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In this study, in situ polyurethane (PU) bionanocomposites of poly(ethylene glycol) (PEG)/poly(ε-caprolactone) (PCL) polyols, bare cellulose nanocrystals (CNCs) and PCLgrafted CNCs (G-CNC) were synthesized with different contents of CNCs as crosslinking agent to control the extent of phase separation. The effect of confining the chains between CNCs through urethane linkages and presence of PCL grafts on phase and crystallization behavior was evaluated. Crystallization and chemical networking were controlled to tune the shape fixity (SF) and recovery (SR) of the specimens, resulting in a SF of 100% for linear and PU nanocomposites of G-CNC (0.5% and 1%) samples. The PU nanocomposite of G-CNC (0.5%) was selected as the optimum sample with the highest SR of 100%. The effect of surface hydrophobicity on cellular behavior of Human Foreskin Fibroblast (as a normal cell) and HepG2 (as a cancerous cell) cells was evaluated. Cell adhesion analysis of the prepared samples indicated two different behaviors possibly due to the difference in the epigenetic nature of the cells and cellular integrin-based bonds showing a great potential for a variety of tissue engineering applications.

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In this research work, a group of thermoset polyurethane (tPU) nanocomposites were synthesized. Poly(εcaprolactone) (PCL 2000 ), Poly (tetramethylene glycol) (PTMG 2000 ), and different architecture and compositions of PCL and PTMG were used as diols. Cellulose nanowhisker (CNW), with 1.0 wt% content, was used to cross-link the prepolymers and to produce high-modulus specimens for high shape memory performance. The analyses of crystallization showed that thermal stability of the PTMG and PCL crystallites decreases upon block copolymerization, blending and incorporation of the block copolymer into the blend (about 10℃ decrease). Cross-linking of the prepolymers using CNW has also reduced the crystallites' thermal stability to a large extent (about 50℃ decrease). The results of the Dynamic Mechanical Thermal Analysis (DMTA) also showed that the thermoset PUs have a large elastic modulus at above room temperature (higher than 10 MPa) and very small tanδ height (below 0.15), which was attributed to its semi-crystalline nature and presence of CNW with high elastic modulus (110-220 GPa).The thermomechanical behavior of the tPUs proved to be ideal for acquiring high shape memory performance. The tPUs have also proved to be highly biocompatible. HighlightsSynthesis of thermoset PU nanocomposites of CNW with high elastic modulus; Prohibited clustering of CNWs (1.0 wt% content);The change in soft segments' architecture affects Young's modulus; Intense decline of soft segments' crystallization;Wide tanδ peak and T g transition allowed for tuning shape xity;Obtaining high shape memory performance due to high elastic nature of the PUs.

In this research paper, we investigated the impact of soft segment crystallization, the cross‐linking density (CLD) and elastic modulus of the synthesized thermoset polyurethanes on their shape memory performance (SMP). A group of tri‐block copolymers of poly(ϵ‐caprolactone) (PCL) and poly(tetramethylene glycol) (PTMG) with PCLx‐PTMG2000‐PCLx architecture were synthesized and used as polyols in a thermoset polyurethane (PU) structure. Crystallization of the soft segments was controlled through changing PCLx blocks’ length. Graphene nanoplatelets, with a fixed content of 0.50 wt.%, was used as the cross‐linker and the nano‐filler to tune elasticity of the PUs. Analysis of crystallization showed that by increasing PCLx’s length from 0 to 2000 D caused a drastic change in the crystallization behavior of the polyols. The polyols used in the thermoset PU nanocomposite led to a wide spectrum of elastic modulus at temperatures close to room temperature. The elastic modulus at room temperature ranged from 20 to 100 MPa. The changes in elastic modulus, CLD and soft segments’ crystallization resulted in a complex SMP behavior, which was studied in‐detail. The shape recovery rate was also studied, which showed the impact of crystallites’ melting, CLD and elastic modulus through a three‐stage shape recovery.

The need for multi-functional biomaterials has driven researchers towards more complex multi-component structures with tailor-made surface modifications. In this research, thermoset polyurethanes (tPUs) of PCL y -PEG x -PCL y , with variable block lengths, and graphene were developed and further surface-modified by Polydopamine (PDA) to improve cell adhesion. The viscoelastic and thermal proper-