To investigate the role of hydrogen-bonding on colorimetric transition of polydiacetylene supramolecules, novel diacetylene derivatives allowing various hydrogen-bonding states were synthesized by coupling carboxy-substituted (ortho-, meta-, and para-) anilide groups with a typical single-chain diacetylene lipid. One with a terminal carboxyl group at the meta position provided the resulting supramolecular Langmuir-Schaefer films with enhanced hydrogen-bonding, and hence resulted in unprecedented colorimetric reversibility under both thermal and pH stimuli.

Biodegradable polymers, such as poly(glycolic acid) (PGA), poly(L-lactic acid) (PLLA) and poly(lactic-co-glycolic acid) (PLGA), were dissolved individually in the proper solvents and then subjected to electrospinning process to make nanofibrous scaffolds. Their surfaces were then chemically modified using oxygen plasma treatment and in situ grafting of hydrophilic acrylic acid (AA). The fiber thickness, pore size and porosity were estimated to 200-800 nm, 2-30 microm and 94-96%, respectively, and these properties were insignificant in the PGA, PLLA and PLGA nanofibrous scaffolds. The ultimate tensile strength of PGA was about 2.5 MPa on average and that of PLGA and PLLA was less than 2 MPa. The elongation-at-break was 100-130% for the three nanofibrous scaffolds. When the surface properties of AA-grafted scaffolds were examined, higher ratios of oxygen to carbon, lower contact angles and the presence of carboxylic (-COOH) groups were identified. The properties were significantly different from those of the unmodified nanofibrous scaffolds. Fibroblasts once seeded on the scaffolds were spreading over large surface area on the AA-grafted surface as compared to the unmodified PGA, PLLA and PLGA nanofibrous scaffolds. Cultured for up to 6 days, the fibroblast proliferation was found to be much better on the surface-modified nanofibrous scaffolds. The present study showed that, with the use of plasma treatment and AA grafting, the hydrophilic functional groups could be successfully adapted on the surface of electrospun nanofibrous scaffolds. Those surface-modified scaffolds made significant improvement on cell attachment and proliferation in vitro.

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The ring-opening polymerization of L-lactide with stannous octoate was investigated in the presence of pentaerythritol. By this way it was possible to prepare higher molecular weight starshaped poly(L4actide)s compared with the linear ones obtained by stannous octoate only. The weight-average molecular weights of linear and star poly(L4actide)s were measured by light scattering analysis from hexafluoro-2-propanol solution, and the respective Mark-Houwink equations were derived. The second virial coefficient and the intrinsic viscosity of the star polymers were lower than those of the linear ones, which confirms the star-shaped architecture.

A polymerizable quinizarin (Qz) dye precursor having both methacrylate and tertbutoxycarbonyl (t-BOC) groups has been prepared and radically copolymerized to obtain mono-t-BOC-protected quinizarin polymers as fluorescent imaging materials. The mono-t-BOC-protected quinizarin methacylate 3 (t-BQzMA) is a unique monomer having an acidlabile t-BOC blocking group along with a polymerizable methacrylate group. The t-BOCprotected quinizarin polymers obtained by copolymerization of t-BQzMA with methyl methacrylate were readily modified to regenerate phenol groups by deprotection of t-BOC groups in the quinizarin moieties with photochemical treatment in the presence of a photoacid generator. The polymers rendered color and fluorescent imaging properties based on a photolithographic method: fluorescent images obtained without wet development and fluorescent relief patterns after wet development followed by flood exposure.

Surfaces of commercial polyurethanes (PUs) were modified by poly(ethylene oxide) (PEO) grafting and/or heparin immobilization for long-term biomedical applications. PU surfaces were treated with diisocyanate and then reacted with PEO or heparin. The heparin immobilized by various methods on the PU surface was very stable, with concentrations of 1.45-1.84 micrograms/cm2. Surface structure and characteristics of each modified PU were examined by performing the following surface analyses: attenuated total reflection infrared (ATR-IR), electron spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM), and dynamic contact angle measurements. The reaction scheme and surface chemical structure of modified PUs were confirmed by ATR-IR and ESCA, respectively. SEM results showed that the PU-PEO surface was very smooth and that the smoothness of the heparinized PU surfaces varied, depending upon the solvent and coupling agent used in the process. The hydrophilicity of the surface was significantly increased after PEO grafting or heparin immobilization. Increase in the chain length of the grafted PEO resulted in significant increases in hydrophilicity and surface mobility.

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