Syntheses and properties of poly(diethyl vinylphosphonate) initiated by lanthanide tris(borohydride) complexes: Polymerization controllability and mechanism

Polymerization of diethyl vinylphosphonate (DEVP) is achieved by using lanthanide tris(borohydride) complexes, Ln(BH 4 ) 3 (THF) 3 (Ln = Y, La, Nd, Sm, Gd, Dy, Lu) as an initiator. The characteristics and mechanism of polymerization as well as the properties of the resulting poly(diethyl vinylphophonate)s (PDEVPs) are studied. The effects of the lanthanide elements, the molar ratios of monomer to initiator ([ M ]/[ln]), reaction temperature and time on polymerization have been investigated in detail. The optimized polymerization conditions are 40 °C, 1 h in bulk with [ M ]/[ln] = 300. The kinetic study indicates that the polymerization of DEVP undergoes a controlled manner as the molecular weights (MWs) of PDEVPs increase with monomer conversion linearly maintaining moderate MW distribution (1.7–1.9). Additionally, a coordination anionic polymerization mechanism is proved by end‐group analysis with ESI mass and 1 H NMR spectroscopy. The obtained PDEVPs have low glass transition temperature ( T g = −62 °C) and high thermal decomposition temperature ( T d > 300 °C) determined by differential scanning calorimetry and thermogravimetric analysis respectively. The thermosensitive behavior of PDEVP is characterized by evaluating the lower critical solution temperature of PDEVP in water by ultraviolet transmittance.