| Summary: | 碩士 === 國立海洋大學 === 食品科學系 === 90 === The objectives of this study are to explore the effect of degree of deacetylation (DD), molecular weight (MW) of chitosan, concentration of NaCl on their liquid crystal properties. The study includes the preparation of chitosan samples with various degrees of deacetylation from β-chitin that was purified from squid pens. Those chitosan samples will then be degraded with ultrasonic radiation to different molecular weights. The degree of deacetylation and molecular weight of chitosan samples were determined by IR and size-exclusion high performance liquid chromatography, respectively. The critical concentrations of chitosan to form liquid crystal were observed by polarized microscope. The concentration at which liquid crystal phase occurred was defined as the critical concentration. The results are as follows: The DD of chitin was 20.67%. After deacetylation, the DD of chitosan were 67.2%, 73.34%, 76.20% and 83.60%, for samples treated with 95℃ alkaline solution for 1hr, 2hr, 3hr and 110℃ for 3hr, respectively. The DDs of chitosan increased with increasing reaction time. The DDs of chitosan increased rapidly at the beginning of deacetylation reaction then the deacetylation rate slowed down. Chitosan was degraded by ultrasonic radiation to different molecular weights. The MW of chitosan decreased with increasing ultrasonic time The MW of chitosans decreased rapidly at the beginning of ultrasonication then the degradation rate slowed down. The specific viscosity of chitosan solution increased with increasing chitosan concentration, the DD of chitosan, and the MW of chitosan. On the contrary it increased with decreasing pH and ionic strength of chitosan solution.The intrinsic viscosity of chitosan showed similar dependence on these variables. The Mark-Houwink exponents decreased with increasing ionic strength of chitosan solution. Persistence length decreased with increasing DD and ionic strength, but it decreased with decreasing MW. All of the chitosan samples formed cholesterol lyotropic liquid crystal when they were dissolved in 1.85M malic acid. The critical concentrations of chitosan increased with increasing DD, but it decreased with increasing MW and increasing concentration of NaCl or malic acid. Chitosan liquid crystal samples were loaded with 100 mg erythromycin. The chitosan liquid crystal released 25 mg erythromycin after 4 hr in alcohol. Only 80 μg of erythromycin released from the liquid crystal sample through a polycarbonate membrane mounted in a diffusion cell. The amount of erythromycin released decreased with increasing chitosan concentration and increasing ionic strength of chitosan solution.
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