冷冻对甲壳素固体结构的影响

Effect of alkali-freezing treatment on the solid state structure of chitin

甲壳素和质量浓度45%的NaOH溶液按料液比1∶10充分混匀,分别在-18℃和-35℃下冷冻处理,研究碱-冷冻处理对甲壳素凝聚态结构的影响。采用酸碱滴定法测定样品的脱乙酰度,X-射线衍射、红外光谱和差示扫描量热分析研究经冷冻后样品聚集态结构的变化情况。结构分析结果表明,慢速冷冻过程中,冰晶的形成和生长能够破坏分子内/分子间氢键相互作用,使有序的分子结构紊乱,破坏致密的晶体结构,使甲壳素结晶度下降。但是这种结晶结构的破坏作用是不稳定的、可逆的。尽管如此,碱-冷冻处理仍可以作为一种有效的甲壳素化学修饰前处理手段,能够明显加快反应速率而不影响甲壳素分子链主体结构。

The effects of alkali-freezing treatment on the condensed state structure of chitin were explored.Chitin powder was soaked in concentrated sodium hydroxide（with a mass concentration of 45%, and the ratio of chitin and NaOH solution was 1：10, W/V）and freezed at -18℃ and -35℃ for further modification. The degree of deacetylation （DDA） was determined by acid- base titration method.X- ray diffraction （ XR D）, infrared spectroscopy （IR） and differential scanning calorimetry（DSC） measurements were employed to investigate the condensed state structural changes of the freezing-treated chitin powders.Structural analysis results showed that the formation and growth of ice crystal during the slowly freezing process that can break the intra-and/or inter-molecular hydrogen bonds interaction, disorder the ordered molecular structure and destruct the compact crystal structure and decline the crystallinity of chitin.The study explained that the alkali-freezing treatment was beneficial for further modification of chitin, which can increase the chemical reaction rate and keep the main molecular chain structure of chitin completely.