Preparation of IPN-type Polyelectrolyte Films Attached to the Electrode Surface and Their Humidity-Sensitive Properties

Copoly(2-(dimethylamino) ethyl methacrylate) (DAEMA)/butyl acrylate (BA) and copoly(methyl methacrylate) (MMA)/BA/2-(cinnamoyloxy)ethyl methacryate (CEMA), which were crosslinked with dibromoalkane and UV irradiation, respectively, were prepared for the precursors of interpenetrating polymer network (IPN) humidity-sensitive films. 3-(Triethoxysilyl)propyl cinnamate (TESPC) was used as a surface-pretreating agent for the attachment of IPN-polyelectrolyte to the electrode surface by UV irradiation. Humidity sensitive polymeric thin films with an IPN structure were prepared by crosslinking reactions of copoly(DAEMA/BA) with 1,4-dibromobutane (DBB) and copoly(MMA/BA/CEMA) by UV-irradiation The anchoring of an IPN-polyelectrolyte into the substrate was carried out via the photochemical [2 pi+2 pi] cycloaddition. The resulting humidity sensors showed a high sensitivity in the range of 20 similar to 95%RH and a small hysteresis (<1.5%RH). The response time for adsorption and desorption process at 33 similar to 94%RH was 48 and 65 s, respectively, indicating a fast response. The effects of the concentration of copolymers, molar ratio of crosslinking agents and time of the precursor solution for dip-coating on their humidity sensitive properties including water durability were investigated.