Uniform TitleModulation of molecular mobility in sucrose-based amorphous solids detected by phosphorescence of erythrosin B
NameYou, Yumin (author), Ludescher, Richard (chair), Takhistov, Paul (internal member), HUANG, QINGRONG (internal member), Seetharaman, Koushik (outside member), Rutgers University, Graduate School - New Brunswick,
DescriptionThis project studied the temperature and composition dependence of molecular mobility in amorphous sucrose. Phosphorescence of erythrosin B provided parameters sensitive to localized molecular mobility in the glass and to more global modes of mobility activated at the glass transition and provided evidence of dynamic site heterogeneity in amorphous sucrose solids. In sucrose-based binary matrices, plasticizer (glycerol), salts (NaCl, CaCl2, MgCl2, Na-citrate, Na-acetate, Na-phosphates), maltodextrins (DE 5 to 18), protein (gelatin), and polysaccharides (xanthan and high amylose starch) were selected to investigate how variations in nature and content of each additive influence the molecular mobility as well as dynamic site heterogeneity in amorphous sucrose matrix.
Measurements of phosphorescence intensity, lifetime, and emission energy were made in amorphous sucrose-additive films containing the probe erythrosin B. Results showed the complex effects of additives on the mobility in a hydrogen-bonded sugar matrix. Glycerol exhibited an antiplasticization effect shown as decreased mobility at glycerol/sucrose mole ratio ≤ 0.27 and at temperature ≤ 45° C. On the contrary, all the polymers studied, including gelatin, xanthan and high amylose starch, displayed a ‘plasticization’ effect (increasing mobility) at very low while a rigidification effect (decreasing mobility) at higher concentration without significant change in Tg. Maltodextrins, mixtures of molecules with a variety of molecular weights, increase the mobility in spite of their high Tg. Sodium chloride showed a strong rigidification effect on the sucrose matrix; however, this effect was weakened at mole ratio NaCl/sucrose above 0.5. Other salts showed effects resulting from a compromise between two opposite actions (decreasing mobility due to salt itself and increasing mobility due to absorbed moisture). All above behaviors are difficult to interpret using Tg alone. Molecular mobility appears to be more accurate to evaluate the physical stability of the matrix.
Phosphorescence of erythrosin B was also able to report dynamic site heterogeneity that is an intrinsic property of the amorphous solid state. The heterogeneity was be evaluated by the variation of lifetime and lifetime heterogeneity across the excitation and emission band and the temperature dependence of bandwidth and lifetime heterogeneity. The composition influence on the dynamic site heterogeneity was discussed as well.
NoteIncludes bibliographical references.
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.