Understanding the mechanisms of motion and relaxation of associating polymers at the molecular level is fundamental for applications such as self-healing materials, enhanced oil-recovery or drug delivery. In unentangled associating polymers, the strength and rates of association/dissociation of the reversible physical crosslinks govern the dynamics of the network and all macroscopic properties, like self-diffusion and rheology. Recently, by means of forced Rayleigh scattering (FRS) experiments, we have proved that associating polymers of different architectures show three regimes of molecular diffusion, including a regime with super-diffusive scaling. Here we propose a new molecular model for unentangled associating polymers that considers the effect of concentration, molecular weight, number of associating groups and strength and rate constants of association/dissociation. By means of simulations and scaling arguments, we show that the model predicts super-diffusive behavior at FRS grating distances much larger than the molecular radius of gyration, in qualitative agreement with the results observed in experiments. This apparent super-diffusion regime can be attributed to a combination of different molecular diffusion modes which continuously exchange between each other due to the association/dissociation kinetics. We also fit the preditions of the model to different sets of experimental data and discuss the limits of the theory and the molecular meaning of the fitting parameters.

Mechanisms of diffusion in associating polymer networks

254th National Meeting (2017)

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