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基甲酸酯、芳香族取代物的形成等。通过反应聚合反应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。
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. 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. The synthesis of polyamides illustrates both groups of polymerization reactions. Thus, polyamides can be obtained from the reaction of diamines with diacids
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。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种单体。聚酰胺的合成说明了聚合反应的两个官能团。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。 nH2N-R-NH2+nHO2C-R’-CO2H→
H-(-NH-R-NHCO-R’-CO-)n-OH+(2n-1)H2O (3.1) or from the reaction of amino acids with themselves nH2R-CO2H→ H-(-NH-R-CO-)n-OH+(n-1)H20 (3.2)
The two groups of reactions can be represented in a general manner by the equations as follows
A+B-B →–[-A-A-B-B-]-A-B→–[-A-B-]-
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 反应式略
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。 图3.1 逐步聚合的示意图 未反应单体；（b）50%已反应；（c）83.3%已反应；(d) 100%已反应（虚线表示反应种类） Polyesterification, whether between diol and dibasic acid or intermolecularly between hydroxy acid molecules, is an example of a step-growth polymerization process. 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. The net effect of this is that monomer molecules are consumed rapidly without any large increase in molecular weight. Fig. 3.1 illustrates this phenomenon. Assume, for example, that each square in Fig. 3.a 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. As trimer and more dimer molecules form (c), more than 80% of the monomer molecules have reacted (d), DP is 4. But each polymer molecule that forms still has reactive end
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groups; hence the polymerization reaction will continue in a stepwise fashion, with each esterification of monomers. 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.
聚酯化，是否在二元酸和二元醇或羟基酸分子间进行，是逐步聚合反应过程的一个例子。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。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。图3.1说明了这个现象。例如，假定图3.1中的每一个方格代表一个羟基酸分子。（b）中的二聚体分子，消耗二分之一的单体分子聚合物种类的聚合度（DP）是2。（c）中当三聚体和更多的二聚体形成，大于80%的单体分子已反应，但DP仅仅还是2.5。（d）中当所有的单体反应完，DP是4。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。因此，分子量缓慢增加直至高水平的单体转化率，而且分子量将继续增加直到粘度的增加使其难以除去酯化反应的水或难以找到相互反应的端基。
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. 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.
在A-A+B-B的聚合反应中也可以看到，精确的当量平衡是获得高分子量所必需的。假如存在一些但官能团杂质，由于链的端基失活，反应将使分子量减少。同样，在A-B类的缩聚反应中高纯度的单体是必要的，而且可以归结高收率的反应仅是形成聚合物的实际反应，因为副反应会破坏当量平衡。 -------Stevens M P. Polymer Chemistry. London: Addison-Wesley Publishing Company, 1975. 13
UNIT 4 Ionic Polymerization 第四单元 离子聚合反应
Ionic polymerization, similar to radial 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，也有链反应的机理。但是，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. Ionic polymerizations occur in many cases with explosive violence
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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 ).
(1)离子聚合的引发反应仅需要很小的活化能。因此，聚合反应的速率仅对温度有较少的依赖性。在许多情况下离子聚合猛烈地发生甚至低于50℃（例如，苯乙烯的阴离子聚合反应在-70℃在四氢呋喃中，或异丁烯的阳离子聚合在-100℃在液态乙烯中）。
(2) With ionic polymerization there is no compulsory chain termination through recombination, because the growing chains can not react with each other. 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. 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. （2）对于离子聚合来说，不存在通过再结合反应而进行的强迫链终止，因为生长链之间不能发生链终止。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，这种化合物在中性聚合物或没有聚合活性的离子型聚合物生成的过程中可以和活性聚合物离子进行反应。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 polymerization can be initiated through acidic or basic compounds. 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:
通常离子聚合反应能通过酸性或碱性化合物被引发。对于阳离子聚合反应来说，BF3,AlCl3,TiCl4和SnCl4与水、或乙醇，或叔烊盐的络合物提供了部分活性。正离子是产生链引发的化合物。例如：(反应略) 三乙基硼氟酸烊 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. To this group belong also the so called Alfin catalysts, which are a mixture of sodium isopropylate, allyl sodium, and sodium chloride.
然而，BF3也可以与HCl、H2SO4和KHSO4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，它们在不同的溶剂中或多或少地强烈分解。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。
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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. 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”. BF3为引发剂（异丁烯为单体），证明仅在痕量水或乙醇的存在下聚合反应是可以进行的。如果消除痕量的水，单纯的BF3不会引发聚合反应。按照上述反应为了能形成BF3-络合物和引发剂离子水或乙醇是必需的。但是不应将水或乙醇描述成“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. As has been described in detail with radical polymerization, one can characterize each monomer pair by so-called reactivity ratios r1 and r2. The actual values of these two parameters are, however, different from those used for radical copolymerization.
正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。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。然而，这两个参数的实际意义不同于那些用于自由基共聚合反应的参数。 ---Vollmert B. Polymer Chemistry. Berlin: Sping-Verlag, 1973.163
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