Advanced Materials Research Vols. 284-286

Abstract: The feasibility of using two step procedures with thermal imidization of polyamic acid (PAA) for synthesizing hydroxyl group polyimide (PI), based on 2,2-Bis(3-amino-4-hydroxyphenyl)hexafluoropropane (Bis-AP-AF), was studied. It was found that a high molecular weight PAA could be successfully synthesized from Bis-AP-AF with 3,3',4,4'-Benzophenone tetracarboxylic dianhydride (BTDA). The optimum polycondensation reaction time on synthesizing molecular weight of the PAA was 4 hours. The PI films could be successfully prepared by thermal imidization of the PAA. The higher the inherent viscosity of the PAA is, the more beneficial for the tensile properties of the PI films. All the results indicate that two step procedures with thermal imidization of the PAA under appropriate conditions represented a promising way for preparation PI films, with a reasonable level of mechanical properties.

Abstract: Melanin was isolated from the mycelium of Lachnum singerianum YM-292 (LSM) by alkaline extraction, acid hydrolysis, and repeated precipitation with a yield of 8.85 g/100 g (dry weight basis). Scanning electron microscopy showed that LSM had a blocky crystal structure with an irregular surface. The percentages of C, H, N, O and S in LSM measured by the elemental analyzer were 54.44%, 6.65%, 8.25%, 24.24% and 6.42%, respectively. Infrared spectroscopy indicated that LSM had a typical indole structure, and ¹H-NMR spectroscopy revealed signal peaks in the aliphatic and aromatic regions. It was concluded that LSM had a structural model of pheomelanin-like pigment.

Abstract: Polyurethane-imide is a novel kind of po lymer with excellent heat-resistant and mechanical properties. This overview embracing microstructure, synthesis and properties of polyurethane-imide is given and provided representative examples to reflect the state of the research for polyurethane-imide. The microstructure includes molecular structure and phase structure. Synthesis of linear PUI and network PUI is given in next and, Mechanical properties, Thermal performance and other properties is also recommended. The shortages of PUI research is imperfection of synthesis and the theoretical analysis, so the prospect of the study on polyurethane-imide is also displayed.

Abstract: In order to reduce the cost of the polylactic acid (PLLA) material and to improve its flexibility to expand the application of PLA-based plastic, a series of PLLA/SA blends with tetrabutyl titanate (Ti(OBu)₄) used as compatibilizer were prepared in the presence of 10% triethyl citrate (TEC) as plasticizer. It was investigated the effect of the compatibilizer and its content on the mechanical properties, structure and morphologies, heat-resistant performance, melt flow rate, and water-resistant performance and other implications of blends. The results showed that: adding the compatibilizer Ti(OBu)₄ could significantly improve the compatibility of PLLA and SA, the mechanical properties and thermal stability of the blends were increased, while melt flow rate and water absorption were decreased. When the content of compatibilizer Ti(OBu)₄ was 8 wt%, PLA/SA blends(75/25 wt%) had the best overall performance.

Abstract: As a biofilm carrier for wastewater treatment, PAN-based carbon fiber (CF) was usually modified with different ways. The double modification treatment composed of surface oxidation and maleic anhydride (MA) graft was used in current research and it’s regarded to be a favorable surface treatment for CF carrier. The consequent CF surface morphology and natures were then characterized by laser confocal microscopy (LCM), X-ray photoelectron spectroscopy (XPS) and the degree of moisture. In addition, biocompatibility of CF was discussed through immobilization behavior of microorganisms. The results indicated that the immobilization ability of microorganisms will be improved if the CF surface is modified to better hydrophilicity by producing oxygen-based functionalities. Furthermore, the configurations and the adhesion forms of cells were affected by the properties of CF surface.

Abstract: Chitosan/Hydroxyapatite composites with a homogeneous nanostructure have been prepared by a co-precipitation method. Initially, a chitosan solution was prepared and mixed with the (NH₄)₂HPO₄ solution. After homogenizing, the obtained chitosan/ (NH₄)₂HPO₄ solution was gradually dropped into the Ca (NO₃)₂^.4H₂O solution under stirring. The solution pH was adjusted to 9 using NH₃^.H₂O. The precipitate was compressed into a cylindrical form followed by post treatment. The microstructure, phase composition and mechanical properties of the resulting chitosan-HAp composites were characterized. In the presence of chitosan, HAp crystallites were found to be well aligned along the c-axes in the respective aggregates. Fourier transform infrared spectrometer results indicated that an intermolecular bridging complexes might have been developed between the chitosan and HAp. The compact composites obtained were mechanically flexible, the highest strength was found to be 38.4 MPa for chitosan/HAp samples with a 20 wt% of chitosan.

Abstract: Sorption experiments of bovine serum albumin (BSA) on hydroxyapatite (HAp) ceramic granules, prepared at three temperatures 900°C, 1000°C and 1150°C were performed at room temperature 18,6 °C and phosphate buffer, pH 5,83; 6.38 and 7,39. Thermal treatment contributed to the decrease of bovine serum albumin immobilization indicating that sorption process depended on HAp ceramics specific surface area and pH values of phosphate buffer solution. However, it was confirmed that granule size was also an important parameter for bovine serum albumin adsorption. As a result of these experiments, the most appropriate adsorption conditions and phosphate buffer pH values influence on to BSA sorption were analyzed.

Abstract: In the current research slow release anticancer drug delivery system was prepared and drug release kinetics in vitro evaluated. Porous hydroxyapatite (HAp) as carrier material and doxorubicin hydrochloride (DOX) as anticancer agent was used. DOX is an anthracycline drug commonly used in cancer chemotherapy. Unfortunately, its therapeutic potential is restricted cardiotoxicity and resistance developed by the tumor cells to the molecule after treatment. To prepare HAp-DOC composites, the porous bioceramic scaffolds were impregnated with doxorubicin in low vacuum conditions. 10% (HAp-10%PLA) and 20% (HAp-20%PLA) poly lactic acid and 20% (HAp-20%PCL) poly(e-caprolactone) solutions in dichloromethane were used to form the polymer coatings on the drug/bioceramic composites. In general there was a burst release observed from all the samples during the first 2 hours followed by a much reduced release profile. In the next 5 days the drug release from all the samples decreased in the following order: 20% PLA (from 56 ng/ml to 3 ng/ml), 20% PCL (from 196 ng/ml to 6 ng/ml), 10% PLA (from 497 ng/ml to 18 ng/ml). HAp-DOX composite without the polymer coating demonstrated the drug release reduction from 230 ng/ml to 13 ng/ml. The cumulative drug release was observed over 19 days.

Abstract: Biodegradable fibers of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) were prepared by melt spinning, followed by one-step-drawing with small crystal nuclei grown after isothermal crystallization near the glass transition temperature (Tg) and annealing at room temperature under tension. This new drawing technique is a very attractive method for obtaining flexible fibers from low-molecular-weight biopolyesters produced by recombinant bacteria. The ordered structure of PHBHHx fibers was investigated by tensile measurement, scanning electron microscopy, and wide-angle X-ray diffraction (WAXD). The tensile strength of 10 times one-step-drawn fiber after isothermal crystallization increased to 100 MPa. The WAXD profiles of PHBHHx fibers showed sharp reflections corresponding to highly oriented α-form (2₁ helix conformation) crystal.

Abstract: The composites of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with different microcrystalline cellulose (MCC) contents were prepared by a solvent casting method. The effects of MCC on the thermal properties of PHBV were studied by TGA and DSC. The DSC results showed that the melt crystallization temperature of the PHBV/MCC increased from 41.9 °C for PHBV to 59.8 °C for the composites containing 20 wt. % MCC, which indicated that the crystallization of PHBV became easier with the addition of MCC. It also illustrated that the MCC could be used as an effective nucleation agent for the crystallization of PHBV. Moreover, it was found that the thermal stability of the PHBV/MCC composites increased compared with the neat PHBV.