Access Type

Open Access Dissertation

Date of Award

January 2019

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Physics and Astronomy

First Advisor

Ashis Mukhopadhyay

Abstract

Soft matter is a subfield of condensed matter physics including systems, such as polymers, colloidal dispersions, liquid crystals, surfactants. Understanding their interaction and dynamics is essential for many interdisciplinary fields of study as well as important for technological advancements. We used gold nanoparticles (AuNPs) to investigate the length-scale dependent dynamics in dilute, semidilute, entangled polymer solutions and gels. Two-photon fluctuation correlation spectroscopy (FCS) technique was used to investigate the translation diffusion coefficient of AuNPs. For polymer solutions, we found that existing hydrodynamic and obstruction models are inadequate to describe the size dependence of the particle diffusion coefficient. Within entangled Poly (vinyl) alcohol solutions, our results qualitatively agreed with the scaling theory prediction of ‘hopping motion’. In semidilute xanthan solutions, we observed that polymer network relaxation is much slower compared to the diffusive time-scale of particles, and AuNP diffusion could not be explained by a single theory. The system was better explained by additionally considering the modified Darcy flow with the hydrodynamic screening. In the semidilute polyelectrolyte solution, measured diffusion coefficients (D) showed a scaling relation, D(R/)-1 in the range of 2R/ between 0.05 and 0.85, where R is the particle radius and  is the correlation length. The results are compared with nanoparticle diffusion in semidilute uncharged polymer solutions.

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