Synthesis and cell adhesion studies of linear and hyperbranched poly(butyl methacrylate) and poly(t-butyl acrylate)

A library of polymers/oligomers with three different architectures was synthesised. Short chain, linear oligomers were produced by performing oxidative cleavage on a poly(butyl methacrylate-co-butadiene) polymer. Although butadiene is a gaseous monomer, it was found that careful control over the reaction conditions led to successful copolymerisation in an unpressurised reactor. Hyperbranched polymers of n-butyl methacrylate and t-butyl acrylate
were synthesised by RAFT polymerisation with 4-vinylbenzyl-pyrrolecarbodithioate (CTA1) and 4-vinylbenzyl dithiobenzoate (CTA2). A variety of analytical techniques, such as elemental analysis and NMR, were used to characterise the polymers and confirm the hyperbranched structure. Some variation in monomer conversion and CTA uptake was seen under different polymerisation conditions.
After synthesis and characterisation, it was found that the polymer end groups could be modified through work up with diamine or 4.4‘-azobiscyanovaleric acid. Linear oligomers of
butyl methacrylate were functionalised with amines whilst hyperbranched polymers were given acid functional end groups. FT-IR and elemental analysis were used to monitor the success of the end group reactions. As the polymers could be applied as films, they were assessed as cell culture substrates using Human dermal fibroblasts (HDF) and Human renal epithelial cells (HREp). A linear butyl
methacrylate-co-4-vinyl benzoic acid copolymer was also assessed in comparison to the hyperbranched structures. It was observed that the two cell types had different responses to each of the polymers. Fibroblast cells showed better rates of adhesion and proliferation on
acid-functionalised polymers, whilst epithelial cells performed best on the aminefunctionalised moieties.
This work provides useful information for the synthesis and preparation of new biomaterials. It has been found that polymer functionality must be considered when compatibility with a specific cell type is desired, and polymers with the potential to be incorporated into future biomaterials are highlighted.