Insight into Poly(l-lactic acid) Coexisting Amorphous and Semicrystalline Phases Using FT-IR Imaging and Four Polarization-Three Dimensional Macromolecular Orientation Calculation

A recently developed concurrent analysis of four-polarization IR (4P) data offers retrieval of three-dimensional (3D) orientation angles of macromolecules. Since it has only been for highly structured samples, it is important to explore its capabilities in samples lacking structure. Therefore, the nondestructive and label-free four polarization methodology was used to image the 3D orientation angles (4P-3D) and order parameters in different regions of anisotropic poly(l-lactic acid) thin film with coexisting amorphous and crystalline phases. The results show the variety of macromolecule three-dimensional organization in different types of polymer structures: the single circular spherulite, neighboring spherulites, and the amorphous phase. The arrangement of the chains and the degree of deviation from the normal of the film vary, depending on the morphology of the polymer film.