Cross-linkable, thermo-responsive Pluronic® building blocks for biomedical applications: Synthesis and physico-chemical evaluation

The present work describes the development and evaluation of a series of thermo-responsive methacrylate end-capped commercially available triblock copolymer derivatives which consist of an ABA architecture with the A block being polyethylene oxide and the B block being propylene oxide. Different Pluronics® including F127, L35, L43 and L62 were included as starting material, in this way enabling variation of the A and B block lengths. Starting from the above-mentioned materials, polymerizable Pluronic® derivatives were obtained by esterification of their terminal hydroxyl groups using methacryloylchloride. The macromonomers developed were characterized for their chemical structure using Nuclear Magnetic Resonance spectroscopy and Fourier Transform Infrared spectroscopy. For all Pluronics® included, the degree of functionalization was ranging from 85% to 98%. The gelation behavior was determined by both differential scanning calorimetry and oscillation rheology. The macromonomers were cross-linked via random free radical polymerization in aqueous solution, in the presence of a UV-active photo-initiator. Finally, the materials developed were compared in terms of their physico-chemical properties including sol/gel fractions, temperature-dependent swelling capacity, mechanical properties and static contact angle measurements. The present study clearly indicates that fine-tuning of the final material physico-chemical properties is feasible by varying either the hydrogel building blocks or the polymer concentration used for developing hydrogels.