苯乙烯-双烯A交联共聚凝胶、溶胶的生成与转化

THE FORMING AND TRANSFORMING OF GEL AND SOL IN THE CROSSLINKING COPOLYMERIZATION OF STYRENE WITH BISMETHYL ACRYLATE BISPHENOL-A

本文结合提取、凝胶色谱等方法测定了苯乙烯-双烯A交联共聚过程的转化率曲线。通过研究发现,凝胶在交联共聚一开始就产生,且整个反应过程都在不断地生成;转化率40％以前几乎无溶胶生成,此后生成的溶胶仍不断地向凝胶转化;刚生成溶胶时其分子量高、分布窄,其后分子量变低、分布变宽;T_g以上温度的热处理发生进一步聚合反应,当双烯A摩尔浓度<3.3×10^(-4)时,溶胶分数增加,A-MA摩尔浓度>5.0×10^(-4)时,凝胶分数增加,这是双烯A悬吊双键及单体苯乙烯进一步反应的结果。

In this paper, abstraction and gel permeation chromatography (GPC) were used to determine the monomer conversion in the crosslinking copolymerization of styrene with bismethyl acrylate bisphenol-A. It is indicated that A-MA possesses high copolymerizing reactive with styrene. Affected by heat of polymerization and viscosity of the system, the crosslinking copolymerization has obvious self-acceleration. In the self-acceleration, the temperature of the system is higher than the water bath temperature (58℃), so the crosslinking copolymerization will reach high monomer conversion comparing to homopolymerization of styrene. The experimental results showed that because of the high copolymerization reactivity of A-MA, gel forms as soon as the reaction starts, but sol forms very little, before the monomer conversion rises to 40%. When sol forms 2. 4% in the system, the monomer conversion will reach 63.1 %, and the sol is continuously transfer to gel in the whole polymerization. This is opposite to the gelation in the condensing polymerization of multi-functional groups. Gel fraction of crosslinking copolymer is affected by the heat treatment at temperature above Tg. When A-MA is up to a certain content (A-MA>5. 5×10-4), the gel fraction will increase. At the same time, the amount of styrene will decrease after heat treatment; The sol fraction will decrease when the concentration of A-MA is high (>5. 5× 10-4) and increase when the concentration of A-MA is low (<3. 3× 10-4), because of the reaction of the double bond suspending in the system. The initial formed sol has very high MW. Through studying the GPC curves, it is found that the higher the monomer conversion is, the lower the MW of forming sol becomes. This lead to the widening of MW distribution and the lowering of MW of whole sol in the sample.