Crosslinking of poly(epibromohydrin) containing the aryl prop-2-ynyl ether terminated side group

Poly(epibromohydrin) (PEBH) was chemically modified using 1,8-diazabicyclo-(5.4.0)-7-undecene to catalyze the substitution of the bromine atom by 4-(propargyloxy)benzoic acid. The linear polyethers obtained showed a degree of substitution from 36 to 82% depending on the PEBH/Nu ratio. A model compound, aryl propargyl ether terminated monomer (II), was synthesized to study the crosslinking. Differential scanning calorimetry (DSC), IR, H-1 and C-13 NMR analysis showed that this process first involves a sigmatropic rearrangement reaction of the aryl propargyl ether groups to form 2H-1-benzopyran structures which subsequently polymerize. Linear polymers undergo a similar process of crosslinking leading to thermostable polymers. The activation energies are independent of the degree of modification but the final thermal properties depend on the crosslinking density.