季铵盐改性壳聚糖原位调控碳酸钙合成

Calcium carbonate is a kind of important biomineral, and is also a kind of important papermaking filler. Firstly, the chitosan is modified by 2,3-epoxypropyltrimethyl ammonium chloride, and several influencing factors such as the material proportion, temperature, reaction time and reaction media on the reaction sites and grafting rate, as well as the physicochemical properties of modified chitosan are investigated. Then, the modified chitosan is used to in-situ modulate the crystallization of calcium carbonate, based on the electrostatic interaction between HCO3- and quaternary ammonium ion and the arrangement of HCO3- along the modified chitosan molecules. The calcium carbonate is crystallized by the decomposition of calcium bicarbonate following the method of biomineralization, and characterized by different methods. The influence of modified chitosan concentration, Ca(HCO3)2 concentration, temperature, pH and other factors on the morphology, aspect ratio and particle size distribution of calcium carbonate, and the amount of modified chitosan that coated in calcium carbonate are investigated. The modulation mechanism of the modified chitosan on calcium carbonate is proposed, based on the aqueous properties of modified chitosan and the structural characteristic of the crystallized calcium carbonate. The calcium carbonate with different morphology, aspect ratio, size distribution and amount of modified chitosan is used as paper filler, the filling amount and the paper properties are comparatively studied, which will provide theoretical foundation for the application of calcium carbonate.

碳酸钙是一种重要的生物矿物，也是一种重要的造纸填料。本文拟以2,3-环氧丙基三甲基氯化铵对壳聚糖改性，得到季铵盐改性壳聚糖，考察反应物物料比、反应温度、时间、不同介质等因素对反应位点、接枝率以及改性壳聚糖物理化学性质的影响。其次，利用HCO3-与季铵根离子因静电作用沿改性壳聚糖分子链排布的特点，采用模拟生物矿化法以改性壳聚糖原位调控Ca(HCO3)2分解制备碳酸钙，考察不同改性壳聚糖浓度、Ca(HCO3)2浓度、温度、pH等因素对碳酸钙的形貌、长径比、粒径分布、包覆改性壳聚糖的量等性质的影响，并以多种方法表征碳酸钙。结合改性壳聚糖的水溶液性质和碳酸钙的结构特征，揭示改性壳聚糖调控碳酸钙的机理。将制得的碳酸钙用作造纸填料，初步考察其形貌、长径比、粒径分布等因素对加填性能和对纸品性质的影响，研究其影响规律，为拓展碳酸钙在造纸中的应用提供科学数据。

碳酸钙是一种重要的生物矿物，其形成过程中在生物体内有机物的调控下形成特定结构，具有非常强的力学性质，受此启发，人们投入大量精力探究碳酸钙生物矿化的基本原理，以期制备理想的功能化材料。壳聚糖是甲壳素的水解产物，含量丰富，但是其水难溶性限制了更广阔的应用。. 本项目首先将壳聚糖溶解于AmimCl等多种离子液体，以2,3-环氧丙基三甲基氯化铵通过均相反应对其改性，得到水溶性良好的N-取代壳聚糖季铵盐(HTCC)；发现温度80oC、溶解时间4h、反应时间8h、环氧基团与-NH2物料比3/1、壳聚糖经过稀盐酸预处理后，取代反应发生在-NH2、取代度最大。通过改变改性壳聚糖浓度、[Ca2+]、[Mg2+]、温度、陈化时间等因素可以调控出六面体状、束状、六边形盘状、棒状等形貌的碳酸钙晶体。对比研究了羟丙基壳聚糖和2,3-环氧丙基三甲基氯化铵改性明胶调控碳酸钙结晶行为。与商用碳酸钙相比调控碳酸钙的造纸加填性明显增加，对纸品的性质也有明显的正影响。. 通过体相流变、AFM、SEM等方法研究了HTCC水溶液性质，发现HTCC水溶液的弹性远大于粘性、而且粘弹性随剪切频率变化不大，呈现弱凝胶的性质；表观粘度随剪切速率增大而减小。HTCC溶液的表观粘度和粘弹性基本不受温度影响；但是受取代度和无机盐的种类和价态影响显著。HTCC通过静电屏蔽、交联等作用方式影响羧甲基纤维素钠溶液的表观粘度和粘弹性；显著提高羧甲基纤维素钠膜的力学性质(拉伸强度断裂伸长率)、热稳定性、杀菌抑菌性，降低膜的玻璃化转变温度，这说明HTCC在纤维素基食品药品包装膜的制备中有潜在的应用价值。