【摘要】 甲壳素具有许多独特的性质,但不能溶于常规溶剂,极大地限制了其广泛应用,提高其溶解性成为迫切需要解决的问题。对甲壳素和浓NaOH混合物进行反复冻融处理,慢速冷冻/低温解冻的冻融循环处理过程中冰晶的反复形成和重结晶作用,能够破坏甲壳素凝聚态特别是晶态结构,促使甲壳素溶于一定浓度的NaOH溶液中。探讨了冻融次数、冷冻温度、NaOH浓度和甲壳素与溶剂的比例分别对溶解性的影响。结果表明,-18℃、40%NaOH(甲壳素∶水=1∶4,W/V)经过3次冻融循环处理,可以形成均一、透明的甲壳素均相溶液,甲壳素终浓度约为4%,NaOH终浓度约为10%,为用均相脱乙酰法制备半脱乙酰水溶性甲壳素提供前提。结果表明,冻融循环处理能显著降低甲壳素分子内和分子间强氢键相互作用,破坏甲壳素分子致密的晶体结构,使分子结构紊乱,从而为制备水溶性甲壳素提供了可能。更多还原

【Abstract】 Due to the special chemical structure,chitin had many unique properties.However,it was insoluble in water,diluted acid,alkaline solution and common organic solvents.This was the major problem that confronted the application of chitin,hence it was an urgent need to resolve how to improve the poor solubility of chitin.This paper explored the effects of freezing-thawing cyclic( FTC) treatment on the solubility in alkaline solution and condensed state structure of chitin. The mixture of chitin and concentrated NaOH solutions was freezed and thawed, repeatedly.With slowly freezing and low temperature thawing cycle process that could destruct the condensed matter especially the crystalline state structure more thoroughly,because of the ice crystals’repeatedly formed and recrystallizated.Therefore,chitin could dissolve in a certain concentration diluted NaOH after some times of FTC treatment.Effects of FTC times,freezing temperature,NaOH concentration and the ratio of chitin and water on the solubility of chitin were investigated.The results showed that via three times of FTC treatment at-18℃ with NaOH concentration of 40%( the ratio of chitin and water was 1∶4,W/V) ,chitin could be completely dissolved in NaOH aqueous solution and formed a limpidity homogeneous solution with a chitin concentration about 4%( W/W) and a final NaOH concentration of approximately 10% ( W/W) ,which was possible to prepare partial N-deacetylated water-soluble-chitin.The results indicated that the formation and growth of ice crystal in the slowly freezing process could break the intra-and /or inter-molecular hydrogen bonds interaction,and destruct the compact crystal structure and decline the crystallinity of chitin,it could also disorder the ordered molecular structure,which might be used to prepare water-soluble-chitin.更多还原