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Segmented polyurethane (SPU) materials based on different soft-segment component (PPG, PTMO and PBA) and various length of soft-segment (molecular weight of PBA: 500, 700 and 1000) were synthesized in this research. The soft-segment components were synthesized from polyether-polyols (PPG and PTMO) or from polyester-polyol (PBA). The physical properties and structure characterization of the synthesized SPUs were fully investigated using differential scanning calorimetry (DSC) analysis, and stress-strain measurements. Blood compatibility was evaluated with the platelet adhesion ratio (PAR) and the morphological observation for adhering platelets. Our results showed that the physical properties and blood compatibility of SPUs were closely related to its composition, which was controlled by (1) the types of the soft-segment component employed and (2) the length of soft segments. Polyether-polyol-based SPUs exhibited greater phase separations, poorer tensile strengths, and better blood compatibility, compared with polyester-polyol-based SPUs. SPUs with shorter soft-segment component exhibited greater phase mixing, higher tensile strength, but lower blood compatibility of SPUs, as compared with its counterparts with longer soft-segment component.

In this study, the depolymerization of chitosan was carried out in an acetic acid aqueous solution and was followed by viscometry for molecular weight determination. It was found that the depolymerization rate increased with elevated temperatures and with high acid concentrations. Based on FTIR analysis, the chitosan was depolymerized randomly along the backbone; no other structural change was observed during the acid depolymerization process. Revealed in the TGA study, the degradation temperature and char yield of LMWCs (low molecular weight chitosan) were molecular weight dependent. The blood compatibility of LMWCs was also investigated: rouleaux formation was observed when erythrocyte contacted with LMWCs, which showed that LMWCs are able to interfere with the negatively charged cell membrane through its polycationic properties. Furthermore, as regards a kinetics investigation, the values of M(n) (number-average molecular weight) were obtained from an experimentally determined relationship. The kinetics study showed that the complex salt, formed by amine on chitosan and acetic acid, acted as catalyst. Finally, the activation energy for the hydrolysis of the glycosidic linkage on chitosan was calculated to be 40kJ/mol; the mechanism of acid depolymerization is proposed. In summary, LMWCs could be easily and numerously generated with acid depolymerization for further biological applications., (2010 Elsevier Ltd. All rights reserved.)

In this study, we prepared a polyelectrolyte complex (PEC) hydrogel comprising chitosan as the cationic polyelectrolyte and gamma-poly(glutamic acid) (gamma-PGA) as the anionic polyelectrolyte. Fourier transform infrared spectroscopy revealed that ionic complex interactions existed in the chitosan-gamma-PGA PEC hydrogels. The compressive modulus increased upon increasing the degree of complex formation in the chitosan-gamma-PGA PEC hydrogel; the water uptake decreased upon increasing the degree of complex formation. At the same degree of complex formation, the compressive modulus was larger for the chitosan-dominated PEC hydrogels; the water uptake was larger for the gamma-PGA-dominated ones. Scanning electron microscopy images revealed the existence of interconnected porous structures (pore size: 30-100mum) in all of the chitosan-gamma-PGA PEC hydrogels. The chitosan-gamma-PGA PEC hydrogels also exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus. In addition, in vitro cell culturing of 3T3 fibroblasts revealed that all the chitosan-gamma-PGA PEC hydrogels were effective in promoting cell proliferation, especially the positively charged ones (chitosan-dominated). Therefore, the chitosan-gamma-PGA polyelectrolyte hydrogel appears to have potential as a new material for biomedical applications., (Copyright 2010 Elsevier Ltd. All rights reserved.)

In this paper a new technique is proposed for the fabrication of two-dimensional (2D) and three-dimensional (3D) photonic crystals using monodisperse polystyrene microspheres as the templates. In addition, the approaches toward the creation of their corresponding inversed structures are described. The inversed structures were prepared by subjecting an introduced silica source to a sol-gel process; programmed heating was then performed to remove the template without spoiling the inversed structures. Utilizing these approaches, 2D and 3D photonic crystals and their highly ordered inversed hexagonal multilayer or monolayer structures were obtained on the substrate.