SUPRAMOLECULAR CHEMISTRY WITH MACROMOLECULES - MACROMOLECULAR KNITTING, REVERSIBLE FORMATION OF BRANCHED POLYROTAXANES BY SELF-ASSEMBLY

Mechanically Linked branched polymer 10 was prepared via rotaxane form ation by self assembly (''knitting'') of poly[bis(5-methylene-1,3-phen ylene)-32-crown-10 sebacate] (4) and preformed polyurethane 9 containi ng N,N'-bis(beta-oxyethyl)-4,4'-bipyridinium 2PF(6)(-) (''paraquat'') moieties in tetrahydrofuran (THF). The interpenetrating structure resu lting from ''knitting'' the bipyridinium units of the polyurethane thr ough the crown ether cavities of the polyester structure was proved by its color, NMR studies and gel permeation chromatography (GPC) measur ements. In accord with its equilibrium nature, the branching process ( rotaxane formation) was reversible depending on the solvent and temper ature. The branched material was soluble because the two polymeric com ponents were designed to have relatively low molecular weights and the polyurethane to contain only about two paraquat units, so as to be ab le to carry out solution characterization. However, extension of this concept to higher molecular weight and/or more highly functionalized s ystems provides interesting possibilities for reversible processing of thermoset-like materials and production of new types of polymeric sup ermolecules with potentially interesting and controllable properties.