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CPP: Chemische Physik und Polymerphysik

CPP 15: POSTER: Polymers and Biomaterials

CPP 15.29: Poster

Dienstag, 9. März 2004, 17:00–19:00, B

Changes in the mechansim during isothermal polymer crystallizations: Indications in scattering experiments on P(E-co-O) andPεCL — •Barbera Heck, Peter Kohn, and Gert Strobl — Physikalisches Institut der Albert-Ludwigs-Universität, 79104 Freiburg, Germany

The kinetics of crystallization in polymer systems can be followed in different experiments, and a comparison of the corresponding isotherms provides special insights with regard to the mechanism. We carried out such comparative studies for samples of poly(ethylene(0.86)-co-octene(0.14)) and poly(ε-caprolactone), employing time-dependent absolute intensity SAXS coupled with WAXS, density measurements by dilatometry and optical microscopy.

The measurements on P(E-co-O) showed a strict proportionality of the Porod-coefficient P and a Bragg-reflection intensity I, but strong deviations of the development of the density. Optical microscopy shows objects with constant size but increasing birefringence rather then growing spherulites. Obviously some densification occurs prior to the formation of crystals.

For PCL it was found that the power-laws describing the increase in P and I during the initial stage differ from each other, which is indicative for a change of the inner order of the growing lamellae. The WAXS-pattern includes in addition to contributions associated with melt-like regions and crystals also a third contribution associated with a mesomorphic phase.