X-RAY-INVESTIGATION OF THE STRUCTURE OF POLY(TETRAMETHYLENE TEREPHTHALATE)

Poly(tetramethylene terephthalate) (PTMT) undergoes a reversible stress-induced crystal-crystal phase transition. X-ray fiber-diffraction photographs were obtained from the oriented, unstressed ( alpha ) phase. Relative intensities were measured from these photographs. These were used to help check the reported structures of the alpha phase. Structures and observed intensity data from other authors were also utilized. Results show the alpha phase contains a non-trans, non-gauche bond rotation in the tetramethylene chain and a nonplanar terephthalic acid residue. A tilt of 3. 5 degree between the fiber axis and the c axis was determined in a direction 21 degree counterclockwise from the b* axis.