Search

Poly(L-lactic acid)/hydroxyapatite (PLLA/HAp) composites were fabricated by in situ polymerization of L-lactide in porous HAp disks, using lipase as a catalyst. The effect of using various lipase species on the molecular weight of the resulting PLLA was investigated, as was the effect of varying the lipase concentration. Lipase CA, derived from Candida antarctica, was found to promote the polymerization of L-lactide in bulk form as well as within porous HAp disks. The in situ polymerization of L-lactide within lipase CA-coated HAp disks at 130°C for 7 days resulted in PLLA/HAp composites with a PLLA content in the range of 16 to 19 wt.%. The weight average molecular weights of the PLLAs formed in these composites were in the range of 1.6 x 104 to 3.0 x 104 g mo1-1 and varied with the lipase CA concentration. The PLLA/HAp composites exhibited a maximum bending strength of 72 MPa and a fracture toughness value of 0.93 MPa⋅m1/2, as estimated by three point bending tests. The cell adhesion and proliferation properties of these materials with osteoblast-like MC3T3-E1 cells suggest that these PLLA/HAp composites have suitably bioactive surfaces. [ABSTRACT FROM AUTHOR]

We synthesized sulfonated poly[(4-phenoxybenzoyl)-l,4-phenylene-co-anthraquinone] copolymers (S-P(PBP-co-ANQ)s) in order to investigate the effect of polycyclic units on the water uptake, dimensional stability, and proton conductivity. The effect of the binding positions of anthraquinone (ANQ) was also investigated by preparing S-P(PBP-co-l,4ANQ) and S-P(PBP-co-l,5ANQ), each with 5mol% ANQ. Number-average molecular weights and thermal decomposition temperatures of S-P(PBP-co-ANQ)s were about 50-70 kg mol-1 and 220°C, which were sufficient for polymer electrolyte fuel cell (PEFC) applications. S-P(PBP-eo-1,5ANQ) membranes showed higher dimensional stability and proton conductivity than S-P(PBP-co-1,4ANQ) and S-PPBP membranes. The maximum current densities and power densities of S-P(PBP-co-1,5ANQ) fuel cells were 2200 mA cm-1 and 80°C and 100% relative humidity. These results suggest that the improvement of dimensional stability and electrochemical properties is due to strong aggregation of the copolymer chains induced by ANQ at an appropriate coupling position. [ABSTRACT FROM AUTHOR]