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Preparation and Functionalization of Complex Microgels and Nanocomposite Hydrogels

Author: HuXiaoBo
Tutor: TongZhen
School: South China University of Technology
Course: Polymer Chemistry and Physics
Keywords: Precipitation polymerization Response Biodegradable microgel Core - shell microgel Nanocomposite Hydrogels Super- stretch
CLC: O631.3
Type: PhD thesis
Year: 2011
Downloads: 412
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Abstract

The hydrogel material as with most biological tissues contain large amounts of water, has the potential of good biocompatibility, which has great application value in biomedical been extensively studied. The main purpose of this work is to create a the response complex structure microgel and Nanocomposite Hydrogels (nanocomposite hydrogels, NC gel) was prepared. The basic idea of ??the research is to first select the appropriate system the microgel preparation of non-self-crosslinked network chemical decomposition, response to micro-and multi-step precipitation polymerization method Multi-responsive core-shell separation decline gel contains nanoparticles capsules. Furthermore, by controlling the preparation process of the microgel electrostatic interaction of the primary amine of microgel and research with anionic the microgel assembled into a micro-gel film with healing properties. Finally, by controlling the process conditions and select suitable ionic monomers with N-isopropyl acrylamide (NIPAM) in the dispersion, Laponite in situ copolymerization, was prepared having the super drawing environmental response transparent NC gel. The main content of the work and the results are as follows: using ammonium persulfate / tetramethylethylenediamine (APS / TEMED) redox initiators or UV irradiation of 2,2 '- azobis isobutyl amidine dihydrochloride salt (V50) at 37 ° C and 45 ° C caused by precipitation polymerization, poly-N-isopropyl acrylamide (PNIPAM) microgel. Photon correlation spectroscopy (PCS) and atomic force microscopy (AFM) studies have shown that the resulting PNIPAM microgel particle size distribution is relatively narrow, and all MICROGELS volume phase transition temperature (VPTT) at 32 ° C or so. In addition, the APS / TEMED initiator system can prevent the formation of self-crosslinking network, and thus the use of biodegradable crosslinking agent N, N'-(1,2 - dihydroxy-vinyl)-bis-acrylamide (DHEA) prepared microgel NaIO4 completely decomposed. We also use the one-pot at 45 ℃ for successful protein avidin copolymer into PNIPAM micro-gel. 2 by precipitation poly the legitimate first introduced on the poly (N-isopropyl methacrylamide) (pNIPMAm) microgel nuclear the DHEA crosslinked pNIPMAm shell. Subsequently, the resulting core-shell microgel shell of poly (N-isopropyl acrylamide-co-acrylic acid) (PNIPAm--AAc) seeds, the introduction of the crosslinked by N, N'-methylene-bis-acrylamide (BIS) , the formation of \CDS microgel DHEA cross-linked pNIPMAm shell after NaIO4 decomposition of the formation of the CDS-D microgel. CDS-D microgel intuitive display in the AFM height map of the surface of the glass after drying and phase diagram of PNIPAM-AAC the shell losing support of pNIPMAm shell becomes very flat. CDS and the CDS-D micro-gel solution fluorescence absorption intensity differences also confirmed the pNIPMAm shell is completely degraded. The microgel particle diameter in a different pH buffer solution and the light scattering intensity variation with temperature is further illustrated the successful preparation of the the multiple response nucleocapsid separation decline gel. 3 Use a pot of precipitation polymerization of the PNIPAM / pNIPMAm core-shell microgel. The variation with temperature, the particle diameter and the intensity of light scattering showed that the resulting core-shell microgel having a dual temperature-responsive. Subsequent use of the APS / TEMED initiator triggered NIPAm polymerization to form a narrow particle size distribution pNIPAm particle dispersion in the absence of cross-linking agent, the introduction of BIS cross-linked pNIPMAm and the proceeds pNIPAm particle seeds in situ to form a core-shell microgel . The PNIPAM particles nuclear dissolved into the polymer chain reaches room temperature, and spread to the solution through pNIPMAm shell. The microgel solution of light scattering intensity at 35 ° C after gradual increase that still left a small amount of gel PNIPAM chain formed is the half hollow pNIPMAm of microcapsules. The AFM height diagram illustrates the temperature rose to 40 ° C. Nuclear within the PNIPAM gathered in swelling state pNIPMAm, into a large number of nanoparticles, formed contains a large number of PNIPAM nanoparticles pNIPMAm microcapsules. 4 to NIPMAm and N-(3 - aminopropyl) methacrylamide hydrochloride (APMH) is a monomer copolymerizable precipitation polymerization primary the amination pNIPMAm microgel. Use of AFM PCS characterized the morphology and hydrodynamic diameter of the microgel. NaCl content in the reaction system, and the initiator type size and yield of the resulting microgel. The results show that using V50 raised in pure water the polymerization proceeds microgel yield is very low, the particle size of 160 nm or so. Polymerization in NaCl solution or triggered by the APS, the yield and particle size of the microgel can be improved. Between 160 to 950 nm in diameter can be generated by controlling the content of NaCl in the reaction system (0 to 150 mM), a primary the amination pNIPMAm micro gel. Swelling of the microgel size or? Potential value with the solution pH, ionic strength and temperature changes that resultant the primary amine pNIPMAm micro gel having multiple response. Microgel 5 (6) - carboxyfluorescein succinimidyl ester of the reaction showed that the primary amine on the microgel having a strong chemical reactivity, can be used the late MICROGELS modified. 5 to the primary amine pNIPMAm microgels and anionic PNIPAM-AAC microgel assembly unit by alternately the centrifugal deposition layer-by-layer (LBL) assembly into a micro-gel film. With the increasing number of layers of microgel, AFM height map shows the gradual increase of the bulk density of the surface of the glass substrate microgel; the fluorescence intensity of the film increases linearly with the film in of PNIPAM-AAC micro gel layers increase; fluorescence microscope test. LBL the PNIPAM-AAC microgel gradually introduced. Subsequently, we also used the AFM measurement of the film thickness of the type microgel results show that the the microgel film thickness increases with the increasing number of layers of microgel. Finally, the comparative study of the microgel film and PNIPAM-AAC polyallylamine hydrochloride (PAH) assembled microgel film tensile and repair ability. The results show that a film composed by the the PNIPAM-AAC and primary amine pNIPMAm microgel is crisp, repairable ability is worse. For the first time as the crosslinking agent Sol lithium diatomaceous earth Laponite XLS, Laponite dispersion of sodium methacrylate (SMA) NIPAm, in situ copolymer prepared transparent, ultra-stretch, temperature and pH dual response the ionic pNIPAm-SMA/Laponite XLS NC gel. The the ionic NC gel temperature and pH-responsive, light transmittance and mechanical properties. The results show that the addition of 2 mol% of SMA conferred the NC gel in the pH-responsive, and can be maintained in the pH range of really temperature-sensitive. The all NC gel light transmittance of more than 75%. NC SMA gel content of 8 mol%, the tensile strength is reduced to 45 kPa 60 kPa; elongation at break increasing with the rise of the SMA content, NC gel containing 10 mol% SMA The elongation at break of up to 2900%. Effective network chain density draw ionic equilibrium shear modulus Ge calculated according to the temperature and frequency sweep from the small strain NC gel in 0.28 mol / m 3 or so. Ionic NC gels ultra stretch due to its lower network chain density. 7 in the the Laponite dispersion of adsorbed polyethylene glycol (PEG) in situ polymerization prepared NIPAm PNIPAM / Laponite NC gel. Laponite dispersion (?) Potential value with the improvement of the PEG content lower that the PEG chains can be effectively adsorbed on Laponite surface. The mechanical properties of the test results show that the tensile strength of the gel is reduced with the PEG content increased, the elongation at break increased. Isothermal frequency scan obtained at small strains Ge draw NC gel effective network chain density decreases with the adding of PEG. Showed that PEG can be preferentially adsorbed in the the Laponite surface, effectively prevent the PNIPAM polymer chain growth from the the Laponite surface of the graft, thereby reducing the cross-linking of the Laponite PNIPAM. A small amount of PEG added to and not significantly affected NC gel temperature-responsive, but due to decreased crosslink density, the larger PEG-containing NC equilibrium degree of swelling of the gel at room temperature. Thus, by adjusting the amount of PEG added, it is possible to effectively regulate the mechanical and swelling properties of the gel of the NC.

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