Synthesis and Properties of a Novel Thermostable Polymer: Fluorinated Polycarbodiimide

A new fluorinated linear polycarbodiimide (F-PCD) was synthesized by solution polycondensation of a new fluorinated diisocyanate monomer, 4″, 4″′-(hexafluoroisopropylidene) bis(4-phenoxyphenyl isocyanate) (HPI) in the presence of 3-methyl-1-phenyl-2-phospholene-1-oxide (PMO). HPI was prepared from 4″, 4″′-(hexafluoroisopropylidene)bis(4-phenoxyaniline) (HPA) by three steps. The reaction of HPA with phenyl chloroformate gave the corresponding carbamate, which upon reaction with trimethylsilylchloride (TMS-Cl)-triethylamine (TEA), followed by thermal decomposition, provided HPI. The polymer having a number average molecular weight up to 8400 was obtained in quantitative yield. Thermal properties were investigated and we found that the polymer has a higher glass transition temperature ( Tg)upto 230 °C, and a lower dielectric constant at 2.98 at 1 MHz than the conventional polycarbodiimides (PCDs). The linear F-PCD was soluble in a wide range of common organic solvents such as toluene and dichloromethane.