Unsaturated polyesters based on terephthalic acid: 3. Characterization of poly(propylene terephthalate) prepolymer by gel permeation chromatography

• Published in: Polymer (Guilford) 1980-01, Vol.21 (6), p.632-638
• Main Authors: Birley, A.W., Dawkins, J.V., Kyriacos, D.
• Format: Article
• Language: English
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/0032-3861(80)90319-5

Oligomers in prepolymers prepared by the polyesterification of terephthalic acid (T) with excess 1,2-propylene glycol (P) have been separated by gel permeation chromatography (g.p.c.). The assignment of chromatogram peaks to oligomers according to the structure P (TP) n where n is the number of 1,2-propylene terephthalate repeating units has been confirmed by a g.p.c. examination of bis(2-hyroxypropyl) terephthalate and by a 1H nuclear magnetic resonance (n.m.r.) spectroscopic study of fractions isolated from a preparative separation. The infrared g.p.c. detector response has been interpreted quantitatively in order to deduce the concentration of each oligomer from the area of its chromatogram peak. Mol fraction distributions as a function of n have been determined for the prepolymer samples. Number average molecular weights have been calculated for the terephthalate-based components of the prepolymer and for all components including excess propylene glycol. These g.p.c. molecular weights are in excellent agreement with values previously reported in a study of prepolymers by 1H n.m.r. spectroscopy. G.p.c. studies on prepolymers after reactions with a carbodiimide and diazomethane suggest a very minor quantity of carboxyl terminated species in the prepolymer samples.