Photochemical surface modification of polymers for improved adhesion

Abstract

A method using photoactivatable reagents is described to modify organic polymer surfaces without changing the bulk properties of the material. The reagents contain a benzophenone or other photoactivatable group which, when exposed to light of appropriate wavelength, generates highly reactive intermediates that covalently bond with nearly any organic material. Some general surface characteristics that can be achieved by this approach, on a wide range of materials, are good wettability, good lubricity, passivation, and priming for either adhesion or immobilization of other molecules. This technology provides tremendous flexibility for tailoring surface characteristics for a broad range of applications. Some materials that have desirable bulk properties for specific applications, however, have surface characteristics that make bonding them to other materials difficult. By photocoupling water-soluble polymers onto the surfaces of such materials, the surface properties can be modified to achieve greatly increased bond strengths with conventional adhesives. For example, using such techniques, the strength of bonding two pieces of high-density polyethylene to each other using a cyanoacrylate adhesive was increased by about 17-fold. Similarly, in preliminary experiments, the bond strengths of silicone rubber to polyvinyl chloride, using cyanoacrylate adhesive, were increased by more than 18-fold. This technology offers great potential for surface modification for improved adhesion.

Keywords:

• Photochemistry
• surface modification
• adhesion
• hydrophilic polymers