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由表3、表4可以看出,引发剂的浓度升高，得到的单体总转化率呈现出增大的趋势，而共聚物的分子量却呈现出减小的趋势。因为升高引发剂的浓度，单位时间内产生的自由基数目增多,加速了聚合过程，增大了反应的转化率，但是同时增加了自由基向引发剂的转移反应，转移的结果使得原来的部分自由基终止成稳定分子，从而导致了聚合物的分子量减小，因此，在进行聚合反应时，要想得到一定的反应转化率及合适分子量的产物，选择合适的引发剂浓度是十分必要的。 由表1可见,随着MAn含量的增加,反应转化率呈现上升的趋势。当单体配比为4:1时聚合物的颜色及状态发生了明显的变化：由白色蓬松固体变为黄色粘状固体。变黄是由于增加单体配比中MAn含量的增多，产物中MAn的比例增加，随反应的进行含有MAn较多的聚合物从超临界二氧化碳介质中沉淀下来，在釜底形成块状固体。（对釜底的块状固体进行含量分析得出MAn的含量为68.56％） [ Last edited by nizenmezhidao on 2008-8-23 at 23:21 ] |
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From Table 3, Table 4 shows that the higher the concentration of initiator, the monomers are showing a conversion rate of increase of the trend, and the molecular weight of copolymer Quecheng show decreasing trend. Because the higher the concentration of initiator, the unit time of the radical increase in the number and speed up the polymerization process and increase the conversion rate of the reaction, but also an increase of free radicals to the initiator of the transfer reaction, the result of the transfer made the original Termination of some radical elements into stability, leading to the molecular weight of the polymer decreases, therefore, in polymerization reactions, to obtain a suitable response and conversion of the molecular weight of the product, choose a suitable initiator concentration is very necessary. From Table 1 that, with the MAn of the increase in the conversion rate showed an upward trend. When monomer ratio of 4:1 at the color and polymer state in a significant change: from a white fluffy solid into a yellow stick-like solid. Discolouration is due to an increase in the MAn monomer ratio of the increase, the product of an increase in the proportion of MAn, with the reaction of a polymer containing MAn more supercritical carbon dioxide from the medium of precipitation down in the cauldron at the end of a solid block. (Cauldron at the end of the block of solid analysis of the content that MAn the content of 68.56%) |
2楼2008-08-26 20:19:08
3楼2008-09-04 11:14:46