Dissolution of Hydrogen Bonded Polymers in Water: From Synthetic to Biopolymers

The field of supramolecular materials explores the use of intermolecular, non-covalent bonding to obtain novel self-assembled structures. Self-assembly is a method of spontaneous organisation of molecules into higher order structures ranging from the nano to the macro scale and is defined by boundary conditions such as pH, temperature, H-bonding strength, ionic strength, polarity of the solvent. Nature operates in this manner and produces myriads of meso- and macroscopic structures based on the underlying molecular architectures (e.g. from polysaccharides, proteins, polynucleotides). These principles are scarcely exploited for industrial purposes and still require significant levels of scientific understanding to explore such possibilities. In this paper we will show that it is feasible to dissolve (or hydrolyse) hydrogen bonded synthetic as well as bio-polymers in superheated water. During the process water molecules reside within the lattice forming clathrates. The strengthening or weakening of hydrogen bonds in presence of water molecules is investigated by NMR spectroscopy in the solid state. Structural and morphological changes are followed by X-rays and microscopy, whereas conformational changes by vibrational spectroscopy. The methods are successfully applied to follow dissolution process of synthetic nylons, bis-amide diols, TPUs. The process has been extended to biopolymers for example keratin from different natural sources such are feathers, hair etc. Single crystals obtained from the water solution of synthetic and biopolymers have been further investigated. Reference: Dissolution of Hydrogen-Bonded Polymers in Water: A Study of Nylon-4,6; S Rastogi, AE Terry, E Vinken; Macromolecules 2004; 37(24) pp 8825 – 8828