Hailan Kang

Synthesis and characterization of biobased isosorbide-containing copolyesters as shape memory polymers for biomedical applications

Novel biobased isosorbide-containing copolyesters (PBISI copolyesters) with both biocompatibility and sustainability were synthesized by using commercially available biobased diols and diacids. Due to the presence of itaconate in copolyesters, it can be readily crosslinked by peroxide into a crystallizable network. The structure and thermal properties of PBISI copolyesters were determined by 1H NMR, FTIR, DSC, and WAXD. The chain composition, melting point and crystallinity of the PBISI copolyesters can be tuned continuously by changing the content of isosorbide. The crosslinked copolyester is demonstrated to be a promising shape memory polymer (SMP) with excellent shape memory properties including shape fixity and shape recovery rate close to 100%. The switching temperatures of PBISI-based SMPs can be tuned between 26 °C and 54 °C by altering the composition of PBISI copolyesters and curing extent. Cell adhesion and proliferation were adopted to evaluate the potential biocompatibility of PBISI-based SMPs, and the results indicated that all the PBISI-based SMPs were essentially noncytotoxic, making them suitable for fabricating biomedical devices.

Novel biobased thermoplastic elastomer consisting of synthetic polyester elastomer and polylactide by in situ dynamical crosslinking method

Owing to the sustainability and environmental friendliness of biobased polymers, we adopted synthesized biobased polyester elastomer (BPE) and polylactide (PLA) as the two components to produce a new biobased thermoplastic vulcanizate (TPV) by an in situ dynamical crosslinking and mixing method. The effect of blending ratio on the dynamic crosslinking and micromorphology of TPV was investigated by mixing torque measurements, degree of crosslinking measurements, TEM, DSC, and rheological properties. A large amount of crosslinked BPE particles were dispersed in the PLA continuous phase, with the particle sizes ranging from 1 to 4 μm, indicating the occurrence of phase inversion during the dynamical crosslinking and mixing process. The tensile strength and elongation at break of the biobased TPVs ranged from 11.4 MPa to 17.8 MPa and 154% to 184%, respectively. Reprocessing did not significantly reduce the mechanical properties, as an indication that biobased TPVs, like thermoplastics, have good reprocessability. In vitro cytotoxicity tests showed that our TPVs were nontoxic, at least towards mouse fibroblasts. Thus, these novel biobased TPVs with excellent mechanical properties and low cytotoxicity are reported for the first time in the flied of thermoplastic elastomers for engineering and biomedical applications.

Preparation and characterization of high strength and noncytotoxic bioelastomers containing isosorbide

Biobased elastomers (bioelastomers) with high strength and good biocompatibility have emerged as promising biomaterials for soft tissue engineering. In the present work, we synthesized a series of biobased copolyesters, converting semicrystalline copolyesters into elastomers by introducing isosorbide, a bicyclic carbohydrate-based diol. The molecular weights, polymer structures and thermal transitions of the synthesized bioelastomers were characterized by GPC, NMR, FTIR, TGA, DSC and WAXD. The composition, melting point, and crystallinity of the bioelastomers could be tuned by changing the content of isosorbide. Furthermore, high strength composites could be prepared by compositing the synthesized bioelastomers with nanosilica. To substantiate the potential biocompatibility of the reinforced bioelastomers, the cell adhesion and proliferation were evaluated, and the results indicated that the reinforced bioelastomers were essentially noncytotoxic. The combination of sustainability, high strength and noncytotoxicity makes these bioelastomers potential candidates for high-strength biomedical materials.

Miscibility, intramolecular specific interactions and mechanical properties of a DGEBA based epoxy resin toughened with a sliding graft copolymer

The “sliding graft copolymer” (SGC), in which many linear poly-ɛ-caprolactone (PCL) side chains are bound to cyclodextrin rings of a polyrotaxane (PR), was prepared and employed to toughen diglycidyl ether of bisphenol A (DGEBA) based epoxy resin. The aim of the work is to understand the effect of SGC on the miscibility, morphology, thermal behavior, curing reaction and mechanical performance of the cured systems. From differential scanning calorimetry (DSC) analysis and dynamic mechanical thermal analysis (DMTA) of DGEBA/SGC thermosetting blends, it is found that DGEBA and SGC are miscible in the amorphous state. Fourier transform infrared spectroscopy (FTIR) suggested that the miscibility between SGC and DGEBA is due to the existence of intermolecular specific interactions (viz. hydrogen bonding). The impact strength is improved by 4 times for DGEBA/SGC (80/20) blends compared with that of the unmodified system. The increase in toughness of SGC-modified thermosets can be explained by the effect of intermolecular specific interactions of SGC with DGEBA, which is beneficial to induce the plastic deformation of matrix. This is the first report on utilizing this novel supramolecular polymer to toughen rigid epoxy matrix.