Quantifying Photochemical Transformations of Poly(butylene adipate- co-terephthalate) Films

We report the photochemically induced molecular transformations of the poly(butylene adipate-co-terephthalate) (PBAT) polymer by quantifying the reaction rate constants (k) and yields for the primary photochemical pathways, including Norrish type I and II scission reactions, oxidation through hydroxylation of the terephthalate, and cross-linking. A suite of analytical techniques was used to quantify the reactions. Methodologies such as 1H nuclear magnetic resonance were used to identify molecular moieties that could be used as indicators for the chemical reaction pathways, with some photoinduced products (e.g., terminal aldehydes) being reported for the first time. Subsequently, doped-polymer film systems, analyzed with fluorescence spectroscopy, gas chromatography with flame ionization detection, and gas chromatography-mass spectrometry, were used to calibrate and quantify these molecular moieties upon photolysis. Ultimately, this uniquely comprehensive work culminates in quantification of the primary chemical reactions occurring in solid-state PBAT thin films. By quantifying photochemical transformations, this work will aid in predictive modeling of environmental transformations of polymers and guide the design and use of such technologies.