Polycondensation of diglycerol with H₃ PO₄ . Reversibly degradable gels giving multireactive, highly branched macromolecules

Abstract

Polycondensation of H 3 PO 4 with diglycerol (DGL) involves biobased, commercial products and leads, via hydrolyzable gels, to highly branched reactive macromolecules. These reactive macromolecules have been applied as multiacidic catalysts with hydroxyl groups in polymerization of L-lactide, consuming entirely the starting highly branched macromolecules. Polycondensation was performed in bulk, at 110-120 8C with efficient elimination of water under vacuum. The process with DGL differs substantially from the previously studied polycondensation with ethylene glycol and glycerol. Formation of pyrophosphoric acid (PY) constitutes the rate determining step: the rate of PY formation is the same in the absence and presence of DGL. Kinetic studies explained why the rate of monoesters (M) accumulation may be the same as the rate of accumulation of di-(D), and triesters (T). This is because the rate of M formation is relatively low when compared with rates of further reactions of M, leading to D and T.

Design, Synthesis and Actual Applications of the Polymers Containing Acidic P–OH Fragments: Part 1. Polyphosphodiesters

“…The reaction of H 3 PO 4 with glycerol is a more complex process [ 40 , 41 , 42 ]. This reaction was conducted at 100 °C with azeotropic water removal (heptane) or under reduced pressure.…”

“…Polycondensation of diglycerol (HOCH 2 CH(OH)CH 2 ) 2 O) with H 3 PO 4 resulted in the formation of highly branched gels [ 42 ]. The prospects of the further use of these polymers still remains unclear due to the unpredictability of their microstructure and hydrolytic behavior.…”