Poly(N-isopropylacrylamide) Related Thermoresponsive Copolymer Microgels: Preparation, Properties, and Application
Date Issued
2005
Date
2005
Author(s)
Lin, Chia-Lung
DOI
en-US
Abstract
This research was divided into three parts to study the preparation, properties, and application of poly(N-isopropylacrylamide) related thermoresponsive copolymer microgels.
In the first, the thermoresponsive copolymer latex particles with the average diameter of about 200~500nm were prepared via surfactant-free emulsion polymerization. The effects of co-monomers and composition on the synthesis mechanism, kinetics, particle size, morphology, and thermoresponsive properties of the copolymer latex were first studied to realize the relationship between the synthesis condition, the particle morphology and the thermoresponsive properties successfully. The LCST of the latex copolymerized with AA monomers was raised to higher temperature, the LCST of the latex copolymerized with SA monomers was not changed. A proposed model with a few adjustable model parameters, which first considered the contributions of mixing, elasticity and electrostatic effect, was established to represent swelling behavior of the poly(NIPAAm) homopolymer and poly(NIPAAm-co-AA) copolymer microgels. A good agreement between the experimental data and our proposed model was obtained. The polymerization of pyrrole in presence of poly(NIPAAm-co-AA) microgels resulted in a novel composite microgels filled with conducting polypyrrole inclusions. Such smart composite microgels exhibited temperature and humidity dependent electrical conductivity. And its structure was reorganized after the treatment of high temperature and humidity that resulted in an increase of conductivity.
Secondarily, a stable ferrofluid containing Fe3O4 nanoparticles was synthesized via co-precipitation method in the presence of poly(acrylic acid) oligomer. The mechanism, microstructure and properties of the ferrofluid were investigated. This ferrofluid showed superparamagnetic property and could be dispersed in monomer solution stably by adjusting the pH value of solution. Then thermal-responsive poly(NIPAm-co-MAA) copolymer networks containing Fe3O4 nanoparticles was synthesized in the presence of ferrofluid. The effects of the mole ratio of MAA/NIPAAm, the concentrations of monomers and crosslinking agent, the addition of ammonium solution and the content of ferrofluid were discussed. The swelling and thermo-responsive behaviors of the complex polymer networks were also studied, and the composition-morphology-property relationship was established. As soon as this thermoresponsive magnetic hydrogel was prepared and characterized successfully, the thermoresponsive magnetic microgels were prepared in situ by using “W/O miniemulsion polymerization” since the monomer droplets with magnetic nanoparticles acted as ‘‘nanoreactors’’ in this process. This polymerization was proceeded in cyclohexane at room temperature with span80 as the emulsifier, and APS / SMBS were used as redox initiator system. Fe3O4 nanoparticles were homogeneously encapsulated inside the poly(NIPAAM-co-MAA) latex particles. The properties of the composite latex were examined by using DSC, TGA and FTIR. Finally, the superparamagnetic and thermoresponsive characteristics of this functional composite latex were also investigated.
Finally, the synthesis, properties, and application of a thermal-sensitive core-shell copolymer latex were studied, where the crosslinked copolymer of N-isopropylacrylamide (NIPAAm) and chitosan was prepared as the core, and the copolymer of methacrylic acid (MAA) and methyl methacrylate (MMA) was prepared as the shell. The core-shell copolymer latex was synthesized by soapless dispersion polymerization. The weight ratio of chitosan/NIPAAm and the concentration of crosslinking agent or the weight ratio of MAA/MMA and the concentration of shell monomers (MAA and MMA) in feed had been changed to investigate their effects on the particle size, reaction rate, zeta-potential, surface functional groups, and specific surface area of latex particles. The swelling and thermo-sensitive behavior of the film made from these core-shell latexes were also studied under different pH values of buffer solution. A series of experiments on the application of this latex on drug release were performed, and the potential of the latex being applied on targeting drug carrier was evaluated.
Subjects
氮-異丙基丙烯醯胺
溫度感應性
微膠體
導電度
核殼型態
磁性流體
超順磁性
複合乳膠顆粒
藥物釋放
無乳化劑乳化聚合
水/油 迷你乳化聚合
N-isopropylacrylamide
thermoresponsive property
microgel
electrical conductivity
core-shell morphology
ferrofluid
superparamagnetic
composite latex
drug release
surfactant-free emulsion polymerization
W/O miniemulsion polymerization
Type
thesis