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The paper investigates the influenceof the crystalline structurein the dynamical behavior of semicrystalline Triton X-100 allowingenlightening the reason for the detection/nondetection of the α′-process.The work was preceded by the study of the full amorphous materialfor which dielectric relaxation spectroscopy (DRS) identified multiplerelaxations: the α-process associated with the dynamical glasstransition and two secondary relaxations (β- and γ- processes).To evaluate how crystallinity affects the detected relaxation processes,different crystallizations were induced under high and low undercoolingconditions. While the secondary relaxations are unaffected by crystallization,the mobility of the cooperative bulk α-process is sensitiveto the distinct morphologies. The distinct semicrystalline stateswere structurally characterized by X-ray diffraction and polarizedoptical microscopy (POM). Differential scanning calorimetry (DSC)was used as a complementary tool. Depending on the extension of undercooling,large and well-defined shperulites or grainy-like structure emerge,respectively, for low and high undercooling degrees, as monitoredby POM. In the two crystalline structures, X-ray diffraction patternsdetected the amorphous halo meaning that both are semicrystalline.However, no differences between the amorphous regions are indentifiedby this technique; the distinction was done by means of dielectricmeasurements probing different mobilities in each of those regions.When the large spherulites evolve, the bulk-like α-process nevergoes to extinction and slightly shifts to low frequencies increasingthe associated glass transition by 2–3 K, as confirmed by DSC;the slight change is an indication that the dimensions of the persistingamorphous regions become comparable to the length scale inherent tothe cooperative motion that determines the glass transition in thefull amorphous material. For the grainy-like structure, the α-processbecomes extinct and an α′-process evolves as revealedby isochronal plots of dielectric measurements, with the featuresof a glass transition as confirmed by temperature modulated differentialscanning calorimetry; both techniques indicate a 10–12 K displacementof the associated hindered glass transition toward higher temperaturesrelative to the amorphous glass transition. It is concluded that thedetection of the α′-process in Triton X-100 is greatlydetermined by the high degree of constraining of the amorphous regionsimposed by the grainy crystalline structure disabling the occurrenceof a bulk-like α-process. Triton X-100 can be taken as a modelfor understanding low molecular weight materials crystallization,allowing correlating the observed dynamical behavior with the achievedcrystalline morphology. [ABSTRACT FROM AUTHOR]

Annealing of the quenched ibuprofen at 258 K yielded a new crystalline form, called phase II. Powder X-ray diffraction patterns of this phase II were recorded with a laboratory diffractometer equipped with an INEL G3000 goniometer and a curved position-sensitive detector CPS120. The starting structural model was found by a Monte-Carlo simulated annealing method. The final structure was obtained through Rietveld refinements with rigid-body constraints for the phenyl group and soft restraints on the other interatomic bond lengths and bond angles. The cell volume is 5% larger than that of the conventional phase I at 258 K. It is also shown that the orientation of the propanoic acid group is drastically changed with respect to phase I, leading to strong modifications of the orientation of the O-H∙∙∙0 hydrogen bonds with respect to the chains of dimers. These structural considerations could explain the metastable character of this phase II. [ABSTRACT FROM AUTHOR]