% of the monomer molecules have reacted, but DP is still 2.5. When all the monomer molecules have reacted (d), DP is 4.
（c）中形成三聚体和更多的二聚体，超过80%的单体分子已参加反应，但DP仅仅还是2.5。（d）中所有的单体反应完，DP是4。
But each polymer molecule that forms still has reactive end groups; hence the polymerization reaction will continue in a stepwise fashion, with each esterification step being identical in rate and mechanism to the initial esterification of monomers.
但形成的每一种聚合物分子还有反应活性的端基；因此，聚合反应将以逐步的方式继续进行，其每一步酯化反应的反应速率和反应机理均与初始单体的酯化作用相同。 Thus, molecular weight increases slowly even at high levels of monomer conversion, and it will continue to increase until the viscosity build-up makes it mechanically too difficult to remove water of esterification or for reactive end groups to find each other. 这样，分子量在高单体转化率下缓慢增加，继续增加直到粘度增加到难以除去酯化反应的水或端基难以相互反应为止。
It can also be shown that in the A-A+B-B type of polymerization, an exact stoichiometric balance is necessary to achieve high molecular weights. If some monofunctional impurity is present, its reaction will limit the molecular weight by rendering a chain end inactive.
在A-A+B-B的聚合反应中，精确的定量配比是获得高分子量所必需的。假如存在一些单官能团杂质，由于链的端基失活，其反应将限制分子量。
Similarly, high-purity monomers are necessary in the A-B type of polycondensation and it follows that high-yield reactions are the only practical ones for polymer formation, since side reactions will upset the stoichiometric balance. 同样，在A-B类的缩聚反应中高纯度的单体是必要的。因为副反应会破坏定量配比，能形成聚合物的实用方法只能是高收率的反应。
UNIT 4 Ionic Polymerization
Ionic polymerization, similar to radical polymerization, also has the mechanism of a chain reaction. The kinetics of ionic polymerization are, however, considerably different from that of radical polymerization.
离子聚合反应，与自由基聚合反应相似，也是链反应机理。但离子聚合的动力学明显地不同于自由基聚合反应。
(1) The initiation reaction of ionic polymerization needs only a small activation energy. Therefore, the rate of polymerization depends only slightly on the temperature.
(1)离子聚合的引发反应仅需要很小的活化能。因此，聚合反应的速率与温度关系不大。
Ionic polymerizations occur in many cases with explosive violence even at temperature. below 50℃(for example, the anionic polymerization of styrene at –70℃ in tetrahydrofuran, or the cationic polymerization of isobutylene at –100℃ in liquid ethylene ).
在许多情况甚至低于50℃下离子聚合反应剧烈（例如，苯乙烯的阴离子聚合在-70℃在四氢呋喃中反应，异丁烯的阳离子聚合在-100℃在液态乙烯中反应）。
With ionic polymerization there is no compulsory chain termination through recombination, because the growing chains can not react with each other.
对于离子聚合来说，因为生长链之间不能发生反应，不存在通过再结合反应而进行的强迫链终止。
Chain termination takes place only through impurities, or through the addition of certain compounds such as water, alcohols, acids, amines, or oxygen, and in general through compounds which can react with polymerization ions under the formation of neutral compounds or inactive ionic species.
链终止反应仅仅通过杂质而发生，或者说通过和某些像水、醇、酸、胺或氧这样的化合物进行加成而发生，且一般来说（链终止反应）可通过这样的化合物来进行，这种化合物可以和活性聚合物离子进行反应生成中性聚合物或没有聚合活性的离子型聚合物。
If the initiators are only partly dissociated, the initiation reaction is an equilibrium reaction, where reaction in one direction gives rise to chain initiation and in the other direction to chain termination. 如果引发剂仅仅部分地离解，引发反应即为一个平衡反应，在出现平衡反应的场合，在一个方向上进行链引发反应，而在另一个方向上则发生链终止反应。
In general ionic polymerization can be initiated through acidic or basic compounds. 通常离子聚合反应能通过酸性或碱性化合物被引发。
For cationic polymerization, complexes of BF3, AlCl3, TiCl4, and SnCl4 with water, or alcohols, or tertiary oxonium salts have shown themselves to be particularly active. The positive ions are the ones that cause chain initiation. For example:
对于阳离子聚合反应来说，BF3,AlCl3,TiCl4和SnCl4与水、或乙醇，或叔烊盐的络合物活性特别高。正离子产生链引发。例如：
However, also with HCl, H2SO4, and KHSO4, one can initiate cationic polymerization. Initiators for anionic polymerization are alkali metals and their organic compounds, such
as phenyllithium, butyllithium, phenyl sodium, and triphenylmethyl potassium, which are more or less strongly dissociated in different solvents.
但BF3与HCl、H2SO4和KHSO4也可以引发阳离子聚合反应。阴离子聚合反应的引发剂是碱金属和它们的有机金属化合物，例如苯基锂、丁基锂和三苯甲基锂，它们在溶剂中高度离解。
To this group belong also the so called Alfin catalysts, which are a mixture of sodium isopropylate, allyl sodium, and sodium chloride.
所谓的Alfin催化剂就是属于这一类，这类催化剂是异丙醇钠、烯丙基钠和氯化钠的混合物。
With BF3 (and isobutylene as the monomer), it was demonstrated that the polymerization is possible only in the presence of traces of traces of water or alcohol. BF3为引发剂（异丁烯为单体），在痕量水或乙醇下聚合反应才可以进行。
If one eliminates the trace of water, BF3 alone does not give rise to polymerization. Water or alcohols are necessary in order to allow the formation of the BF3-complex and the initiator cation according to the above reactions. However, one should not describe the water or the alcohol as a “cocatalyst”.
如果消除痕量的水，BF3单独不会引发聚合反应。对于上述反应，水或乙醇对于形成BF3-络合物和引发剂离子是必需的。但是水或乙醇不应认为是“助催化剂”。
Just as by radical polymerization, one can also prepare copolymers by ionic polymerization, for example, anionic copolymers of styrene and butadiene, or cationic copolymers of isobutylene and styrene, or isobutylene and viny ethers, etc.
与自由基聚合反应一样，通过离子聚合反应也能制备共聚物，例如，苯乙烯-丁二烯阴离子共聚物，或异丁烯-苯乙烯阳离子共聚物，或异丁烯-乙烯基醚共聚物，等等。 As has been described in detail with radical polymerization, one can characterize each monomer pair by so-called reactivity ratios r1 and r2.
正如对自由基型聚合已经详细描述过那样，人们可以用所谓的竞聚率r1和r2来表征每单体对。
UNIT 5 Introduction to Living Radical Polymerization
Traditional methods of living polymerization are based on ionic, coordination or group transfer mechanisms.
活性聚合的传统方法是基于离子，配位或基团转移机理。
Ideally, the mechanism of living polymerization involves only initiation and propagation steps.
理论上活性聚合的机理只包括引发和增长反应步骤。
All chains are initiated at the commencement of polymerization and propagation continues until all monomer is consumed. 在聚合反应初期所有的链都被引发，然后增长反应继续下去直到所有的单体都被消耗殆尽。
A type of novel techniques for living polymerization, known as living (possibly use “controlled” or “mediated”) radical polymerization, is developed recently. 最近开发了一种叫做活性自由基聚合的活性聚合新技术。
The first demonstration of living radical polymerization and the current definition of the processes can be attributed to Szwarc.
第一个活性自由基聚合的证实及目前对这一过程的解释或定义，应该归功于Szwarc。
Up to now, several living radical polymerization processes, including atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer polymerization (RAFT), nitroxide-mediated polymerization (NMP), etc., have been reported one after another.
到目前为止，一些活性自由基聚合过程，包括原子转移自由基聚合，可逆加成-断裂链转移聚合，硝基氧介导聚合等聚合过程一个接一个被报道。
The mechanism of living radical polymerization is quite different not only from that of common radical polymerization but also from that of traditional living polymerization. 活性自由基聚合的机理不仅完全不同于普通自由基聚合机理，也不同于传统的活性聚合机理。
It relies on the introduction of a reagent that undergoes reversible termination with the propagating radicals thereby converting them to a following dormant form：
活性自由基聚合依赖于向体系中引入一种可以和增长自由基进行可逆终止的试剂，形成休眠种：
The specificity in the reversible initiation-termination step is of critical importance in achieving living characteristics.
这种特殊的可逆引发-终止反应对于获得分子链活性来说具有决定性的重要意义。 This enables the active species concentration to be controlled and thus allows such a condition to be chosen that all chains are able to grow at a similar rate (if not simultaneously) throughout the polymrization.
可逆引发终止使活性中心的浓度能够得以控制。这样就可以来选择适宜的反应条件，使得在整个聚合反应过程中(只要没有平行反应)所有的分子链都能够以相同的速度增长。
This has, in turn, enabled the synthesis of polymers with controlled composition, architecture and molecular weight distribution.
这样就可以合成具有可控组成，结构和分子量分布的聚合物。
They also provide routes to narrow dispersity end-functional polymers, to high purity block copolymers, and to stars and other more complex architecture.
这些还可以提供获得狭窄分布末端功能化聚合物，高纯嵌段共聚物，星型及更复杂结构高分子的合成方法。
The first step towards living radical polymerization was taken by Ostu and his colleagues in 1982.
活性自由基聚合是Ostu和他的同事于1982年率先开展的。
In 1985, this was taken one step further with the development by Solomon et al. of nitroxide-mediated polymerization (NMP). 1985年，Solomon等对氮氧化物稳定自由基聚合的研究使活性自由基聚合进一步发展。
This work was first reported in the patent literature and in conference papers but was not widely recognized until 1993 when Georges et al. applied the method in the synthesis
of narrow polydispersity polystyrene.
这种方法首先在专利文献和会议论文中报道，但是直到1993年Georges等把这种方法应用在窄分子量分布聚苯乙烯之后，才得以广泛认知。
The scope of NMP has been greatly expended and new, more versatile, methods have appeared.
NMP的领域已经得到很大的延展，出现了新的更多样化的方法。
The most notable methods are atom transfer radical polymerization (ATRP) and polymerization with reversible addition fragmentation (RAFT).
最引人注目的方法是原子转移自由基聚合和可逆加成断裂聚合。
Up to 2000, this area already accounted for one third of all papers in the field of radical polymerization, as shown in Fig.5.1.
到2000年，这个领域的论文已经占所有自由基聚合领域论文的三分之一。如图5.1所示。
Naturally, the rapid growth of the number of the papers in the field since 1995 ought to be almost totally attributable to development in this area.
很自然，自从1995年以来，在这个领域里论文数量的快速增长应当完全归功于这个领域的发展。
Unit 6 Molecular Weight and its Distributions of Polymers
The molecular weight of a polymer is of prime importance in its synthesis and application.
对聚合物的合成和应用而言，聚合物的分子量是最重要的。
The interesting and useful mechanical properties which are uniquely associated with polymeric materials are a consequence of their high molecular weight.
令人感兴趣的和具有使用价值的力学性能与高分子材料存在的唯一的相关性，而这些性能是聚合物的高分子量带来的。聚合物材料的高分子量带来了令人感兴趣的和具有利用价值的力学性能。
Most important mechanical properties depend on and vary considerably with molecular weight.
最重要的力学性能取决于分子量，而且随着分子量变化而发生很大的变化。
Thus, strength of polymer does not begin to develop until a minimum molecular weight of about 5000～ 10 000 is achieved.
因此,直到最小分于量增大到大约5 000～10 000 以后, 聚合物的强度才开始显示出来.
Above that size, there is a rapid increase in the mechanical performance of polymers as their molecular weight increases; the effect levels off at still higher molecular weights. Level off?达到平衡，变平缓，趋缓
分子量大于这个值的时候，随着分子量的增加，聚合物的机械性能快速增加;达到更高的分子量的时候，这种效应才变平缓。
In most instances, there is some molecular weight range in which a given polymer property will be optimum for a particular application.