PLGA-POSS End-Linked Networks with Tailored Degradation and Shape Memory Behavior

Biodegradable PLGA oligomers were synthesized to feature a hybrid organic-inorganic moiety, POSS, incorporated at the center of each chain by using it as the ring-opening initiator. After end-capping with vinyl groups, the macromers were photocured into networks with POSS content ranging from 10 to 41 wt %. Increasing POSS inclusion increased the crystallinity of the network while decreasing the degradation rate due to its hydrophobic and nonhydrolyzable properties, It was found that co-curing PLGA oligomers with and without POSS in the backbone Could be utilized to create networks witha reduced POSS loading level, at a given cross-link density, allowing tuned crystallinity. Hydrolytic degradation of the co-cured networks was slower than for the PLGA homonetwork but still led to complete degradation after 14 weeks in PBS buffer at 37 degrees C. The networks exhibited versatile shape memory properties, exploiting the combination of covalent cross-linking and the glass transition, POSS-phase inciting temperature, or both as the shape-switching trigger. Using the glass transition was found to yield the best. shape fixing, while the best recovery percentages (similar to 100%) were achieved when the melting transition was used. One network, with 24 wt % POSS, was able to be fixed in a temporary shape by POSS crystallization and to largely preserve this shape during degradation. After 4 weeks and 60% mass loss, 50% of the initial deformation still remained while the PLGA network (shape fixed through T-g) had recovered fully. Our findings are expected to impact future design of biodegradable polymers with shape memory, having revealed the precise tuning of properties possible through controlled placement of a crystallizable and hydrophobic moiety in the polymer network chain.