Synthesis and Characterization of Biobased Lactose Hydrogels: A Teaching Experiment on Sustainable Polymers and Waste Biomass Valorization

Abstract

Hydrogels are soft water-rich materials with physical properties that can be easily tuned by modifying their network structure. For instance, increasing or decreasing the cross-linking density has a profound effect on their water absorption capabilities and mechanical strength. These physical changes are showcased in a new experiment for organic chemistry and polymer science teaching laboratories based on the practical green synthesis and characterization of lactose methacrylate derived hydrogels. Lactose, a disaccharide derived from dairy waste byproducts, is functionalized with photoreactive methacrylate groups using methacrylic anhydride. The resulting mixture is subsequently photoirradiated to generate a cross-linked hydrogel. Structure–property relationships are assessed through comparative studies of three hydrogels of varying compositions. Compression tests and swelling studies in different aqueous environments offer a guided-inquiry experience. Students determine a relationship between cross-linking density and the physical properties of the hydrogels. This experiment highlights the valorization of biomass and multiple green chemistry principles including use of renewable feedstocks, atom economy, energy efficiency, waste prevention, and water as a benign solvent. Learning outcomes for an organic chemistry laboratory course include introduction to disaccharide and cross-linked polymer structures, observable physical change dependency with cross-linking density, and laboratory methods for evaluating water absorption capacities. Objectives aligned with a polymer course are incorporating mechanical compression instrumentation, mechanistic understanding of light-induced free radical polymerizations, and an appreciation for the application of hydrogels to commercial products. Overall, the translation of a current literature publication to an inexpensive and versatile experiment engages students in a modern example of sustainable polymer chemistry.

An Undergraduate Laboratory Module Integrating Organic Chemistry and Polymer Science

“…This comprehensive guided-inquiry laboratory module motivates students to think more critically about their learned chemistry. We expect this current work will contribute to the recent developments ,,− in implementing polymer synthesis and characterizations into undergraduate teaching laboratory.…”

Direct Catalytic Conversion of Lignocellulosic Biomass Wastes to Ethylene Glycol: Practical Learning for Chemical Engineering Students

“…Thus, these areas are of great interest to Chemical Engineers. In fact, over the past years, many works have been published studying the catalytic conversion of biomass to valuable chemicals, focusing on the development of efficient and stable catalysts, study of reaction mechanisms, and optimization of reaction conditions. − However, from all those more than 115,000 papers above-mentioned, only 92 (61 for “heterogeneous catalysis” and 31 for “biomass conversion”) are categorized as educational (“Education Educational Research” or “Education Scientific Disciplines”), − which indicates that research and education are generally divided as two different matters. According to these numbers, there is very limited research on educational practices considering biomass conversion and heterogeneous catalysis.…”

Metal-Free Ring-Opening Polymerization of Propylene Oxide: Synthesis and Characterization of Polyether in the Undergraduate Organic Chemistry Laboratory

“…Over the past decade, publications on polymer topics in this Journal have been increasing to address the lack of polymer experiments in undergraduate teaching laboratories. Such developed experiments include extensive topics related to polymer science, − such as polycarbonates, polyamides, self-healing polymers, vitrimers, polystyrenes, polyesters, − poly( N -isopropylacrylamide), polyanilines, poly(methyl methacrylate), , and their synthesis, characterization, and applications.…”