过氧化聚合物的合成及引发聚合研究

发布时间：2018-10-19 17:41

【摘要】：过氧化聚合物是单个大分子链内含有多个过氧键的一类聚合物,可以分为酸聚过氧化物和乙烯基聚过氧化物,其中乙烯基聚过氧化物具有分解放热、可自动热分解及自动加速等特点,常可作为固体燃料和引发剂等使用。与传统引发剂相比,乙烯基聚过氧化物不仅可以引发聚合反应而且还可以合成嵌段、接枝等特殊结构的聚合物。乙烯基聚过氧化物通常由乙烯基单体和氧气在低温、常压条件下共聚而成。采用该方法合成的乙烯基聚过氧化物的分子量和产率都非常低,其分子量只有4000-5000,产率仅为10%左右,再加上低温引发聚合(100?)时过氧化聚合物的引发效率极低,因此乙烯基聚过氧化物作为引发剂并未得到广泛应用。但近期的一些研究表明,乙烯基聚过氧化物可能是一种合适的高温引发剂,在高温引发聚合时可能有较高的引发效率,如果乙烯基聚过氧化物的分子量足够大,那么就可以用乙烯基聚过氧化物作引发剂通过自由基聚合合成链段较长的嵌段共聚物。基于上述想法,本文首先研究了以甲基丙烯酸甲酯作为乙烯基单体,氧作为共聚单体合成高分子量聚甲基丙烯酸甲酯过氧化物(PMMAP)的合成方法;然后,对合成的高分子量PMMAP引发不同烯类单体高温自由基聚合的引发能力及引发聚合后形成的聚合产物的结构与性能进行了研究;在此基础上,利用高分子量PMMAP在选择性溶剂中原位引发苯乙烯聚合合成核壳结构PMMA-b-PS嵌段共聚物。通过上述研究最终得出如下结论:(1)采用高温自由基聚合在无引发剂的条件下可以合成分子量在1.78×104~6.35×104范围内的高分子量聚甲基丙烯酸甲酯过氧化物,合适的聚合温度为120℃~140℃,氧气压力为0.1MPa~0.7MPa。(2)采用高温自由基聚合合成的高分子量聚甲基丙烯酸甲酯过氧化物在聚合温度大于110℃时可以引发丙烯酸甲酯、丙烯酸羟乙酯及苯乙烯等单体聚合,且聚合温度越高,聚合速率越大,其引发聚合的最佳温度范围为120℃~150℃。(3)聚甲基丙烯酸甲酯过氧化物引发聚合时,其合成条件、浓度及聚合温度都对聚合反应速率有影响。聚合温度相同时,过氧化聚合物的合成温度越低,浓度越大,聚合反应速率越高,反应的转化率越高。(4)聚甲基丙烯酸甲酯过氧化物作引发剂引发聚合时可以合成嵌段长度可控的嵌段共聚物,嵌段共聚物的比例大于90wt%。嵌段共聚物中PMMA链段的长度可以通过调节PMMAP的分子量来进行控制。在适当的溶剂中通过原位自组装可以合成粒径为100nm~800nm的核壳结构PMMA-b-PS嵌段共聚物微球。
[Abstract]:Peroxide polymer is a kind of polymer containing multiple superoxide bonds in a single macromolecular chain, which can be divided into acid polyperoxide and vinyl polyperoxide, in which vinyl polyperoxides have partial liberation fever. It can be used as solid fuel and initiator. Compared with traditional initiators, vinyl peroxide can not only initiate polymerization but also synthesize block, graft and other special structure polymers. Vinyl peroxide is usually copolymerized by vinyl monomer and oxygen at low temperature and atmospheric pressure. The molecular weight and yield of vinyl polyperoxide synthesized by this method are very low, its molecular weight is only 4 000 to 5 000, the yield is only about 10%, and the polymerization initiated at low temperature (100?) Therefore, vinyl peroxide as initiator is not widely used. However, some recent studies have shown that vinyl peroxide may be an appropriate initiator at high temperature and may have a higher initiation efficiency when initiated at high temperature, if the molecular weight of the vinyl peroxide is large enough, The long block copolymers can be synthesized by free radical polymerization with vinyl peroxide as initiator. Based on the above ideas, the synthesis of high molecular weight poly (methyl methacrylate) peroxide (PMMAP) using methyl methacrylate as vinyl monomer and oxygen as monomer was studied. The initiation ability of high molecular weight PMMAP to initiate the high temperature free radical polymerization of different alkenes and the structure and properties of the polymerization products formed after initiation polymerization were studied. Core-shell PMMA-b-PS block copolymers were synthesized by in situ polymerization of styrene with high molecular weight PMMAP in selective solvent. The conclusions are as follows: (1) the high molecular weight polymethyl methacrylate peroxide with molecular weight in the range of 1.78 脳 10 ~ 4 ~ 6.35 脳 10 ~ 4 can be synthesized by high temperature radical polymerization without initiator. The appropriate polymerization temperature is 120 鈩，

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