PLA-PEO-PLA hydrogels and their mechanical properties

Poly(lactide) - block - poly(ethylene oxide) - block - poly(lactide) [PLA-PEO-PLA] triblock copolymers are known to form physical hydrogels in water, due to the polymer's amphiphilic architecture. Their biodegradability has made them attractive for use as soft tissue scaffolds and other biological applications such as drug delivery. In many cases, their mechanical properties have been poorly investigated and “rules” for tuning their stiffness are missing. Often the network junction points are only physical cross-links, not covalent, and in a highly aqueous environment, these hydrogels will absorb more water, transform from gel to sol, and lose the designed mechanical properties. New insights into the self-assembly of these materials have resulted in new PLA-PEO-PLA gels with novel structural and mechanical properties. Here, we summarize our recent efforts to understand these novel hydrogels and control their mechanical properties. This is highlighted by a new approach in which the system is allowed to self-assemble and then it is covalently cross-linked to capture this self-assembled architecture. This produces hydrogels with permanent cross-links and allows their mechanical properties to be studied in much more detail.