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Preparation and Self-assembly Behavior in Aqueous Solution of Thermosensitive Polymer Based on Hydroxyethyl Cellulose

Author: SongXiaoQing
Tutor: YangCheng；LiuXiaoYa
School: Jiangnan University
Course: Applied Chemistry
Keywords: Hydroxyethyl cellulose Poly - N- isopropyl acrylamide Polymeric micelles Thermosensitive Full hydrophilic
CLC: R318.08
Type: Master's thesis
Year: 2006
Downloads: 207
Quote: 0
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Abstract


In recent years, polymer micelles due to its low critical micelle concentration, circulating in the blood for a long time and maintain stability, biocompatibility characteristics, are widely used in biomedical fields. The amphiphilic copolymer may be formed in an aqueous solution having a hydrophobic the kernel - hydrophilic shell structure nano-sized micelles. But because of the organic solvent is usually not necessary to introduce the hydrophobic chain, and prepared early is biocompatible, so it is difficult to meet the requirements of the biomedical field. Biotechnology development makes polymer micelles following new trends and requirements: (1) The hydrophilic - prepared by full-hydrophilic copolymer micelles is using some of its segment's sensitivity to environmental stimuli under corresponding conditions make it change the dissolution properties in water and thus do not need to introduction of organic solvent can be prepared in the whole hydrophilic environment micelles; (2) the stimuli-responsive - refers to a polymer micelle structure, physical properties, chemical properties change with the changes in the external environment (stimulatory signals, such as pH, temperature, ionic strength, light, electricity), which embodies the smart nanoparticles; (3) biocompatibility - applications in the biomedical field The materials must be biocompatible. New trend above the field of self-assembly of experimental new design, selection of a biocompatible and source a wide range of water-soluble cellulose ether, hydroxyethyl cellulose (HEC) and N-isopropyl acrylamide ( NIPAAm) monomer copolymerizable obtain Thermosensitivity wholly hydrophilic block / graft copolymer, obtained by changing the temperature range of nanoparticles micelles. Specifically mainly carried out the following tasks: (1) using mercaptoethylamine as chain transfer agent to obtain a prepolymer PNIPAAm-NH2. With HEC as starting materials, to NaCNBH3 as a reducing agent in a DMF solvent in the Maillard reaction with the PNIPAAm-NH2 prepolymer creatively synthesized wholly hydrophilic block copolymer based on the HEC HEC-b-PNIPAAm . FTIR and NMR confirmed the structure of the block copolymer. The GPC and SLS test the molecular weight of the HEC and the block copolymer. (2) found that the temperature of the aqueous solution of HEC-b-PNIPAAm response micellar behavior, when the temperature is higher than the LCST of the block copolymer, and the solution may be formed in a radius of 400 ~ 600nm large aggregates. UV, DSC measured copolymers the LCST approximately 32 ° C. Micelles using the fluorescent probe technique and surface tension method test the critical micelle concentration (CMC). DLS and SLS combined to study the behavior of copolymer micelles in water system. Examine solution concentration, holding time micellization behavior, the results showed that when the temperature is higher than the LCST of the block copolymer, the higher the concentration, the the thermostatic longer easy to form the large size of the multi-molecular micelles. Micelle morphology was observed by TEM, and found that the micelles are formed at 38 ℃ nanometer size \PNIPAAm segment in 50% methanol / 50? Mm NaCl aqueous system, poor solubility, at room temperature, the block copolymer can in this mixed solvent to form micelles. The starting material (3) HEC HEC macromolecular chain hydroxy carbon active sites, ceric ammonium nitrate / nitrate (CAN/HNO3), Catalytic triggered NIPAAm graft copolymer obtained based on the full HEC hydrophilic The graft copolymer of HEC-g-PNIPAAm. By FTIR, 1H-NMR confirmed the copolymer structure; obtained copolymer and enzymatic degradation was measured by GPC, the molecular weight of the the PNIPAAm branched chain. By DSC, fluorescence probe techniques, surface tension and DLS study copolymer aqueous solution of temperature-sensitive micellization behavior.

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CLC: > Medicine, health > Basic Medical > Medical science in general > Biomedical Engineering > General issues > Biomaterial
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