| A novel ABCD poly4-vinylpyridine-b-PNLO-b-polystyrene-b-poly-(4-vinylphenol) tetrablock copolymer, containing a non-linear optical polymeric B block (P4VP-b-PNLO-b-PS-b-PVPh), was synthesized by a combination of step and anionic vinyl polymerization. The tetrablock copolymer is designed to form asymmetric lamellar structures by self-assembly prompted by the interactions between the donor (D) and acceptor (A) blocks which are expected to align the dipole moments of PNLO block in one direction. The synthesis was carried out by reaction of a P4VP-b-PNLO-Ph-NH 2 block copolymer containing an on-line end group with a poly-4-(tert-butyldimethylsiloxy)styrene-b-PS-CO 2H (PBDMSS-b-PS-COOH) diblock copolymer containing a t-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-bPBBDMSS tetrablock copolymer the PVPh block was obtained by deprotection of t-butyldimethylsilyly group of the PBDMSS block with tetrabutylammonium fluoride in THF.The PBDMSS-b-PS-COOH precursor was synthesized by initiation of 4-(t-butyldimethylsiloxy)styrene by t-butyllithium, in THF at −78°C followed by the addition of styrene and end-functionalized with carbon dioxide. The end-functionalized P4VP-bPNLO-Ph-NH 2 block copolymer was synthesized by step polymerization of 4-(4-(4-fluorophenylsulfonyl)- phenyl)sulfonyl-4′-N-ethyl-N-2-(4-hydroxyphenol)ethyl-azobenzene and coupling of the resulting polymer to P4VP end-functionalized with a phenolic end group. |
