Synthesis, structure and ring-opening polymerization of phenolphthalein macrocyclic polyarylates

Phenolphthalein based polyarylate macrocyclic oligomers were selectively sy nthesized by an interfacial polycondensation reaction of o-phthaloyl dichlo ride with phenolphthalein. The high selectivity benefits from the role of p henolphthalein as a color indicator, an efficient phase transfer catalyst, acid a preferred conformation of the starting materials as indicated by ana lyzing a single-crystal X-ray structure of an analogous macrocycle. The mel t ROP of phenolphthalein polyarylate cyclic dimer was studied using nucleop hilic initiators, The molecular weight of the resulting polymers builds up very rapidly at the very early stage of polymerization but decreases with t ime. During the ROP of cyclic dimer, analogous macrocycles with higher degr ee of polymerization (n greater than or equal to 3) and linear oligomers we re produced by backbiting reaction especially at later stage of polymerizat ion. Conversion of cyclic dimer is very fast at the earlier stage of polyme rization and then increases slowly with time as analyzed by gel permeation chromatography. However, the total amount of cyclic oligomers in the ROP sy stem increases with time at the later stage of polymerization because of th e formation of larger macrocycles. The resulting polymers are amorphous. Gl ass transition temperatures (T(g)s) of these polymers are influenced by the polymerization time, type of initiator, and initiator concentration.