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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.

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We present a model that describes mechanical unfolding behavior in rod-like macromolecules. We propose that the unfolding occurs via the motion of a folded/unfolded interface along the molecule. We predict the speed of this interface as a function of the pulling velocity such that the resulting force-extension curve replicates the overstretching transition typical of coiled coils and DNA. We model the molecules as one-dimensional continua capable of existing in two metastable states under an applied tension. The interface separates these two metastable states and represents a jump in stretch, which is related to the applied force by the worm-like chain relation. The Abeyaratne-Knowles theory of phase transitions in continua governs the mechanics of the interface.

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We present applications of a model developed to describe unfolding in macromolecules under an axial force. We show how different experimentally observed force-extension behaviors can be reproduced within a common theoretical framework. We propose that the unfolding occurs via the motion of a folded/unfolded interface along the length of the molecule. The molecules are modeled as one-dimensional continua capable of existing in two metastable states under an applied tension. The interface separates these two metastable states and represents a jump in stretch, which is related to applied force by the worm-like-chain relation. The mechanics of the interface are governed by the Abeyaratne-Knowles theory of phase transitions. The thermodynamic driving force controls the motion of the interface via an equation called the kinetic relation. By choosing an appropriate kinetic relation for the unfolding conditions and the macro-molecule under consideration, we have been able to generate a variety of unfolding processes in macromolecules.

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