Benzyl dimethyl 2-methacryloxyethyl ammonium chloride (BDMAC) was prepared for the humidity-sensitive membrane, which could measure the atmospheric moisture content. The membranes were composed of copolymers of various content of BDMAC and methyl methacrylate (BDMAC : MMA=1:0, 6:1, 4:1, 2:1, 1:1, 1:2, 1:4, and 1:6). They were syringe-coated onto the alumina substrate printed with graphite electrode and then polymerized through photoinitiated radical polymerization. The electrical changes of copolymers with relative humidity were measured. It was found that the impedance of humidity-sensitive membrane decreased with an increase of the content of BDMAC in the copolymer. In the case of copolymer composed of same equivalent of BDMAC and MMA, the impedance was varied from 7.5 MΩ to 3.6 KΩ in the range 30∼90%RH. The temperature-dependent coefficient between 15℃ and 35℃ was found to be -0.5%RH/℃ and the hysteresis was less than ±2%RH. The response time was found to be 38 seconds for varing relative humidity from 33%RH to 85%RH and vice versa.

Benzyl dimethyl 2-methacryloxyethyl ammonium chloride(BDMAC) 단량체를 감습막으로 사용하기 위하여 합성하였다. 감습막 성분은 서로 다른 조성의 BDMAC와 MMA의 공중합체 (BDMAC : MMA=1:0, 6:1, 4:1, 2:1, 1:1, 1:2, 1:4, and 1:6)들이며 흑연 전극이 인쇄된 알루미나 기판위에 도포되어 광개시 라디칼 중합에 의해 중합되었다. 감습막의 상대 습도 변화에 대한 전기적 성질의 변화를 측정하였다. 임피던스는 감습막중 BDMAC의 함량이 증가할수록 감소하였다. 감습막중 BDMAC와 MMA의 성분비가 1:1인 감습막의 임피던스는 상대숩도 30∼90%RH 범위에서 7.5MΩ에서 3.6KΩ 사이에서 변하였다. 15℃∼35℃ 범위에서의 온도 의존 상수는 -0.5%RH/℃ 이었으며 히스테리시스는 ±2%RH의 범위 안에서 나타났다. 응답속도는 상대습도가 33%RH에서 85RH%까지 또는 역으로 변화할 때 38초이었다.

Keywords: humidity sensor; quarternary ammonium methacrylate; humidity-sensitive monomer; copolymers; methyl methacrylate