Crystal structure of poly(pentamethylene 2,6-naphthalate)

The crystal structure of poly(pentamethylene 2,6-naphthalate) (PPN) was determined by using X-ray diffraction and molecular modeling. The unit cell of PPN was found to be triclinic (P1̄ space group) with dimensions of a=0.457 nm, b=0.635 nm, c=2.916 nm, α=121.6°, β=90.4°, γ=87.6°, and the calculated crystal density was 1.311 g cm−3. The unit cell contains one polymer chain with two repeating units. In the unit cell, the PPN backbone takes gauche/gauche conformation in the middle part of each pentamethylene unit, and two naphthalene rings are in face-to-face arrangement.