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몬테칼로 기법을 이용한 반응상용화제의 미시적 구조가 비상용성 고분자 계면두께에 미치는 효과에 관한 연구
차국헌,양유성 한국화학공학회 2001 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.39 No.1
본 연구에서는 몬테칼로 시뮬레이션 기법 중의 하나인 bond fluctuation model (BFM)을 이용하여 섞이지 않는 고분자 계를 모사하고 반응성 고분자의 미시적 구조가 계면두께에 미치는 영향을 살펴보았다. 우선 비상용성 고분자 계에서 시뮬레이션을 통해 계면두께를 구한 후, 평균장이론으로부터 구한 계면두께와 비교해 보았을 때 시뮬레이션에서 구한 계면두께가 컸다. 이는 고분자 계면에서의 모세파 섭동(capillary wave fluctuation)이 발생하고 있음을 의미하며 이로 인해 시뮬레이션 결과는 계면을 완전한 2차원 평면으로 가정한 평균장 이론과 일치하지 않게 된다. 사슬의 말단에 반응기를 가진 낮은 밀도의 반응상용화제가 계면에서 반응을 시작하여 반응시간이 지남에 따라 계면에 형성되는 블록공중합체 밀도의 시간 의존성을 살펴본 결과, 한쪽 말단에만 반응기가 존재하는 고분자를 포함하는 계에서, 반응초기에는 기존의 이론에서 제시한 내용과는 달리 반응초기에 반응성 고분자의 반응이 급격히 이루어졌다. 말단에 도입된 반응기의 개수를 한 개와 두 개로 달리 하였을 때, 계면에서 형성되는 블록공중합체의 양을 비교한 결과, 양쪽 말단에 반응기가 있는 반응성 고분자가 계면에서 반응을 많이 했음을 알 수 있었는데, 이는 반응기 개수의 증가가 계면에서 서로 비상용인 고분자 간의 반응확률을 높임으로써 계면에서 형성된 블록공중합체의 양을 증가시키고 결국 섞이지 않는 고분자 블랜드의 물성을 향상시키는데 중요한 요인들 중의 하나인 계면두께의 증가가 이루어졌다. Interfacial properties between two immiscible polymers and the effect of functionality of end-functional polymers on the interfacial thickness were studied with one of Monte Carlo simulations; bond fluctuation model(BFM). We note that the interfacial thickness estimated from the mean field theory is smaller than that obtained from the BFM and the increase in the interfacial thickness for the BFM is due to the capillary wave fluctuations responsible for the interfacial instability between two inhomogeneous phases. A low concentration of reactive chains wide one terminal reactive group or two reactive groups at both ends is allowed to stag to react at the interface forming block as a function of time. Simulation results show that copolymer coverage at the interfacial region for die case of mono-endfunctional reactive polymers significantly increases at the initial stage of the interfacial reaction, which is different from the theoretical prediction of the linear increase of the interfacial coverage in the early stage of reaction. We also found that di-endfunctional reactive polymers ate more effective than mono-endfunctional reactive polymers in forming block copolymers at the interface as well as in the increase of interfacial width that are crucial fads in improving physical of otherwise immiscible polymer blends.
Thermally Induced Mesophase Development in Ethanesilica Films via Macromolecular Templating Approach
Cho, Whirang,Char, Kook-Heon,Kwon, Su-Yong The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.9
Mesoporous ethanesilica thin film was prepared using PEO-PLGA-PEO triblock copolymers as structure-directing agents and (1,2-bis(triethoxysilyl) ethane BTESE; bridged organosilicates) as inorganic precursors via one-step sol-gel condensation of ethanesilica precursors. The mesostructure of ethanesilica films is critically dependent on the processing experimental parameters after the hydrolyzed silica sol mixture was spin-cast. This study examined the effects of the block copolymer template/organosilica precursor ratio in the casting solution and aging period before calcination of the mesostructure. It was further demonstrated that mesoscopic ordering of organosilicate thin films is induced by the rearrangement of block copolymer template/organosilica hybrid during thermal decomposition of the PEO-PLGA-PEO triblock copolymer. The mesoporous structure and morphology were characterized by SAXS, TEM and solid-state NMR measurement.
Kang, Sang-Wook,Char, Kook-Heon,Kim, Jong-Hak,Kang, Yong-Soo The Polymer Society of Korea 2007 Macromolecular Research Vol.15 No.2
The reduction behavior of silver ions to silver nanoparticles is an important topic in polymer/silver salt complex membranes to facilitate olefin transport, as this has a significant effect on the long-term performance stability of the membrane. In this study, the effects ofthe solvent type on the formation of silver nanoparticles, as well as the long-term membrane performance of a solid polymer/silver salt complex membrane were investigated. These effects were assessed for solid complexes of poly(N-vinyl pyrrolidone) $(PVP)/AgBF_4$, using either an ionic liquid (IL), acetonitrile (ACN) or water as the solvent for the membrane preparation. The membrane performance test showed that long-term stability was strongly dependent on the solvent type, which increased in the following order: IL > ACN >> water. The formation of silver nanoparticles was more favorable with the solvent type in the reverse order, as supported by UV-visible spectroscopy. The poor stability of the $(PVP)/AgBF_4$ membrane when water was used as the solvent might have been due to the small amount of water present in the silver-polymer complex membranes actively participating in the reduction reaction of the silver ions into silver nanoparticles. Conversely, the higher stability of the $(PVP)/AgBF_4$, membrane when an IL was used as the solvent was attributable to the cooperative coordination of silver ions with the IL, as well as with the polymer matrix, as confirmed by FTIR spectroscopy.