title: Molecular relaxation behavior and isothermal crystallization above glass transition temperature of amorphous hesperetin.
abstract: The purpose of this paper was to investigate the relaxation behavior of amorphous hesperetin (HRN), using dielectric spectroscopy, and assessment of its crystallization kinetics above glass transition temperature (Tg ). Amorphous HRN exhibited both local (β-) and global (α-) relaxations. β-Relaxation was observed below Tg , whereas α-relaxation prominently emerged above Tg . β-Relaxation was found to be of Johari-Goldstein type and was correlated with α-process by coupling model. Secondly, isothermal crystallization experiments were performed at 363 K (Tg + 16.5 K), 373 K (Tg + 26.5 K), and 383 K (Tg + 36.5 K). The kinetics of crystallization, obtained from the normalized dielectric strength, was modeled using the Avrami model. Havriliak-Negami (HN) shape parameters, αHN and αHN .βHN , were analyzed during the course of crystallization to understand the dynamics of amorphous phase during the emergence of crystallites. HN shape parameters indicated that long range (α-like) were motions affected to a greater extent than short range (β-like) motions during isothermal crystallization studies at all temperature conditions. The variable behavior of α-like motions at different isothermal crystallization temperatures was attributed to evolving crystallites with time and increase in electrical conductivity with temperature.
authors.affiliation: Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), S.A.S. Nagar, Punjab, 160062, India.
authors.forename: Ganesh
authors.initials: G
authors.lastname: Shete
authors.forename: Kailas S
authors.initials: KS
authors.lastname: Khomane
authors.forename: Arvind Kumar
authors.initials: AK
authors.lastname: Bansal
mesh_terms: D003460:Crystallization / Q000379:methods*; D005898:Glass / Q000737:chemistry*; D006569:Hesperidin / Q000737:chemistry*; D007700:Kinetics; D013696:Temperature; D044366:Transition Temperature
chemical_list: D006569:Hesperidin; C013015:hesperetin
keywords: Materials science; amorphous; crystallization; formulation; glass transition; mathematical models; mobility; nanotechnology; relaxation time; thermal analysis