Synthesis of block copolymers containing a main chain polymeric NLO segment

摘要

A novel poly-4-vinylpyridine-b-PNLO (nonlinear optical material)-b-polystyrene-b-poly(4-vinylphenol) tetrablock copolymer (P4VP-b-PNLO-b-PS-b-PVPh) was synthesized containing an NLO polymeric segment prepared by step polymerization. The tetrablock copolymer is designed to form an asymmetric lamellar structure by self-assembly prompted by the interactions between the donor and acceptor blocks which are expected to help to align the dipole moments of PNLO block into one direction. The synthesis was carried out by reaction of a P4VP-b-PNLO-Ph-NH2 block copolymer containing an aniline end group with a poly(4-tert-butyldimethylsiloxy)styrene-b-PS-CO2-H (PBDMSS-b-PS-COOH) diblock copolymer containing a tert-butyldimethylsilyl-protected polyvinylphenol endowed with a carboxylic end group in the presence of diphenylphosphoryl azide (DPPA) in N,N-dimethylacetamide. After the formation of the P4VP-b-PNLO-PhNH-CO-PS-b-PBDMSS tetrablock. copolymer the PVPh block was obtained by deprotection of tert-butyldimethylsilyl group of the PBDMSS block with tetrabutylammonium fluoride in THF. The PBDMSS-b-PS-COOH precursor was synthesized by initiation of 4-(tert-butyldimethylsilyl)oxystyrene by tert-butyllithium in THF at -78 degrees C followed by the addition of styrene and end functionalized with dried carbon dioxide gas. The end-functionalized P4VP-b-PNLO-Ph-NH2 block copolymer was synthesized by step polymerization of 4-(4-(4-fluorophenylsulfonyl)phenyl)sulfo 4'-N-ethyl-N-2-(4-hydroxyphenolic)ethylazobenzene and coupling to P4VP-Ph-OH that was end-functionalized with a phenolic end group followed by end capping with 4-(4-(4-fluorophenylsulfonyl)phenyl)sulfonyl-4'-N-ethyl-N-2-(4-aminophenol ic)ethylazobenzene. The end-functionalized P4VP-Ph-OH was synthesized by the 1,1-diphenyl-3,3-dimethylbutyllithium-iniated polymerization of 4-vinylpyridine in THF at -78 degrees C followed by addition of 4-(tert-butyldimethylsiloxy)bromomethylbenzene. [References: 46]