We have studied crystallization in thin films of isotactic polystyrene (iPS) to better understand the morphology and formation of these structures through the use of polarization modulation near-field scanning optical microscopy (PM-NSOM). Polymer crystallites consisting of ordered layers (lamella) of folded chains are grown from amorphous iPS film. While the structure of bulk polymer crystallites (spherulites) is well established,1 a variety of less-understood forms, including dendritic structures, are found in ultra-thin (<100 nm) films. In addition, there are questions regarding how crystallization occurs in these constrained systems where the film thickness is comparable to the polymer chain dimensions. By combining polarimetric techniques with NSOM, we can measure the local linear birefringence (retardance) and the linear dichroism of thin-film samples, which provides quantitative information regarding molecular alignment in thin films with spatial resolution as high as 50 nm. NSOM-generated polarimetric images of polymer crystallites should provide valuable information regarding the mesoscopic morphology of these structures and give clues to their formation.
Citation: Polymeric Materials: Science & Engineering
Pub Type: Journals
NSOM, polarimetry, polymer crystallites, polymer thin films