Nanoparticle Enlarged Interfacial Effect on Phase Transition of 1‑Octadecanol/Silica Composites

• Published in: The journal of physical chemistry. B Vol. 119; no. 5; pp. 2074 - 2080
• Main Authors: Gao, Xia, Xie, Baoquan, Su, Yunlan, Fu, Dongsheng, Wang, Dujin
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 05.02.2015
• Subjects: Diffraction; Expansion; Nanocomposites; Nanoparticles; Nanostructure; Phase transformations; Polymer matrix composites; Silicon dioxide
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp512124s

Motivated by the interest in an interfacial effect on crystallization behaviors and material properties of polymer nanocomposites, phase behaviors of a novel model system for polymer nanocomposite, 1-octadecanol/silica nanosphere composites (C18OH/SiO2), were studied by means of thermal analysis and wide-angle X-ray diffraction. Although a huge specific surface area of silica nanoparticles enlarges the surface–volume ratio of C18OH molecules, surface freezing phenomenon is not observed by DSC in the C18OH/SiO2 composites. While pure C18OH exhibits rotator RIV phase with molecules tilted with respect to the layer normal, the silica network favors and enhances untitled RII phase by disturbing the layering arrangement. Moreover, the confined C18OH shows a polycrystalline mixture of orthorhombic β form and monoclinic γ form. It is demonstrated that the interfacial interaction between the C18OH molecules and the silica surface contributes to the peculiar phase transition behaviors of C18OH/SiO2 composites. The investigation of the model system of long-chain alcohol/nano-SiO2 composites may help us to understand the complicated interfacial effect on phase behaviors and material properties of polymer nanocomposite systems.