均聚物调控的PS-b-P4VP薄膜的微相分离形貌

Micro-phase separation morphologies in thin films of PS-b-P4VP tuned by blending with homopolymers

分别以聚丙烯酸(PAA)和聚氧化乙烯(PEO)与苯乙烯与4-乙烯基吡啶二嵌段共聚物(PS-b-P4VP)进行溶液共混并且旋涂成膜,采用原子力显微镜(AFM)研究了这两种均聚物对PS-b-P4VP薄膜微相分离形貌的调控作用。结果表明,PAA与P4VP链段之间强烈的氢键作用使得P4VP链段对PS链段的热力学排斥作用增强,当PAA质量分数为10%时,PS分散相区以规则的柱体垂直分布于由P4VP/PAA链段相互溶解所形成的连续相基体中。对于PS-b-P4VP/PEO共混体系,共混薄膜形成了PEO/P4VP分散相以柱状形态垂直分布在以PS链段聚集区为薄膜连续相基体中的微相分离形貌,由于PS链段无法在PEO/P4VP柱状微区上方形成覆盖,导致共混薄膜表面出现许多孔洞,孔洞底部伴有PEO链段部分结晶形成的锥状突起。随PEO含量增加,孔洞直径增大,孔洞底部的锥状突起也增大。

PS-b-P4VP block copolymers were solution-blended with polyacrylic acid （PAA） and polyethylene oxide （PEO）, respectively, followed with spin-coating on glass substrates. The resulting thin films were imaged by atomic force microscope （AFM） to investigate the tuning effects of the two homopolymers on the micro-phase separation morphologies of PS-b-P4VP thin films. The results showed that thermodynamic repulsion between P4VP and PS segments was enhanced due to strong interaction between PAA and P4VP by hydrogen bonds. In the thin film with 10% （mass） of PAA, micro-phase separation morphology with cylindrical PS micro-domains dispersed regularly into P4VP/PAA matrix was observed. The cylindrical PS micro-domains oriented perpendicularly to the film surface. In the PS-b-P4VP/ PEO thin films, micro-phase separation morphologies with PS as matrix and cylindrical micro-domains of PEO/P4VP oriented perpendicularly to the film surface were formed. The top of PEO/P4VP cylindrical micro-domains was not covered by PS segments, leading to the holes on the surface of the film. Also, coneshaped projections could be found at the bottom of holes due to crystallization of PEO segments inside PEO/P4VP micro-domains. With the increase of PEO content, the size of holes increased and the coneshaped projections at the bottom of holes became more apparent.