Effect of in-situ reactive compatibilization on the structure and properties of SiO₂/PEG/PLA shape memory composites

To address the inherent trade-off between strength and toughness and the issue of PEG migration and exudation commonly observed in polyethylene glycol/polylactic acid (PEG/PLA) plasticized systems, this study introduces γ-glycidoxypropyltrimethoxysilane (GPTMS)-modified nano-SiO₂ (mSiO₂) as a functional filler, yielding SiO₂/PEG/PLA (SPP) composites with good mechanical properties, suppressed PEG migration and exudation, and excellent shape memory performance. In-situ compatibilization driven by mSiO₂ reactions with PLA and PEG optimized the interface, significantly enhancing the comprehensive properties of the SPP composites, thereby endowing the composites with markedly enhanced mechanical properties. The SPP composites achieved a tensile strength of 40.4 MPa and a tensile modulus of 1073.4 MPa, while retaining a high elongation at break of 167.7%. The SPP composites exhibited a confined crystallization mode, and the crystallinity increased to 7.8%, representing an improvement of 36.8% over the neat PEG/PLA blend. In addition, the SPP composites maintained excellent optical transparency, with transmittance exceeding 83% at a wavelength of 550 nm. Attributed to the dual effects of chemical anchoring and physical barrier, the PEG mass retention ratio of the SPP composites increased by 4.1% (compared to the PEG/PLA composites) after heat treatment at 90 °C for 5 days. Furthermore, the SPP composites demonstrated excellent shape memory performance, achieving a shape memory fixity ratio above 94% and a shape memory recovery ratio above 80% when recovered after being pre-strained to 100% strain at 85 °C.