Quantifying polymer structural component evolution using X-ray scattering and mixed-integer network component analysis

In this work we present a novel computational approach for the extraction of underlying polymer structural component signatures and corresponding structural evolution through decomposition of multivariate X-ray scattering (SAXS/WAXS) datasets. Without assumptions based on structural geometry, this mixed-integer network component analysis (NCA) methodology generates a reduced set of component scattering signatures and component fraction evolution. Structural models are then assigned to each component based on a generalized expression for scattering from multi-phase materials. The methodology is applied systematically to the study of ethylene/alpha-olefin copolymer isothermal crystallization. The decomposition generates component signatures defining structures of varying extent within the sample but with constant average local structure. For WAXS datasets, these components can be correlated to crystalline and amorphous regions, while for SAXS datasets they can be correlated to ordered and disordered crystalline lamellae. These model choices agree with structures observed in the literature and are confirmed by comparison to reference crystallinity data.

► We develop an approach for extracting X-ray scattering component signatures.
► The approach is implemented using mixed-integer network component analysis (NCA).
► We systematically study ethylene/alpha-ole_n copolymer isothermal crystallization.
► WAXS components describe crystalline and amorphous regions.
► SAXS components describe ordered and disordered crystalline lamellae.