Surface segregation of fluorinated moieties on poly(methyl methacrylate-ran-2-perfluorooctylethyl methacrylate) films during film formation: Entropic or enthalpic influences.
Surface segregation of fluorinated moieties on poly(methyl methacrylate-ran-2-perfluorooctylethyl methacrylate) films during film formation: Entropic or enthalpic influences.
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DOI：
10.1016/j.jcis.2010.05.042
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发表时间：
2010-09
影响因子：
9.9
通讯作者：
Xiuyun Ye;B. Zuo;M. Deng;Yanlin Hei;H. Ni;Xiaolin Lu;Xinping Wang
中科院分区：
文献类型：
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作者：
Xiuyun Ye;B. Zuo;M. Deng;Yanlin Hei;H. Ni;Xiaolin Lu;Xinping Wang
采用接触角法、X射线光电子能谱、和频振动光谱和表面张力法研究了溶剂、含氟单体含量和成膜方式对甲基丙烯酸甲酯（MMA）和甲基丙烯酸2-全氟辛基乙酯（FMA）无规共聚物表面结构的影响。结果表明，以环己酮为溶剂时，存在一个临界FMA含量（9mol%），低于此值时，旋涂法制备的共聚物膜中含氟基团的表面偏析程度大于溶液浇铸法制备的共聚物膜;高于此值时，溶液浇铸法制备的共聚物膜中含氟基团的表面偏析程度大于旋涂法制备的共聚物膜。而以甲苯为溶剂时，FMA的临界含量降低到3mol%。我们认为，溶剂性质和含氟基团的含量在无规共聚物中有很大的影响，因为这两个因素的综合作用可以决定无规共聚物链构象和它们的热力学主导因素在溶液中和溶液-空气界面。一个热力学分析相结合的熵和热效应的建议来解释所观察到的现象。这项研究被认为是获得一个增强的理解的聚合物膜的表面形成机制，从而展示了如何促进在聚合物膜表面的氟化部分的隔离。
The effects of solvents, fluorinated monomer content and film-formation methods on the surface structures of random copolymers composed of methyl methacrylate (MMA) and 2-perfluorooctylethyl methacrylate (FMA) were investigated by contact angle goniometry, X-ray photoelectron spectroscopy, sum frequency generation (SFG) vibrational spectroscopy and surface tension measurement. It is found that, with cyclohexanone as the solvent, there is a critical FMA content of 9mol%, below which the copolymer films by spin coating have a more surface segregation extent of fluorinated moieties than those by solution casting; above which the copolymer films by solution casting have a more surface segregation extent of fluorinated moieties than those by spin coating. However, with toluene as solvent, the critical FMA content lowers down to 3mol%. We believe that the solvent nature and the content of fluorinated moieties in the random copolymer have the great effect because the combined effect of these two factors can determine the random copolymer chain conformations and their thermodynamic dominating factors in the solution and at the solution–air interface. A thermodynamic analysis combining the entropic and enthalpic effects is suggested to explain the observed phenomenon. This research is believed to obtain an enhanced understanding of the surface formation mechanism of the polymer films and thus demonstrate how to promote the segregation of fluorinated moieties at the polymer film surfaces.