Formation and properties of multivariant assemblies of surface-tethered diblock and triblock copolymers

We present methodologies for fabricating block copolymer assemblies grafted onto flat solid substrates, where each block of the copolymer possesses a systematic and gradual variation of molecular weight as a function of the position on the substrate. We demonstrate the utility of this technique on two case studies. In the first project, we generate surface-tethered poly[(2-hydroxyethyl methacrylate)-b-(methyl methacrylate)] (PHEMA-b-PMMA) diblock copolymer brushes and study systematically morphological transitions associated with collapsing either the top PMMA or the bottom PHEMA block while keeping the other block solvated. Scanning force microscopy studies of systems having the top block collapsed reveal the presence of either flat (F), or micellar (M) or bicontinuous (BC) morphologies, whose locus in the phase diagram agrees with theoretical predictions and results of computer simulations. The second case study demonstrates the extension of the deposition method to the case of surface-anchored triblock copolymer brushes. Specifically, we present results pertaining to the formation of poly[(2-hydroxyethyl methacrylate)-b-(methyl methacrylate)-b-(dimethylaminoethyl methacrylate)] brushes with independent variation of all three block lengths.