Electroresponsive Polymer Brushes for Molecular Adsorption

Polymer brushes are an excellent way to modify the properties of surfaces on a molecular level. These arrays of densely grafted polymer chains exhibit stimulus-responsive properties. For instance, some brushes change in thickness when the temperature is increased and others collapse when the acidity of the surrounding solution is changed. Changes in surface properties could be useful in molecular enrichment and separation. In fact, if changes can be brought about reliably with a well-controlled stimulus, responsive surfaces could become a core component in novel separation technologies.

This thesis explores how electric fields can be used as a stimulus to modify the properties of polymer brushes such that reversible molecular enrichment can be achieved. The question is studied through a comprehensive review of the literature (Chapter 2), chapters focusing on computation work using molecular dynamics and self-consistent field theory (Chapters 3-5, 7-9), and a chapter that combines experiments and simulations (Chapter 6).

The original contributions in this thesis are divided into three parts. The first part (Chapters 3,4) explores how the response characteristics of polymer brushes are influenced by choices in the physical design of the brush such as the grafting density or the fraction of charged moieties in the brush. The second part (Chapters 5,6) studies how the presence of salt in the surrounding solution affects these response characteristics, particularly for brushes with a non-homogeneous charge distribution. Finally, the third part (Chapters 7-9) describes how polymer brushes interact with small molecules. These chapters explore these interactions with varying levels of detail ranging from atomistic molecular dynamics simulations to a analytical polymer scaling theory.