X-ray analysis and Rietveld refinement of polyvinyl alcohol

•Rietveld refinement of the polyvinyl alcohol semicrystalline structure.•New structural model of the polyvinyl alcohol.•X-ray diffraction analysis of polymeric polyvinyl alcohol.•Experimental X-ray diffraction of polyvinyl alcohol. The Rietveld method has been used to refine the polyvinyl alcohol (PVA) structure. The PVA is a polymeric material exhibiting a semicrystalline “head-to-tail” arrangement of repeating units. Experimental X-ray pattern of PVA was adjusted considering a model based on monoclinic symmetry, but using the P21/m and P21/c spatial groups. The lattice parameters and atomic positions were adjusted in each case. The P21/c based model showed a better Rietveld adjust than the P21/m. Then, the P21/c model was used to analyze the structural behavior of the PVA subjected to different pH environments. From refinement results, the PVA subjected to acid environment remained unchanged and suffered a regalement of its crystalline structure when it is subjected to a basic pH, causing a loss of its permanence and crystallinity. The results provide a powerful model to evaluate the crystallinity degree of the PVA and its structural variations using the Rietveld refinement method.