以Ca Cl2为交联剂制备NOCC/海藻酸钠混合水凝胶,研究NOCC与SAL质量比、Ca Cl2含量、交联p H值和NOCC取代度对水凝胶在p H 1.2、6.8和7.4溶液中溶胀性的影响,同时研究了NOCC取代度对NOCC∕SAL水凝胶质构性能的影响。试验结果表明,NOCC与SAL按1:3的质量比混合,保持总固形物含量为2%,Ca Cl2含量为1%、交联p H值为7时形成的水凝胶在p H 1.2溶液中溶胀率较小,而在p H 6.8溶液中的溶胀率最大。NOCC取代度对水凝胶的溶胀性和质构性能有显著影响,水凝胶在p H 6.8和p H 7.4溶液中的溶胀率均随着取代度的增加而增大,且在p H 6.8溶液中的溶胀率大于在p H 7.4中的溶胀率。取代度为1.1的NOCC/SAL水凝胶硬度最大。 相似文献
采用氯乙酸法制备不同取代度的O-羧甲基壳聚糖(OCC),将其与海藻酸钠(SAL)混合后滴入Ca Cl2溶液中制备微球,系统研究OCC与SAL配比、Ca Cl2溶液质量浓度、Ca Cl2溶液p H值和交联温度对微球在p H 1.2、p H 6.8和p H 7.4溶液中溶胀率的影响,并就OCC取代度对OCC/SAL微球在上述溶液中的溶胀性影响进行探讨。试验结果表明,将OCC与SAL以质量比1∶3混合,保持总质量浓度20 mg/m L,60℃条件下在p H 7的20 mg/m L Ca Cl2溶液中固化0.5 h,室温下固化1.5 h后所得微球在p H 1.2溶液中溶胀率较小,在p H 7.4溶液中溶胀率较大。OCC取代度对微球的溶胀特性有重要影响,在上述反应条件下所得微球在p H 1.2溶液中的溶胀率随着OCC取代度的增大而减小,而在p H 6.8和7.4溶液中的溶胀率随着取代度的增大而增大。此外,OCC的取代度对微球的机械强度和稳定性也有重要影响。 相似文献
O-羧甲基壳聚糖(OCC)与海藻酸钠(SAL)形成的水凝胶微球,在肠道靶向传输过程中具有很大的应用潜力。将不同的OCC与SAL混合后滴入Ca Cl2溶液中制备微球,研究OCC黏均分子质量对OCC/SAL微球在p H 1.2,p H 6.8和p H 7.4溶液中溶胀性的影响。采用扫描电子显微镜分析微球的微观结构。结果表明:OCC黏均分子质量对OCC/SAL微球在p H 1.2溶液中的溶胀性和稳定性无显著影响,而对其在p H 6.8和p H 7.4溶液中的溶胀差异、稳定性和微观结构有重要影响,并且该影响与OCC的取代度有密切关系。当OCC取代度为0.9时,OCC的黏均分子质量对OCC/SAL水凝胶微球在不同p H条件下的溶胀性能均无显著影响,而显著影响水凝胶的稳定性。OCC的黏均分子质量越小,水凝胶在中性及弱碱性条件下的稳定性越差。当OCC取代度为0.83时微球的稳定性也有相似的变化规律,而对其在p H 6.8和p H 7.4溶液中的溶胀性有显著影响,即溶胀率随着黏均分子质量的增加而降低。当取代度为0.53时,OCC/SAL微球在p H 6.8和p H 7.4溶液中的溶胀率随着OCC黏均分子质量的增加而增加,且高黏均分子质量OCC/SAL水凝胶微球在p H 6.8和p H 7.4溶液中均未被观察到裂解,而低分子质量OCC与SAL形成的微球在p H 6.8和p H 7.4溶液中均发生了裂解。扫描电子显微镜分析表明,OCC的黏均分子质量越大,微球表面的凸起越明显,而且聚集很多纳米级的小微球。 相似文献
Starch has been used over several millennia for a number of different applications. However, research on understanding this substance only spans about three centuries starting with Leeuwenhoek who observed it in 1716. This story of discovery of the molecular structure and architectural makeup of starch is chronicled in a series of six essays of which this is the third with a focus on contemporary terminologies used in the 19th and early 20th centuries and its impact on advances in starch. Following the discovery of diastase, researchers focused on understanding the action of diastase on “transforming” starch into sugar. Besides maltose, they found that the products consisted of a range of dextrins with different abilities to complex with iodine. However, the nomenclature of the products that were obtained under a myriad of experimental conditions gave rise to confusions and misinterpretations, which transpired for over 30 years. Researchers also attempted to understand starch structure through systematic analyses of the different stages of starch breakdown. A new era of confusion in both nomenclature and structural interpretation started in the early 20th century with the discovery of cyclodextrins that were obtained from starch using the microorganism B. macerans. This gave rise to the school of “the low molecular elementary unit hypothesis” for starch structure, which lasted for about 25 years.