Synthesis of unsaturated polyester resins from various bio-derived platform molecules

Utilisation of bio-derived platform molecules in polymer synthesis has advantages which are, broadly, twofold; to digress from crude oil dependence of the polymer industry and secondly to reduce the environmental impact of the polymer synthesis through the inherent functionality of the bio-derived platform molecules. Bulk polymerisation of bio-derived unsaturated di-acids has been employed to produce unsaturated polyester (UPEs) which have been analysed by GPC, TGA, DSC and NMR spectroscopy, advancing on the analysis previously reported. UPEs from the diesters of itaconic, succinic, and fumaric acids were successfully synthesised with various diols and polyols to afford resins of MN 480-477,000 and Tg of -30.1 to -16.6 °C with solubilities differing based on starting monomers. This range of properties allows for many applications and importantly due to the surviving Michael acceptor moieties, solubility and cross-linking can be specifically tailored, post polymerisation, to the desired function. An improved synthesis of itaconate and succinate co-polymers, via the initial formation of an itaconate bis-diol, is also demonstrated for the first time, resulting in significantly improved itaconate incorporation

On the Effect of Microwave Energy on Lipase-Catalyzed Polycondensation Reactions

Microwave energy (MWe) is, nowadays, widely used as a clean synthesis tool to improve several chemical reactions, such as drug molecule synthesis, carbohydrate conversion and biomass pyrolysis. On the other hand, its exploitation in enzymatic reactions has only been fleetingly investigated and, hence, further study of MWe is required to reach a precise understanding of its potential in this field. Starting from the authors’ experience in clean synthesis and biocatalyzed reactions, this study sheds light on the possibility of using MWe for enhancing enzyme-catalyzed polycondensation reactions and pre-polymer formation. Several systems and set ups were investigated involving bulk and organic media (solution phase) reactions, different enzymatic preparations and various starting bio-based monomers. Results show that MWe enables the biocatalyzed synthesis of polyesters and pre-polymers in a similar way to that reported using conventional heating with an oil bath, but in a few cases, notably bulk phase polycondensations under intense microwave irradiation, MWe leads to a rapid enzyme deactivation

Circular economy design considerations for research and process development in the chemical sciences

A circular economy will look to chemistry to provide the basis of innovative products, made from renewable feedstocks and designed to be reused, recycled, or the feedstock renewed through natural processes. The substances that products are made of will increasingly be treated as a resource equal to the raw materials, and not just disposed of. This perspective discusses the role of chemists in a world without waste

Opportunities for Bio-Based Solvents Created as Petrochemical and Fuel Products Transition towards Renewable Resources

The global bio-based chemical market is growing in size and importance. Bio-based solvents such as glycerol and 2-methyltetrahydrofuran are often discussed as important introductions to the conventional repertoire of solvents. However adoption of new innovations by industry is typically slow. Therefore it might be anticipated that neoteric solvent systems (e.g., ionic liquids) will remain niche, while renewable routes to historically established solvents will continue to grow in importance. This review discusses bio-based solvents from the perspective of their production, identifying suitable feedstocks, platform molecules, and relevant product streams for the sustainable manufacturing of conventional solvents

N-Butylpyrrolidinone as a dipolar aprotic solvent for organic synthesis

Dipolar aprotic solvents such as N-methylpyrrolidinone (or 1-methyl-2-pyrrolidone (NMP)) are under increasing pressure from environmental regulation. NMP is a known reproductive toxin and has been placed on the EU “Substances of Very High Concern” list. Accordingly there is an urgent need for non-toxic alternatives to the dipolar aprotic solvents. N-Butylpyrrolidinone, although structurally similar to NMP, is not mutagenic or reprotoxic, yet retains many of the characteristics of a dipolar aprotic solvent. This work introduces N-butylpyrrolidinone as a new solvent for cross-coupling reactions and other syntheses typically requiring a conventional dipolar aprotic solvent

P-cymenesulphonyl chloride : A bio-based activating group and protecting group for greener organic synthesis

A bio-derived protecting/activating group has been synthesized by introducing a sulphonyl chloride group to the aromatic ring of p-cymene derived from citrus peel waste. The resulting p-cymenesulphonyl chloride was evaluated as an activating group by reacting with 1-octanol, 2-octanol, phenol and piperidine, and further reactions of the activated alcohols. The comparison to tosyl chloride demonstrates that the bio-based alternative can be effectively utilized as a direct replacement for the current fossil derived equivalent

Facile and rapid decarboxylation of glutamic acid to γ-aminobutyric acid via microwave-assisted reaction : towards valorisation of waste gluten

The growing trend towards the utilisation of biomass to produce fuels and chemicals has the potential to produce large quantities of protein-rich wastes that may be unsuitable for use as a feed. This protein waste could instead serve as a sustainable feedstock for the production of useful nitrogen-containing bio-based chemicals. We report herein the production of γ-aminobutyric acid from glutamic acid via a microwave-assisted decarboxylation reaction using isophorone as an inducer reagent. High yields of 63% can be achieved with only short reaction times (7 min) required. The influences of inducer loading, reaction time and hydrochloric acid concentration used for hydrolysis step of the work up were investigated at different scales. As a proof of concept, glutamic acid was facilely isolated from waste gluten, via microwave assisted hydrolysis, and subsequently decarboxylated with success. To the best of our knowledge this is the first organocatalytic route to γ-aminobutyric acid using glutamic acid as a reagent, and represents an alternative cleaner route to a valuable precursor for bio-based solvents, polymers and pharmaceuticals

Elucidating enzymatic polymerisations : Chain-length selectivity of Candida antarctica lipase B towards various aliphatic diols and dicarboxylic acid diesters

The sustainable synthesis of polymers is a field with growing interest due to the need of modern society to preserve the environment whilst making used products and food sustainable for the future generations. In this work we investigate the possibility of synthesizing aliphatic polyesters derived from various dicarboxylic acid diesters and diols in a solvent-free reaction system. Candida antarctica lipase B was selected as biocatalyst and its selectivity towards the carbon and ester chain length were elucidated. The selected enzyme was able to synthesize various polyesters combining C4-C10 diesters and C4-C8 diols. All combinations led to monomer conversions above 90% in 24 h with the best number average molecular weights (Mn) being obtained through the combination of dimethyl adipate and 1,8-octanediol leading to a Mn of 7141 Da. Differential scanning calorimetry analysis shows a clear trend with an increase in melting temperature of the polymers that correlates with both the increase of the Mn or of the polymer's constitutional repeat unit carbon chain length. Thermogravimetric analysis and rheology measurements performed on selected samples also confirm the trend showing a variation of the polymer's degradation temperatures and viscosity profiles