A fluorescence correlation spectroscopy study of macromolecular tracer diffusion in polymer solutions

TL;DR

This study uses fluorescence correlation spectroscopy to measure how tracer and matrix polystyrene chains diffuse in solution, revealing the independence of cooperative diffusion from tracer molecular weight in entangled regimes.

Contribution

It demonstrates that fluorescence correlation spectroscopy can simultaneously measure both self and cooperative diffusion coefficients in polymer solutions across various concentrations.

Findings

Cooperative diffusion coefficient is independent of tracer molecular weight.

FCS can measure diffusion in semidilute entangled regimes.

Self-diffusion and cooperative diffusion are distinguishable in measurements.

Abstract

We discuss the manner in which the dynamics of tracer polystyrene chains varies with the concentration of matrix polystyrene chains dissolved in toluene. Using fluorescence correlation spectroscopy and theory, it is shown that the cooperative diffusion coefficient of the matrix polystyrene chains can be measured by fluorescence correlation spectroscopy in the semidilute entangled concentration regime. In addition the self-diffusion coefficient of the tracer polystyrene chains can be detected for arbitrary concentrations. The measured cooperative diffusion coefficient is independent of the molecular weight of the tracer polystyrene chains because it is a characteristic feature of the transient entanglement network.