Nature inspires and informs the design of new materials. By looking to nature, we can design materials offering desirable properties such as response to environmental stimuli, improved safety, and sustainability. This talk will span our progress on two projects in the areas of bio-inspired and bio-based polymers that were realized by undergraduate researchers at Lafayette College, a primarily undergraduate institution. In the first portion, efforts towards the development and characterization of a responsive hydrogel will be discussed. Carbon dioxide (CO2) has garnered interest as a stimulus as it is abundant, inexpensive, and non-toxic. Here, CO2 is used to trigger pronounced yet reversible swelling of a crosslinked hydrogel. We show that these gels display a CO2-switchable volume phase transition that enables isothermal gas-triggered swelling. Compositional studies were conducted to measure the initial volume phase transition temperature (VPTT) and the shift in the VPTT after CO2 exposure. Isothermal swelling studies performed at a temperature between the VPTTs before and after CO2 exposure show that CO2 triggers a reversible volume transition and controls the extent of swelling. Our results demonstrate the utility of CO2 as a stimulus for the design and study of smart materials, which are suitable for applications in drug delivery, microfluidics, and soft actuators. The second portion of this talk will focus on our efforts to develop bio-based thermosets from birch bark. In particular, we use betulin, a naturally occurring diol that can be extracted from birch bark in high yields, as a building block for the formation of polyester thermosets. We systematically assess the choice of co-monomers on the thermomechanical and degradative properties of the resulting polymers. Our results show that the glass transition temperatures are tunable over a 100°C range depending upon the co-monomer selected. Moreover, all samples exhibit thermal stability above 300°C in both nitrogen and air. The results presented here demonstrate that betulin is a promising building block for the design of bio-based thermosets. This work is part of a larger, collaborative study to develop and evaluate bio-based plastics at all stages of life, from monomer extraction, to polymer synthesis, to end of life.

Material design from nature: Bio-inspired and bio-based polymers

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ACS Spring 2023

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