The tensile shear adhesive-free adhesion properties induced by electrostatic interactions between poly(acrylic acid) (PAA) and poly[2-(dimethylamino)ethyl methacrylatel (PDMAEMA) chains grafted onto polyethylene (PE) with low-density (LDPE) or high-density (HDPE) plates were studied. PAA- or PDMAEMA-grafted PE plates were immersed in a HCl or NaOH solution or water for 24 h, and their electrostatic properties were changed before they were overlapped with each other and heat-pressed. The breaking of the substrate between the two plates with water-swollen grafted layers was observed in the low range of grafted amounts in comparison with immersion in the acidic and basic solutions. The ability of the two plates with grafted polymer chains swollen in water to strongly bond with each other was a result of electrostatic interactions formed by positively charged PDMAEMA and negatively charged PAA chains. The breaking of the substrate in the case of adhesive-free adhesion between quaternized PDMAEMA-grafted and PAA-grafted PE plates immersed in the basic solution occurred with lower grafted amounts of PAA. This came from the strong attractive force between dissociated anionic PAA chains and quaternized cationic PDMAEMA chains in the basic solution. In addition, the adhesive-free adhesion strength of HDPE plates with the same grafted polymer chains encountered the breaking of the substrate with lower grafted amounts than that of LDPE plates. It was concluded that the grafting of polymer chains onto HDPE plates with high crystallinity was considerably restricted to the outer surface regions. (c) 2006 Wiley Periodicals, Inc.