Preparation of hydrophilic polymeric materials with movable cross-linkers and their mechanical property

Abstract

Hydrophilic polymeric materials with movable cross-linkers were obtained by the bulk copolymerization of a hydrophilic cyclodextrin monomer (γCDAAmMe) and liquid acrylamide monomers. A 2D 1H-NOESY NMR study revealed that the main chains penetrated the CD ring units, which acted as movable cross-linking points. Copolymerization of γCDAAmMe with N,N-dimethyl acrylamide (DMAA) as a small main chain monomer results in hydrophilic movable cross-linked materials (pDMAA-γCDAAmMe (x)). On the other hand, using 4-acryloylmorpholine (ACMO) or N,N-dimethylaminopropyl acrylamide (DMAPAA) as a bulky main chain monomer disfavours the formation of movable cross-links due to steric hindrance between γCDAAmMe and the side chains. In the water content range of approximately 40–80 wt%, the Young's moduli of pDMAA-γCDAAmMe (1)s are similar to those of pDMAA-MBAAm (1). However, the fracture energy of movable cross-linked materials is higher than that of than materials covalently cross-linked with N,N′–methylenebis(acrylamide) (MBAAm). An addition of water enhanced the mobility of the main chain polymers, allowing the movable cross-linking points.