Optical spectroscopy study of the interaction between curcumin and acrylic polymers

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Vol. 260; p. 119954
• Main Authors: van Riel Neto, Francisco, Foschini, Maurício, Tozoni, José Roberto, Piovesan, Erick, Cristovan, Fernando Henrique, Marletta, Alexandre
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.11.2021
• Subjects: Curcumin; De-aggregation; Optical Spectroscopy; Optical Spectroscopy; Curcumin; De-aggregation
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2021.119954

Fluorescence analyses show how the lateral chain of the acrylic polymers is related with the de-aggregation of the curcumina molecule in a blend. [Display omitted] •PnBMA de-aggregate Curcumin molecules in the guest/host system.•Connection between lateral chain of the acrylic polymers and de-aggregation process.•Interaction between polymers and curcumin molecule occur via lateral alkyl groups. This paper presents the results of a study conducted on the interaction between curcumin, a compound with several biomedical applications in traditional and modern medicine, and the acrylic polymers poly(methyl methacrylate), poly(ethyl methacrylate), and poly(n-butyl methacrylate), through photophysical experiments in curcumin/acrylic polymers casting films. Optical absorption intensity at ~340 nm increases relatively to its maximum at ~417 nm when the amount of curcumin in the polymeric film decreases, due to a significant change in the concentration of the isomers cis- or trans-form of curcumin, regardless of the acrylic polymer. Fluorescence (FL) spectra of the films depend on the curcumin concentration in the matrix with well-resolved line shape. They show two distinct bands, one at ~525 nm, for higher curcumin concentration (5.00 mmol.L-1), related to the aggregated curcumin species, and another at ~465 nm, for lower concentration of curcumin (0.10 mmol.L-1), related to the effects of the solvent on the conformational structure of the curcumin molecule and the presence of the trans-form of curcumin. The parameter Kagg, related to the contribution of the aggregated curcumin, shows the influence of the polymeric lateral chain length of the matrix in the de-aggregation of the curcumin. The Huang-Rhys factor indicates that curcumin aggregated species are conformationally more stable, and that the isolate species depends on the chemical environment and the matrix/curcumin interaction, decreasing its conformational degrees of freedom. Arrhenius plots, obtained via FL experiment in function of the sample temperature, show that, for higher curcumin concentration, the value for the relaxation energy process is not well defined, due the decrease in the interaction between the matrix and the curcumin molecules. With these results, it is possible to infer that the interaction matrix/curcumin must occur via lateral chemical alkyl groups.