Abstract:
The demand for biodegradable polymer-based
aerogels with superior comprehensive properties has escalated in
various fields of application, such as packaging, tissue engineering,
thermal insulation, acoustic insulation, and environmental
remediation. In this work, we report a facile strategy for enhancing
the thermal and mechanical properties of polylactide (PLA)
aerogels through the stereocomplex (SC) formation between the
opposite enantiomers. Thermoreversible gelation of poly(L-lactide)
(PLLA)/poly(D-lactide) (PDLA) blend in crystal complex forming
solvent and the subsequent thermal annealing of the gel resulted in
crystalline pure SC gel, which, upon solvent exchange with water
and freeze-drying, furnished robust SC aerogel. It was found that the SC content could be tuned by varying the annealing
temperature of the blend gel and that we could prepare blend aerogels with pure α crystalline form and a mixture of α and SC.
Crystalline pure blend α aerogel showed fibrillar morphology, whereas SC aerogel exhibited unique interwoven ball-like
microstructures interconnected by PLLA and PDLA chains. The structural evolution during SC formation at the molecular level and
the micrometer length scale instigated better properties in the PLA aerogels. When compared with the homopolymer aerogels, the
crystalline pure SC aerogel showed an enhanced melting temperature of 227 ± 2 °C (50 °C higher), better thermal stability (onset
of degradation was delayed by ∼40 °C), enhanced mechanical strength (compression modulus of 3.3 MPa), and better sound
absorption ability. The biodegradability of PLA and the superior properties induced by stereocomplexation make these aerogels
potential candidates for applications such as tissue engineering scaffolds, packaging, acoustic insulation, etc.
