Study On Hydrophobic Modification Of Sodium Carboxymethyl Cellulose And Ph-Sensitive Hydrogel

Carboxymethyl cellulose (CMC) is a natural polymeric derivatives with ether struct obtained from cellulosic chemical modification and whose macromolecular chain contains amounts of carboxyl and hydroxyl groups with a certain reactivity.Sodium carboxymethyl cellulose (CMC-Na)esterify with long-chain molecules are more difficult than short-chain molecules , and the degree of esterification is lower . A hydrophobically modified CMC-Na(Ln-CMC-Na) with high degree of esterification was carried out by long-chain chlorides in a new solvent.Firstly,n-C18 acyl chloride was prepeard through C18 acyl acid and thionyl chloride in n-heptane medium under the optimal reaction conditions;and then use it as a reaction raw material to react with CMC-Na in n-heptane medium to get hydrophobically modified CMC-Na.The optimal reaction condition was established according to the discussion of sodium carboxymethyl cellulose'concentration in the solvent,the ratio of reactants,reaction temperature and time.The degree of esterification of the product can reach 0.6.With the same reaction conditions,the hydrophobic modified water-soluble products Ln-CMC-Na were prepared by esterifying agents of n-C10, n-C12,n-C14,n-C16 and n-C18 acyl chloride under the molar ratio of 0.08: 1 of esterifying agents to CMC-Na.The surface active properties of the Ln-CMC-Na, such as HLB value, surface tension and critical micelle concentration, were determined respectively. Having taken eight metal salts as crosslinker, pH-sensitive hydrogels were formed by Ln-CMC-Na solution with AlCl₃ or Fe(NO3)₃·9H₂O, which can changes between solid and liqurd phase as pH value. The hydrogels were characterized by FTIR and its crosslinking mechanism was put forward.