Orientation of hot-drawn poly(butylene terephthalate) films as determined from the intrinsic polarized fluorescence

As far as indicated by the spectra and the fluorcence time decay law, the properties of the fluorescence of poly(butylene terephthalate) (PBT) are almost identical to those of PET. The groundstate-stable sandwich dimers in the noncrystalline regions of uniaxially-drawn PBT films were used as chain-intrinsic fluorescent label for studying the orientation distribution function. The dimers are formed only in the amorphous regions; concerning the fluorescence signal, «amorphous» includes all the material outside perfect crystallites