Oxygen-Initiated Free-Radical Polymerization of Alkyl Acrylates at High Temperatures
Oxygen-Initiated Free-Radical Polymerization of Alkyl Acrylates at High Temperatures
复制标题
DOI：
10.1021/acs.macromol.1c00669
复制
发表时间：
2021-08-16
期刊：
影响因子：
5.5
通讯作者：
Rappe, Andrew M.
中科院分区：
文献类型：
--
作者：
Liu, Shi;Chua, Lauren;Rappe, Andrew M.
据报道，分子氧在低温下是一种强抑制剂。在此，表明将氧气引入丙烯酸正丁酯（nBA）的自由基聚合中导致单体在高于140 ° C的温度下在非常短的时间内的高转化率，而不使用任何常规引发剂。通过进行基于密度泛函理论的第一性原理计算，这项工作首次确定和动力学研究的最可能的反应，通过分子氧有助于聚合物链引发。为分子氧在丙烯酸烷基酯高温自由基聚合中起催化剂作用提供了理论和实验依据。由溶剂化氧与丙烯酸烷基酯单体反应生成三重态双自由基中间体。然后，中间体与另一种单体反应，并从分子氧中热解离以进行聚合。这一理论发现得到了实验室实验的支持，实验表明，在存在非常少量的分子氧和不存在任何热引发剂的情况下，nBA的自由基聚合可持续地发生，并进行到非常高的单体转化率。这项工作为使用分子氧作为引发剂催化剂更经济和可持续地生产更高质量的丙烯酸聚合物开辟了一条新途径。
Molecular oxygen has been reported to be a strong inhibitor at low temperatures. Here, it is shown that the introduction of oxygen gas into the free-radical polymerization of n-butyl acrylate (nBA) results in high conversion of the monomer in a very short time at temperatures above 140 degrees C without the use of any conventional initiators. By conducting first-principles calculations based on density functional theory, this work for the first time identifies and kinetically studies the most-likely reactions via which molecular oxygen contributes to polymer chain initiation. It provides theoretical and experimental evidence that molecular oxygen acts as a catalyst in alkyl acrylate free-radical polymerization at high temperatures. A triplet diradical intermediate is generated from solvated oxygen reacting with an alkyl acrylate monomer. The intermediate then reacts with another monomer and thermally dissociates from molecular oxygen to proceed toward polymerization. This theoretical finding is supported by laboratory experiments showing that in the presence of a very small amount of molecular oxygen and in the absence of any thermal initiators, free-radical polymerization of nBA occurs sustainably and proceeds to a very high monomer conversion. This work opens a new path for a more economic and sustainable production of higher-quality acrylic polymers using molecular oxygen as an initiator catalyst.