Polarized Raman scattering studies of chain orientation in hydrostatically extruded polypropylene

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Abstract
Polarized Raman scatteringmeasurements have been used to study chain orientation statistics in uniaxial hydrostatically extruded isotactic polypropylene. By investigating the CH2 twisting mode at 1256 cm−1, quantitative results for <P 2(cosϑ) ≳ and <P 4(cosϑ) ≳ have been obtained. Functions <P 2(cosϑ) ≳ and <P 4(cosϑ) ≳ are the second and fourth moments of the orientational distribution function, where ϑ is the angle between the chain axis and the direction of extrusion. Alignment of polymer chains has been found to increase with the increase of extrusion ratio. The measured <P 2≳ values are found to be in good agreement with the birefringence data. Values of orientational order parameter <P 4≳ for an extruded polymer are reported for the first time.