The direct and autocatalytic ionic cyclization mechanism of copolymers of acrylonitrile-itaconic acid P(AN-IA) have been studied using density functional theory (DFT) at B3LYP/6-31+G (d, p) level, respectively. By comparing the direct mechanism with autocatalytic mechanism, it was found that the free energy barriers of the cyclization reaction were hugely lowered by including a nearby P(AN-IA) copolymer serving as a catalyst. The calculated free energy barrier of cyclization is about 22.74 kcal·mol^-1, which is in good agreement with the experimental activation barrier of 26.1 kcal·mol^-1. The cyclization of P(AN-IA) would proceed by rather an autocatalytic mechanism than a direct mechanism.

中文翻译：

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DFT研究丙烯腈-衣康酸共聚物的离子环化机理：直接还是自催化？

分别使用密度泛函理论（DFT）在B3LYP / 6-31 + G（d，p）水平上研究了丙烯腈-衣康酸P（AN-IA）共聚物的直接和自催化离子环化机理。通过将直接机理与自催化机理进行比较，发现通过包含附近的P（AN-IA）共聚物作为催化剂，大大降低了环化反应的自由能垒。计算得出的环化自由能垒约为22.74 kcal·mol ^-1，与实验激活活化能垒26.1 kcal·mol ^-1吻合良好。P（AN-IA）的环化将通过自动催化机制而非直接机制进行。