Conformational Ordering on the Growth Front of Isotactic Polypropylene Spherulite

The growth front of isotactic polypropylene (iPP) spherulites is studied with series of in-situ microanalyzing techniques: conventional source infrared microspectroscopic (CS-μIR), polarized infrared microspectroscopic imaging (SR-μPIR), and scanning X-ray microdiffraction (SR-μSXRD). By SR-μSXRD, the actual growth front boundary of spherulite was clearly defined, which is the boundary observed with an optical microscope. Measurements of CS-μIR and SR-μPIR on growing spherulites reveal that a growth front layer (GFL) with high content of conformational ordered long helices exists outside the growth front of spheurlite, which has a thickness up to 30 μm above 142 °C. These long helices preferentially orient perpendicular to the radial direction of spherulite, whose growth fashion seems correlating with the growth of spherulite.