Synthesis of Well-Defined Chiral Oligopinanylsiloxane Graft Copoly(phenylacetylene)s Using the Macromonomer Method and Their Enantioselective Permeability

As enantioselectively permeable membrane materials showing high permeability and good self-membrane forming ability, 24 well-defined chiral graft copolymers (PPA-graft-OMPS) consisting of flexible chiral oligomethylpinanylsiloxane (OMPS) grafts and a rigid poly(phenylacetylene) (PPA) backbone were synthesized stepwise in a well-controlled manner. First, synthesized cyclic OMPS monomers containing one or two chiral pinanyl groups were used in living anion ring-opening polymerization to produce the precursors of the corresponding macromonomers whose degrees of polymerization were controlled. Then, by introducing a triple bond at one end of the precursors, the macromonomers were obtained. Finally, PPA-graft-OMPSs with controlled numbers of the grafts were synthesized by copolymerization of the macromonomers with phenylacetylene comonomers. The PPA-graft-OMPSs show good self-membrane forming abilities in spite of the very high content of the flexible OMPS unit because of the rigid conjugated backbone. They show stable enantioselective permeation with high permeability for around 1000 h based on solution selectivity.