Self assembly in gel systems

• Main Author: Razali, Azaima
• Other Authors: Royall, Cp
• Published: University of Bristol 2018
• Subjects: 530
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.761129

In this work we have studied the structural evolution of colloid polymer system reaching equilibrium ordered states. Throughout the work in this thesis, confocal microscopy was primarily used to capture the local structural changes. We employed the depletion mechanism from the addition of nonadsorbing polymer to colloidal dispersion in order to obtain short ranged attractive systems. The changes of local structures towards crystallisation in the colloid polymer systems are analysed using topological cluster classification (TCC), common neighbour analysis (CNA) and bond order parameter ψ6. Initial work studies the ageing of gels with different interaction strengths in experiment and simulation. Structural analysis of the gels shows significant similarity between experiment and simulation. In both, we find crystallisation in gels with intermediate interaction strength and formation of five-fold symmetry clusters in gels with higher interaction strengths. Then we examine the effects of confinement to the sedimentation of colloids and gels. We find that gelation enhances sedimentation of colloids whereas there is no sedimentation in a same system without polymer. The structural analysis of the simulation results show that the local structural changes is not related to sedimentation. By manipulating the polymer response to temperature, we change the interaction strength in the colloid polymer system in order to obtain better crystallisation. This work is based on the idea from simulation work [1], where tuning the interaction strengths during self assembly leads to better and larger ordered structures. However, contrary to the simulation results, we find that tuning the interaction strengths result to disruption to the crystallisation pathway thus more disordered structures is formed.