Photochemical anchoring of polyelectrolyte to the electrode surface using polymeric silane-coupling agents and their water durability.

This paper reports a simple effective way to photochemically attach a polyelectrolyte layer to an electrode substrate. The system is based on photoreactive benzophenone (BP)-containing copolymers that are bound to alumina surfaces via an alkoxysilane coupling reaction. The alumina substrate was then covered with a BP film that can be reacted with the polyelectrolyte by irradiation with UV light. As a result of the photochemical reaction, the polyelectrolyte was bound covalently to the electrode surfaces. As an example, a thin layer of copolymer of [2-(acryloyloxy)ethyl]trimethyl ammonium chloride (AETAC), styrene (ST), 2-hydroxyethylacrylate (HEA), and 4-acryloxybenzophenone (BPA) (AETAC/ST/HEA/BPA=60/33/4/3) was attached successfully. A pretreatment of the substrate with BP-containing polymeric silane-coupling reagents, AETAC/3-(trimethoxysilyl)propyl methacrylate (TMSPM)/HEA/BPA=50/30/10/10 or TMSPM/HEA/BPA=50/25/25, was performed to improve the water durability and stability at high temperatures and humidity. Their water durability, high temperature/humidity stabilities and long-term stability were evaluated to confirm their usefulness as a humidity-sensing polyelectrolyte membrane. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]