New macromolecular architectures for permselective membranes - Gas permselective membranes from dendrimers and enantioselectively permeable membranes from one-handed helical polymers

Chemistry of macromolecular architecture is one of the fastest growing branches of polymer chemistry. The present review describes macromolecular architectures for permselective membranes relating their structures and permselectivity, and is focused on dendrimers for gas permselective membranes and one-handed helical polymer membranes for enantioselectively permeable membranes (optical resolution). The first part of this review described the three kinds of permselective membranes prepared from pure polydendrons or dendronized polymers having self-membrane-forming ability by us, and from another polymer and dendrimers or hyperbranched polymers as a crosslinker, and from another supporting membrane and dendrimers as a modifier. The membranes from polydendrons showed better oxygen permselectivities than those of conventional polymer membranes. In the second part, three kinds of enantioselectively permeable membranes reported by many researchers, i.e., chiral carriers-containing composite membranes, membranes based on chiral HPLC stationary phase polymers, and chiral molecular imprinting membranes, are reviewed briefly. In particular, the detail of our macromolecular designs of one-handed helical poly(substituted acetylene)s as materials for enantioselectively permeable membranes is discussed as the fourth category. When the content of the chiral groups was higher, the permselectivity was enhanced. The one-handed helical backbones were found to be effective for enantioselective permeation. It was also shown that the disadvantage of this method, i.e., low permeation rate was improved by using thinner membranes. In addition, enantioselectively permeable membranes are classified from the view point of their permeation mechanisms.