Self-condensing reversible complexation-mediated copolymerization for highly branched polymers with in situ formed inimers†
In this work, reversible complexation-mediated polymerization (RCMP) was modified to suit self-condensing vinyl polymerization (SCVP) aimed at the synthesis of highly branched polymers. For this purpose, two azo-containing pre-inimers with divinyl (DMACPO) or monovinyl (MACPO) substitution groups were synthesized and copolymerized with methyl methacrylate (MMA). The effects of the pre-inimer structure, the feed ratio, and oxygen on the monomer conversions and on the degree of branching of the obtained polymers were investigated thoroughly. The polymerization process and the branching behaviour were also studied in detail. The study of the DMACPO system revealed that the branched structures were synthesized from the beginning of the polymerization and that substantial branching occurred when the MMA conversion reached 54.7%. At the end of the polymerization, the MMA conversion was greater than 80%. The use of a small amount of additional azo initiator substantially increased the CC bond content among the inimers and the MMA conversion, affording polymers with a high degree of branching. The study of the MACPO system suggested that the monovinyl-functional inimer was much more effective than the divinyl-functional inimer, as the MMA conversion reached as high as 98.0% without inducing gelation. Moreover, the present synthesis could be conducted without additional deoxygenation irrespective of the pre-inimer employed. The current work provides a simple, easy, and versatile method for the synthesis of highly branched polymers from commercially available compounds and will facilitate the application of this method in various highly branched polymer syntheses.