Novel approach to trigger nanostructures in thermosets using competitive Hydrogen-Bonding-Induced Phase Separation (CHIPS)

A new route to prepare nanostructured thermosets by the utilization of intermolecular hydrogen-bonding interactions is demonstrated here. In this study, competitive hydrogen-bonding-induced microphase separation (CHIPS) in epoxy resin (ER) containing an amphiphilic block copolymer poly(ε-caprolactone)-block-poly(2-vinylpyridine) (PCL-b-P2VP) is investigated for the first time. The phase separation takes place due to the disparity in the hydrogen-bonding interactions in ER/P2VP and ER/PCL pairs leading to the formation of ordered nanostructures in the ER/block copolymer blends. SAXS and TEM results indicate that the hexagonally packed cylindrical morphology of neat PCL-b-P2VP block copolymer remains but becomes a core-shell structure at 10 wt % addition of ER, and changes to regular lamellae structures at 20-50 wt % then to disordered lamellae with 60 wt % ER. Wormlike structures are obtained in the blends with 70 wt % ER, followed by a completely homogeneous phase of ER/P2VP and ER/PCL. The formation of nanostructures and changes in morphologies depend on the relative strength of hydrogen-bonding interactions between each component block copolymer and the homopolymer. This versatile method to develop nanostructured thermosets, involving competitive hydrogen-bonding interactions, could be used for the fabrication of hierarchical and functional materials.

Conjugation of bioactive groups to poly(lactic acid) and poly[(lactic acid)-co-(glycolic acid)] films

A novel PLA-based polymer containing reactive pendent ketone or hydroxyl groups was synthesized by the copolymerization of L-lactide with epsilon-caprolactone-based monomers. The polymer was activated with NPC, resulting in an amine-reactive polymer which was then cast into thin polymeric films, either alone or as part of a blend with PLGA, before immersion into a solution of the cell adhesion peptide GRGDS in PBS buffer allowed for conjugation of GRGDS to the film surfaces. Subsequent 3T3 fibroblast cell adhesion studies demonstrated an increase in cellular adhesion and spreading over films cast from unmodified PLGA. Hence the new polymer can be used to obtain covalent linkage of amine-containing molecules to polymer surfaces.