A novel poly-4-vinylpyridine-b-PNLO (nonlinear optical material)-b-polystyrene-b-poly(4vinylphenol) 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-NH 2 block copolymer containing an aniline end group with a poly(4-tert-butyldimethylsiloxy)styrene-b-PS-CO2H (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-(tertbutyldimethylsilyl)oxystyrene by tert-butyllithium in THF at -78 °C followed by the addition of styrene and end functionalized with dried carbon dioxide gas. The end-functionalized P4VP-b-PNLO-Ph-NH 2 block copolymer was synthesized by step polymerization of 4-(4-(4-fluorophenylsulfonyl)phenyl)sulfonyl-4′-N-ethyl-N-2-(4-hydroxyphenolic)ethylazobenzene and coupling to P4VP-Ph-OH that was endfunctionalized with a phenolic end group followed by end capping with 4-(4-(4-fluorophenylsulfonyl)phenyl)sulfonyl-4′-N-ethyl-N-2-(4-aminophenolic)ethylazobenzene. The end-functionalized P4VP-Ph-OH was synthesized by the 1,1-diphenyl-3,3-dimethylbutyllithium-initiated polymerization of 4-vinylpyridine in THF at -78 °C followed by addition of 4-(tert-butyldimethylsiloxy)bromomethylbenzene.

The synthesis of poly(4-vinylpyridine) block copolymers containing a poly(4-(4-(4-fluorophenyl)sulfonylphenyl)sulfonyl-4′-N-ethyl-N-2-(4-hydroxyphenolic)ethylazobenzene) (PNLO) segment with a MW between 7300 and 19 300 was carried out by the reaction of the 4-fluorophenyl end group of the PNLO segment with a low molecular weight (DP ) 33 or less) phenol end-functionalized P4VP under basic conditions. Self-assembly of this diblock copolymer occurs with polystyrene-b-poly(vinylphenol) (PSb-PVPh) or PMMA-b-poly(2-hydroxyethyl methacrylate) (PMMA-b-PHEMA) block copolymers, having short H-bond donor blocks, through the formation of H-bonds with the acceptor P4VP blocks. This process was studied by the increased solubility of the P4VP-b-PNLO copolymer in toluene/CH 2Cl2 (99/1, v/v) or in ethyl acetate due to the formation of the more soluble block copolymer complexes. The increases in solubility were monitored by visible absorption at about 456 nm, the absorption maximum of the PNLO segment. The apparent binding constants to the PS-b-PVPh and the PHEMA-b-PMMA block copolymers in toluene/CH 2Cl2 (99/1, v/v) and in ethyl acetate were on the order of 10 5 and 10 3 M -1 , respectively.

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