Molecular Length Dependence of the Melting Temperature Elevation for the Encapsulated Linear Monocarboxylic Acids inside Titania Nanotubes

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• 作者：Xiao-Ping Tang ; Eddie Z. Y. Ding ; Nitzia C. Ng ; Benjamin K. Mezick
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：August 6, 2009
• 年：2009
• 卷：113
• 期：31
• 页码：13488-13497
• 全文大小：246K
• 年卷期：v.113,no.31(August 6, 2009)
• ISSN：1932-7455

文摘

A series of linear monocarboxylic acids (specifically, decanoic, dodecanoic, tetradecanoic, hexadecanoic, and octadecanoic acids) encapsulated in titania nanotubes was studied by ¹³C nuclear magnetic resonance. The ¹³C CP-MAS spectra for the encapsulated acids display a broad peak representing the molecules chemisorbed on the nanotube surface and two new, sharp peaks representing the molecules trapped in the pore shielded by the chemisorbed molecules. The two new, sharp CP peaks for the trapped acids are readily differentiable from the sole sharp CP peak for the bulk neat acids. They were assigned to the trapped dimers and monomers, which are alternately distributed in the pore. The trapped acids thus possess a novel molecular arrangement, in contrast to the bulk neat acids’ containing solely dimers. The melting temperatures of all the trapped acids were measured higher than the corresponding bulk melting temperatures. The degree of the melting temperature elevation was observed inversely proportional to the effective pore diameter for the trapped acids, bearing a resemblance to the Gibbs−Thomson equation. With respect to using encapsulated fatty acids for thermal energy storage, the present work gives insight to lessening the latent heat loss induced by encapsulation.