Positron Annihilation Study of Biopolymer Inulin for Understanding its Structural Organization

Inulins are nano-meter size semi-crystalline particles, composed of oligomeric fructose units. It has been subjected to fine micro-structural analysis under temperature variations using mainly positron annihilation spectroscopy. The results show a non-monotonous temperature sensitive behaviour of the positron parameters, with considerable variation of its free volume size. The ortho-positronium pick-off component shows a major thermotropic transition at ~320K and a structure loss due to glass transition. Differential scanning calorimetry confirms the onset of the major molecular transition around the same temperature with an enthalpy change of {\Delta}H ~379J /gm and thermo-gravimetric analysis shows mass loss in the said transition. Keywords: Inulin, fructose units, positron annihilation spectroscopy, microstructure, free volume analysis. thermotropic transition, thermal analysis.