کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5189166 | 1381178 | 2006 | 11 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Non-linear changes in the specific volume of the amorphous phase of poly(4-methyl-1-pentene); Kauzmann curves, inverse melting, fragility
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی آلی
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
The existence of a re-entrant phase at high temperature and high pressure has been reported for a polymer, poly(4-methyl-1-pentene), recently [Rastogi S, Newman M, Keller A. Nature 1991;55:353; Rastogi S, Newman M, Keller A. J Polym Sci, Phys Ed 1993;31B:125; Rastogi S, Höhne GWH, Keller A. Macromolecules 1999;32:8909; Greer AL. Nature (News Views) 2000;404:134; Van Ruth NJL, Rastogi S. Macromolecules 2004;37:8191 [1-5]]. In a similar manner to the general phase behaviour proposed by Tammann in 1903 [Tammann G. Kristallisieren und Schmelzen; 1903; Metzger and Wittig Leipzig [6]], a re-entrant region exists where the entropy of a crystal is greater than that of its liquid. The existence of a crystal having entropy greater than its corresponding liquid is in contradiction to the Kauzmann paradox [Kauzmann W. Chem Rev 1948;43:219 [7]]. Here, we show how by careful study of its origin, a re-entrant phase can exist without invoking a paradox. Tammann ascribes the origin of the re-entrant behaviour, depicted in a pressure-temperature diagram, to the existence of a line where the difference in specific volume between the liquid and the crystal is zero (ÎV=0 line) and another line where the difference in enthalpy between liquid and crystal is zero (ÎH=0 line). Here, we provide direct experimental evidence for the existence of this ÎV=0 line for the first time. The experimental observations also show the presence of a second ÎV=0 line at lower temperatures. This second ÎV=0 line has an essential role in resolving the apparent entropy crisis [Debenedetti PG, Stillinger FH. Nature 2001;410:259 [8]] in the re-entrant region of the pressure-temperature phase diagram, through a relationship between the specific volume and the entropy. These two ÎV=0 lines, when combined with the melting and glass transition temperature, describe the shape of the pressure-temperature phase diagram of this polymer.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Polymer - Volume 47, Issue 15, 12 July 2006, Pages 5555-5565
Journal: Polymer - Volume 47, Issue 15, 12 July 2006, Pages 5555-5565
نویسندگان
Sanjay Rastogi, Juan Fran Vega, Nico J.L. van Ruth, Ann E. Terry,