Chemical and thermal stability of surface-modified porous polyethylene membranes

In this paper, we describe the surface modification of porous polyethylene by the adsorption of polyelectrolyte mutilayers on plasma-activated polyethylene surfaces. We use the migration rates of deionized water as an effective alternative to contact angle measurements in order to probe the interfacial energy of the modified surface. The newly acquired surface properties that result from the surface modification are monitored with respect to several key chemical and environmental variables. These variables were chosen so that they will reflect some of the common handling procedures in a laboratory or health care environments, such as exposure to solvents of different pH and polarities, and fluctuations of ambient temperature over an extended period, i.e., "shelf-life" duration. The stability of these surface properties of the modified membranes is a fundamental requirement for their potential use in a variety of applications involving lateral flow and binding media for bio-assays. In this paper, we show that a membrane modified by a polyelectrolyte monolayer is more stable than a membrane that has undergone plasma activation alone, while a membrane modified by a polyelectrolyte bilayer exhibits retention of the enhanced surface hydrophilic properties under various conditions and over a long period of time.