Morphology of amorphous polyethylene terephthalate

A number of years ago the morphology of amorphous polyethylene terephthalate (PET) quenched from the melt at 280°C into ice water and cast from solution was reported [1]. A nodular structure ca. 75 Å in diameter was described, the electron diffraction pattern consisting of a single diffuse ring. Based on brightfield and dark-field diffraction contrast micrographs, which showed the presence of ordered domains of similar size, it was proposed that the molecules in amorphous PET both above and below Tg are locally aligned and have a nematic liquid-crystal-like arrangment, in domains of the size of the nodules. The proposal of order in the amorphous material above Tg was based on the assumption that the quenching was sufficiently rapid that the morphology observed in the glass reflected that present above Tg at the instant of quenching; in the melt itself the ordered domains were presumed to undergo continuous fluctuation.