Hierarchical and microscopic studies of colored polymer band structures in MAA-based frontal polymerization reactions and their mathematical validation

Abstract

Frontal polymerization (FP) is an innovative process that uses a reactive front of monomers to quickly transform into a solid polymer within a localized, self-sustaining reaction zone. FP has gained considerable attention for its energy-efficient characteristics and its ability to rapidly cure polymer composites for modern applications. In this study, periodic white-brown band structures have been investigated in the methacrylic acid (MAA) monomer system, which includes benzoyl peroxide (BPO), resorcinol, and N, N-dimethyl aniline (DMA). BPO initiates the formation of free radicals that subsequently react with the MAA monomer to form an active monomer radical, initiating the FP reaction through a free-radical mechanism. Periodicity in structures and the morphological variation of the produced colored polymer bands have been significantly altered by variations in the concentration of ethanol (EtOH), resorcinol, and BPO, as studied. High-resolution field-emission scanning electron microscopy (FESEM) and fourier transform infrared (FTIR) analyses revealed the production of two distinct polymer phases, which crystallized simultaneously during the FP reactions. The solid-state UV-Vis spectra results indicate that the white polymer phase exhibits a reflectance peak around 254 nm, while the brown polymer materials show reflectance peaks near 900 nm. Raman spectra and X-ray diffraction (XRD) analysis indicate that both white and brown polymeric materials were crystalline in nature and showed evidence of ring structures. Numerical simulations were conducted to examine the response of polymer front initiation and propagation under various FP reaction conditions, validating the structural development of colored polymer band structures. MATLAB plotting tools were utilized to visualize the results, enabling a thorough analysis of key performance metrics. The validated visual outputs and trends of polymerization reactions provide effective insight into the operational characteristics of FP reaction systems with high accuracy.