AB-INITIO STUDIES OF SUBSTITUTED P-PHENYLENETEREPHTHALATES

Ab initio HF/STO-3G studies of the repeat units for a series of copoly mers of substituted hydroquinone and terephthalic acid are reported. T hese molecules are quite flexible with respect to internal rotation ar ound the C(phenyl)-O ester bonds, and twisted conformations with relat ively flat potential surfaces are preferred. The barriers to internal rotation around this bond are around 2 kcal mol(-1) for all species. B oth fragments of the molecules separated by this C-O bond are planar ( disregarding the orientation of the substituents). The preferred confo rmations and the rotational barriers are largely unaffected by substit ution on the aromatic ring.