Fourier Transform Infrared Imaging Analysis of Interactions Between Polypropylene Grafted with Maleic Anhydride and Silica Spheres Using Two-Trace Two-Dimensional Correlation Mapping

Hideyuki Shinzawa; Aki Sugahara; Hideaki Hagihara; Junji Mizukado; Ryota Watanabe

doi:10.1177/00037028211007872

Fourier Transform Infrared Imaging Analysis of Interactions Between Polypropylene Grafted with Maleic Anhydride and Silica Spheres Using Two-Trace Two-Dimensional Correlation Mapping

Appl Spectrosc. 2021 Aug;75(8):947-956. doi: 10.1177/00037028211007872. Epub 2021 Apr 15.

Authors

Hideyuki Shinzawa¹, Aki Sugahara¹, Hideaki Hagihara¹, Junji Mizukado¹, Ryota Watanabe¹

Affiliation

¹ National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.

PMID: 33783240
DOI: 10.1177/00037028211007872

Abstract

A technique for analyzing infrared imaging data based on two-trace two-dimensional (2T2D) correlation analysis is presented to extract pertinent information underlying spectroscopic imaging data. In 2T2D correlation mapping, each spectrum in hyperspectral data is individually compared with a reference spectrum to generate 2T2D asynchronous correlation intensity at the x- and y-coordinates on a 2T2D correlation map. Asynchronous correlation intensity develops only when the signal contribution from a certain species becomes even more significant in the sample spectrum compared with the reference spectrum. This feature can be advantageously utilized to examine molecular interaction or an intermediate form of the component present in a system of interest. 2T2D correlation mapping is examined using Fourier transform infrared imaging data of polymer composites based on polypropylene grafted with maleic anhydride melt-mixed with silica spheres. Infrared images derived by using conventional visualization based on a single wavenumber (i.e., 1713 cm^-1) are dominated with the overwhelming infrared absorbance induced by the normal maleic anhydride species, making the identification of subtle but pertinent changes in the composite system difficult. A 2T2D correlation map derived from the maleic anhydride/silica spheres composite developed a significant asynchronous correlation intensity between the infrared bands at 1695 and 1713 cm^-1 around a specific region on the map where the maleic anhydride and silica spheres coexist. On the other hand, such a correlation pattern becomes less acute when the silica spheres is modified with the octadecyldimethyl group to prevent the hydrogen bonding with the maleic anhydride. It thus revealed that the silanol groups on the surface of the silica spheres substantially interact with the maleic anhydride via the development of the hydrogen bonding.

Keywords: 2T2D; FT-IR; Fourier transform infrared imaging; IR spectroscopy; MAPP; polypropylene grafted with maleic anhydride; silica sphere; two-trace two-dimensional correlation spectroscopy.