Low ceiling temperature, thermodynamically unstable polymers have been troublesome to synthesize and keep stable during storage. In this study, stable poly(phthalaldehyde) has been synthesized with BF 3 -OEt 2 catalyst. The role of BF 3 in the polymerization is described. The interaction of BF 3 with the monomer is described and used to maximize the yield and molecular weight of poly(phthalaldehyde). Various Lewis acids were used to investigate the effect of catalyst acidity on poly(phthalaldehyde) chain growth. In situ nuclear magnetic resonance was used to identify possible interactions formed between BF 3 and phthalaldehyde monomer and polymer. The

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Knowledge of the ceiling temperature and thermodynamic variables for low ceiling temperature polymers is critical to understanding the material's synthesis and use. Synthesis of the polymer below its ceiling temperature is the routine polymerization route. In situ 1H NMR of the equilibrium polymerization reaction can provide critical information for determining the enthalpy and entropy of polymer formation. Three polyaldehydes were synthesized with in situ 1H NMR, and their energies of formation were determined for the linear region of ceiling temperature. Insights into the mechanism of polymerization were also found using this method. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 221–228

The study and development of transient devices is an emerging field where the disposal of a device after use is desired to avoid reverse engineering and minimize the environmental impact. Polyaldehydes with phototriggers have been investigated because the radiation wavelength can be adjusted to meet the transient application. Polynuclear aromatic hydrocarbons (PAHs) were used as the optical sensitizer for photoacid generators (PAGs). Photoinduced electron transfer (PET) with an iodonium-based PAG was used to expand the spectral sensitivity range. Anthracene, tetracene, and pentacene derivatives were synthesized with appended phenylethynyl groups to improve the solubility of the sensitizer and adjust the absorption wavelength. Sensitization of the iodonium-based PAG with the PAH derivatives was found to have thermodynamically favorable PET reactions for depolymerization of poly(propylene carbonate) and poly(phthalaldehyde) (PPHA). The Rehm-Weller equation and Stern-Volmer analysis were used to study the electron transfer and the fluorescence quenching rates of the PAHs with the iodonium salts, respectively. The photosensitivity, efficiency, and byproducts of the PET reactions in the decomposable polymer films are reported. A rapid photoreaction is reported for the depolymerization of PPHA exposed to a sunlight dose of <6 J cm −2 (i.e., 1 min of direct sunlight) with a pentacene-based sensitizer.

We demonstrate phototriggered depolymerization of a low ceiling temperature ( T) polymer, poly(phthalaldehyde) (PPHA), via internal light emission from integrated organic light-emitting diodes (OLEDs) fabricated directly on flexible PPHA substrates with silver nanowire electrodes. The depolymerization of the PPHA substrates is triggered by absorption of the OLED emission by a sensitizer that activates a photoacid generator via energetically favorable electron transfer. We confirm with Fourier-transform infrared spectroscopy that the photon doses delivered by the integrated OLED are sufficient to depolymerize the PPHA substrates. We determine this critical dosage by measuring the operating lifetimes of the OLEDs whose failure is believed to be due to significant mechanical softening during the liquefaction of decomposed phthalaldehyde monomers.