嘉兴学院高分子系吴佰程整理
Reading Materials
第6单元
Purification of Polymers聚合物的提纯
The usual purification operations used with low molecular weight compounds (for example, distillation and recrystallization) are usually not applicable to macromolecular compounds. 针对低分子量化合物通常的提纯方法，如蒸馏和重结晶通常都不能用于高分子化合物。Distillation, 蒸馏
Macromolecular compounds are not volatile and cannot simply be recrystallized from saturated solutions. One therefore has to be satisfied with extracting them in suitable solvents and thus removing the impurities.
Volatile[volə’tail], 飞行的，易挥发的，快活的，爆炸性的，易激动的，反复无常的，短暂的。Extract, v，萃取，extraction, 萃取
高分子化合物不是挥发性的，而且不能简单地从饱和溶液中再结晶。因此人们不得不用合适的溶剂来萃取这些高分子，从而去除杂质。
The purification effect of the extraction is in most cases rather slight because in many instances the impurity is held to the polymer by strong secondary valence forces. Secondary valence force, 次（化合）价力
Hold to 坚持，紧握
在大多数场合，萃取的提纯效果是很有限的，因为在许多情况下杂质被聚合物强的次价力束缚。
Consequently, one usually first dissolves the macromolecular compound and then precipitates it by addition of a nonsolvent.
因此，我们通常首先溶解高分子化合物，然后用非溶剂填加物把高分子沉淀下来。Precipitate，沉淀
The precipitate comes out as a more or less strongly swollen gel.
Come out，长出，（花）开，由。。。产生，由。。。出来，结果是，显现，（污点）被去掉，（颜色）被褪去，（题目）被解出，（商品）被展出，被供应，（总数）计，总计
Swell，溶胀，
gel，凝胶，溶胶，sol，溶胶-凝胶法，sol-gel
沉淀大体上以强烈溶胀的凝胶形式产生出来。
And the impurities remain at least partly in solution.
而杂质至少有一部分保留在溶液中。
The gel can be removed by sedimentation if necessary, in the centrifuge.
如果需要的话，凝胶可以用离心机沉降移出。
Usually it is necessary to repeat this precipitation 10-20 times.
通常这个沉淀过程有必要重复10到20次。
The solvents and precipitating agents have to be carefully selected from case to case.
根据不同场合，溶剂和沉淀剂必须仔细选择。
Many vinyl polymers are easily dissolved in benzene and toluene and precipitate under addition of methanol.
Toluence，甲苯
Methanol，甲醇
许多乙烯基聚合物容易溶解在苯或甲苯中，而在添加甲醇的情况下发生沉淀。
Methanol is a sort of general precipitating agent in which most polymers, both the benzene soluble ones and the water-soluble polymers, are insoluble.
甲醇是一种常见的沉淀剂，无论是苯溶还是水溶聚合物，大多数聚合物在甲醇里是不溶解的。Since methanol is miscible in all proportion both with benzene and with most other organic solvents and also with water, it can be used as a precipitant in both cases, i.e., with organic and with aqueous polymer solutions.
Miscible, 可混溶的，miscibility，相溶性（分子层面上的混溶）
compatible,相容的，Compatibility,相容性（相层面上的混溶）
因为甲醇与苯等有机溶剂，与水都可以所有的比例混溶的。在有机和水的高分子溶液中，甲醇可以用来做沉淀剂。
One has to expect that the polymers is somehow affected by the extraction, regardless of whether this is done by heating or by precipitation.
聚合物受萃取过程的影响是肯定的，不管这个过程是通过加热还是沉淀。
Thus if one extracts with acids or bases, hydrolytic degradation usually causes a lowering in the degree of polymerization (for example, hydrolytic degradation of polysaccharides). Hydrolytic, 水解的，
Degradation, 降解反应。
Polysaccharide, 多糖，聚糖
因此如果我们用酸或碱来萃取，水解降解反应通常导致聚合度降低，如聚糖的水解。
In the process of dissolving and reprecipitation, one usually finds that low molecular weight components remain in solution (fractionation), and therefore the precipitated part has a higher average molecular weight and more uniform molecular weight distribution. Uniform, （尺寸、大小，形状等）均一的，distribution,分布
在溶解和再沉淀过程中，通常我们发现低分子量组分保留在溶液中（分级），因此，沉淀部分具有高的平均分子量，而且分子量分布更均一。
This may or may not be desirable, but in any case one should be aware of it.
这可能和我们的意，也可能不合我们的意，但是，无论什么情况，我们都应该知道这一点。With synthetic polymers, purification may be avoided sometimes by choosing a method of synthesis where the polymer is immediately obtained in pure form.
对合成聚合物而言，提纯过程有时是可以避免的。通过选择合成方法，我们可以很快得到纯的聚合物，
Usually an extreme purification of the monomer is simpler and more effective than a later
