Lignin is a compelling feedstock for the preparation of bisphenols and thermosetting resins. Phenols derived from lignin and other renewable sources often contain methoxy groups that can impact the properties and cure characteristics of derivative resins. To directly evaluate the effect of methoxy groups on the properties of renewable cyanate esters, a series of "deoxygenated" resins were prepared from renewable bisphenols by conversion to triflates followed by Pd-catalyzed elimination and hydrolysis of the methoxy groups. Reaction with CNBr and base then yielded the cyanate ester resins. The physical properties, cure chemistry, and decomposition pathways of the oxygenated (prepared previously) and deoxygenated resins were then compared. Deoxygenation was found to decrease the melting points of the resins, increase the dry and wet Tgs, decrease the water uptake, and increase the thermo-oxidative stability. The thermal degradation of both sets of resins was monitored by TGA/FTIR. Due to the higher thermal stability of the deoxygenated resins, decomposition proceeded primarily via evolution of small molecules including CO2 and NH3. This was in contrast to the lower temperature degradation of the oxygenated resins that resulted in the evolution of phenols and isocyanic acid. A different approach was then explored to take advantage of methoxy-functionalized phenols. New hybrid resins were prepared by allowing a methoxy or alkoxy-functionalized phenol to react with a a chlorophosphate. Conversion of the alkoxy-group to a phenol then allowed for the preparation of a series of cyanate ester resins with bridging phosphate groups. Tgs of these materials ranged from 130 to &gt;&gt;300 °C depending on the number of cyanate ester groups per bridging phosphate and the substitution pattern of the aromatic rings. These hybrid resins may have applications in fire resistant composite materials.

High temperature cyanate ester resins from renewable feedstocks: Upgrading through deoxygenation or conversion to hybrid resins

249th National Meeting (2015)

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