Hydrated polyelectrolyte (PE) complexes and multilayers undergo a well-defined thermal transition that bears resemblance to a glass transition. Even though its origins are not clear, this transition of the complex coacervate phase is widely used in, e.g., thermo-responsive drug delivery and in the emerging field of saloplastics. We have probed via molecular simulations interconnected with QCM-D experiments the fundamental nature of this thermal transition.<br/><br/>Our molecular modelling findings show that the diffusion behavior, hydrogen bond formation, and bridging capacity of water molecules plasticizing the PE assemblies experiences a sudden change at the transition temperature. The simulations enable mapping the ionic strength and hydration dependencies of the intrinsic and extrinsic charge compensation of the PE assemblies and associating the transition with the hydration of intrinsic PE-PE ion pairs. We quantify the behavior and map its chemistry specificity through comparison of PE and salt species, as well as, water content. We conclude that the thermal transition is actually via a dehydration mechanism and not a glass transition as previously supposed. In total, the findings rise attention to water in PE systems.

Thermal response of hydrated polyelectrolyte complexes and multilayers: Lessons learned via molecular modelling

254th National Meeting (2017)

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