Transient electronics are electronics with the ability to disappear to reduce environmental impact and avoid reverse engineering. Recent advances in the field of transient electronics have driven the need for fast depolymerizing polymer substrates. One such approach to a polymer that offers a catalytic response to a stimulus is poly(phthalaldehyde). Long shelf life and high molecular weight poly(phthalaldehyde) have been inconsistently achieved. Polymerizations with boron trifluoride etherate (BF3-OEt2) show promise for providing consistent, high molecular weight polymerizations. The polymer product, however, has shown stochastic depolymerization during storage. The importance of BF3 for the polymerization and shelf life of phthalaldehyde is investigated. In-situ 1H nuclear magnetic resonance shows a complex of BF3 with the polymer backbone that likely causes the short shelf life. A mechanism is proposed to explain the role of BF3 in the polymerization of phthalaldehyde. Accelerated aging shows poly(phthalaldehyde) that is stable for long storage times. All attempts for a disappearing poly(phthalaldehyde) substrate rely on the use of elevated temperatures and long evaporation times. The long times are a consequence of the low vapor pressure of phthalaldehyde, which is the sole degradation product. This work also seeks to decrease evaporation times and the need for elevated temperatures by incorporating high vapor pressure aldehydes with phthalaldehyde into a copolymer. Phthalaldehyde is necessary to retain solubility of the polymer in common solvents. Aldehydes attempted in copolymerizations include acetaldehyde, propionaldehyde, butyraldehyde, benzaldehyde, trans-2-methyl-2-butenal, and 3,4,5-trimethoxybenzaldehyde. Butyraldehyde offers the most benefit to minimizing transience time. High incorporation of butyraldehyde, 18 mol%, was achieved while maintaining solubility in common laboratory solvents. The rate of depolymerization of the butyraldehyde copolymer is almost five times the rate of the phthalaldehyde homopolymer. Evaporation times showed an order of magnitude improvement from the phthalaldehyde homopolymer to the butyraldehyde copolymer.

Stable, high molecular weight polyaldehydes

253rd National Meeting (2017)

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