The Preparation Of High Strength Ionic Monomers/Acrylamide Double Network Hydrogels With PH Response

Polymer hydrogels have been intensively studied for their unique properties and potential applications.However,because of nonuniformity crosslinking structure,tradition chemically crosslinked hydrogels have the defects of low intensity,poor intensity,which limited their applications.The main purpose of this paper is to produce a high strength hydrogels with nimble pH response.The basic idea is that combined nanocomposite hydrogel with double network hydrogel,the first network is the nanocomposite hydrogel,which was then immersed in the reaction mixture of ion monomer,then the double network hydrogels with high strength and pH responsive were synthesized by free radical polymerization.The main contents and results of this paper are as follows:1.The preparation of partially hydrolyzed PAM nanocomposite hydrogels.Firstly,the PAM nanocomposite hydrogels were synthesized using a redox initiator system by the in situ polymerization in the aqueous suspension of Laponite.The hydrogels was then immersed in low concentration of NaOH solutions directly,the PAM nanocomposite hydrogels are swelling in NaOH and fully hydrolysis at the same time,then test their tensile and swelling properties,and the results are as follows: The tensile strength of the hydrogel is higher,which was up to 115 kPa,the degree of swelling of the hydrogels at pH=3 is 2.29,smaller than pH=7(13.43),the hydrogels have pH sensitive;the result of oscillatory swelling-shrinking behavior of the hydrogels shows that the pH sensitive of partially hydrolyzed PAM hydrogels has good repeatability.2.The preparation of polyacrylamide/polyacrylic acid sodium(PAM/PAANa)double network hydrogels.Firstly,the PAM nanocomposite hydrogels were synthesized by the in situ polymerization in the aqueous suspension of Laponite.Then under the situation of ice-cooling,the hydrogels were immersed in aqueous solution of sodium acrylate(SA),TEMED,K2S2O8,after the concentration of the solution in the gels came to equilibrium,the polymerization was performed again at 35? for 48 h to synthesize the PAM/PAANa double nerwork(DN)hydrogel.The results show that: The tensile strength of the hydrogelwas up to 136 kPa.When put the hydrogels into the different pH buffer,its swelling degree(5.26)is smaller in acidic buffer and bigger in alkaline buffer(16.98),the result of oscillatory swelling-shrinking behavior of the hydrogels shows that the pH sensitive of PAM/PAANa double network hydrogels has good repeatability.The best synthesis formulation is as follows: the neutralization of AA was 125%,the crosslinker Laponite was0.6 of AM in quality,the monomer mole ratio is AM:AA=9:1(wt),and the crosslinker BIS was 0.2wt%,.3.The preparation of polyacrylamide//poly(2-acrylamide-2-methyl propane sulfonic acid)sodium(PAM/PAMPSNa)double network hydrogels.Firstly,the PAM nanocomposite hydrogels were synthesized by the in situ polymerization in the aqueous suspension of Laponite.Then under the situation of ice-cooling,the hydrogels were immersed in reaction solution of 2-acrylamido-2-methylpropane sulfonate(AMPSNa)to equilibrium,the polymerization was performed again at 35? for 48 h to synthesize the PAM/PAMPSNa double nerwork(DN)hydrogel.The results show that: The tensile strength of the hydrogel was up to 120.57 kPa.When put the hydrogels into the different pH buffer,its swelling degree is smaller in acidic buffer and bigger in alkaline buffer.The best synthesis formulation is as follows: the crosslinker Laponite was 0.7 of AM in quality,the monomer mole ratio is AM:AMPSNa=7:1(wt),and the crosslinker BIS was 0.2wt%.