This work evaluates the surface polarity of five types of nylons: -6, -6,6, -11, -6,10, -6,12 using the py-scale. These nylons can be classified in two categories: AB (nylon-6 and -11) or AABB (nylon 6,6; 6,10 and 6,12). The py-scale is based on the photophysical properties of pyrene, which is obtained using steady-state fluorescence spectroscopy or the lifetime of the singlet excite state. From the steady-state fluorescence spectra we determine the ratio of the intensities of the vibronic bands, I I/I III, which increase with the polymer polarity (nylon-6 higher than nylon-11 and so on). We also observed that the lifetime decreases with the polarity, as expected. From these experiments we also showed that pyrene is a polarity sensor for short distances, i. e. similar to the molecular radius. We also discuss that the major advantage of these methodologies is the facility of the sample preparation because measurements can be performed with samples as powder, pellets or films (independently of the thickness).
Pyrene; fluorescence spectroscopy; nylons; polarity sites
