325: Thin film depositions, microphase separation, and selective grafting of supramolecular assembly of Poly(tert-butyl methacrylate)-b-poly(4-vinyl pyridine) (PtBMA-b-P4VP) using 2-(4-pyridylethyl)triethoxysilane (2,4-PTES) self-assembled monolayer on at

Abstract: The formation and microphase-separation process of supramolecular assemblies (ABCs) of block copolymers (BCPs) in PtBMA-b-P4VP thin films on atomically flat surfaces are studied. ABCs are formed by selective non-covalent interactions between one of the blocks of a BCP and a low-molecular-weight additive1. The PtBMA-b-P4VP BCPs were synthesized via reversible addition-chain transfer (RAFT) polymerization to produce BCPs with a narrow molecular weight distribution. The thin films may be deposited on the surface by dip-coating or spin coating. Upon deposition, they were subjected to solvent vapor annealing (SVA) or thermal annealing (TA) during which they underwent microphase separation to form nanoporous structures. These nanopores are of great interest for electrocatalysis, energy conversion, and related applications, providing large surface areas for chemical activity. The surface type and solvent vapors used for SVA play a key role in the self-assembly and morphology of the obtained nanostructures. In this work, ABCs were prepared from the PtBMA48k-b-P4VP16k BCP and a low-molecular-weight compound, 2-(4-hydroxyphenylazo)benzoic acid (HABA). HABA selectively reacts with the minor block P4VP. The ABCs made from BCPs produced with a lower fraction of the minor block are unable to undergo microphase separation. Thin films of ABC of 50nm in thickness were deposited via dip-coating. Vapor annealing in chloroform was employed to facilitate self-assembly in the thin films of the ABC. The surface may be modified by the 2,4-PTES and used as a self-assembled monolayer SAM to allow further bridging of the pyridyl groups of the SAM and minor block2. Surface features with and without the SAM were characterized using atomic force microscopy (AFM), contact angle measurements, and ellipsometry. Without the SAM layer, cylinders were obtained with a periodicity of 31nm. However, with the SAM layer, the ABCs graft on the pyridyl sites of 2,4-PTES, forming spheres with a periodicity of 30.5nm.