Advances in and utilization of nickel(0)-catalyzed coupling in the synthesis of functional polymeric materials

摘要

A short, simple, versatile methodology was developed for the synthesis of poly(2,5-benzophenone) containing coil-rod-coil triblock copolymers. Poly(2,5-benzophenone) macroinitiators were synthesized via endcapping the Ni(0)-catalyzed polymerization of 2,5-dichlorobenzophenone followed by functionalization of the chain ends utilizing phase transfer chlorination. Varying molecular weights of polystyrene- b-poly(2,5-benzophenone)-b-polystyrene were synthesized using the macroinitiators in the atom transfer radical polymerization of styrene. The Ni(0) coupling reaction was refined through studying the effects of solvent and monomer structure on the polymerization of 2,5-dichloro-3-(2\u27 -thiophenecarbonyl)thiophene, 3-benzenesulfonyl-2,5-dichlorothiophene, 2,5-dichlorobenzophenone, and 2-benzenesulfonyl-1,4-dichlorobenzene. It was shown that the solvent choice has drastic effects upon the catalyst system and the final polymer. The differences in the catalyst resulting from solvent choice were explored by nuclear magnetic resonance (NMR). Effects arising from the structure of the monomer are discussed in relationship to the results obtained and the proposed mechanism. Utilizing the improved Ni(0)-catalyzed coupling conditions, chain end functionalized poly(2,5-benzophenone)s of molecular weights ranging from 2.5 x 103 g/mol to 25.8 x 103 g/mol were synthesized. The chain ends were converted in a versatile manner to yield macroinitiators for atom transfer radical polymerization and varying molecular weights of poly(methylmethacrylate)-b-poly(2,5-benzophenone)- b-poly(methylmethacrylate) were synthesized. The polymers were characterized by gel permeation chromatography (GPC), online-multiangle laser light scattering (MALLS), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), and transmission electron microscopy (TEM).