Phase Transitions of Naphthalene and Its Derivatives Confined in Mesoporous Silicas

• Published in: Journal of physical chemistry. C Vol. 115; no. 11; pp. 4738 - 4748
• Main Authors: Lee, Janice A, Rösner, Harald, Corrigan, John F, Huang, Yining
• Format: Journal Article
• Language: English
• Published: American Chemical Society 24.03.2011
• Subjects: C: Surfaces, Interfaces, Catalysis
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp111432j

The phase transitions of naphthalene and its derivatives including 2-methylnaphthalene, 2-methyoxynaphthalene, and 2-chloronaphthalene confined in mesoporous silicas of spherical and cylindrical pore geometry were investigated by differential scanning calorimetry (DSC), and a depression of the phase transition temperature was observed. It was found that depression and freeze−melt hysteresis are generally greater in spherical pores. Using powder X-ray diffraction, it was observed that the crystal structure of confined naphthalene is the same as the bulk. Using DSC and Raman spectroscopy, it was shown on both a thermodynamic and molecular level that there is a nonfreezing layer on the pore walls for each confined compound and its thickness depends on the pore diameter.