Strong Polymer Gels with Tunable Crystalline Domains

The ability to create synthetic materials that mimic the structural and mechanical properties of soft biological tissues remains a significant challenge. In this presentation, we focus on creating strong hydrogels with a high elastic modulus and compressive modulus by engineering crystalline domains into associative hydrogels of poly(lactic acid)-poly(ethylene oxide)-poly(lactic acid) (PLA-PEO-PLA) triblock copolymers. In aqueous media, these materials form associative gels with PLA domains serving as network junctions. We extend previous studies from our group and others by varying the stereochemistry of the PLA block to create polymers with PLA blocks with ratios of L/D lactide units varying from 100/0 to 50/50. We had previously found that the 100/0 systems (triblocks with poly(L-lactide) blocks) formed gels with nanoscale crystalline domains, and these gels displayed a high value of the elastic modulus which was strongly dependent on PLA block length. Interestingly, we find that the modulus of these gels does not seem to vary monotonically with L/D ratio, with systems at intermediate L/D values displaying higher moduli than the 100/0 systems. Collectively, our work shows that stereochemistry can be used to access novel structures and properties in relatively simple synthetic polymers, perhaps giving insight into new routes for creating complex soft materials.