Examination of the Thermal and Thermomechanical Behavior of Novel Cyanate Ester Homopolymers and Blends with Low Coefficients of Thermal Expansion

A new four-step synthetic method is presented and applied to the preparation in high purity of three novel dicyanate monomers that comprise aryl/alkylene ether backbones with high molecular flexibility. The multistep route involves four individually high-yielding steps (each ≥70%), thus giving overall reaction yields for total synthesis of 42−50% depending on the length of the backbone. All products are characterized using FT-IR and 1H NMR spectroscopy, elemental analysis, and melting point determination. DSC analysis of “uncatalyzed” samples displays relatively sharp melting endotherms ranging from 66 to 125 °C depending on the length (i.e., flexibility) of the backbone. All monomers display broad polymerization exotherms (87 ± 2 kJ/mol cyanate), although the polymerizations occur in different temperature regimes. When catalyzed (aluminum(III) acetylacetonate/dodecylphenol), the exothermic polymerization peaks occur at significantly lower temperatures than the uncatalyzed analogues and have much narrower...