Selectively Sensing Capacities of Biocompatible Shape Memory Materials Based on Cross-Linked Poly(l-malic acid): Visual Discrimination of the Solvents with Similar Structures

A biomass-derived and biocompatible poly(l-malic acid) (PMA) based material with shape memory effect (SME) was developed in this work. 1,8-Octanediol was used as the cross-linker to construct cross-linking networks with hydrophilic backbone chain of PMA, tuning the density of networks and their swelling capacities by controlling −COOH/–OH ratios. The solvent-induced SME of as-obtained cross-linked PMAs was activated under mild conditions in this way. Using the shape recovery levels of U-shaped samples as the probes, the mixed methanol/ethanol/water systems with various ratios could be easily discriminated because the cross-linked PMAs show different sensing capacities to different components. The mechanisms were then studied in terms of the solvent molecule–polymer interactions. This work provides an interesting approach of visible discrimination of the solvents with similar structures, or their mixtures with various ratios, and also opens applications of biocompatible shape memory polymers in biomedical and chemical industries.