| Autor: |
Tanigami, Tetsuya, Kai, Kanna, Tanaka, Koji, Matsuzawa, Shuji |
| Předmět: |
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| Zdroj: |
Journal of Inorganic & Organometallic Polymers; Dec2003, Vol. 13 Issue 4, p237-253, 17p |
| Abstrakt: |
Poly[bis(β-phenoxyethoxy)phosphazene] [PBPEP] had been shown in our previous paper to be a very useful polymer for investigating the crystallization mechanism of polymers, as the crystallization rate of PBPEP is extraordinarily small when isothermally crystallized from the melt. The crystallization of the low molecular weight oligomers of PBPEP was first studied in comparison to the high molecular weight polymers. The oligomer-rich fraction was obtained by fractionation of the as-polymerized sample, which had a broad molecular weight distribution. The fractions thus obtained were characterized by solution viscometry and size exclusion chromatography. The melting temperature and the growth rate of the spherulite from the melt were investigated by differential scanning calorimetry and optical microscopy. The growth rate was one or two orders of magnitude smaller in the oligomer-rich fraction than in the other high molecular weight fractions. A collapsed spherulite appeared in the oligomer-rich fraction at high crystallization temperatures. It is speculated that in the oligomer- rich fraction there is an excess free energy due to defects in the crystal phase. This defect is considerably larger in the oligomer-rich fraction than in the other fractions because a large quantity of short length chains is present. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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