Kinetic studies on the radical ring-opening polymerization of 2-methylene-1,3,6-trioxocane

Radical ring-opening polymerization (RROP) of cyclic ketene acetals allows for the synthesis of functional and biodegradable polyesters. To gain a better understanding of RROP, kinetic studies of this reaction method are thus essential but still rare. In here we conducted kinetic experiments on RROP of 2-methylene-1,3,6-trioxocan (MTC) for the first time. In line with earlier findings, the kinetic behavior could be distributed into a chain growth, stationary and step growth behavior probably caused by dominating branching and recombination reactions impacting the polymerization with increasing conversion. The impact of reaction conditions, such as monomer concentration, reaction temperature and source of energy input (Oil bath, microwave, UV light) were varied systematically. All of these factors were studied towards their influence on polymerization rate constant, density of branches (DB), polymer dispersity and molar mass. While each of these factors were impacted by the reaction conditions, the DB was only depending on monomer conversion. Elution fractionation of PMTC samples with high conversion proved decreasing DB with increasing molar mass. Altogether, this study gives a holistic insight into the kinetics of MTC under various means of free RROP, paving the way for developing a more hydrophilic polyester with adjustable DB and molecular weight.