Synthesis and Self-Assembly of Diblock Copolymers through Hydrogen Bonding. Semiquantitative Determination of Binding Constants

Abstract

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) (PS-b-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/CH2Cl2 (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/CH2Cl2 (99/1, v/v) and in ethyl acetate were on the order of 105 and 103 M-1, respectively.