This work aims to improve the mechanical properties of starch-based hydrogels using a double-network (DN) strategy. The single network (SN) starch hydrogel was first prepared using glutaraldehyde as a crosslinker. The compressive properties of the SN hydrogels were influenced by both crosslinker content and crosslinking time. The SN starch hydrogel possessing the best mechanical properties was then fabricated into DN hydrogels. Poly(vinyl alcohol) (PVA) and borax were used as a secondary polymer and a crosslinker, respectively. The PVA–borax complexation partly enhanced the DN hydrogel’s compressive modulus by 30% and its toughness by 39%. DN hydrogels were found to have denser microstructures than SN hydrogels. To be specific, their walls thickened and grew more continuous while their pores shrank. The increased crosslinking density resulted in changes to the microstructure, which were well correlated with their porosity and water uptake capacity. An in vitro cytotoxicity test of the DN hydrogels revealed that they were non-toxic to chondrocytes. This work demonstrated that double networking is a simple but effective strategy for improving mechanical properties of starch-based hydrogels without sacrificing their biocompatibility. This approach can be used to tailor hydrogel properties to fulfill requirements for biomedical applications, such as tissue engineering and other related fields.

Poly(lactic acid) (PLA) exhibits excellent shape memory properties but suffers from brittleness and a high glass transition temperature (T_g), limiting its utility in flexible and durable applications. This study explored the modification of PLA properties through the incorporation of poly(ethylene glycol) (PEG), varying in both content (5–20 wt%) and molecular weight (4000–12,000 g/mol), to enhance its suitability for specific applications, such as medical splints. The PLA/PEG blend, containing 15 wt% PEG and with a molecular weight of 12,000 g/mol, exhibited superior shape fixity (99.27%) and recovery (95.77%) in shape memory tests conducted at a programming temperature (T_p) of 45 °C and a recovery temperature (T_r) of 60 °C. Differential scanning calorimetry (DSC) analysis provided insights into the thermal mechanisms driving shape memory behavior of the PLA/PEG blend. The addition of PEG to the PLA blend resulted in a reduction in T_g and an increase in crystallinity, thereby facilitating enhanced chain mobility and structural reorganization. These thermal changes enhanced the shape fixity and recovery of the PLA/PEG blend. Synchrotron wide-angle X-ray scattering (WAXS) was further employed to elucidate the microstructural evolution of PLA/PEG blends during the shape memory process. Upon stretching, the PLA/PEG chains aligned predominantly along the tensile direction, reflecting strain-induced orientation. During recovery, the PLA/PEG chains underwent isotropic relaxation, reorganizing into their original configurations. This structural reorganization highlighted the critical role of chain mobility and alignment in driving the shape memory behavior of PLA/PEG blends, enabling them to effectively return to their initial shape. Mechanical testing confirmed that increasing PEG content and molecular weight enhanced elongation at break and impact strength, balancing flexibility and strength. These findings demonstrated that PLA/PEG blends, especially with 15 wt% PEG at 12,000 g/mol, offer an optimal combination of shape memory performance and mechanical properties, positioning them as promising candidates for customizable and biodegradable medical applications.

Generally, poly(ethylene glycol) (PEG) is added to poly(lactic acid) (PLA) to reduce brittleness and improve mechanical properties. However, shape memory properties of PEG/PLA blends suffered due to the blend’s incompatibility. To enhance shape memory abilities of the blends, 0.45% maleic anhydride-grafted poly(lactic acid) (PLA-g-MA) was used as a compatibilizer. Thermal and mechanical properties, morphologies, microstructures, and shape memory properties of the blends containing different PLA-g-MA contents were investigated. The compatibilized blend with 2 wt% PLA-g-MA exhibited enhanced tensile modulus, strength, and elongation at break, as well as a lower glass transition temperature and degree of crystallinity than the uncompatibilized blend. Results revealed that PLA-g-MA improved interfacial adhesion between phases and promoted chain entanglement. Shape fixity performance of the compatibilized blends were comparable to that of neat PLA. The compatibilized blend containing 2 wt% PLA-g-MA possessed the best shape fixity and recovery performance. Although a high recovery temperature was expected to enhance the recovery of the PEG/PLA blends, the compatibilized blends can be recovered to their original shape at a lower temperature than the PLA. This study illustrated the possibility of optimizing PLA properties to meet requirements necessary for biomedical applications.

In this study, the effect of silane treatment methods on cure characteristics and mechanical, dynamic mechanical, and morphological properties of rice husk flour (RHF)/natural rubber (NR) composites was investigated. The RHF surface was pretreated with alkali solution and then treated with bis(triethoxysilylpropyl) tetrasulfide (TESPT) solution using the unwashing silane treatment method and washing silane treatment method. The expected difference between these two methods was the silane layers presented on the RHF surface. Unwashed TESPT‐treated RHF (UW‐ST) and washed TESPT‐treated RHF (W‐ST) were incorporated into NR to prepare RHF/NR composites. The TESPT molecules deposited on UW‐ST and W‐ST surfaces were confirmed by the additional peaks appeared in the FTIR spectra of UW‐ST and W‐ST. In addition, the decrement of decomposition temperatures and the changes in the residue amounts of UW‐ST and W‐ST proved the removal of the physisorbed silane layers after washing. The presence of TESPT molecules on the RHF surface enhanced compatibility and adhesion between RHF and NR matrix. This was confirmed by SEM micrographs of both UW‐ST/NR and W‐ST/NR composites. This result was also supported by the improvement of the mechanical and the dynamic mechanical properties of these two composites. According to mechanical properties of the NR composites, the washing silane treatment method was more effective than the unwashing silane treatment method for compatibility improvement between RHF and NR. The modulus, tensile strength, and tear strength of W‐ST/NR composites can be enhanced without deterioration of their elongation at break.

In this work, nano-size HA was produced from bovine bone. At various heat treatment temperatures, poorly crystalline, partially crystalline and crystalline forms of HA were obtained. PLA composites were prepared by incorporating various forms and contents of HA into PLA matrix. The characteristics of the obtained HA powders affected properties of PLA composites including mechanical properties, morphologies, PLA molecular weight, in vitro bioactivity and in vitro degradation behaviors of the composites. In the case of in vitro bioactivity study, all composites illustrated the induction of bone-like calcium phosphate compounds on their surfaces, especially the PLA/a-HA composites.