Synthesis and Solution Properties of Hydrophobically Modified Polysaccharides
Vitaliy V. Khutoryanskiy
Hydrophobically modified polymers are amphiphilic macromolecules mainly constituted of a hydrophilic backbone and hydrophobic side groups. In aqueous solutions these polymers undergo inter- or intra-molecular hydrophobic association, which results in unusual properties useful for a number of practical applications. The areas of application of these polymers include associative thickeners for enhanced oil recovery, pharmaceuticals, personal care formulations, coatings, adhesives, surfactants, emulsifiers, etc. This review presents the analysis of a literature data on preparation of hydrophobically modified polysaccharides (HMP) and their properties in aqueous solutions. Some of the synthetic methods used for hydrophobic modification of non-ionic (cellulose ethers, starch, dextran, pullulan, etc.), anionic (carboxymethylcellulose, hyaluronic acid, pectic acid, alginic acid, heparin) and cationic polysaccharides (chitosan) are presented. The methodology used for investigation of solution properties of hydrophobically modified polysaccharides is discussed. The special attention is paid to aggregate and micelle formation in solutions of hydrophobically modified polysaccharides, solubilization of hydrophobic compounds, their rheological properties and surface activity. The effects of polymers architecture (level of hydrophobic substitution, nature of hydrophobic groups, molecular weight of a hydrophilic backbone, etc.), concentration, temperature, presence of inorganic salts and organic solvents on solution properties of hydrophobically modified polysaccharides are discussed. Some applications of hydrophobically modified polysaccharides are briefly highlighted.