Synthesis and Self-Assembly of Poly- (diethylhexyloxy-p-phenylenevinylene)-b-poly(methyl methacrylate)

ABSTRACT: A series of poly(diethylhexyloxy-p-phenylenevinylene-b-methyl methacrylate) (DEH-PPV-b-PMMA) polymers with narrow polydispersity (PDI < 1.1) were synthesized using Siegrist polycondensa-tion and anionic polymerizations followed by “click ” chemistry. Alkyne-terminated DEH-PPV and azido-terminated PMMA were synthesized first, and then the two functionalized polymers underwent 1,3-cycloaddition reaction to obtain copolymers. Both the conversion of the end-functionalization of the homopolymers and the yield of the “click ” reaction were higher than 98 % as determined by 1H nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC). Transmission electron micro-scopy (TEM) and small-angle X-ray scattering (SAXS) studies reveal the details of copolymer morphology. TheDEH-PPV-b-PMMA system presented here has higher block segregation strength thanmany previously studied rod-coil block copolymers yet still shows experimentally accessible phase transitions with respect to temperature. As a result, thismolecule offers new insight into the competition between rod-rod and rod-coil interactions that occurs in the system. The DEH-PPV rods are organized as a monolayer that is inclined with the lamellar normal (smectic C) for the copolymers containing low volume fraction of PMMA coil (<54%). However, as the coil fraction increases, the strips containing DEH-PPV pack into hexagonal lattice. In contrast to previous work which demonstrated similar morphologies, the sequence of reversible liqui