Modification of flow through silica micro-capillaries via polymer brushes

Polymer brushes were synthesized on the interior of silica micro-capillaries to study the influence of brushes on solvent flow through a confined space. The synthesis of several polymer brush coatings were performed in fused silica micro-capillary tubing by atom transfer radical polymerization using the “grafting from” approach. The hydrophilic and hydrophobic nature of the polymer coatings led to flow in micro-capillaries that could be manipulated and controlled in a passive fashion without an external stimulus. Backpressure measurements were performed to study how polymer brushes might alter the flow of solvents. An analogous study involved capillaries functionalized with small molecule silanes. Preferential flow experiments were designed to measure the preferred path an aqueous solvent would take when comparing two capillaries containing polymer coatings of different surface energies. Aqueous flow preferred the hydrophilic, higher surface energy coated capillary when comparing capillaries of a similar internal diameter. When the difference in internal size became too large, the surface energy effect mitigated.