Effect of radical copolymerization of the (oxa)norbornene end-group of RAFT-prepared macromonomers on bottlebrush copolymer synthesis via ROMP

Bottlebrush polymers are attractive for use in a variety of different applications. Here we report the synthesis of two novel trithiocarbonate RAFT agents bearing either an oxanorbornenyl or norbornenyl moiety for bottlebrush synthesis via ROMP grafting-through polymerization. RAFT polymerization kinetics was evaluated as a function of the monomer type, number-average degree of polymerization (Xn) and RAFT agent structure. The correlation between the oxa/norbornenyl moiety and the type of RAFT monomer (methyl acrylate, n-butyl acrylate, and styrene) has been investigated. The reactivity of the oxa/norbornenyl group of the RAFT agent towards the radical propagating species during RAFT polymerization influences the molar mass, molar mass distribution and the residual olefinic end-group functionality of the resulting polymeric macromonomers. The RAFT synthesized macromonomers (MMs) are subjected to “grafting-through” ROMP using a Grubbs 3rd generation catalyst, resulting in bottlebrush polymers. The ‘defects’ in the MM structures have been found to be responsible for the higher amount of MM residue after the ROMP process and hence affect the microstructures of the synthesized bottlebrush polymers.