Thermodynamics and kinetics of ring‐opening polymerization of cyclic alkylene phosphates

Abstract

Polymerization of cyclic compounds containing phosphorus has been used to prepare models of chains of nucleic acids and teichoic acids. Polymers of high molecular weight (M̄n≥105) have been prepared in the past in this laboratory by ring‐opening polymerization. These processes have a number of particular features, related to the low ring strain of the involved monomers (the majority of six‐membered esters are strainless) and to the presence of the labile exocyclic groups. Results of the studies of these polymerizations contributed to the understanding of general phenomena of ring‐opening polymerizations related to these features. In this review paper the thermodynamics of strainless rings is discussed. It is shown that for the same monomer, polymerization can either be exothermic (δHSS<0, δSSS<0) or endothermic, driven by positive change of entropy (δHSS>0, δSSS>0). The presence of the labile exocyclic groups introduce a potential possibility of chain transfer. It is shown that in the cyclic, non‐strained six‐membered monomers kP/ktr is relatively low for cyclic triesters but much higher (≈300) in the polymerization of cyclic amides, since the alcoholate is a better leaving group then the amide group. The importance of these findings for other classes of monomers (cyclic amines, siloxanes, orthoesters) having also labile exocyclic groups is discussed.

Water Soluble Polymers for Pharmaceutical Applications

“…They have reported the synthesis of many of these polymers by various methods [93][94][95][96]. The general structure of polyphosphoesters is given in Figure 5.…”

Microstructure analysis of biocompatible phosphoester copolymers

“…PPE chemistry was pioneered by Penczek and co-workers in the 1970s. [5][6][7][8] The biological potential of PPEs was immediately recognized since aliphatic PPEs resemble a simple model for essential biomacromolecules, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). First attempts to synthesize "articial DNA" were also undertaken in Penczek's lab on the basis of poly(1,2-glycerol phosphate) prepared by ring-opening polymerization (ROP) of strained cyclic phosphoesters.…”

High Glass‐Transition Temperature Polymer Networks Harnessing the Dynamic Ring Opening of Pinacol Boronates

“…We infer that this system, with apeculiar thermodynamic balance between the enthalpic and entropic contributions,i sr eminiscent of floor-temperature polymerizations already demonstrated in several lowstrained cyclic monomers. [37,38] Kinetically,t he enthalpy and Gibbs energy barriers corresponding to ring opening is calculated at 27 and 30 kcal mol À1 ,r espectively,a bove the water adduct, with ac lear pyramidalization induced by H 2 O nucleophilic attack at Bt hrough O. Interestingly,t he energy barrier corresponding to ad irect metathesis has been estimated to 70 kcal mol À1 relative to free pinacolboronate. This mechanism can thus be confidently ruled out.…”