title: Rheological response of methylcellulose toward alkanediyl-α,ω-bis(dimethylcetylammonium bromide) surfactants with varying spacer length.
abstract: The modulation of properties of methylcellulose (MC) by cationic gemini surfactants with varying spacer lengths was studied employing tensiometry, rheometry and turbidimetry. Surface tension measurements anticipate that the gemini surfactant with longer spacer chain length saturates MC at lower concentrations owing to its greater hydrophobicity compared to shorter spacer analogues. Rheometric and turbidimetric measurements suggest that at very low concentrations of gemini surfactants, ion-dipole type of interactions between MC and gemini surfactants promote the extension of polymer chains which is manifested by an initial increase in the low shear viscosity and gelation temperature of MC-gemini surfactant systems, and lowering of turbidity. Such interactions were found to be stronger in case of 16-4-16 than 16-5-16, and almost absent in case of 16-6-16 surfactant system. However at concentrations above CAC, hydrophobic forces operative between MC and gemini surfactants were found to be more for 16-6-16 than that of 16-5-16 and 16-4-16. The final levelling of MC viscosity in presence of all the three gemini surfactants and the variation of gelation temperature suggests the solubilization of network junctions in the surfactant micelles. Moreover, the presence of gemini surfactant strongly affects the interaction of MC with a model hydrophobic drug rifampicin.The results highlight the importance of gemini surfactants and their spacer length in controlling the structural dynamics of MC and its effective use in pharmaceutical and food industry.
authors.affiliation: Department of Chemistry, University of Kashmir, Srinagar 190006, J&K, India.
authors.forename: Rais Ahmad
authors.initials: RA
authors.lastname: Shah
authors.affiliation: Department of Chemistry, University of Kashmir, Srinagar 190006, J&K, India.
authors.forename: Oyais Ahmad
authors.initials: OA
authors.lastname: Chat
authors.affiliation: Department of Chemistry, University of Kashmir, Srinagar 190006, J&K, India.
authors.forename: Masrat
authors.initials: M
authors.lastname: Maswal
authors.affiliation: Department of Chemistry, University of Kashmir, Srinagar 190006, J&K, India.
authors.forename: Ghulam Mohammad
authors.initials: GM
authors.lastname: Rather
authors.affiliation: Department of Chemistry, University of Kashmir, Srinagar 190006, J&K, India. Electronic address: aijaz_n5@yahoo.co.in.
authors.forename: Aijaz Ahmad
authors.initials: AA
authors.lastname: Dar
mesh_terms: D004337:Drug Carriers; D057927:Hydrophobic and Hydrophilic Interactions; D008747:Methylcellulose / Q000737:chemistry*; D015394:Molecular Structure; D009391:Nephelometry and Turbidimetry; D044367:Phase Transition; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D012212:Rheology; D012293:Rifampin / Q000737:chemistry; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature; D014783:Viscosity
chemical_list: D004337:Drug Carriers; D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents; D008747:Methylcellulose; D012293:Rifampin
keywords: Gelation; Gemini surfactant; Methylcellulose