Preparation of Sequence-Controlled Polymers using Traceless Protecting Groups:
The preparation of alternating copolymers mostly relies on strongly differing electron densities of the monomers, thereby severely limiting the possible combinations of monomers with which these copolymers can be synthesized. To circumvent this limitation we present a novel strategy for the synthesis of alternating copolymers, in which commercially available monomers are copolymerized with sterically hindered, non-homopolymerizable derivates of common monomers. Three promising monomers
were synthesized and their free-radical homopolymerization and copolymerization with styrene, methyl methacrylate and methyl acrylate was investigated. The resulting copolymers were characterised by NMR spectroscopy, MALDI-ToF MS and GPC. It could be shown that these sterically hindered monomers can be copolymerized with common monomers, but that the efficiency is determined by electronic and steric effects. When using large excesses of the sterically hindered monomer it is possible to obtain the desired alternating copolymers. The bulky protecting groups can be removed to create highly alternating copolymers of monomers which would not typically yield such monomer sequences. This strategy can be used to investigate the influence of monomer sequence on the properties of the polymers and to access highly functional materials. Moreover, the TMS- and Bpin-protecting groups allow a direct modification on the polymer backbone in a post-polymerization functionalization.