Preparation, Complexation And Performance Studies Of Cellulose-based Molecular Brush

Cellulose is the most abundant and biomacromolar polysaccharide in nature.Celluose and its derivatives have excellent biodegradability and biocompatibleproperties with tissue and cell in living beings. It is a biological resource waiting tobe exploited.The research contents of the dissertation were as follows：(1) Two comb polymers were synthesized by the ATRP and ROP method. EthylCellulose-g-Poly Caprolactone-g-Poly Dimethyl amine ethyl methacrylate(EC-g-PCL-g-PDMAEMA) was pH and temperature dual sensitive polymer.Ethyl Cellulose-g-Poly Acrylate (EC-g-PAA) was pH sensitive one. The twocomb polymers were characterized by FT-IR and~1H NMR.(2) The self-assembling behavior and pH sensitivity of the EC-g-PAA were studiedby Surface Tention、DLS and TEM. Reaults showed that surface tentiondecreased sharply at low concentration. The plateau of surface tension meantthat intramolecular aggregation was formed in the aqueous solution in the rangeof concentration from0.2wt%to0.5wt%. The microstructure of aggregationwas the loose dendritic struture. When the concentration exceeded0.5wt%，thepolymer chain aggregated into the compact dendritic structure with thedecreasing surface tension. The diameter of micelle with core-shell structurebecame small when pH of the solution was less than2.96，which was the pHvalue of mother solution. Below this pH, the solution became opaque. As pHchanged from2.96to12.60，the diameter of micelle increased and thenmaintained a constant followed by a decrease in diameter. Rsults of staticrheology test of EC-g-PAA solution showed that the solution was a Newtonionfluid in the whole range of concentration.(3) The complex system of EC-g-PAANa and C12TAB was studied by surfacetention、DLS and TEM. The critical aggregation concentration (CAC) of thesystem was0.8mM. Below the CAC，the surfactant binded to the comb polymerby electrostatic interaction，which weakened the electrostatic repulsion betweenthe grafted chain. As a result, slight decrease in the diameter occured. Thediameter exhibited an increase when the concentration of surfactant reached the CAC. This was ascribed that polymer/surfactant complexation was formed bythe micellization of electrostatically bound surfactant molecules at the polymerchains. As the C12TAB was added，the micelle self-reorganized from lamellarstack to a spherical structure. Hence the diameter decreased. The solutionbecame opaque from transparent，then gelled in the whole process. The resultsfrom the TEM were in accordance with the ones from DLS.