Methacryloxyethyl dimethyl 2-hydroxyethyl ammonium bromide (MDHAB) was prepared for the moisture-absorptive material for low temperature application. The humidity-sensitive membranes were composed of terpolymers of various content of MDHAB, methyl methacrylate and 2-(N,N-dimethylamino)ethyl methacrylate (DAEM) (MDHAB:MMA:DAEM=60:30:10,45:45:10,30:60:10,27:63:10 and 18:72:10). The humidity- sensitive membranes were fabricated on the gold electrode by dipping and cross-linked by reacting terpolymer with 1,5-dibromopentane. It was found that the impedance of humidity-sensitive membrane decreased with an increase of the content of MDHAB in the copolymer. In the case of copolymer composed of MDHAB:MMA:DAEM=45:45:10, the impedance varied from 310 kHz to 2.4 kHz in the 40∼90%RH range. The temperature-dependent coefficient between 5℃ and 20℃ was found to be -0.8%RH/℃ and the hysteresis falled in the ±3% RH range. The response time was found to be 38 sec for the relative humidity ranging from 33%RH to 85%RH at 25℃.

Methacryloxyethyl dimethyl 2-hydroxyethyl ammonium bromide (MDHAB) 단량체를 저온 작동 감습막으로 사용하기 위하여 합성하였다. 감습막 성분은 서로 다른 조성의 MDHAB, MMA 그리고 DAEM의 비가 60:30:10, 45:45:10, 30:60:10, 23:67:10 그리고 18:72:10의 3원 공중합체들이다. 습도센서는 감습막을 금 전극위에 침적에 의하여 도포하였고 1,5-dibromopropane과 반응하여 가교화하였다. 감습막의 상대습도 변화에 대한 전기적 성질의 변화를 측정하였을 때 임피던스는 감습막 중 MDHAB의 함량이 증가할수록 감소하였다. 감습막 중 MDHAB와 MMA의 성분비가 1대 1인 감습막의 임피던스는 상대습도 40∼90%RH 범위에서 310kHz에서 2.4kHz 사이에서 변하였다. 5∼20℃ 범위에서의 온도 의존상수는 -0.8%RH/℃이었으며 히스테리시스는 ±3%RH의 범위 안에서 나타났다. 응답속도는 상대습도가 33%RH에서 85%RH까지 또는 역으로 변화할 때 38초이었다.

Keywords: humidity sensor; dip coating; low-temperature humidity sensor; humidity sensitive membrane methacryloxyethyl dimethyl 2-hydroxyethyl ammonium bromide