Enhanced mechanical property of polyacrylic acid composite hydrogel by the synergistic role of core-shell structured SiO2@PDMAEMA nano-objects

Abstract In this work, several polyacrylic acid (PAA) nanocomposite hydrogels containing different dimensional silica nanoparticles densely grafted with poly(2-(dimethylamino)ethyl methacrylate) (SiO2@PDMAEMA nano-objects) have been fabricated. Firstly, the spherical and sheetlike SiO2@PDMAEMA core/shell nano-objects were prepared based on self-assembly of poly(2-(dimethylamino)ethyl methacrylate)-block-poly(3-(triethoxysilyl)propyl methacrylate) (PDMAEMA-b-PTEPM) gelable block copolymers in bulk. Then, two different shaped SiO2@PDMAEMA nano-objects were introduced into the PAA hydrogel construction processes to obtain the corresponding PAA composite hydrogel, respectively. The results indicated that core/shell nano-objects were well dispersed in the PAA matrix, and the ionic bonds were formed between –N(CH3)2 groups in shell of nano-objects and –COOH units in matrix. The compressive strength of composite hydrogels containing 1–3 wt% of sheetlike or spherical nano-objects dramatically increased. For example, when the strain was 65%, it was increased to its maximum by 355.8% and 113.5% compared with that of pure PAA hydrogel (163.92 kPa), respectively. In addition, as induction of hybrid nanofillers, the swelling degree and water absorption behavior of composite hydrogels changed. Especially, the spherical nano-objects-doped composite hydrogel showed a lower swelling degree than others. The synergistic role from the shape of inorganic SiO2 core and alkaline component of shell was demonstrated to affect mechanical performance in PAA composite hydrogel.