The Development of a Photodegradable Polyester

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The Development of a Photodegradable Polyester
Bailey Phelps
Matthew Baker
SUNY Oswego Creative Writing Program
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Plastics have become one of the most easily produced, utilized, and discarded products in the modern world. As production costs of plastics dropped, the amount of plastic found in landfills has grown drastically. In response, many attempts have been made to develop biodegradable plastics, also known as polymers. This project focused on the synthesis, depolymerization, and characterization of a light sensitive polymer. Hydroxycinnamic acid was used as the precursor to our polymer. This compound is commonly found in foods and spices such as cinnamon. After successful synthesis and purification of the polymer it was then characterized by nuclear magnetic resonance (NMR). Following characterization, the polymer was exposed to UV light in order to initiate degradation. The product of degradation was later characterized by NMR and found to be coumarin. This is an ideal outcome because coumarin is a naturally occurring compound found in many plants. The focus of the project then turned to studying the kinetics of the depolymerization process by NMR, gel permeation chromatography, and high-performance liquid chromatography. The rate and extent of depolymerization was then determined using the aforementioned methods. The main goal of the project was to synthesize a photodegradable polymer; this concept coupled with the use of a naturally occurring precursor and the production of another natural compound after degradation results in the potential for a more environmentally friendly plastic.
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The Development of a Photodegradable PolyesterBailey Phelps and Dr. Matthew Baker1 1Department of Chemistry, State University of New York at Oswego, Oswego, NY Introduction:Plastics have become one of the most easily produced, utilized, and discarded products in the modern world . As production costs of plastics dropped, the amount of them found in landfills has grown drastically . In the United States alone, 38. 5 million tons of plastic waste was produced in 2018 while only 9 % of plastics were recycled .1This leaves millions of tons of plastic to either end up in landfills or pollute the environment . In response to this, many attempts have been made to develop degradable plastics and polymers .2For degradable plastics to meet their full potential they should be designed to degrade selectively when exposed to a specific stimulus. In this context, a variety of stimuli have been explored for polymer degradation, including chemical, biological, mechanical, thermal, and photo chemical means . Of these stimuli, arguably the most interesting is photochemical degradation because of the ease in which light can be controlled . For example, the duration, the intensity, and the wavelength of light can be easily modified providing a wider variety of control over the degradation process . This poster describes the development and analysis of a photo degradable plastic. Our goal:The goal of this project was to develop and analyze a photodegradable plastic. To accomplish this task we focused on polymerizing 2 hydroxycinnamic acid and studying the plastic that resulted . Hydroxycinnamic acid was chosen because it has the ability to respond to light and undergo a cyclization reaction, leading to the cleavage of adjoining bonds . As a result, when polymerized we hypothesized that our plastic would undergo degradation when exposed to light, leading to complete degradation of the plastic and the formation of coumarin as the product (figure 1 ) .Figure 1 . Image showing degradation of poly( hydroxycinnamic acid) (1 ) to form coumarin (2 ) when exposed to UV light .Conclusion:Synthesis of a photodegradable polyester was successful . Additionally, degradation studies were carried out proving our plastic was capable of completely degrading when exposed to UV light .Results and discussion:After synthesis and purification, polymer 1 was analyzed by gel permeation chromatography (GPC). Using GPC we monitored the degradation of polymer 1 when exposed to UV light (figure 2 ) . Upon exposure to 300 nm light, polymer 1 completely degraded over the period of 96 hours. Subsequently, we characterized our polymer via1H NMR (figure 3 a) . Analysis of the spectra confirmed that the polymer was formed successfully . D epolymerization under UV light was tracked yet again across a 96hour period . After 96 hours the product of our experiment was characterized by1H NMR and determined to be coumarin , as expected (figure 3 b).References:1) Dell, J. U.S. Plastic Recycling Rate Projected to Drop to 4.4% in 2018, Environmental Protection Agency, 2018. 2) Mostafa, N.; Farag, A. A.; Abo-Dief , H. M.; Tayeb, A. M. Production of Biodegradable Plastic from Agricultural Wastes. Arabian Journal of Chemistry 2018, 11 (4), 546–553.Experimental:Several sets of conditions were used in an attempt to synthesize the desired polymer . The most successful and consistent method involved thionyl chloride (scheme 1 ) . To synthesize our polymer, 2 hydroxycinnamic acid ( 3 ) was refluxed in thionyl chloride overnight . Subsequently, the reaction mixture was concentrated, redissolved in tetrahydrofuran, and precipitated in methanol . The precipitate was filtered and dried resulting in polymer 1 .Scheme 1 . Synthesis of poly( hydroxycinnamic acid)Figure 3. Proton NMR spectra showing the conversion of polymer 1 (a) to coumarin (b), upon exposure to UV light. O H O O n UV light O O 12 O H O O n 1) SOCl22) MeOH HO OH O 1 3 Figure 3. GPC trace of our polymer before exposure (blue) and after 96 hours of exposure to 300 nm light (black).