Wiring Molecules with Polymer Brushes: End-Functionalization of Conjugated Polymer Brushes via ROMP

摘要

Ring-opening metathesis polymerization (ROMP) using transition- metal carbene catalysts such as Grubbs' Ru catalysts proceeds as a living polymerization. This fact has been utilized in the synthesis of block copolymers and end-functionalized polymers, including conducting block copolymers based on polyacetylene. ROMP is a versatile polymerization technique that proceeds rapidly and is tolerant of a broad spectrum of functionality. ROMP has been used in the growth of a wide variety of surface-bound polymer brushes as well; metathesis catalysts such as the family of Grubbs catalysts can be covalently attached to a surface by means of a terminal vinyl group in a self-assembled monolayer (SAM). While there are several reports of block copolymer brushes prepared using ROMP, end-functionalization by quenching the propagating metal center with small molecules containing vinyl functionality is a largely unexplored topic. Furthermore, while most surface-based ROMP polymers have been based on a monomer with the highly strained norbornenyl ring structure, any cyclic, unsaturated ring structure with appreciable strain can be subjected to ROMP, and ultrathin polyacetylene brushes have been formed on silicon surfaces by ROMP of cyclooctatetraene (which has a ring strain of ～2.5 kcal/mol)