Investigation of solid-liquid phase transition dynamics in microgels by video microscopy method

Microgel collidal particles are used as an ideal model for studying formation of crystal and glassy states of atomic or molecular materials. Microgels are hydrogel globules which are composed from crosslinked polymers that have high water absorbance and release capacities. In this thesis, NIPAM( Poly(Nisopropylacrylamide)) colloidal particles have been used to produce colloidal crystal. The elastic properties of this crystal have been investigated under different temperature values. The expansion and contraction dynamics of microgels particles proceed under different chemical mechanisms. This difference can affect the elasticity of colloid crystals and formation of different crystal types. At different temperature values, calculating the locations of colloidal particle and their change in time have been used to measure elasticity of colloid crystal via video microscopy method. The Lindemann parameter which is found by the ratio of vibration of colloidal particle to its neighboring distance is calculated at each temperature value. At the same time pair correlation function and the change of it at different temperatures have been calculated. It is shown that the elasticity of the crystal is decreasing as it approaches towards liquid phase at both methods.