4D Printing of TBCHA-Based Shape Memory Polymer Composites: Bioglass 45S5 Addition Improves Stability Retention and...

Shape memory polymer composites (SMPCs) were developed by incorporating Bioglass 45S5 into a polycaprolactone diacrylate (PCL-DA)/4-tert-butylcyclohexyl acrylate (TBCHA) network to enhance the mechanical robustness, thermal stability, and bioactivity. TBCHA, a bulky acrylate featuring a cyclohexyl-mediated steric architecture, provides a balanced rigid-flexible microstructure that improves interfacial confinement and shape-memory response. Melt-quenched Bioglass 45S5 was uniformly dispersed within the SMP matrix, and the resulting SMPCs were characterized by DSC, DMA, flexural testing, hardness, degradation in PBS, and SBF-induced hydroxyapatite formation. For the SMP30 (lower TBCHA content) network containing 3 wt % Bioglass (SMP 30 BG 3), the glass transition temperature increased from 40 to 45 °C, while the flexural strength increased from 4.3 to 17.46 MPa (≈4.06-fold), together with improved surface hardness. A composition-dependent degradation trend was observed: 1 wt % accelerated degradation, whereas ≥2 wt % slowed it. Even after 2 weeks of accelerated degradation, the 3 wt % composite retained excellent shape-memory performance, with Rf reaching 98.05% (≈3.43-fold that of the degraded neat SMP30), while Rr remained ∼98%. Manual cyclic shape-memory testing over five consecutive thermomechanical cycles further confirmed good cyclic stability, with both Rf and Rr remaining ∼97% after the fifth cycle for SMP 30 BG 3. The steric confinement effect of TBCHA was quantitatively analyzed to elucidate filler-matrix reinforcement. These results demonstrate tunable properties in 4D printable degradable SMPCs with enhanced bioactivity.