Watunyu Thanongsak, Suwabun Chirachanchai
The development of biobased polymers for biomedical applications poses a significant challenge, as it requires a delicate balance among biocompatibility, biodegradability, mechanical performance, and functional adaptability. The present work proposes a shape memory biobased polymer designed as a semi-interpenetrating network (semi-IPN), comprising a switching segment based on linear polylactic acid (PLA) and net-points formed by thiol–ene cross-linked multibranched poly(butylene itaconate- co -lactide) matrices. By employing multibranched polyethylenimine (mPEI) terminated with poly(butylene itaconate- co -lactide) (PBILA), the resulting copolymer, referred to as mPBILA, can be cross-linked with thiol-terminated pentaerythritol. When blended with polylactic acid (PLA) and subjected to UV exposure, this system undergoes in situ thiol–ene cross-linking to form a semi-interpenetrating network (semi-IPN), and the transition temperature ( T trans ) can be finely tuned by varying the mPBILA content. At 50 wt % mPBILA, the material exhibits a T trans of 38 °C, with shape memory behavior confirmed by cyclic thermomechanical testing via dynamic mechanical analysis. Cytotoxicity evaluation using normal human dermal fibroblast (NHDF) cells indicates the biocompatibility of the material. Structurally, PLA/mPBILA is a semi-IPN generated via a simple UV cross-link process rather than those solution cross-link systems reported in the past. The thermally induced shape memory behavior of the PLA/mPBILA system confirms its promise in a range of biomedical applications requiring responsive or adaptive properties, such as minimally invasive implants, tissue scaffolds, and drug delivery systems.