Synthesis of Biodegradable Thermo/pH-Sensitive Core-Shell Copolymer in Supercritical CO2
Date Issued
2009
Date
2009
Author(s)
Chen, Chi-Ching
Abstract
The supercritical carbon dioxide is applied in this research to synthesize the temperature/pH value sensitive biodegradable core-shell smart copolymer materials. Supercritical fluid technology has the advantages of reducing significantly the amount of solvent in traditional process. It can also avoid the oxidation of initiators, and simplify the following separation steps. The dry products can be obtained after depressurization and the desired smart copolymer material is used for the controlled release of drugs, or the phase separation for protein recovery. In this study, poly[(2-(2-methoxyethoxy)ethyl methacrylate)-co-(oligo(ethylene glycol) methacrylate)] [P(MEO2MA-co-OEGMA)] with great temperature-sensitive properties was synthesized by polymerization reaction in the medium of supercritical carbon dioxide (scCO2). Its LCST (lower critical solution temperature) value was changed by adjusting the compositions of monomers. Furthermore, the copolymers with fine temperature- and pH-sensitive properties have been obtained through the single step supercritical carbon dioxide chemical reaction process for the polymerization of temperature-sensitive material and cross-linking with the [(polydimethylsiloxane)-graft-(polyacrylate)] (PDMS-g-PAA). The particles transform between swelling and shrinking with the temperature and pH value limits of 35℃and 7, respectively. The core-shell structure was observed by TEM images. The characteristics of the products were examined using UV, FTIR, TGA, SEM, and swelling ratio analysis. The optimal process parameters in the synthesis of smart core-shell copolymers were reported in this study. The particles with great pH/T-sensitive properties, smaller average particle size and size distribution were obtained at the following operating condition: T=100℃, P=300bar, Reaction Time=4hr, Reactants composition=60wt% PDMS-g-PAA. From SEM images and the analysis of image J software, we observed the morphology of original PDMS-g-PAA particle was amorphous with an approximately particle size = 11μm . After reaction process, the grafted copolymer particle became globular shape. The particle size was reduced to 0.15μm.
Subjects
supercritical carbon dioxide
pH-sensitive
temperature-sensitive
hydrogel
core-shell
smart material
LCST
Type
thesis
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