Ferroelectric behavior in Poly(trimethylene terephthalate)

Poly(trimethylene terephthalate) (PTT), a flexible polymer containing C=O dipoles in its main chain is synthesized by the polycondensation of 1,3-propanediol and terephthalic acid. Numerous studies on the crystal structure of PTT have been reported. Analysis of crystalline structure of PTT shows that the trimethylene glycol unit in PTT takes a highly coiled structure of trans-gauche-gauche-trans conformation. PTT has a triclinic crystalline structure, each cell of which contains two chemical repeat units. The physical properties of PTT are known to be quite different from those of PET and PBT, since PTT has odd number of methylene units. The crystal structure is nonpolar because of the antiparallel crystal packing of C=O dipoles. However external treatments such as poling and stretching can change the conformation of the PTT chains, to have ferroelectricity. In this study, we investigated the ferroelectric structural change of PTT upon application of an external electric field treatment.