480737 Low Ceiling Temperature Polyaldehydes for Transient Electronic Devices
Jihyun Lee, Jared M. Schwartz, Paul A. Kohl
Georgia Institute of Technology
The ceiling temperature (Tc) is the temperature at which de-propagation and propagation rates of chain polymerizations are equal, so the net polymer production is zero. Below ceiling temperature is the temperature at which polymerization will occur . Low Tc polymers can be trapped in the polymer form above Tc if the mechanism of depolymerization is suppressed. Low Tc polymers are attractive for use in ‘transient devices’ because the mechanism of depolymerization can be triggered by external stimulus, making them capable of rapid and complete depolymerization at the breaking of one bond. This property is ideal for ‘transient’ electronics which can’t be retrieved after use of those where its desirable to lower the environmental impact.
The aim is to synthesize polymer that is stable at room temperature but rapidly depolymerizes upon triggering. The monomer that has shown stability and high molecular weight is phthalaldehyde (PHA). Polymerizations using PHA have been studied by several researchers, and it was proposed that PHA of high molecular weight, when sensitized by addition of cationic photoinitiators, results in a rapid depolymerization. PHA can be depolymerized by raising its temperature, even though it is the reaction is kinetically slow. Strong acid is an efficient catalyst PHA depolymerization. Acid can be created by the addition of a thermal acid generator, or by the addition of the photoacid generator and UV radiation. Once depolymerized, the monomer will eventually evaporate.
To reduce the transience time of PHA due to the low vapor pressure of the monomer, higher vapor pressure aldehydes can be copolymerized with PHA. The copolymerized aldehydes include butyraldehyde, benzaldehyde, trans-2-methyl-2-butenal, and 3,4,5-trimethoxybenzaldehyde.
The shortest transience time was achieved when butyraldehyde was used as the co-monomer, and boron trifluoride etherate (BF3OEt2) as the catalyst. Incorporation of 18 mol% butyraldehyde, was achieved in the copolymer. The rate of depolymerization of the butyraldehyde copolymer was nearly five times the rate of the phthalaldehyde homopolymer. The copolymers were synthesized at different PPA:butyraldehyde ratios to determine the maximum incorporation of butyraldehyde.
 Odian, G. G. (2004). Polymerization–Depolymerization Equilibria. In Principles of Polymerization (4th ed., p. 789). NY: Wiley-Interscience.
 Kaitz, J. A. (2014). Depolymerizable, Adaptive Supramolecular Polymer Nanoparticles and Network. Polymer Chemistry, 5, 3794.
 Ito, H., & Willson, C. G. (1983). Chemical Amplication in the Design of Dry Developing Resist Materials. Polymer Engineering and Science, 23(18), 1014.
 Phillips, S. T. (2014) Amplified Responses in Materials Using Linear Polymers that Depolymerize from End-to-End When Exposed to Specific Stimuli. Journal of Applied Polymer Science, 10, 40992
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