Research On The Synthesis Of A Cationic Hydrogel Based On DMDAAC

As one of the most commonly and widely used cationic monomers,dimethyl diallyl ammonium chloride（DMDAAC）had been studied mainly on its linear homopolymers and copolymers,but rarely on their hydrogels based on crosslinking function.In this paper,the synthetic process of poly dimethyl diallyl ammonium chloride（PDMDAAC）cationic hydrogel was studied,and then a kind of high absorbent hydrogel products were obtained.The structure,properties of the products and their influencing factors were studied.Details are as follows.Concerning their synthetic conditions,firstly,based on the literature about linear polymers and preliminary exploration experiments,the hydrogel synthesis methods and crosslinking agents were screened out,by using the water absorption rate of the polymer products.Both the better synthesis method（three-step heating aqueous solution polymerization）and the better crosslinking agents（EGDMA and TAA）were obtained.Secondly,the orthogonal optimization methods was employed to optimize the monomer mass fraction w（DMDAAC）,initiator dosage m（APS）∶m（DMDAAC）,crosslinking agent dosage m（crosslinking agent）∶m（DMDAAC）,temperature in the first stage（T₁）,second（T₂）and third stage（T₃）.The polymer products with the best water absorption performance and their synthesis conditions were obtained.The optimum synthesis condition of PDMDAAC hydrogel using EGDMA as crosslinkingagentwereasfollows:w（DMDAAC）=66.00%,m（Persulfate）∶m（DMDAAC）=4.50%,m（EGDMA）∶m（DMDAAC）=1.00×10^-2%,m（Na₄EDTA）∶（DMDAAC）=7.10×10^-2%.The product reacted at T₁（47.5℃）for 3h,then at T₂（50.0℃）for 3h,and finally at T₃（70.0℃）for 3h.Under this condition,the equilibrium swelling of the product in deionized water,1.0mol/L brine and normal saline were 3357.80g/g,54.61g/g and 102.03g/g,respectively.The optimum synthesis condition of PDMDAAC hydrogel using TAA as crosslinking agent were as follows:w（DMDAAC）=66.00%,m（Persulfate）∶m（DMDAAC）=3.50%,m（TAA）∶m（DMDAAC）=1.00×10^-2%,m（Na₄EDTA）∶m（DMDAAC）=7.10×10^-2%.The product reacted at T₁（45.0℃）for 3h,then at T₂（52.0℃）for 3h,and finally at T₃（75.0℃）for 3h.Under this condition,the equilibrium swelling of the product in deionized water,1.0mol/L brine and normal saline were 3847.09g/g,66.23g/g and 105.61g/g,respectively.Finally,based on the two optimum synthesis conditions,single factor experiments were carried out in terms of the monomer mass fraction,initiator dosage and crosslinking agent dosage.The dependence of these three factors on performance and structure were obtained.FTIR,¹³C-NMR,SEM and other means were used to characterize the samples under optimum synthetic conditions,which demonstrated that the DMDAAC was properly polymerized and cross-linked to form a well-defined hydrogel structure.This study laid a foundation for the synthesis,characterization and application of PDMDAAC hydrogel.Finally,based on the two optimum synthesis conditions,the experiments of single factor influencing the product properties were carried out in terms of the monomer mass fraction,initiator dosage and crosslinking agent dosage.The dependence of these three key factors on the structures,properties and performance were investigated.FTIR,¹³C-NMR,SEM and other means were used to characterize the samples obtained from the optimum synthetic conditions,which demonstrated that the monomer DMDAAC was properly polymerized and cross-linked to form a well-defined hydrogel structure.The results laid a foundation for studying furtherly on the synthesis,characterization and application of PDMDAAC hydrogel.