Estimativa do percentual de cristalinidade de polímeros semicristalinos derivados da anilina através dos Padrões de Difração de Raios X

Abstract

The separation of the crystalline and non-crystalline contributions of diffraction patterns is a necessary step for the study of these regions and for the estimation of the crystallinity percentage of a semicrystalline polymer. Several methods have been proposed for this purpose and, due to this, it is observed in literature that the results of crystallinity for the same material are different when submitted to them, giving room for the questio-ning as to the veracity and/or efficiency of these methods . In this research the intrinsic conductive polymers Polyaniline, Poly(o-methoxyaniline), Poly(o-ethoxyaniline) were ob-tained through conventional chemical synthesis, characterized both morphologically and structurally, as well as submitted to the analysis of percentage crystallinity estimation by peak deconvolution, simple area separation and internal standard. Through the XRD technique, there were indications of unit cell increase in the POMA and POEA samples in relation to Polyaniline, due to the incorporation of the functional groups (—OCH3) and (-0C2H5) in the ortho position of the carbon rings. The structural refinement corrobo-rates with the results of XRD, evidencing also the increase of the unit cell of the samples of Poma and Poea in directions a and b. The XRD patterns were used for the application of peak deconvolution methods, with percentages of crystallinity estimated at 52%, 59% and 58% for PANI, POMA and POEA, respectively. Using the simple area separation method, percentages of 63%, 61% and 60% of crystallinity for PAM, POMA and POEA, respectively, and percentages of 67%, 62% and 54% of crystallinity were obtained for the same samples using Internal standard method. SEM images allowed analysis of the morphology of the samples, observing that the initial morphology of PANI (nanofibers of varying lengths and thicknesses) on significant modifications with the introduction of lateral groups, since the morphologies of POMA and POEA presented agglomerates In-complete vesicular nanospheres of varying sizes The electrical conductivity measurements corroborated with the results of the crystallinity percentage estimation obtained by the internal standard method, showing that the PANI presented the highest value, 2.1.10-3, followed by the values, respectively, of the POMA and POEA, 1.2.10-3 and 9.4.10-4.