The industry has gone to enormous lengths to achieve sustainability, but plastics (or polymers) are mostly made using non-renewable fossil fuels. In the meantime, scientists have developed a practicable method to produce bio-based acrylate resins.
Image Credit: Wiley-VCH, Angewandte Chemie.
The newly developed process encompasses all synthesis steps, from the first building blocks to polymerization, in a single reactor (one-pot), thus reducing environmental pollution. The research and its results have been published in the journal Angewandte Chemie.
Most paints, varnishes, and adhesives are made from acrylate resins, which are polymers made from methacrylic acid esters and acrylic acid esters. The raw materials that make up these esters are methacrylic acid, acrylic acid, and alcohol. The alcohol gives plastic properties such as hardness or softness and water repellency or absorption.
To convert the polyacrylates and polymethacrylates into many sustainable ones, Christophe Thomas and his group from the Institut de Recherche de Chimie in Paris, France, used alcohols from natural or bio-based sources instead of fossil sources. Sources include menthol, vegetable lauryl alcohol, vanillin, ethyl lactate, and tetrahydrogeraniol (a pheromone-like substance).
In addition to sustainability through the use of renewable raw materials, the researchers also concentrated on the synthesis in fewer steps, also known as the one-pot process. This required identifying a catalyst that was suitable for several steps in the process, as well as fine-tuning all other synthesis conditions, such as temperature, concentrations, and solvents.
The first step in this type of synthesis is the activation of acrylic or methacrylic acid. The scientists identified suitable catalysts from simple salts. The catalysts were also suitable for the following steps – the reaction of the bio-based alcohols with acrylic or methacrylic anhydride (a condensed form of the acids) to give the corresponding esters. They are considered to be the building blocks of the resulting polymer.
This monomer production step is highly efficient and allowed us to run the polymerization in the same reactor.
Christophe Thomas, Research Institute for Chemistry
The researchers were able to make block copolymers without purifying the intermediates. Block copolymers are used extensively in plastics production, from two or three different individual polymers that are produced separately.
The bio-based plastics made by the researchers had numerous beneficial properties based on the monomers with which they were formed. For example the resin made with a lactic acid side chain [poly(ELMA)] was brittle and hard; however, the one made with the more flexible tetrahydrogeraniol side chain [poly(THGA)] was pliable at room temperature.
The scientists shed light on the different perspectives of the numerous bio-based alcohols that are available to them.
Aside from the versatility of the group’s approach, the one-pot synthesis also helps reduce the environmental footprint. Since work-up solvents make up a larger proportion of the E-factor or the environmental pollution of plastic synthesis, the one-pot processes without work-up greatly reduce this factor. This synthesis process resulted in an E-factor reduced by three quarters, which underscores the importance of this research.
Journal reference:
Fouilloux, H., et al. (2021) Multi-catalytic transformation of (meth) acrylic acids: a one-pot approach for bio-based poly (meth) acrylates. Applied Chemistry. doi.org/10.1002/anie.202106640.
Source: https://onlinelibrary.wiley.com/
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