Clean Technology, Vol.24, No.2, 112-118, June, 2018
스마트 윈도우용 가교 열감응성 폴리(N-이소프로필아마이드) 겔 소재의 제조 및 특성 물/글리세롤 혼합용매 중의 글리세롤 함량의 영향 -
Preparation and Properties of Crosslinked Thermo-responsive Poly(N-isopropylacrylamide) Gel Materials For Smart Windows - Effect of Glycerol Content in Water/Glycerol Solvent -
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초록
온도 변화에 따라 상 전이를 나타내는 열 감응성 고분자는 외부 온도 감응으로 태양광 투과 조절이 가능하므로 스마트 윈도우용 소재로 적용 가능하다. 넒은 온도 범위에서 사용 가능한 스마트 윈도용 열감응성 고분자의 개발은 바람직하다. 고 성능 스마트 윈도우용 소재를 얻기 위하여, 단량체 N-isopropylacrylamide, 가교제 N, N’-methylenebisacrylamide (MBAm), 산화개 시제 ammonium persulfate (APS)/촉매 tetramethylene diamine 및 혼합용매(물/글리세롤)을 사용하여 3차원의 열감응성(thermoresponsive) poly(N-isopropylacrylamide) (PNIPAm) 겔을 제조하였다. 본 연구에서는 혼합용매 중의 글리세롤의 함량이 가교된 PNIPAm 겔 필름의 하한임계온도(low critical solution temperature, LCST), 어는점 및 태양광의 투광도에 미치는 영향을 조사하였다. 글리세롤 함량이 0 wt%에서 10 wt%로 증가하면 PNIPAm 겔 필름의 LCST/어는점은 각각 34.3/6.3 ℃에서 28.2/-6.5 ℃로 감소함을 알 수 있었다. LCST보다 낮은 25 ℃에서는 본 연구에서 합성한 모든 PNIPAm 겔 필름은 투명(광투과)하지만 LCST보다 높은 45 ℃에서는 불투명하다는 것을 알 수 있었다. 이러한 결과는 본 연구에서 합성한 PNIPAm 겔소재는 -6.5 ℃ 부근에서도 스마트 윈도우용 소재로 활용할 가능성이 높음을 알 수 있다.
Thermo-responsive polymers that exhibit phase transition in response to temperature change can be used as materials for smart windows because they can control solar light transmission depending on the outside temperature. The development of thermo-responsive polymers for smart windows that can be used over a wide temperature range is desirable. To obtain high performance smart windows materials, three-dimensional thermo-responsive poly(N-isopropylacrylamide) (PNIPAm) gels were prepared by free radical polymerization from monomer N-isopropylacrylamide, N, N’-methylenebis acrylamide (MBAm) as a crosslinking agent, ammonium persulfate (APS) as a strong oxidizing agent/tetramethylene diamine as a catalyst, and a mixture of two solvents (water/glycerol). This study examined the effect of glycerol content on the lower critical solution temperature (LCST), freezing temperature and the solar light transmittance of crosslinked PNIPAm gel films. The LCST and freezing temperature of PNIPAm gel films were found to be significantly decreased from 34.3 and 6.3 ℃ to 28.2 and -6.5 ℃ with increasing glycerol content from 0 wt% to 10 wt%, respectively. It was found that the transparent PNIPAm gel films at 25 ℃ (temperature < LCST) were converted to translucent gels at higher temperature (45 ℃) (temperature > LCST). These results suggested that the crosslinked PNIPAm gel materials prepared in this study could have high potential for application in smart glass materials.
Keywords:Thermo-responsive polymer;poly(N-isopropylacrylamide);Glycerol;Low critical solution temperature;Smart window
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