Block phosphorus-containing poly(trimethylene terephthalate) copolyester via solid-state polymerization: Reaction kinetics and sequential distribution

Phosphorus-containing flame-retardant monomer entitled 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phospha-phenanthrene-10-oxide (DDP) was first esterified with 1,3-propane diol, then incorporated in poly(trimethylene terephthalate) (PTT) chain via solid-state polymerization (SSP) at 200 °C. Reaction kinetics of incorporation was studied choosing 30 wt% DDP content as representative example. The reaction rate constant kf was calculated to be 1.68 h−1. The intrinsic viscosity increased with the increase of tssp, and decreased with the increase of DDP content. The sequence distribution of resulted copolyester was also analyzed with 1H NMR. Results suggested that all of the samples possess block chemical structure, and the degree of randomness increased with the increase of transesterification. For the transesterification reaction occurs only in amorphous phase of the material, the copolyester exhibited greater tendency to form block constitution when increasing DDP content. DSC investigation further confirmed the non-random constitution of the resulted copolyester.