Characterization of Ammonio-Methacrylate Copolymer-Clay Composite Dispersions and Films

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Thitiphorn Rongthong
Srisagul Sungthongjeen
Thaned Pongjanyakul



Introduction: Ammonio-methacrylate copolymer (AM), a cationic polymer, has been used as a tablet film forming agent for controlling drug release. The commercial products in dispersion form are Eudragit® RL 30D and Eudragit® RS 30D. However, these polymers showed undesirable drug permeability, low mechanical properties, and tacking problem. Magnesium aluminum silicate (MAS), a negatively charge clay, could change permeability and mechanical properties of polymeric films. Consequently, it is interesting to incorporate MAS into AM films for modifying the properties of films. The objective of this preliminary study was to investigate the interaction of AM with MAS in the form of dispersions and films. Materials and Method: AM-MAS composite dispersions with various ratios were prepared and investigated particle size and zeta potential of flocculates formed. The AM-MAS composite films with 15% plasticizer were prepared using casting method. The matrix and surface morphology and crystallinity of the films were investigated using SEM and PXRD, respectively. Intermolecular interaction of AM and MAS in the composite films was investigated using ATR-FTIR method. Results: Incorporation of MAS into AM dispersion caused a flocculation of AM particles. The zeta potential of AM-MAS flocculates was positive and tended to decrease with increasing MAS amount. The smaller flocculate size was formed with increasing MAS content in the dispersions. Eudragit® RL-MAS flocculates had greater particle size than Eudragit® RS-MAS flocculates due to higher quaternary ammonium group content. The AM-MAS composite films showed an opaqueness and a rough surface morphology. Electrostatic interaction of quaternary ammonium group (-N+(CH3)3) of AM and silanol group (-SiO-) of MAS was found with a shift of ATR-FTIR spectra. The intercalated nanocomposite of AM and MAS was formed in the films with the increasing of interlayer spacing of MAS. Conclusion: This finding suggests that quaternary ammonium groups of AM could interact with silanol groups of MAS via electrostatic interaction. This interaction causes a change of zeta potential and particle size of flocculates formed in the composite dispersion, leading to a change of morphology and crystallinity of the composite films.


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