title: The influence of cosolvent polarity on the flow properties of hydroalcoholic gels: empirical models.
abstract: The aim of this study was to investigate the influence of cosolvent polarity on the rheological flow properties of aqueous and hydroalcoholic gels obtained from the Carbopol Ultrez 10 base and used for topical applications. Specifically, we have examined the effect of pH (range 4.0--7.0) on the consistency and flow properties of dispersed systems in water and mixtures--15 : 85% v/v of methanol : water, ethanol : water, n-propanol : water and n-butanol : water--at a constant polymer concentration of 0.3% w/w. The gels, which had decreasing polarity values in the jellifying medium, showed qualitatively similar flow behavior, characteristic of pseudoplastic systems, and all of the flow curves were adjusted to the Ostwald model. Sigmoidal dose response functions were calculated to describe the flow and consistency indexes as a function of pH. As a result, the influence of alcohol polarity on the polymer network has been assessed meaningfully using the empirical parameters obtained: maximum consistency index value (k(max)), pH value required for 50% development of polymer network (pH(50)), and asymptotic flow index value (n(min)) for the fully structured gels.
authors.affiliation: Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, Alcalá University; Campus Universitario E-28871 Alcalá de Henares, Madrid, Spain.
authors.forename: María Magdalena
authors.initials: MM
authors.lastname: Jiménez
authors.forename: María José
authors.initials: MJ
authors.lastname: Fresno
authors.forename: Alain
authors.initials: A
authors.lastname: Ramírez
mesh_terms: D000180:Acrylic Resins; D000438:Alcohols / Q000737:chemistry*; D000465:Algorithms; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003358:Cosmetics; D003879:Dermatologic Agents; D005079:Excipients / Q000737:chemistry*; D005782:Gels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D016014:Linear Models; D015233:Models, Statistical; D011145:Polyvinyls / Q000737:chemistry; D012212:Rheology; D012995:Solubility; D012997:Solvents / Q000737:chemistry*; D014783:Viscosity; D014867:Water
chemical_list: D000180:Acrylic Resins; D000438:Alcohols; D003358:Cosmetics; D003879:Dermatologic Agents; D005079:Excipients; D005782:Gels; D011145:Polyvinyls; D012997:Solvents; D014867:Water; C006912:carboxypolymethylene