TY - JOUR
T1 - Molecular motions in sucrose-PVP and sucrose-sorbitol dispersions
T2 - I. Implications of global and local mobility on stability
AU - Bhattacharya, Sisir
AU - Suryanarayanan, Raj
PY - 2011/9
Y1 - 2011/9
N2 - Purpose:To characterize molecular mobility by dielectric spectroscopy and determine the effect of additives on α-and β-relaxation times in amorphous sucrose solid dispersions. Methods:Sucrose was co-lyophilized with either PVP or sorbitol. The lyophiles were subjected to dielectric spectroscopy and differential scanning calorimetry. Results: The additives did not have an appreciable effect on the calorimetric Tg. However, dielectric spectroscopy revealed pronounced effects on global mobility (α-relaxation) , which correlated with the crystallization tendency of sucrose. The systems were characterized by two β-relaxations, and the relaxation times as well as their temperature dependence were influenced by the additive. Although sorbitol acted as a plasticizer of sucrose with respect to global mobility, it antiplasticized sucrose in terms of local motions. PVP, on the other hand, acted as an anti-plasticizer with respect to both global and local mobility. The slower β-relaxation in amorphous sucrose was found to correlate with the α-relaxation and was identified as the Johari-Goldstein relaxation. Conclusions:Amorphous systems with identical calorimetric Tg could have significantly different mobility and physical stability as revealed by dielectric spectroscopy. Additive effect on global mobility cannot be a predictor of the effects on local mobility. Additives could also be used to inhibit local mobility.
AB - Purpose:To characterize molecular mobility by dielectric spectroscopy and determine the effect of additives on α-and β-relaxation times in amorphous sucrose solid dispersions. Methods:Sucrose was co-lyophilized with either PVP or sorbitol. The lyophiles were subjected to dielectric spectroscopy and differential scanning calorimetry. Results: The additives did not have an appreciable effect on the calorimetric Tg. However, dielectric spectroscopy revealed pronounced effects on global mobility (α-relaxation) , which correlated with the crystallization tendency of sucrose. The systems were characterized by two β-relaxations, and the relaxation times as well as their temperature dependence were influenced by the additive. Although sorbitol acted as a plasticizer of sucrose with respect to global mobility, it antiplasticized sucrose in terms of local motions. PVP, on the other hand, acted as an anti-plasticizer with respect to both global and local mobility. The slower β-relaxation in amorphous sucrose was found to correlate with the α-relaxation and was identified as the Johari-Goldstein relaxation. Conclusions:Amorphous systems with identical calorimetric Tg could have significantly different mobility and physical stability as revealed by dielectric spectroscopy. Additive effect on global mobility cannot be a predictor of the effects on local mobility. Additives could also be used to inhibit local mobility.
KW - Amorphous
KW - Dielectric spectroscopy
KW - Global and local mobility
KW - Solid dispersions
KW - Sucrose
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U2 - 10.1007/s11095-011-0447-0
DO - 10.1007/s11095-011-0447-0
M3 - Article
AN - SCOPUS:85027919300
SN - 0724-8741
VL - 28
SP - 2191
EP - 2203
JO - Pharmaceutical Research
JF - Pharmaceutical Research
IS - 9
ER -