Time-Resolved Fourier Transform Infrared Spectroscopy, Gravimetry, and Thermodynamic Modeling for a Molecular Level Description of Water Sorption in Poly(蔚-caprolactone)
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- 作者：Pellegrino Musto ; Michele Galizia ; Marianna Pannico ; Giuseppe Scherillo ; Giuseppe Mensitieri
- 刊名：Journal of Physical Chemistry B
- 出版年：2014
- 出版时间：July 3, 2014
- 年：2014
- 卷：118
- 期：26
- 页码：7414-7429
- 全文大小：586K
- ISSN：1520-5207
文摘
Sorption of water in poly(蔚-caprolactone) (PCL), with specific focus on the hydrogen-bonding interactions, has been analyzed by combining ab initio calculations, macroscopic thermodynamics modeling, and relevant features emerging from spectroscopic and gravimetric measurements. Fourier transform infrared (FTIR) data, analyzed by difference spectroscopy, two-dimensional correlation spectroscopy, and least-squares curve-fitting analysis associated with gravimetric determination of water sorption isotherm provided information on the system鈥檚 behavior and on the molecular interactions established between the polymer and the penetrant. A consistent physical picture emerged pointing to the presence of two spectroscopically discernible water species (first-shell and second-shell layers) that have been quantified. Water molecules are present in the form of dimers within the polymer equilibrated with water vapor up to a relative humidity of 0.65. At higher humidities, clustering of water sorbed molecules starts to take place. The multicomponent 谓(OH) band representative of absorbed water has been interpreted with the aid of ab initio calculations performed on suitably chosen model systems. The outcomes of spectroscopic analyses were interpreted at a macroscopic level by modeling the thermodynamics of water sorption in PCL based on a nonrandom compressible lattice theory accounting for hydrogen-bonding (HB) interactions. Starting from the fitting of the gravimetric sorption isotherm, the model provided quantitative estimates for the amount of self- and cross-HBs which compare favorably with the FTIR results.