Stimuli-responsive and Emulsifying Properties of Water-soluble Graft-copolymers of Methylcellulose and Acrylic Acid

Rauash A. Mangazbaeva1, Grigoriy A. Mun1, Zauresh S. Nurkeeva1, Elena Vecherkina1, Vitaliy V. Khutoryanskiy2

1Kazakh National University, Department of Chemical Physics & Macromolecular Chemistry, Karasai Batyra 95, 480012 Almaty, Kazakhstan

2University of Reading, School of Pharmacy, Whiteknights, PO Box 224, Reading RG6 6AD, Berkshire, United Kingdom

Abstract

Stimuli-responsive water-soluble polymers were prepared by grafting of acrylic acid onto methylcellulose in aqueous solutions using free-radical polymerization initiated by thermal decomposition of ammonium persulfate. The degree of grafting was determined by potentiometric titration and the structure of graft-copolymers was confirmed by infrared spectroscopy. The molar ratio [methylcellulose]:[polyacrylic acid] in graft-copolymer was found to be close to 2:1 mol.%. It was demonstrated that the grafting significantly influences the temperature-responsive properties of methylcellulose in aqueous solution. The effect of pH and ionic strength on the temperature-induced phase separation in aqueous solutions of these graft-copolymers has been studied. It was found that the graft copolymers exhibit pH- and ionic strength-sensitivity unlike unmodified methylcellulose. The formation of hydrogen-bonded inter- and intra-polymer complexes in aqueous solutions of these graft-copolymers is discussed. The synthesized graft-copolymers were assessed as emulsifying reagents for stabilisation of water-n-hexane emulsions. It was shown that the graft-copolymers exhibit better emulsification potential compared to unmodified methylcellulose and it can be adjusted by changes in solution pH.