Swelling signals of polymer films measured by a combination of micromechanical cantilever sensor and surface plasmon resonance spectroscopy

Swelling of plasma-polymerized allylamine (PPAA) films has been investigated by using a combination of micromechanical cantilever sensor (MCS) and surface plasmon resonance (SPR) spectroscopy. The bending responses of the polymer-coated MCS were compared with simultaneously measured reflectivity changes recorded by SPR for both, highly and low crosslinked plasma-polymerized films in N2 atmospheres with different humidity. Signals attributed to reversible swelling for both plasma polymers were obtained. With increasing the humidity, the thickness increase of a highly crosslinked film was lower than that of a low crosslinked film. In contrast, the MCS coated with a highly crosslinked film exhibited a larger deflection. This demonstrates that a plasma-polymerized allylamine film of higher crosslink density can transduce more efficiently the swelling to the MCS bending than a film of lower crosslink density under identical environmental conditions.