Liu Xiangyu, Bhandaru Nandini, Banik Meneka, Wang Xiaoteng, Al-Enizi Abdullah M, Karim Alamgir, Mukherjee Rabibrata
Department of Polymer Engineering, University of Akron, Akron, Ohio 44325, United States.
Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal, India.
ACS Omega. 2018 Feb 21;3(2):2161-2168. doi: 10.1021/acsomega.7b02078. eCollection 2018 Feb 28.
We report capillary force lithography pattern-directed self-assembly (CFL-PDSA), a facile technique for patterning immiscible polymer blend films of polystyrene (PS)/poly(methyl methacrylate) (PMMA), resulting in a highly ordered phase-separated morphology. The pattern replication is achieved by capillary force lithography (CFL), by annealing the film beyond the glass transition temperature of both the constituent polymers, while confining it between a patterned cross-linked poly(dimethyl siloxane) (PDMS) stamp and the silicon substrate. As the pattern replication takes place because of rise of the polymer meniscus along the confining stamp walls, higher affinity of PMMA toward the oxide-coated silicon substrate and of PS toward cross-linked PDMS leads to well-controlled vertically patterned phase separation of the two constituent polymers during thermal annealing. Although a perfect negative replica of the stamp pattern is obtained in all cases, the phase-separated morphology of the films under pattern confinement is strongly influenced by the blend composition and annealing time. The phase-separated domains coarsen with time because of migration of the two components into specific areas, PS into an elevated mesa region and PMMA toward the substrate, because of preferential wetting. We show that a well-controlled, phase-separated morphology is achieved when the blend ratio matches the volume ratio of the elevated region to the base region in the patterned films. The proposed top-down imprint patterning of blends can be easily made roll-to-roll-compatible for industrial adoption.
我们报道了毛细管力光刻图案导向自组装（CFL-PDSA），这是一种用于对聚苯乙烯（PS）/聚甲基丙烯酸甲酯（PMMA）的不混溶聚合物共混物薄膜进行图案化的简便技术，可产生高度有序的相分离形态。图案复制是通过毛细管力光刻（CFL）实现的，即将薄膜在高于两种组成聚合物的玻璃化转变温度下进行退火，同时将其限制在有图案的交联聚二甲基硅氧烷（PDMS）印章和硅衬底之间。由于聚合物弯月面沿限制印章壁上升而发生图案复制，PMMA对氧化硅涂层硅衬底的亲和力较高，而PS对交联PDMS的亲和力较高，这导致在热退火过程中两种组成聚合物实现了良好控制的垂直图案化相分离。尽管在所有情况下都能获得印章图案的完美负片复制品，但图案限制下薄膜的相分离形态受到共混物组成和退火时间的强烈影响。由于两种组分因优先润湿而迁移到特定区域，PS迁移到凸起的台面区域，PMMA迁移向衬底，相分离域会随时间粗化。我们表明，当共混比与图案化薄膜中凸起区域与基部区域的体积比相匹配时，就能实现良好控制的相分离形态。所提出的共混物自上而下压印图案化可以很容易地实现卷对卷兼容，以便工业应用。
