Phenylenevinylene Block Copolymers by Ring-Opening Metathesis Polymerization

3 Phenylenevinylene Block Copolymers by Ring-Opening Metathesis Polymerization 

Conjugated block copolymers are of considerable interest as these polymers can self-assemble into a variety of morphologies (Matsen and Bates, 1996 Matsen and Thompson, 1999 Klok and Lecommandoux, 2001). In conventional block copolymers the particular morphology adopted depends primarily on the volume fraction of the two blocks. 

The first monomer 19 was dissolved in THF and ROMP was initiated by addition of a THF solution of the second-generation Grubbs catalyst. The reaction mixture was heated at 40 °C and the conversion of monomer monitored by TLC. After complete consumption of 

15 200 (expected M = 14624) and a polydispersity of 1.37 and a Mn of 28 800 (expected Mn = 29 344) and a polydispersity of 1.39. The increase in polydispersity of the block copolymers over that of the initial block may be related to slow initiation relative to propagation at the second stage that leads to a broadened molecular-weight distribution. 

The DSC traces for these block copolymers exhibited a small transition at —5 °C corresponding to the glass-transition temperature of poly(l,3-phenylenevinylene-2,5-diethylhex-yloxy-1,4-phenylenevinylene) 22. An endothermic peak at 110 °C for block copolymer can be assigned to the melting of the octyloxy side chains of the first blocks. On cooling exothermic peaks for side-chain recrystallization were observed. The observation of transitions associated with both homopolymers 15, 22 in the DSC traces of block copolymers suggests that phase separation of the block copolymer is extensive. 

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