High-Performance biocompatible shape memory polymers for 4D Printing: Effects of 4-tert-Butylcyclohexyl acrylate as a soft component monomer

This study explores the potential of tert-butylcyclohexyl acrylate (TBCHA) as a novel soft-segment monomer in the development of 4D printable shape memory polymers (SMPs), using tert-butyl acrylate (tBA) as a reference material. The highly stretchable SMP resin was prepared by mixing synthesized polycaprolactone diacrylate (PCL-DA) as a crosslinker, 4-tert-Butylcyclohexyl acrylate (TBCHA) or tert-butyl acrylate (tBA) as a monomer, and 3 wt% of diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) as a photoinitiator. Then, the SMP was printed by using a Liquid-Crystal Display (LCD) 3D printer. With systematic variation in monomer content to evaluate printability, mechanical properties, thermal behavior, shape memory performance, and biocompatibility. The TBCHA-based networks demonstrated lower polymerization shrinkage, higher hardness, greater tensile strength, and improved shape fixity and recovery ratios compared to tBA-based counterparts. These improvements are attributed to the conformational flexibility of the cyclohexyl ring in TBCHA, which promotes efficient stress relaxation and a higher degree of conversion during photopolymerization. Dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) revealed higher glass transition temperatures (T_g), which close to body temperature, and storage modulus in TBCHA systems, correlating with their superior mechanical performance. Furthermore, MTT assays confirmed the cytocompatibility of TBCHA-based SMPs, and degradation studies showed tunable hydrolytic degradation behavior when PCL-DA was incorporated. Collectively, this work establishes TBCHA as a promising monomer for advanced SMP applications, offering a versatile platform for 4D printing technologies in biomedical and functional material fields.