Confinement induced stabilization in polymer blend thin films
Confinement induced stabilization in polymer blend thin films
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DOI：
10.1016/s0032-3861(01)00396-2
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发表时间：
2001-10
期刊：
影响因子：
4.6
通讯作者：
B. Newby;K. Wakabayashi;R. Composto
中科院分区：
文献类型：
--
作者：
B. Newby;K. Wakabayashi;R. Composto
利用原子力显微镜研究了聚甲基丙烯酸甲酯(PMMA)/聚苯乙烯-丙烯腈（SAN）薄膜共混物的薄膜稳定性，其厚度从10nm到几微米不等，并沉积在氧化物覆盖的硅衬底上。除了表征表面形貌外，还选择性地蚀刻了湿润表面和氧化物的富PMMA相，以揭示底层或界面相的形貌。对于在158°C下的50/50共混，发现薄膜在20到100nm之间的厚度值是稳定的。分别调用脱湿和相分离机制来理解为什么薄膜在低于和高于此范围时不稳定。通过将25/75、50/50和75/25薄膜共混物在158 ~ 200℃之间退火，构建了一个稳定性图，并表明含有低PMMA体积分数（即润湿成分）的共混物比含有丰富PMMA的共混物更稳定。在某些情况下，在低至158℃的温度下观察到相分离，这比体低临界溶液温度（LCST）低约12℃。通过预测在其平衡厚度处产生表面润湿层所需的PMMA浓度来分析膜的稳定性。
Using atomic force microscopy, film stability is investigated for poly(methyl methacrylate) (PMMA)/poly(styrene-ran-acrylonitrile) (SAN) thin film blends ranging from 10nm to a few microns thick and deposited on an oxide covered silicon substrate. In addition to characterizing the surface morphology, the PMMA rich phase which wets the surface and oxide, is selectively etched to reveal the underlying or interfacial phase morphology. For 50/50 blends at 158°C, films are found to be stable for thickness values between 20 and 100nm. Dewetting and phase separation mechanisms are invoked to understand why films are unstable below and above this range, respectively. By annealing 25/75, 50/50 and 75/25 thin film blends between 158 and 200°C, a stability diagram is constructed and shows that blends with low PMMA volume fractions (i.e. wetting component) are more stable than blends rich in PMMA. In some cases, phase separation is observed at temperatures as low as 158°C, which is about 12°C below the bulk lower critical solution temperature (LCST). Film stability is analyzed by predicting the PMMA concentration necessary to produce a surface wetting layer at its equilibrium thickness.