SUBSURFACE ANCHORING OF FLUORESCENT PROBES IN POLY(ETHYLENE-CO-ACRYLIC ACID) FILM

摘要

Poly(ethylene-co-acrylic acid) (PEAA) films contain reactive carboxylic acid groups that can undergo chemical coupling after activation. However, the chemistry will occur not only on the surface but also in the subsurface of the film. The aim of this work was to study the surface grafting behavior and penetration reaction of a relatively small fluorescently labeled probe molecule, dansyl cadaverine, in PEAA films. A two-step reaction was conducted. First, PEAA film was activated with PCl_5 at room temperature, which could occur throughout the film depending on reaction time. Second, the acid chloride was reacted with dansyl cadaverine to form a modified film. ATR-FTIR spectroscopy and fluorometry were employed to analyze the penetration behavior. Using dichloro-methane as a solvent, it was found that the dansyl cadaveine penetrated throughout the analysis region (～400 nm) of the ATR-FTIR evanescent wave in few minutes and the conversion was approximately 90%. As the penetration depth increased with time, so did the amount and fluorescence intensity of grafted dansyl-cadaverine. However, insignificant changes of surface wettability for dansyl-cadaverine-modified film were observed by contact angle measurements.