Self-assembling study of a cylinder-forming block copolymer via a nucleation-growth mechanism

Block copolymer materials form self-assembling structures at a nanometric scale, of interest in nanotechnology. The organization process of asymmetric poly(styrene-block-methyl methacrylate) (PS-b-PMMA) copolymer thin films is studied. In a first step it is demonstrated that two consecutive mechanisms lead to the formation of a well-ordered phase. The first mechanism is the local segregation of blocks, which leads to a metastable disordered cylinder phase (C(d)). The second mechanism is a transformation of the C(d) phase to a vertical cylinder phase via a nucleation-growth mechanism. The influence of film thickness and surface tension on the organization is also studied. Above the natural cylinder monolayer height, h(1), the kinetics of the cylinder organization strongly depends on the initial film thickness, and below h(1) the film splits into terraces. By varying the interactions between the substrate surface and the different blocks, a disordered phase can be formed instead of terraces.