Rheological characterization of biocompatible associative polymer hydrogels with crystalline and amorphous endblocks

Control over mechanical properties of hydrogels is of primary importance for the use of these materials in drug delivery and tissue engineering applications. We demonstrate here that crystallinity and block length of poly(lactide) (PLA) can be used to tune the elastic modulus of associative network gels of poly(lactide)-poly(ethylene oxide)-poly(lactide) over several orders of magnitude. Polymers made with crystalline L lactic acid blocks formed very stiff hydrogels at 25 wt% concentration with an elastic modulus that was almost an order of magnitude higher than hydrogels of polymers with a similar molecular weight but containing amorphous D/L-lactic acid blocks. The relaxation behavior and crosslink density of gels are also significantly influenced by crystallinity of PLA and are again a function of PLA block length. Using these variables we can design new tailor-made materials for biomedical applications with precise control over their structure and mechanical properties.