Substituted Poly(p-phenylene) Thin Films via Surface-Initiated Kumada-Type Catalyst Transfer Polycondensation
Conjugated polymer films of unsubstituted and alkoxy-substituted poly(p-phenylene) have been prepared via a Kumada-type catalyst-transfer polycondensation in it grafting-from configuration. A surface-bound external initiator wits formed by reacting a Ni(0) complex with it thienyl bromide monolayer, and this surface-bound initiator wits used to polymerize several Grignard monomers prepared from the corresponding 1,4-dihalobenzenes resulting ill surface-bound, conjugated polymer chains with thickness tip to 30 nm. A series of 1,4-diodo monomers with alkoxy side chains ranging from unsubstituted 1,4-diiodobenzene to 1,4-diiodo-2,5-dihexyloxybenzene were polymerized in order to explore the influence of steric bulk oil the surface-initiated polymerization process. Within the series of molecules, it was observed that monomers with smaller, less bulky side chains were more easily polymerized from the surface, resulting in smooth, regular films for unsubstituted and methoxy-substituted polyphenylene. Islands of polymer growth were observed with the ethoxy-substituted material and only sparse, irregular growth for the hexyloxy-substituted polymer. The resulting films were characterized by AFM, infrared spectroscopy, ellipsometry, and UV-vis spectroscopy.