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

In this work, several polyacrylic acid (PAA) nanocomposite hydrogels containing different dimensional silica nanoparticles densely grafted with poly(2-(dimethylamino)ethyl methacrylate) (SiO 2 @PDMAEMA nano-objects) have been fabricated. Firstly, the spherical and sheetlike SiO 2 @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 SiO 2 @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(CH 3 ) 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 SiO 2 core and alkaline component of shell was demonstrated to affect mechanical performance in PAA composite hydrogel.