Polymorphism and crystal morphology of poly(ethylene oxide) 2-methyl resorcinol supramolecular complexes

The crystal structure and the morphology of poly(ethylene oxide) (PEO)-2-me thyl resorcinol (MRES) supramolecular complexes are investigated by differe ntial scanning calorimetry and wide-angle and small-angle X-ray scattering. Depending on the MRES content, two molecular complexes with different stoi chiometries are observed. The first complex with a stoichiometry of 22 mol % MRES melts around 80 degrees C. This complex has a layered structure almo st similar to the structure of the PEO-p-dihalogenobenzene intercalates. Th is complex results from the intercalation of MRES molecules between polymer layers. The second complex with a stoichiometry of 33 mol % MRES melts aro und 90 degrees C. Its crystal structure is dictated by the formation of a t ight network of hydrogen bonds between host and guest molecules. In additio n, depending on the experimental conditions, the growth of nonintegral-fold ed or integral-folded crystals of PEO-MRES complexes is observed from the s mall-angle X-ray diffraction curves. These different crystal morphologies a re finally discussed in terms of the intermolecular interactions in these s olid-state supramolecular assemblies.