New sulfobetaine zwitterion-containing copolymers were prepared by the copolymerization of [2-[(methacryloyloxy)ethyl]dimethyl] propyl ammonium bromide (MEPAB)/N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl) ammonium (DMMSA) for a humidity-sensitive polyelectrolyte. The poly(MEPAB-co-DMMSA)s with a composition of 10/0, 8/2, 6/4, 4/6, 3/7, 2/8 and 0/10 were used to prepare resistive-type humidity sensors. The electrical properties of poly(MEPAB-co-DMMSA) with different amounts of MEPAB and DMMSA were examined as a function of the relative humidity to determine the contribution of the two salts on the sensing properties (linearity and sensitivity). Resistance of the humidity sensors obtained from the copolymers MEPAB and DMMSA varied from 10 7 to 10 2 Ω between 30%RH and 90%RH, which is suitable for a humidity sensor operating at ambient humidity. The humidity-sensing properties of MEPAB were enhanced by doping with a sulfo-betaine-type salt with a significantly different dissociation constant. The temperature dependence, hysteresis, response time, water durability, and long-term stability at high temperature and humidity were also measured.
Fundamental modes (9 & 50 MHz) and overtone modes of 3rd mode of 33MHz (lOO(3) MHz) and 5th mode of 20 MHz (lOO(5) MHz) of quartz crystal microbalances (QCMs) with high frequencies study to increase the frequency response of QCM gas-sensor.On the fundamental and overtone modes, the ratio of mass sensitivity of QCMs calculated from theory is consistent with that of the experimental results.
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.
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