Time-Resolved Fluorescence Measurements on Poly(ethylene naphthalene-2,6-dicarboxylate)

Abstract

The time-resolved fluorescence behavior of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) has been investigated by synchrotron radiation. Solutions of different concentrations of PEN dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) (10-4 and 10-2 M) have been excited at a wavelength of 340 nm, and the emission has been monitored in the wavelength range from 360 to 480 nm in 10 nm steps. The measurements have been performed at two different temperatures (288 and 298 K). Nearly all decay curves can be fitted by a sum of three exponential functions. These three exponential decay time components seem to be parameters which give the main values of a distribution of decay times. We obtained such distribution functions by assuming a simple model on the basis of excitation energy migration from monomer units (donors) to excimer sites (traps) by a Förster type mechanism. These distribution functions can be fitted by a sum of three exponential functions with reliable confidence parameters. The fits on the calculated distribution functions are in good agreement with the fits obtained from the measured data. We compared these results with data obtained on amorphous PEN films excited at the same energy. Again three exponential functions are needed to fit the measured data. The measured fluorescence decay curves can also be explained by our model.

Molecular Mobility of the High Performance Membrane Polymer PIM-1 as Investigated by Dielectric Spectroscopy

“…The activation energy of the β*-relaxation ( E Aβ* ) for PEN is in the similar range as the value obtained for PIM-1. For PEN this is ascribed to the formation of intermolecular sandwich-like agglomerates of aromatic moieties of the polymer chain with strong interaction of the respective π-systems − This leads to higher activation energies and a more cooperative character of the molecular relaxation process. Moreover, recently a similar behavior was found for Matrimid, a commercially available polyimide also considered as potential material for gas separation membranes …”

Fluorescence of Copoly(ester‐imide)s Containing 2,6‐Naphthoate Units

“…Excitation energy transfer (EET) among species of the same type does not influence the fluorescence decay curves, [27] but in the case of trapping of excitation energy by other molecules, or emitting species like excimers, a distribution of decay times is observed. [18] Therefore we will also discuss EET as a possible reason for the observation of multiexponential decay curves of copoly(ester-imide)s. EET followed by trapping reduces the fluorescence lifetime of the species. The naphthoate units with aliphatic ester groups have a fluorescence lifetime of 12.7 ns.…”

“…For data evaluation a least squares fitting procedure with exponential functions was performed as described in ref. [18] Quantum Mechanical Calculations…”

“…All measurements were carried out at 288 °K. For data evaluation a least squares fitting procedure with exponential functions was performed as described in ref 18…”

Preferential Orientation of Poly(ethylene 2,6-naphthalate) Melt-Crystallized on the Friction-Transfer Layer of PTFE.

“…One of such polymers is poly (ethylene terephthalate) (PET),which iscrystallized in an oriented fashion on the layer [3] . Poly (ethylene 2 ,6-naphthalate) [20,21], was prepared at room temperature (RT). A glass slide covered with an ultra-thin friction-transfer layer of PTFE, which layer had been prepared with our homemade apparatus (the temperature of the glass slide = ca.…”