PHYSICO-CHEMICAL AND SURFACE PROPERTIES OF POLYMERS AND POLYMER SOLUTIONS AS RELATED TO PHARMACEUTICAL SOLID DOSAGE FORM DESIGN (POLYMETHYL VINYL ETHER)
Abstract
Physico-chemical parameters potentially reflecting the polar-nonpolar character of four molcular weight fractions of Poly(methyl vinyl ether/maleic anhydride), together with three alkyl ether forms of the copolymer (methyl, ethyl, isobutyl), were determined. Wetting properties of Methocel-6OHG and Ethocel organosols were also studied. The physical parameters determined were solubility parameter, water number, apparent dielectric constant, HLB number and interfacial tension. These parameters were all found to indicate the relative polar-nonpolar nature of the various members of the copolymer series. The physical parameters were also found to be related to each other in reflecting the hydrophile-lipophile character of the polymer. Molecular weight of a PVM/MA series had no significant effect on water number and solubility parameter. The swelling characteristics were studied by observing the surface of compressed copolymer discs in aqueous buffer solutions at 37(DEGREES) (+OR-) 0.1(DEGREES). The maximum swelling of the copolymers was found to decrease with an increase in alkyl ether chain length and a decrease in pH. Solute-solvent interaction was found to be greatest (maximum swelling) when the solubility parameter values of the polymer and media were close to one another. Dissolution rates of the copolymer discs were determined as related to alkyl ether substitution, pH of the media, and compressional load. Dissolution rates and lag periods were found to decrease with an increase in alkyl ether chain substitution and a decrease in the pH of the dissolution media. Dissolution rates were independent of compressional loads above 5000 pounds. Lag periods decreased with a decrease in compressional load which may reflect different rate (or extent) of solvent penetration in the discs thus prepared. Dissolution rates were found to be the greatest when the difference between the solubility parameter values of the polymer and the media was minimum. Wettability and critical surface tension of the alkyl ether copolymers and cellulosics were examined using a goniometer. The contact angles were measured on the compressed polymer disc surfaces. PVIB/MA and Ethocel were shown to have the least wettability and the lowest values of critical surface tension of the polymer series (indicating a more lipophilic nature). The contact angles observed on a Methocel-60HG-50 cps free film surface agreed with those measured on a corresponding compressed disc surface. Contact angles of wetting liquids on free films were independent of the solvent employed in casting the films. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of school.) UMI
Degree
Ph.D.
Subject Area
Organic chemistry
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