Neutral protease was immobilized on glutaraldehyde-pretreated N-succinyl chitosan hydrogel beads and the biocatalyst obtained was used for the preparation of low molecular weight chitosan and chito-oligomers with molecular weight of 1.9-23.5 kDa from commercial chitosan. Factors affecting the chitinolytic hydrolysis were described. The degradation was monitored by gel permeation chromatography. The structure of degraded chitosan was characterized by Fourier transform infrared, X-ray diffraction and liquid chromatography-mass spectrometry. Immobilized neutral protease showed optimal depolymerization at pH 5.7 and 508C. The degree of deacetylation of the hydrolysates did not change compared to that of the initial chitosan. The decrease of molecular weight led to transformation of crystal structure but the chemical structures of residues were not modified. The degree of polymerization of chito-oligomers was mainly from 3 to 8. The method allows cyclic procedures of immobilized enzyme and N-succinyl chitosan support utilization, and is suitable for a large-scale production of the low molecular weight chitosan and chito-oligomers free of protein admixtures.

This study demonstrates the surface modification of carbon fiber by grafting polyglycidyl methacrylate (PGMA) using atom transfer radical polymerization (ATRP). Firstly, the surface of carbon fiber was modified by using 3-aminopropyltriethoxysilane and 2-bromoisobutyryl bromide to immobilize ATRP initiators on the surface. Then the glycidyl methacrylate was initiated and propagated on the carbon fiber surface by ATRP. Characterization of these modified carbon fibers included Fourier transform infrared (FT-IR), Thermal gravimetric analysis (TGA) and 1H nuclear magnetic resonance (NMR). The results indicated that the grafting of PGMA from the carbon fiber surface was successful.

The functionalized TiO2 with poly(methyl methacrylate) (TiO2-PMMA) was prepared by atom transfer radical polymerization (ATRP), and its reinforcement for epoxy composites was studied. The functionalized TiO2 was characterized by Fourier transform infrared (FT-IR), Thermal gravimetric analysis (TGA) and 1H nuclear magnetic resonance (NMR). The properties of nanocomposites were measured by impact testing, bending experiment and Scanning electron microscopy (SEM). Because of the grafting of PMMA and the higher interaction between TiO2-PMMA and epoxy matrix, the composites exhibited the enhancement of mechanical properties at lower content. As the functionalized TiO2 content is 0.5 wt%, the impact strength and bending strength of composite increased nearly 142% and 37%, respectively, compared to the neat epoxy resin.