Calix[4]arenes used as a new type of chain extender in the preparation of polyurethanes

A series of polyether - or polyester - polyurethanes based on tetrahydrofuran - propylene oxide copolyether diol (PTMG/PPG) or poly( ethylene terephthalate) diol ( PET), toluene diisocyanate (TDI), and three kinds of chain extenders including two calix[4] arene derivatives and 3,3 '-dichloro-4,4'-diaminodiphenylmethane (MOCA) were synthesized in toluene. The thermal stability and mechanical properties of solvent-type polyurethanes were investigated. Incorporation of calixarenes into polyurethane backbones improved the thermal properties of the polyurethane as a result of the residual phenol hydroxy groups of the calix[ 4] arene units. Compared with polyurethane chain-extended by MOCA, the polyurethanes with calix[ 4] arene derivatives had higher elongation at break, lower elastic modulus, and lower yield strength, as a result of the larger steric cubage of calix[ 4] arene units and relatively large free volume of the polymer.