Thermodynamics of water sorption in poly(ɛ-caprolactone): A comparative analysis of lattice fluid models including hydrogen bond contributions

Thermodynamics of water sorption in poly(ɛ-caprolactone) (PCL) has been interpreted by using three models based on compressible lattice fluid theories, addressing the issue of self- and cross-hydrogen bond interactions. The models, available in the literature, are of increasing complexity and consist of a compressible lattice fluid term which could account or not for non-randomness of contacts and, in the case of two of the models, of a hydrogen bonding contribution.Models were analysed and compared in terms of fitting capability of the experimental sorption isotherms and, where appropriate, of predicted amount of self- and cross-hydrogen bonds which are established in the PCL–water mixture. Results confirm that, to obtain a satisfactory fitting of data, it is necessary to explicitly account for formation of hydrogen bonds.

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► Thermodynamics of water–PCL mixtures need accounting for hydrogen bonding.
► PS and NRHB lattice models supply the same qualitative results.
► Quantitative differences between PS and NRHB are only in cross-HB entropic parameter.
► Prevailing water–polymer HB interaction are established with carbonyl on PCL.