ISSN:
0887-6266
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
The heat of fusion of perfectly crystalline poly(4-methylpentene-1) (P4MP1), ΔHu, has been determined by two methods. Melting point depressions (A) in concentrated solutions in naphthalene and cyclododecane, and in infinitely dilute solutions in 39 solvents, led to ΔHu = 5.5 ± 0.3 kJ mol-1 (65 ± 4 J g-1). The second method (B) involved new measurements of the crystalline volume Vu,c as a function of temperature, in order to calculate ΔHu from the Clausius-Clapeyron equation: extrapolation to the melting point gave Vu,c = 109.2 cm3 mol-1 (1.298 cm3 g-1) (I), which is in good agreement with the result of Tanigami et al.1 (II) but appreciably lower than the value reported by Zoller et al.2 (III). Possible reasons for the discrepancy are discussed. The values of ΔHu from methods A and BIII are in excellent agreement, whereas BI and BII give a higher figure. There is at present no reason to prefer one set of values to the other, although the degree of crystallinity estimated from the low ΔHu and the experimental heat of fusion is in the 75-85% range, in excellent agreement with x-ray diffraction data. Depending on the selected ΔHu, the entropy of fusion is either similar or lower than for other branched polyolefins. The results are discussed in terms of order in the melt, order seemingly relevant to the understanding of the mechanism of formation of the noncrystalline thermoreversible gels of P4MP1.
Zusätzliches Material:
9 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/polb.1988.090260515
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