The reversible plasticization of the aromatic copolyester of poly(ethylene terephthalate) and 60 mol % p ‐acetoxybenzoic acid with 1,1,1,3,3,3‐hexafluoro‐2‐propanol

In recent mechanooptical studies with solution cast films of the aromatic copolyester of poly(ethylene terephthalate) and 60 mol % p ‐acetoxybenzoic acid from 1,1,1,3,3,3‐hexafluoro‐2‐propanol, a volatile solvent with bp 59°C, we observed that the solvent plasticizes and affects considerably the stress–strain behavior of the copolyester at ambient temperature. Whereas a dry copolyester film is typically brittle failing at ≤ 10% strain, a film containing 12% w/w 1,1,1,3,3,3‐hexafluoro‐2‐propanol can be stretched readily to ≥ 300% strain. When the solvent is removed by evaporation or by heating at an elevated temperature (≥ 120°C), the films lose their ductility, indicating that the plasticization is reversible.