Structural modulation in colored polymer bands of methacrylic acid-based frontal polymerization

Abstract

The periodic colored polymer bands have been investigated in frontal polymerization (FP) reaction containing methacrylic acid (MAA), hydroquinone, Benzoyl peroxide (BP), and N, N Dimethyl aniline (DMA) system. The MAA acts as a monomer, which was diluted adequately with methanol (MeOH), ethanol (EtOH), and butanol (BuOH) separately to observe the patterning characteristics in different reaction schemes. The structural modulations that include the periodicity of colored polymer bands, morphological changes, and spacings between two adjacent layers were studied. The colored variations of polymer bands and their dependency on the concentration of BP, hydroquinone and alcoholic compositions have been studied. The highly consistent pink-white colored polymer bands, loosely-packed band structures, and perfectly ordered band structures resulted in MeOH, EtOH, and BuOH systems, respectively, as discussed. The evolution of tiny bubbles and convection-type instability has been observed in different conditions of the FP reactions that significantly affect the planar movement of the polymer fronts. The hot spots, which usually represent the high-temperature regions of a typical frontal surface, have also been demonstrated in all reacting systems, which may cause spin mode propagation of the fronts and change the surface geometry, as described. The materials characterization was carried out using UV–visible spectrophotometer, NMR, FTIR, and FESEM techniques, providing information about the polymer phases involved in band structures, composition, and surface properties. The analytical data and results obtained during the study further emphasized that two different colored polymers, namely 1, 4-dihydroxy anthraquinone methacrylic acid and poly-methacrylic acid dihydroxy, anthraquinone produced simultaneously and crystallized periodically, results in the development of a colored polymer band structures. The possible reactions and associated chemical mechanisms concerning the observations, the nature of the monomer, and solvent characteristics have been proposed, which show a close agreement with the analytical data and results obtained during the study.