Synthesis and Characterization of Thermo-and pH-Sensitive Poly[(N, N-diethylacrylamide)-co-(acrylic acid)] Hydrogels with Fast Response Rate

This thesis N, N-diethyl acrylamide (DEA) and acrylic acid (AA) were used as temperature-sensitive monomer, and the pH-sensitive monomer, were used porogenic technology, phase separation technology and other physical modification methods and introducing a comb type graft chain and other polymer network chemical modification method, synthesis temperature / pH value of double-sensitive rapid response of poly (N, N-diethyl-acrylamide-co-acrylic acid) (P (DEA-co -AA)) hydrogel system to study copolymer hydrogels in response to changes in the external environment to stimulate behavior, based on doped multi-walled carbon nanotubes (MWCNTs) synthesized fast response and mechanical better strength composite hydrogel. Also, systematic study of the DEA RAFT polymerization conditions copolymer hydrogels laid a theoretical foundation for the subsequent synthesis of structure controlled the PDEA. The main results obtained are: 1, PEG-6000 as porogen by radical crosslinking copolymerization method, through the regulation of the composition of the monomer, synthetic double sensitive fast response temperature / pH value P (DEA-co- AA) hydrogel, FTIR results show that, PEG-6000 can be completely removed through the method of immersion in an alkaline solution. The hydrogel swelling study results showed that: (1) adjusting the composition of the monomer, when AA accounted for 1.1 wt% of the total monomers, the phase transition temperature of the P (DEA-co-AA), the volume of the hydrogel (VPTT ) can reach the human physiological temperature (37.5 ° C) near; (2) Since the comonomers AA containing the dissociated carboxyl group, to give a copolymer hydrogel obvious pH sensitivity; (3) P (DEA-co-AA deswelling rate) hydrogel at 60 ° C (higher than its VPTT) secondary distilled water by the PEG-6000 was added or not, and the impact of the added amount of the copolymerizable monomer AA, while 20 ° C (below the its VPTT) the deswelling behavior into two stages in the acidic medium of the pH = 3.0; (4) when the temperature is between 20 ° C and 60 ℃ alternately change, P (DEA-co-AA) hydrogel having a reversible pulse responsive behavior, and when the pH value is alternately changed between 3.0 and 6.9, P (DEA-co-AA), the hydrogel pulse responsive behavior is affected by the PEG-6000 was added or not added in an amount of comonomer AA. 2, with different concentrations of NaCl aqueous solution as a reaction medium, using a radical crosslinking copolymerization method, synthesis of a series of temperature / pH value Sensitive P (DEA-co-AA) hydrogel prepared in double distilled water the hydrogel compared to P (DEA-co-AA) on the outside temperature and pH changes, the gel having a similar response behavior. The difference is that P (DEA-co-AA) was prepared in aqueous NaCl hydrogel has a faster response speed, temperature and pH changes, and the response speed by the influence of the concentration of the aqueous solution of NaCl. Scanning electron microscope (SEM) analysis showed that the aqueous solution of NaCl is prepared in the reaction medium P (DEA-co-AA) hydrogel having a greater porosity. 3, the phase separation technology and porogen technology two physical modification means the combination of the two-step method of fast response temperature / pH value of dual-sensitive P (DEA-co-AA) hydrogel. The swelling experimental results showed that: (1) hydrogel VPTT only associated with the two monomers copolymerizable gel composition, regardless of the specific polymerization process, i.e. the one-step and two-step Preparation copolymerized hydrogel having same VPTT; (2) due to comonomer AA, the hydrogel has a sensitivity within a very wide range of pH values, and the hydrogel of the two-step method at a high temperature and acidic medium is introduced into the system deswelling speed faster; (3) swelling / deswelling kinetic experiments show that, at any step in the two-step method has an important impact on the fast speed of response of the hydrogel; (4) with a hydrogel deswelling rate is significantly faster than the swelling rate. 4, the synthesis of the end with a double bond PDEA macromer and monomer DEA, AA radical crosslinking copolymerization, prepared with a comb-shaped graft chain P (DEA-co-AA) hydrogel gum, using the chemical modification method, the chemical structure of the hydrogel is modified on the molecular level. The deswelling kinetics as well as on the temperature / pH value alternately changes the prepared hydrogel swelling ability pulse responsive behavior was studied. Results show that in below the hydrogel VPTT, P (DEA-co-AA) of the comb-type graft hydrogel at pH GT; 5.0 has a larger equilibrium swelling in the secondary at the same time (ESRs); The deswelling kinetics distilled water deswelling rate deswelling temperature is important. In addition, the comb-type graft hydrogel alternately changing of the temperature of the impulse response has a superior performance. However, a description is poorly responsive behavior of comb-type graft hydrogel alternately change pulse on the pH value is almost irreversible. In addition, the synthesis of fluorescently labeled comb-type grafted microgel use of the the fluorescent means of rapid response mechanism of the comb-type graft hydrogel. 5, the first synthetic vinyl functionalized MWCNTs and structures were characterized using Raman, FTIR analysis means. On this basis, the vinyl functionality of MWCNTs the DEA, AA crosslinked copolymerization, prepared MWCNT / P (DEA-co-AA) composite hydrogel systematic study of the mechanical strength of the hydrogel as well as on the outside stimulus response behavior and response speed. The study found that, MWCNT / P (DEA-co-AA) The composite hydrogel P (DEA-co-AA) hydrogel having a similar temperature / pH value responsive behavior, but MWCNT / P (DEA-co-AA) The composite hydrogel has a higher modulus of elasticity, and having a faster response time at a high temperature (60 ℃). The hydrogel swelling Mechanism MWCNT / P (DEA-co-AA), the composite hydrogel and P (DEA-co-AA), the diffusion of water in the hydrogel follow Fickian diffusion law. By reversible addition fragmentation chain transfer (RAFT) polymerization method, synthesized a series of different molecular weight PDEA systematic study of the reaction temperature, reaction time, [CTA] 0 / [I] 0 RAFT polymerization of DEA the impact of the results the dithio benzyl benzoate (BDTB) as chain transfer agent can control the DEA RAFT polymerization, copolymer hydrogels laid a theoretical foundation for the subsequent synthesis of structure controllable and fast response PDEA .