Intercalation of cationic aliphatic polyphosphates between montmorillonite nanosheets towards flame-retardant polymer materials

Among the strategies used to impart flame-retardant properties to polymer materials, the most effective ones include the addition of phosphorous compounds such as organic polyphosphates and the dispersion of layered silicates (nanoclays). The aim of this work is to combine both approaches by the dispersion of nanoclays, organomodified by cationic aliphatic polyphosphates, into a polymer matrix. In this work, the synthesis of an aliphatic polyphosphate end-capped by an imidazolium cation followed by its intercalation between montmorillonite nanoclays sheets is reported. In a first step, the polyphosphate was synthesized by ring-opening polymerization of the corresponding cyclic phosphate using 1-(11-hydroxy-undecyl)-3-methylimidazolium bromide as initiator. This polymerization was catalyzed by DBU and a thiourea derivative. This polymer was characterized by different techniques (31P and 1H NMR, SEC, TGA, DSC). Finally, the cationic end-functionalized polymer was exchanged with sodium cations present in montmorillonite. The intercalation of the polyphosphate between the clay nanosheets was proved by X-Ray Diffraction (XRD) and thermogravimetric analysis (TGA). This last technique was also used to determine the influence of the intercalation on the thermal stability of the polyphosphate.polyphosphates, into a polymer matrix. In this work, the synthesis of an aliphatic polyphosphate end-capped by an imidazolium cation followed by its intercalation between montmorillonite nanoclays sheets is reported.
In a first step, the polyphosphate was synthesized by ring-opening polymerization of the corresponding cyclic phosphate using 1-(11-hydroxy-undecyl)-3-methylimidazolium bromide as initiator. This polymerization was catalyzed by DBU and a thiourea derivative. This polymer was characterized by different techniques (31P and 1H NMR, SEC, TGA, DSC).
Finally, the cationic end-functionalized polymer was exchanged with sodium cations present in montmorillonite. The intercalation of the polyphosphate between the clay nanosheets was proved by X-Ray Diffraction (XRD) and thermogravimetric analysis (TGA). This last technique was also used to determine the influence of the intercalation on the thermal stability of the polyphosphate.