"Length and breadth" Polyrotaxane structures - A new concept in three-dimensional polymeric systems

This work describes the synthesis and characterization of rotaxane-crosslinked polymers using macrocyclic poly-(ethylene glycol) (PEG) attached to a vinyl moiety. Diacyl chlorides (fumaryl or itaconyl) and PEG400 were condensed under high dilution conditions to yield the corresponding macrocyclic monomers. These were purified by column chromatography and identified by mass spectroscopy utilizing MALDI-TOF technique and ¹H-NMR. Radical polymerization in bulk of these macrocyclic monomers using benzoyl peroxide as initiator, resulted in soft polymers which are soluble in various organic solvents. Under the same conditions, insoluble gels were obtained by copolymerization of the ring-substituted vinyl monomers with either hydrophobic vinyl monomers (methyl methacrylate, MMA) or with a hydrophilic vinyl monomer (2-hydroxy ethyl methacrylate, HEMA). These results indicate that crosslinking was obtained due to threading of linear chains through macrocycles which act as crosslinkers. The swelling ratios of the gels indicated a correlation between the molar ratios of the macrocycle and the linear chain incorporated with it.