Synthesis and oxygen permselectivity of multi-stranded graft copolymers

New types of multi-stranded graft copolymers (AGSs) were synthesized by selective three-step polymerization of monomer M having three deferent polymerizable groups. First, a rigid cis-cisoidal helical polyphenylacetylene (A) with bromo substituents at the pendants was synthesized by addition polymerization of the triple bond in M with a rhodium catalyst, and then graft copolymers (AGs) with polyphenyleneethynylene grafts having many hydroxy groups were synthesized by Sonogashira-coupling polycondensation in the presence of the rigid polyphenylacetylenes. Finally, multistrands were synthesized in the grafts by etherification of the hydroxyl groups with dibromomethane or dibromoethane. The degree of polymerization of the grafts (q) and the second strands (r) were determined by H-1 NMR and IR, respectively. The q and r could be controlled. Oxygen permeabilities for all the polymers (A, AGs, and AGSs) were able to be measured. AGSs showed the best performance among the three. This may be because micropores and ultramicropores formed in the AGSs played a very important role in enhancing both permeability and permselectivity.