Wetting, symmetric/asymmetric

Fig. 6 Illustration of surface energy effects on the self-assembly of thin films of volume symmetric diblock copolymer (a). Sections b and c show surface-parallel block domains orientation that occur when one block preferentially wets the substrate. Symmetric wetting (b) occurs when the substrate and free surface favor interactions with one block B, which is more hydrophobic. Asymmetric wetting (c) occurs when blocks A and B are favored by the substrate and free surface, respectively. For some systems, a neutral substrate surface energy, which favors neither block, results in a self-assembled domains oriented perpendicular to the film plane (d). Lo is the equilibrium length-scale of pattern formation in the diblock system...

Instead of observing the change of the morphology as a function of the film thickness, surface boundaries could also be used to control the wetting layer morphology at interfaces, the surface topographies, and the microdomain period [148]. In the case of symmetric or asymmetric wetting of the block copolymer at... 

Table 1. Average Values ( Standard Deviation) for PLL(20)-g[3.5]-PEG(5), Adsorbed on a Silica Substrate Surface, of the Wet Mass Density, wei, the Dry Mass Density, mdry, the Solvation, W, the Number of Solvent Molecules per EG Monomer Averaged over the Cross Section of the PEG Brush, A mig, and the Coefficient of Friction for Symmetric (Silicon Wafer and Colloidal Probe Coated with PLL-g-PEG), and Asymmetric (Silicon Wafer Coated with PLL-g-PEG,...

The microinterferometric method has widely been used by many authors to investigate both symmetric thin liquid films (foam and emulsion films) and asymmetric ones (wetting films). This method has been described in several papers, for example. Refs. [2, 3, 32, 33, 37] as well as in a book [1]. Here we give only a brief outline. 

A series of studies of microscopic thin hquid films, both symmetric (foam and 0/Wemulsion films) and asymmetric (wetting films), from aqueous solutions of... 

Walton et al. went on to study the orientation of block copolymers as a function of interaction with blocks when walls are preferential for one of the blocks, parallel orientation forms.In the case of symmetric wetting of preferential walls, unfrustrated spacing occurs for wall spacing h,h = ndg, which is the bulk spatial period do multiplied by the number of layers n. Alternatively, for asymmetric preferential walls (the walls attract opposite blocks), the unfmstrated system forms when the plate spacing corresponds with h = n + Vi)do-This behavior was confirmed experimentally with PS-b-PMMA sandwiched between two walls treated with random copolymers of polystyrene-ran-poly(methyl methacrylate) (PS-r-PMMA) with varying composition and thus varying block interaction. ... 

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