TY - JOUR
T1 - Investigating the Influence of Morphology in the Dynamical Behavior of Semicrystalline Triton X-100: Insights in the Detection/Nondetection of the α'-process
AU - Correia, Natália de Fátima Teixeira
AU - Andrade, Maria Madalena Alves Campos de Sousa Dionísio
AU - Dias, Carlos Jorge Mariano Miranda
N1 - Sem PDF
PY - 2013/1/1
Y1 - 2013/1/1
N2 - The paper investigates the influence of the crystalline structure in the dynamical behavior of semicrystalline Triton X-100 allowing enlightening the reason for the detection/nondetection of the alpha'-process. The work was preceded by the study of the full amorphous material for which dielectric relaxation spectroscopy (DRS) identified multiple relaxations: the alpha-process associated with the dynamical glass transition and two secondary relaxations (beta- and gamma- processes). To evaluate how crystallinity affects the detected relaxation processes, different crystallizations were induced under high and low undercooling conditions. While the secondary relaxations are unaffected by crystallization, the mobility of the cooperative bulk alpha-process is sensitive to the distinct morphologies. The distinct semicrystalline states were structurally characterized by X-ray diffraction and polarized optical microscopy (POW. 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 monitored by POM. In the two crystalline structures, X-ray diffraction patterns detected the amorphous halo meaning that both are semicrystalline. However, no differences between the amorphous regions are indentified by this technique; the distinction was done by means of dielectric measurements probing different mobilities in each of those regions. When the large spherulites evolve, the bulk-like alpha-process never goes to extinction and slightly shifts to low frequencies increasing the associated glass transition by 2-3 K, as confirmed by DSC; the slight change is an indication that the dimensions of the persisting amorphous regions become comparable to the length scale inherent to the cooperative motion that determines the glass transition in the full amorphous material. For the grainy-like structure, the alpha-process becomes extinct and an a'-process evolves as revealed by isochronal plots of dielectric measurements, with the features of a glass transition as confirmed by temperature modulated differential scanning calorimetry; both techniques indicate a 10-12 K displacement of the associated hindered glass transition toward higher temperatures relative to the amorphous glass transition. It is concluded that the detection of the a'-process in Triton X-100 is greatly determined by the high degree of constraining of the amorphous regions imposed by the grainy crystalline structure disabling the occurrence of a bulk-like alpha-process. Triton X-100 can be taken as a model for understanding low molecular weight materials crystallization, allowing correlating the observed dynamical behavior with the achieved crystalline morphology.
AB - The paper investigates the influence of the crystalline structure in the dynamical behavior of semicrystalline Triton X-100 allowing enlightening the reason for the detection/nondetection of the alpha'-process. The work was preceded by the study of the full amorphous material for which dielectric relaxation spectroscopy (DRS) identified multiple relaxations: the alpha-process associated with the dynamical glass transition and two secondary relaxations (beta- and gamma- processes). To evaluate how crystallinity affects the detected relaxation processes, different crystallizations were induced under high and low undercooling conditions. While the secondary relaxations are unaffected by crystallization, the mobility of the cooperative bulk alpha-process is sensitive to the distinct morphologies. The distinct semicrystalline states were structurally characterized by X-ray diffraction and polarized optical microscopy (POW. 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 monitored by POM. In the two crystalline structures, X-ray diffraction patterns detected the amorphous halo meaning that both are semicrystalline. However, no differences between the amorphous regions are indentified by this technique; the distinction was done by means of dielectric measurements probing different mobilities in each of those regions. When the large spherulites evolve, the bulk-like alpha-process never goes to extinction and slightly shifts to low frequencies increasing the associated glass transition by 2-3 K, as confirmed by DSC; the slight change is an indication that the dimensions of the persisting amorphous regions become comparable to the length scale inherent to the cooperative motion that determines the glass transition in the full amorphous material. For the grainy-like structure, the alpha-process becomes extinct and an a'-process evolves as revealed by isochronal plots of dielectric measurements, with the features of a glass transition as confirmed by temperature modulated differential scanning calorimetry; both techniques indicate a 10-12 K displacement of the associated hindered glass transition toward higher temperatures relative to the amorphous glass transition. It is concluded that the detection of the a'-process in Triton X-100 is greatly determined by the high degree of constraining of the amorphous regions imposed by the grainy crystalline structure disabling the occurrence of a bulk-like alpha-process. Triton X-100 can be taken as a model for understanding low molecular weight materials crystallization, allowing correlating the observed dynamical behavior with the achieved crystalline morphology.
KW - ISOTHERMAL CRYSTALLIZATION
KW - MODULATED DSC
KW - POLY(L-LACTIC ACID)
KW - GLASS-TRANSITION
KW - DIELECTRIC-RELAXATION SPECTROSCOPY
KW - POLY(ETHYLENE-TEREPHTHALATE)
KW - LIQUIDS
KW - REAL-TIME
KW - MOLECULAR-DYNAMICS
KW - STRUCTURAL RELAXATION
U2 - 10.1021/jp4042414
DO - 10.1021/jp4042414
M3 - Article
C2 - 23937121
SN - 1520-6106
VL - 117
SP - 9793
EP - 9805
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 33
ER -