Synthesis And Performance Of Acrylic Acid-based Hydrogel By Glow-discharge Electrolysis Plasma

GDEP is a kind of non-Faradaic electrochemical process, which occurs atsolution surface or under solution as the applied voltage over a critical value. Becausethere are many energetic species such as HO2gas+, H3Ogas+，eaq-, OH·, H·, and H2O2inthe glow-discharge area, some unusual chemical reactions in the aqueous solutionwould be initiated. In the present work, GDEP induced simultaneouscopolymerization has been proposed as a new method for synthesis of hydrogel inaqueous solution. Several acrylic acid-based hydrogels, such as acrylamide/acrylicacid, acrylic acid/chitosan and acrylic acid/2-acrylamido-2-methyl-1-propanesulfonicacid, were synthesized by GDEP, and its applications in water treatment and waterretention were studied in detail. The main contents are summarized as below:Chapter1. This work makes a thorough review of the experimental setup,mechanism of plasma and status of research at both home and abroad of GDEP. Inaddition, the synthesis of hydrogel and its application in water purification are alsodescribed.Chapter2. The poly(acrylamide-co-acrylic acid)(P(AM-co-AA)) hydrogel wasprepared in aqueous solution by using glow-discharge-electrolysis plasma (GDEP)induced graft copolymerization of acrylamide (AM) and acrylic acid (AA), in whichN,N’-methylenebisacrylamide (MBA) was used as a crosslinker. To optimize thesynthesis conditions, the following parameters are examined for adsorption ofMalachite green in detail, such as discharge voltage, discharge time, content ofcrosslinker, degree of neutralization, and mass ratio of AM to AA. The structure ofP(AM-co-AA) hydrogel is characterized by Fourier transform infrared spectroscopy(FT-IR), scanning electron microscopy(SEM), and thermogravimetric analysis (TGA).The maximum adsorption capacity of P(AM-co-AA) hydrogel for MG was850mg/g.The induced mechanism by GDEP was also discussed.Chapter3. A acrylic acid/chitosan (AA/CS) superabsorbent hydrogel wassynthesized in aqueous solution by a simple one-step using glow-dischargeelectrolysis plasma (GDEP) technique, in which N,N’-methylenebisacrylamide (MBA) was used as a crosslinking agent. The structure, thermal stability and morphology ofAA/CS hydrogel were characterized by Fourier transform infrared spectroscopy(FT-IR), thermogravimetric analysis (TGA), and scanning electron microscopy(SEM). The reaction parameters affecting the equilibrium swelling (i.e., dischargevoltage, mass ratio of CS to AA, and content of crosslinker) were systematicallyoptimized. The hydrogel of the optimized product was used to study the influence ofvarious pH values and salts solutions (NaCl, KCl, MgCl2, and CaCl2) on theequilibrium swelling.Chapter4. Highly swelling P(2-acrylamido-2-methyl-1-propanesulfonicacid-co-acrylic acid)(P(AMPS-co-AAc)) superabsorbent hydrogel was synthesized inaqueous solution by a simple one-step using glow-discharge electrolysis plasma(GDEP) technique, in which N,N’-methylenebisacrylamide (MBA) was used as acrosslinking agent. The structure, thermal stability and morphology ofP(AMPS-co-AAc) superabsorbent hydrogel were characterized by Fourier transforminfrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and scanningelectron microscopy (SEM). A mechanism for synthesis of P(AMPS-co-AAc)superabsorbent hydrogel was proposed. The reaction parameters affecting theequilibrium swelling (i.e., discharge voltage, discharge time, discharge temperature,mass ratio of AMPS to AAc, and content of crosslinker) were systematicallyoptimized to achieve a superabsorbent hydrogel with a maximum swelling capacity.The hydrogel formed which absorbed about1685g H2O/g dry hydrogel of theoptimized product was used to study the influence of various pH values and saltssolutions (NaCl, KCl, MgCl2, and CaCl2) on the equilibrium swelling. In addition,swelling kinetics in distilled water and on-off switching behavior were preliminarilyinvestigated. The results showed that superabsorbent hydrogel was responsive to thepH and salts.