Role of interface in dispersion and surface energetics of polymer nanocomposites containing hydrophilic POSS and layered silicates

Three different hydrophilic nanofillers – natural and synthetic layered silicate as well as octaammonium polyhedral oligomeric silsesquioxane (POSS) – were incorporated into polyamide-6 by a solution-mixing method. The surfaces of the resulting polymer nanocomposites were characterized by X-ray diffraction, polarized optical microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and contact angle measurements. All polymer nanocomposites displayed enhancement in surface hydrophilicity as well as increase in surface free energy due to surface enrichment of the nanofillers. The degree of enhancement was found to depend on both nanofiller type and dispersion state. Interfacial interactions in the form of hydrogen bonding played an important role in affecting the dispersion state of the layered silicates. Exfoliated layered silicates caused a larger increase in hydrophilicity than aggregated layered silicate. On the other hand, aggregated POSS molecules were able to induce a large increase in hydrophilicity. Significant spreading of water was also observed on surfaces containing POSS molecules. Surface models have been proposed to explain these phenomena.

Effect of different nanofillers and morphology on the hydrophilicity of the nanocomposite surfaces.Figure optionsDownload high-quality image (91 K)Download as PowerPoint slideResearch highlights
► The degree of enhancement in hydrophilicity of polymer nanocomposite surface depends on both nanofiller type and dispersion state.
► Interfacial interactions in the form of hydrogen bonding play an important role in affecting the dispersion state of the layered silicates.
► Exfoliated layered silicates and aggregated POSS molecules cause a larger increase in surface hydrophilicity than aggregated layered silicates.
► Aggregated POSS molecules also cause significant spreading of water on the surface.