Preparation of block copolymers with a single Tg based on segments of poly(oxy-2,6-dimethyl-1,4-phenylene) and polycarbonate of bisphenol A

The synthesis and the properties of block copolymers based on PPO and PC segments are reported. Copolymers that have a multi-block structure are synthesized by a polycondensation reaction that employs oligomeric PPO and PC diol terminated with phosgene or bischloroformate of bisphenol A. In the reaction scheme two steps are involved: first, the reaction of one of the oligomeric diols (PPO or PC) with the bischloroformate or phosgene; second, the oligomeric bischloroformate is reacted with the other diol. The molecular characteristics of the prepared samples are studied by SEC, H-1 and C-13 NMR, and FT-IR spectroscopy. The thermal and rheological properties and the thermal stability have also been investigated by means of DSC, rotational rheometry, and TGA, respectively. Polymers that have a single glass transition temperature are obtained if low-molecular-weight segments are used. From a rheological point of view, these materials show a remarkably lower melt viscosity compared with a PPO homopolymer that has a comparable average molecular weight.