Electrospun multi-scale hybrid nanofiber/net with enhanced water swelling ability in rubber composites

Water-swellable rubber (WSR) is a kind of elastomeric material that possesses properties of rubber together with water swelling ability. In WSR, however, super water-absorbent resin does not disperse well in hydrophobic rubber, with very poor interfaces between them, so the hydrophilic part can easily break off from rubber networks and the swelling ability is ultimately lost. This study reports the improved water absorption property and stability of WSR obtained by using electrospun multi-scaled hybrid fiber mats of crosslinked poly(acrylic acid) (PAA) nanocomposite as water channels. Electrospinning of various superabsorbent fibers with hyperbranched polymer (HB) and/or graphene oxide (GO) was performed. With hybrid fillers added into PAA, spun fiber mats showed the increased water swelling ability due to the presence of spiderweb-like multi-scale structures and enhanced specific surface areas. The mats were added into conventional WSR and the resultant composites showed enhanced water swelling ability. The electrospun fibers acted as internal multi-scale water channels to bridge isolated PAA particles wrapped in hydrophobic rubber together and link the internal PAAs with the composite surface to enhance the short- and long-term water swelling ability of WSR. The effects and mechanisms of those fibers on enhancing water swelling properties of WSR are discussed.