Effect of molecular mass on the melting temperature, enthalpy and entropy of hydroxy-terminated PEO

P. J. Sanchez-Soto; J. M. Gines; M. J. AriasCs. NovakA. Ruiz-Conde

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Effect of molecular mass on the melting temperature, enthalpy and entropy of hydroxy-terminated PEO

机译：Effect of molecular mass on the melting temperature, enthalpy and entropy of hydroxy-terminated PEO

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This paper studies the effect of molecular mass on the melting temperature, enthalpy and entropy of hydroxy-terminated poly(ethylene oxide) (PEO). It aims to correlate the thermal behaviour of PEO polymers and their variation of molecular mass (MW). Samples ranging from 1500 to 200,000 isothermally treated at 373 K during 10 min, were investigated using DSC and Hot Stage Microscopy (HSM). On the basis of DSC and HSM results, melting temperatures were determined, and melting enthalpies and entropies were calculated. Considering the melting temperatures, it was found that the maximum or critical value of MW was found around 4000, and then these remain almost constant. This behaviour was interpreted assuming that lower MW fractions (MW4000), as folded chains. The melting enthalpies showed a scattering effect at least up to MW 35,000. It was difficult to obtain any relationship between melting enthalpies in Jg~(-1) and MW. These variations seem to be of statistical nature. Corrected enthalpy data on a molar basis (kJ mol~(-1)) exhibited a linear relationship with MW. Considering the solid-liquid equilibrium, the melting entropies (in kJ mol~(-1)) were calculated. These values were more negative as compared with molar enthalpy increases. It was explained because the changes in melting temperatures are much smaller than those observed in the enthalpy values. Linear relationship between enthalpies and entropies as a function of MW was deduced.

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来源
《Journal of thermal analysis and calorimetry》 |2002年第1期|189-197|共9页
作者
P. J. Sanchez-Soto; J. M. Gines; M. J. AriasCs. NovakA. Ruiz-Conde;
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作者单位

Instituto de Ciencia de Materiales de Sevilla (ICMSE), Centro Mixto Consejo Superior de Investigaciones Cientificas (C.S.I.C.), Universidad de Sevilla, c/Americo Vespucio s/n, Isla de la Cartuja, 41092 Sevilla, Spain;

Departamento de Farmacia y Tecnologia Farmaceutica, Facultad de Farmacia, Universidad de Sevilla, c/Profesor Garcia Gonzalez s/n, 41080 Sevilla, Spain;

Institute for General and Analytical Chemistry, Budapest University of Technology and Economics, Budapest, H-1521 Hungary;

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正文语种英语
中图分类物理化学（理论化学）、化学物理学;
关键词
DSC; melting enthalpies; melting temperatures; molecular mass; PEO polymers;

Effect of molecular mass on the melting temperature, enthalpy and entropy of hydroxy-terminated PEO

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