Charge-transfer fluorescent probes applied to the characterization of thermal and mechanical properties of polymers

Charge-transfer fluorescence probes show a strong response of the intensity and wavelength positions of their spectra to solvent polarity and mobility . Such properties have been applied in the past to follow polymerization ki netics and solvent-induced effects (e.g., swelling) in polymeric materials. An important advantage of charge-transfer fluorescence probes is that they can be measured at extremely low concentrations, hence interference with t he polymeric system is limited. Furthermore they report from "within," sinc e they are only sensitive to phenomena which occur in their immediate surro undings. In this paper it is shown that charge-transfer fluorescence probes can also be applied to study mechanical and thermal properties of polymers . The charge-transfer fluorescence probe Fluoroprobe (1 -phenyl-4-[(4-cyano - 1 -naphthyl)methylene]piperidine) was doped into a polyether-polyester bl ock copolymer, which was submitted to thermal and mechanical stress. The ef fect of strain applied to the polymers in various forms (fibers, sheets) an d the effect of thermal processes (glass transition temperatures, phase tra nsitions, melting points) are clearly reported by the changes in fluorescen ce intensity and wavelength of the Fluoroprobe molecule.