Preparation of alkyl substituted cationic starch-oligomers and their applications as skin moisturizing agent

Abstract

This study was about the development of new synthetic moisturizing material using the starch. Starch has many advantages economically and environmentally, but it is not proper to use the raw starch directly as the moisturizing ingredients, as it consists of amylopectin (80~100%) and amylose (0~20%) showed the low water-solubility by high molecular weight over $10^6$ and cross-linking structure. Therefore, the chemical modification such as Mw control, cationic substitution and alkyl ($C_{12~18}$) cationic substitution was performed to improve the adsorption ability on skin, film rigidity after drying, feeling in skin, water absorption ability and moisture blocking ability. In the synthesis of chapter 2, various cationic modified products were synthesized according to molecular weight (Mw 4,000, Mw 3.6x$10^4$, Mw 7.1x$10^4$ and Mw > $10^6$) and length of alkyl chain ($C_1, C_12, C_14, C_16 and C_18$). The reaction yield of GTMAC substitution ($C_1$ substitution; cationic starches without alkyl chains) was nearly 100%, but those of alkyl cationic intermediate ($C_{12~18}$) decreased generally from 80% to 40% with increasing the length of alkyl chain owing to the steric hindrance of aggregations of alkyl cationic reaction intermediate. In physical properties of synthetic products, the alkyl cationic substituted starches showed the similar properties with cationic surfactants. The results of CMC, particle size analysis by DLS and EF-TEM indicated that they were able to make any aggregation like micelle. In addition, they had sufficient adsorption ability to attach on an anionic surface such as skin, hair, and clothes at a low grafting rate (DS 2.2mol%), according to the results of zeta-potential measurements. In chapter 3, QCM-D was measured in order to investigate the detailed adsorption behaviors such as adsorbed amounts, the thickness, density and visco-elasticity of adsorbed layers about the synthetic products, because these factors were related to the mo...