Tremendous efforts have been put forth by industries to attain sustainability, but plastics (or polymers) are mostly manufactured with non-renewable fossil fuels. Meanwhile, scientists have now come up with a feasible process to produce biobased acrylate resins.
Image Credit: Wiley-VCH, Angewandte Chemie.
The newly developed process encompasses all the synthesis steps, beginning with initial building blocks right up to polymerization, in a single reactor (one-pot), thereby reducing environmental impact. The research and its outcome have been published in the Angewandte Chemie journal.
The majority of paint, varnishes and adhesives are made from acrylate resins, which are polymers of methacrylic acid esters and acrylic acid esters. The raw materials that make up these esters are methacrylic acid, acrylic acid and alcohol. The alcohol provides plastic with properties like hardness or softness and water repulsion 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, employed alcohols from natural or biobased sources, instead of fossil sources. The sources comprise menthol, plant-based lauryl alcohol, vanillin, ethyl lactate and tetrahydrogeraniol (a pheromone-like substance).
Apart from inducing sustainability by using renewable resources, the researchers also focused on synthesis in fewer steps, alternatively called, a one-pot process. This required identifying a catalyst that was appropriate for several steps of the process along with fine-tuning all other synthesis conditions, like temperature, concentrations and solvents.
The initial step in this kind of synthesis is the activation of acrylic or methacrylic acid. The scientists identified appropriate catalysts from simple salts. The catalysts were also suited the subsequent steps — the reaction of the biobased alcohols with acrylic or methacrylic anhydride (a condensed form of the acids) to yield the corresponding esters. They are considered to be the building blocks of the resultant polymer.
This monomer preparation step is highly efficient and allowed us to perform the polymerization in the same reactor.
Christophe Thomas, Institut de Recherche de Chimie
The researchers were able to create block copolymers without purifying the intermediate products. Block copolymers are extensively employed in plastics production, from two or three different individual polymers manufactured separately.
The biobased plastics produced by the researchers had numerous beneficial properties, based on the monomers with which they are formed. For instance, the resin produced with a lactic acid side chain [poly(ELMA)] was brittle and hard; however, the one produced with the more flexible tetrahydrogeraniol side chain [poly(THGA)] was pliable at room temperature.
The scientists highlight the different available prospects with the numerous varieties of biobased alcohols at their disposal.
Apart from the versatility of the group’s approach, the one-pot synthesis also helps decrease the environmental footprint. As work-up solvents attribute to a larger proportion of the E-factor, or environmental impact, of plastics synthesis, the one-pot processes without work-up greatly decrease this factor. This synthesis process resulted in a reduced E-factor by three-quarters, highlighting the importance of this research.
Journal Reference:
Fouilloux, H., et al. (2021) Multicatalytic Transformation of (Meth)acrylic Acids: a One-Pot Approach to Biobased Poly(meth)acrylates. Angewandte Chemie. doi.org/10.1002/anie.202106640.