STRUCTURE OF ALPHA-POLYPIVALOLACTONE - A REFINEMENT BASED ON THE RIETVELD METHOD

A comparative study is carried out on the structure of the ? form of polypivalolactone obtained (i) from the analysis of oriented-fibre X-ray diffraction diagrams, (ii) from conformational energy calculations and (iii) by refining the first two models through best fitting on the powder X-ray diffraction profile according to the Rietveld method. A single refined model is obtained that shows very good agreement both with experimental fibre intensities and with the powder profile. This result is discussed in terms of the accuracy of structural parameters derived from the Rietveld method compared with the much more numerous determinations based on X-ray diffraction from oriented samples.