A study on the preparation and performance of SiO2 nanocomposite hydrogels with electrostatic interactions
Enhancing the degree of binding of nanoparticles to the gel polymer network in order to improve the heterogeneity between them is extremely critical for improving the mechanical properties of nanocomposite hydrogels.To this end,electrostatic interactions were introduced into the nanocomposite hydrogels to further enhance the mechanical properties of the composite hydrogels.Firstly,the surface modification of silica(SiO2)nanoparticles was performed to prepare poly(sodium p-styrene sulfonate)(PSS)-grafted PSS-SiO2 nanoparticles,which were then composited with poly(N,N,N-trimethyl-3-(2-methylallylamino)-1-propylammonium chloride(PMPTC))copolymerization-modified poly(acrylamido)(PAM)hydrogel to obtain the PSS-SiO2/P(AM-co-MPTC)nanocomposite hydrogels.The effects of electrostatic interactions between-SO3-of PSS-SiO2 nanoparticles and-N+(CH3)3 of PMPTC in PSS-SiO2/P(AM-co-MPTC)composite hydrogels on their micro-morphology,solubility,rheological and mechanical properties were investigated.The electrostatic interactions between the polyanions on the surface of PSS-SiO2 nanoparticles and the polycations of the hydrogel network significantly enhanced the bonding degree between the SiO2 nanoparticles and the hydrogel matrix.Compared with the SiO2/P(AM-co-MPTC)nanocomposite hydrogel with the addition of pure SiO2 nanoparticles,the mechanical properties of the PSS-SiO2/P(AM-co-MPTC)nanocomposite hydrogel with the addition of PSS-SiO2 nanoparticles were significantly improved,and the optimal component had a tensile modulus of up to 160.9 kPa,a strength of 95.7 kPa and a toughness of 31.1 kJ/m3,which increased by 176％,297％and 556％,respectively.The as-fabricated hydrogels also exhibited salt-responsive behavior of anti-polyelectrolyte effects.This study shows that the introduction of electrostatic interactions between nanoparticles and the composite gel matrix helps to further enhance the mechanical properties of the composite hydrogels while endowing them with salt-responsive behaviors similar to the inverse polyelectrolyte effect.The design strategy is informative for the development of high-performance nanocomposite hydrogels.
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