【摘要】 研究了以 2 ,2 ,6 ,6 四甲基 1 哌啶氧化物 (TEMPO)作为稳定自由基 ,过氧化苯甲酰 (BPO)为引发剂 ,三氟乙酸酐 (TFA)为加速剂 ,极性单体甲基丙烯酸甲酯的聚合 .在TFA的促进下 ,聚合速率明显加快 ,17h可达 6 2 %的转化率 .在单体转化率低于 30 %时 ,分子量随转化率线形增长 ,分子量分布较窄 .转化率较高时 ,分散性变大 ,分子量变化不大 .随着聚合体系温度升高 ,分散性变窄 .14 0℃为其较理想的聚合温度 .通过对模型聚合物的核磁共振 (1HNMR)分析 ,发现氧氮自由基部分脱落 ,解释了极性单体不能在稳定自由基存在下进行活性聚合的原因 .对氧氮自由基易从主链脱落的可能解释是酯基的强吸电子效应削弱了C O键 ,从而使氧氮自由基与主链的连接减弱 ,导致分子量不可控制 .更多还原

【Abstract】 Poly (methyl methacrylate) was synthesized starting from benzoyl peroxide and TEMPO (2,2,6,6 tetramethylpiperidinyl 1 oxy). It was found that nitroxide mediated polymerization of methyl methacrylate was distinctly accelerated by the addition of small amount of trifluoroacetic acid anhydride (TFA). When the conversion was under 30%, the molecular weight increased with conversion and time. However, as the reaction proceeded, the molecular weight stopped increment, which demonstrated that some termination reactions occurred. Furthermore, when the reaction temperature was enhanced, the rates increased and the polydispersities narrowed down.140 ℃ is the optimal temperature for this system. Through the 1H NMR analysis of PMMA, it was found TEMPO partly departed from the main chain, which explained that polar monomer couldn’t proceed in a living manner in the presence of stable free radical.更多还原