Synthetic Strategies for Accessing Phosphorus-containing Polyesters

Abstract

The work herein presented pertains synthetic strategies to access phosphorus-functionalized lactones and their use for production of polyesters via ring opening polymerization (ROP). Due to the literature scarcity in this area, we developed from the ground up an easy methodology for obtaining phosphorus-functionalized lactones via the phospha-Michael addition of secondary phosphine oxides and α, β-unsaturated lactones. A series of sub- strates with different ring sized and position of the phosphorus moiety, both on the ring and in the -exo position were synthesized and characterized (Chapter 2). n the second part of the work (Chapter 3) we selected and tested two (out of the 7) developed monomers in ring opening polymerization (ROP) and ring opening copolymerization (ROcP). The 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD)/isopropanol (iPrOH) system was successful in performing ring opening polymerization (ROP) and ring opening copolymerization (ROcP). The 6-membered functionalized lactone (2) was not able to homopolymerize, however we were able, by paring it with ǫ-caprolactone to obtain its copolymers. On the other hand, the 6-membered functionalized lactone with the substituent in the -exo position (1) was successful in homopolymerization, yielding a functionalized phosphorus-polyester. These phosphorus functionalized polyesters are the first examples of their own kind in the literature. In the third part of the work (Chapter 5) we developed a phosphorus-lactone (CU–DPPO which was used as an additive in the production of a flame-retardant poly(lactic acid) (PLA) using a ‘green’ methodology: reactive extrusion (REX). 4–(Diphenylphosphoryl)chroman–2–one (CU–DPPO) was synthesized easily by the developed tetramethylguanidine (TMG) protocol and up-scaled up to 200 g. Composites through melt-blending and reactive extrusion (REX) were produced with poly(lactic acid) (PLA) affording a flame retardant bio-polymer. Cone-calorimetry, limiting oxygen index (LOI) and UL 94 tests were performed on the composite showing improved thermal properties and displaying flame retardant behaviour compared to blank PLA