Relaxation Kinetic Study of Eudragit® NM30D Film Based on Complex Modulus Formalism

Abstract

Abstract. This study is aimed at resolving and characterizing the primary (α) and secondary relaxations (β) in Eudragit® NM30D film based on apparent activation energies derived from complex modulus formalism using dielectric analysis (DEA). The glass transition (T g ) of the film was determined using differential scanning calorimetry (DSC). The α relaxation corresponding to T g and the β relaxations occurring below T g were probed using DEA. The occurrence of α and β relaxations in Eudragit® NM30D film was elucidated using the complex modulus of the dielectric response employing loss modulus and permittivity data. Activation energies of these relaxations and the fundamental frequency so determined support the assignment of the relaxation pattern in the Eudragit® NM30D film. DEA methodology of the complex modulus formalism is a useful tool for differentiating the α and β relaxation kinetics in Eudragits® not easily studied using traditional thermal methods such as DSC. The kinetics associated with α and β relaxations so determined will provide formulation design support for solid orals that incorporate Eudragit® polymers. As mobility changes can affect stability and diffusion, the dipolar α and β relaxations revealed through DEA analysis may enable a better correlation to functionality of Eudragit® based pharmaceutical dosage forms.

Interrelationships Between Structure and the Properties of Amorphous Solids of Pharmaceutical Interest

“…20,36,37 These JG motions occur at higher frequencies, that is, shorter timescales, than the a motions, but slower than the picosecond motions associated with intramolecular mobility and appear to be associated with hindered intermolecular rotational and translational rearrangements of molecules "loosely caged" by larger regions of "tightly caged" molecules restricted in their diffusive motion by ultraviscous conditions and the requirement of a high level of cooperativity to initiate the a motions. 21 As illustrated in Figure 8, with plots showing the temperature dependence of both a and JG relaxation times for an organic amorphous solid above and below T g , the kinetics of these 2 motions are indistinguishable above the "crossover" temperature, T x and then decouple at lower temperatures into the glassy state.…”