Progress in non-isocyanate polyurethanes synthesized from cyclic carbonate intermediates and di- or polyamines in the context of structure–properties relationship and from an environmental point of view

Ionic Liquid Catalysis in Cyclic Carbonate Synthesis for the Development of Soybean Oil-Based Non-Isocyanate Polyurethane Foams

A method for obtaining non-isocyanate polyurethane (NIPU) foams from cyclic carbonate (CC) based on soybean oil was developed. For this purpose, cyclic carbonate was synthesized from epoxidized soybean oil and CO2 using various ionic liquids (ILs) as catalysts. Among the tested ILs, the highest selectivity (100%) and CC yield (98%) were achieved for 1-ethyl-3-methylimidazolium ([emim]Br). Without any purification, the resulting cyclic carbonate was reacted directly with diethylenetriamine as a model crosslinking agent to produce NIPU foams. It was found that the soybean oil-based CC synthesized with bromide imidazolium ionic liquids exhibited significantly shorter gelling times (8 min 50 s for [emim]Br and 9 min 35 s for [bmim]Br) compared to those obtained with the conventional TBAB catalyst (26 min 15 s). A shorter gelling time is a crucial parameter for the crosslinking process in foams. The obtained foams were subjected to mechanical tests and a morphology analysis.

Preparation of Non-Isocyanate Polyurethanes from Mixed Cyclic-Carbonated Compounds: Soybean Oil and CO2-Based Poly(ether carbonate)

This study presents the synthesis and characterization of non-isocyanate polyurethanes (NIPU) derived from the copolymerization of cyclic-carbonated soybean oil (CSBO) and cyclic carbonate (CC)-terminated poly(ether carbonate) (RCC). Using a double-metal cyanide catalyst, poly(ether carbonate) polyol was first synthesized through the copolymerization of carbon dioxide and propylene oxide. The terminal hydroxyl group was then subjected to a substitution reaction with a five-membered CC group using glycerol-1,2-carbonate and oxalyl chloride, yielding RCC. Attempts to prepare NIPU solely using RCC and diamine were unsuccessful, possibly due to the low CC functionality and the aminolysis of RCC's linear carbonate repeating units. However, when combined with CSBO, solid NIPUs were successfully obtained, exhibiting good thermal stability along with enhanced mechanical properties compared to conventional CSBO-based NIPU formulations. Overall, this study underscores the potential of leveraging renewable resources and carbon capture technologies to develop sustainable NIPUs with tailored properties, thereby expanding their range of applications.

A review on vegetable oil-based non isocyanate polyurethane: towards a greener and sustainable production route

The transition from conventional polyurethane (PU) to non isocyanate polyurethane (NIPU) is driven mainly by safety concerns, environmental considerations, and sustainability issues associated with the current PU technology. NIPU has emerged as a promising alternative, addressing limitations related to traditional PU production. There has been increasing interest in bio-based NIPU aligning with the aspiration for green materials and processes. One important biomass resource for the development of bio-based NIPU is vegetable oil, an abundant, renewable, and relatively low cost feedstock. As such, this review aims to provide insight into the progression of NIPU derived from vegetable oils. This article highlights the synthetic and green approach to NIPU production, emphasizing the method involving the polyaddition reaction of cyclic carbonates and amines. The review includes case studies on vegetable oil-based NIPU and perspectives on their properties. Further, discussions on the potential applications and commercial importance of PU and NIPU are included. Finally, we offer perspectives on possible research directions and the future prospects of NIPU, contributing to the ongoing evolution of PU technology.

Polylactide-Based Nonisocyanate Polyurethanes: Preparation, Properties Evaluation and Structure Analysis

This study investigated the successful synthesis and characterization of nonisocyanate polyurethanes (NIPUs) based on polylactide. The NIPUs were synthesized by a condensation reaction of oligomers with hard segments (HSs) and synthesized carbamate-modified polylactic acid containing flexible segments (FSs). The oligomers with HSs were prepared from phenolsulfonic acid (PSA) or a mixture of PSA and hydroxynaphthalenesulfonic acid (HNSA), urea and formaldehyde. The mixing of oligomeric compounds with different amounts of formaldehyde was carried out at room temperature. Obtained NIPU samples with different hard segment content were tested for their mechanical and thermal properties. The tensile strength (TS) of all NIPU samples increased with an increasing amount of HSs, attaining the maximum value at an HS:FS ratio of 1:3. Samples prepared from PSA and HNSA showed higher tensile strength (TS) without significant change in elongation at break compared to the samples based only on PSA. Thermogravimetric analysis data indicated an absence of weight loss for all samples below 100 °C, which can be considered a safe temperature for using NIPU materials. Maximum degradation temperatures reached up to 385 °C. Fourier transform infrared spectroscopy results confirmed the existence of expected specific groups as well as the chemical structure of the prepared polyurethanes. DSC analysis showed the existence of two characteristic phase transitions attributed to the melting and crystallization of hard segments in the NIPU samples.

Innovations in applications and prospects of non-isocyanate polyurethane bioplastics

Currently, conventional plastics are necessary for a variety of aspects of modern daily life, including applications in the fields of healthcare, technology, and construction. However, they could also contain potentially hazardous compounds like isocyanates, whose degradation has a negative impact on both the environment and human health. Therefore, researchers are exploring alternatives to plastic which is sustainable and environmentally friendly without compromising its mechanical and physical features. This review study highlights the production of highly eco-friendly bioplastic as an efficient alternative to non-biodegradable conventional plastic. Bioplastics are produced from various renewable biomass sources such as plant debris, fatty acids, and oils. Poly-addition of di-isocyanates and polyols is a technique employed over decades to produce polyurethanes (PUs) bioplastics from renewable biomass feedstock. The toxicity of isocyanates is a major concern with the above-mentioned approach. Novel green synthetic approaches for polyurethanes without using isocyanates have been attracting greater interest in recent years to overcome the toxicity of isocyanate-containing raw materials. The polyaddition of cyclic carbonates (CCs) and polyfunctional amines appears to be the most promising method to obtain non-isocyanate polyurethanes (NIPUs). This method results in the creation of polymeric materials with distinctive and adaptable features with the elimination of harmful compounds. Consequently, non-isocyanate polyurethanes represent a new class of green polymeric materials. In this review study, we have discussed the possibility of creating novel NIPUs from renewable feedstocks in the context of the growing demand for efficient and ecologically friendly plastic products.

Biodegradable isocyanate-free polyurethane films via a noncatalytic route: facile modified polycaprolactone triol and biobased diamine as precursors

A facile synthesis of isocyanate free polyurethanes (PU) was executed by the reaction of biodegradable cyclic carbonate and sustainable diamines generated via chemical modification. The biodegradable polyol polycaprolactone triol (PCL) was transformed into a new glycerol carbonate derivative, PCL-(COOGC)₃, and subjected to polyaddition with the diamines linalool diamine (LLDA), isosorbide diamine (ISODA) and hexamethylene diamine (HDA). Polyaddition of PCL-(COOGC)₃ with the above diamine precursors was conducted via a one-pot reaction under catalyst-free reaction conditions prior to film casting. The above precursors were characterized by Fourier-transform infrared (FTIR) and ¹H and ¹³C nuclear magnetic resonance spectroscopies, high-resolution mass spectrometry and electrospray ionization matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, whereas the PU films were studied by attenuated total reflectance-FTIR spectroscopy, solid state ¹³C NMR, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, X-ray diffractometry, differential scanning calorimetry and thermogravimetric analysis. High onset degradation temperature (T _d) values were observed for the PU films PU-1 (345.8 °C), PU-2 (309.6 °C) and PU-3 (344.6 °C), and further studies, including cross-link density, water contact angle, swelling behaviour and biodegradation (phosphate-buffered saline medium, pH = 7.2 at 45 °C) measurements, were conducted.

Lignin as a Renewable Building Block for Sustainable Polyurethanes

Currently, the pulp and paper industry generates around 50-70 million tons of lignin annually, which is mainly burned for energy recovery. Lignin, being a natural aromatic polymer rich in functional hydroxyl groups, has been drawing the interest of academia and industry for its valorization, especially for the development of polymeric materials. Among the different types of polymers that can be derived from lignin, polyurethanes (PUs) are amid the most important ones, especially due to their wide range of applications. This review encompasses available technologies to isolate lignin from pulping processes, the main approaches to convert solid lignin into a liquid polyol to produce bio-based polyurethanes, the challenges involving its characterization, and the current technology assessment. Despite the fact that PUs derived from bio-based polyols, such as lignin, are important in contributing to the circular economy, the use of isocyanate is a major environmental hot spot. Therefore, the main strategies that have been used to replace isocyanates to produce non-isocyanate polyurethanes (NIPUs) derived from lignin are also discussed.

Bio-Based Polyurethane Resins Derived from Tannin: Source, Synthesis, Characterisation, and Application

Tannins are soluble, astringent secondary phenolic metabolites generally obtained from renewable natural resources, and can be found in many plant parts, such as fruits, stems, leaves, seeds, roots, buds, and tree barks, where they have a protective function against bacterial, fungal, and insect attacks. In general, tannins can be extracted using hot water or organic solvents from the bark, leaves, and stems of plants. Industrially, tannins are applied to produce adhesives, wood coatings, and other applications in the wood and polymer industries. In addition, tannins can also be used as a renewable and environmentally friendly material to manufacture bio-based polyurethanes (bio-PUs) to reduce or eliminate the toxicity of isocyanates used in their manufacture. Tannin-based bio-PUs can improve the mechanical and thermal properties of polymers used in the automotive, wood, and construction industries. The various uses of tannins need to be put into perspective with regards to possible further advances and future potential for value-added applications. Tannins are employed in a wide range of industrial applications, including the production of leather and wood adhesives, accounting for almost 90% of the global commercial tannin output. The shortage of natural resources, as well as the growing environmental concerns related to the reduction of harmful emissions of formaldehyde or isocyanates used in the production of polyurethanes, have driven the industrial and academic interest towards the development of tannin-based bio-PUs as sustainable alternative materials with satisfactory characteristics. The aim of the present review is to comprehensively summarize the current state of research in the field of development, characterization, and application of tannin-derived, bio-based polyurethane resins. The successful synthesis process of the tannin-based bio-PUs was characterized by Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), MALDI-TOF mass spectrometry, and gel permeation chromatography (GPC) analyses.

Recent Developments in Lignin- and Tannin-Based Non-Isocyanate Polyurethane Resins for Wood Adhesives—A Review

This review article aims to summarize the potential of using renewable natural resources, such as lignin and tannin, in the preparation of NIPUs for wood adhesives. Polyurethanes (PUs) are extremely versatile polymeric materials, which have been widely used in numerous applications, e.g., packaging, footwear, construction, the automotive industry, the lighting industry, insulation panels, bedding, furniture, metallurgy, sealants, coatings, foams, and wood adhesives. The isocyanate-based PUs exhibit strong adhesion properties, excellent flexibility, and durability, but they lack renewability. Therefore, this study focused on the development of non-isocyanate polyurethane lignin and tannin resins for wood adhesives. PUs are commercially synthesized using polyols and polyisocyanates. Isocyanates are toxic, costly, and not renewable; thus, a search of suitable alternatives in the synthesis of polyurethane resins is needed. The reaction with diamine compounds could result in NIPUs based on lignin and tannin. The research on bio-based components for PU synthesis confirmed that they have good characteristics as an alternative for the petroleum-based adhesives. The advantages of improved strength, low curing temperatures, shorter pressing times, and isocyanate-free properties were demonstrated by lignin- and tannin-based NIPUs. The elimination of isocyanate, associated with environmental and human health hazards, NIPU synthesis, and its properties and applications, including wood adhesives, are reported comprehensively in this paper. The future perspectives of NIPUs’ production and application were also outlined.

Tough amphiphilic antifouling coating based on acrylamide, fluoromethacrylate and non-isocyanate urethane dimethacrylate crosslinker

This study is focused on the development of tougher gels using combinations of acrylamide, fluoromethacrylate and a non-isocyanate urethane dimethacrylate (NIUDMA) crosslinker. The NIUDMA was tailored with 2, 3-epoxypropoxy propyl-polydimethylsiloxane segments E9 (MW = 0.36 kg mol^-1), E11 (MW = 0.5-0.6 kg mol^-1) and E12 (MW = 1-1.4 kg mol^-1). A 3 level Taguchi design was used to evaluate the role of each component of the ternary copolymer gel on the elastic modulus and toughness. The toughness ranged from 2.5-7 MJ m^-3 whereas the modulus ranged from 27-70 MPa. The formulations with the highest toughness and modulus were screened for their antifouling potential in biological assays against the microalga Navicula incerta and the bacterium Cellulophaga lytica. The E9 gels showed the best performance, achieving a 73% reduction in N. incerta cells and a 92% reduction in C. lytica biofilm remaining after water jetting treatments, when compared with the commercial Intersleek product IS700.

Synthesis and structural characterization of bio-based bis(cyclic carbonate)s for the preparation of non-isocyanate polyurethanes

Full chemical structure characterization of cyclic carbonates from diepoxides synthesized using sustainable bio-based polyols with different molecular weights and carbon dioxide.

NNC-Scorpionate Zirconium-Based Bicomponent Systems for the Efficient CO2 Fixation into a Variety of Cyclic Carbonates

Two new derivatives of the bis(3,5-dimethylpyrazol-1-yl)methane modified by introduction of organosilyl groups on the central carbon atom, one of which bearing a chiral fragment, have been easily prepared. We verified the potential utility of these compounds through the reaction with [Zr(NMe₂)₄] for the preparation of novel zirconium complexes in which an ancillary bis(pyrazol-1-yl)methanide acts as a robust monoanionic tridentate scorpionate in a κ³-NNC chelating mode, forming strained four-membered heterometallacycles. These κ³-NNC-scorpionate zirconium amides were investigated as catalysts in combination with tetra-n-butylammonium bromide as cocatalyst for CO₂ fixation into five-membered cyclic carbonate products. The study has led to the development of an efficient zirconium-based bicomponent system for the selective cycloaddition reaction of CO₂ with epoxides. Kinetics investigations confirmed apparent first-order dependence on the catalyst and cocatalyst concentrations. In addition, this system displays very broad substrate scope, including mono- and disubstituted substrates, as well as the challenging biorenewable terpene derived limonene oxide, under mild and solvent-free conditions.

Bimetallic scorpionate-based helical organoaluminum complexes for efficient carbon dioxide fixation into a variety of cyclic carbonates

The binuclear aluminum complexes [AlR₂(κ²-NN′;κ²-NN′)AlR₂] with TBAB/PPNCl behave as excellent systems for cyclic carbonate formation from CO₂ with challenging epoxides.

Facile and Sustainable Synthesis of Erythritol bis(carbonate), a Valuable Monomer for Non-Isocyanate Polyurethanes (NIPUs)

Recently, R. Mülhaupt et al. introduced the first high yielding synthesis of erythritol bis(carbonate) from erythritol with diphenyl carbonate (DPC) as reagent. They utilized it as monomer for the synthesis of non-isocyanate polyurethanes (NIPUs). Here, we present a significantly more sustainable procedure for the carbonate formation regarding solvent, carbonyl source, reaction temperature, reaction time, reduced pressure during the reaction, simplicity of the workup as well as recycling of reagents. Catalysed by triazabicyclodecene (TBD), dimethyl carbonate as solvent as well as reagent leads to selective product formation and facile product separation by filtration. After addition of new starting materials, the mixture of catalyst and DMC was reused up to 8 times without loss of catalytic activity.

Systematic synthetic study of four diastereomerically distinct limonene-1,2-diols and their corresponding cyclic carbonates

In order to produce versatile and potentially functional terpene-based compounds, a (R)-limonene-derived diol and its corresponding five-membered cyclic carbonate were prepared. The diol (cyclic carbonate) comprises four diastereomers based on the stereochemical configuration of the diol (and cyclic carbonate) moiety. By choosing the appropriate starting compounds (trans- and cis-limonene oxide) and conditions, the desired diastereomers were synthesised in moderate to high yields with, in most cases, high stereoselectivity. Comparison of the NMR data of the obtained diols and carbonates revealed that the four different diastereomers of each compound could be distinguished by reference to their characteristic signals.

Versatile and scalable synthesis of cyclic organic carbonates under organocatalytic continuous flow conditions

A scalable intensified flow process for the preparation of cyclic organic carbonates relying on a cheap ammonium organocatalyst.

Unmodified kraft lignin isolated at room temperature from aqueous solution for preparation of highly flexible transparent polyurethane coatings

Polyurethane (PU) coatings were successfully produced using unmodified kraft lignin (KL) as an environmentally benign component in contents of up to 80 wt%. Lignin samples were precipitated from industrial black liquor in aqueous solution working at room temperature and different pH levels (pH 2 to pH 5). Lignins were characterized by UV-Vis, FTIR, pyrolysis-GC/MS, SEC and 31P-NMR. Results show a correlation between pH level, OH number and molecular weight M w of isolated lignins. Lignin-based polyurethane coatings were prepared in an efficient one step synthesis dissolving lignin in THF and PEG425 in an ultrasonic bath followed by addition of 4,4-diphenylmethanediisocyanate (MDI) and triethylamine (TEA). Crosslinking was achieved under very mild conditions (1 hour at room temperature followed by 3 hours at 35 °C). The resulting coatings were characterized regarding their physical properties including ATR-IR, TGA, optical contact angle, light microscopy, REM-EDX and AFM data. Transparent homogeneous films of high flexibility resulted from lignins isolated at pH 4, possessing a temperature resistance up to 160 °C. Swelling tests revealed a resistance against water. Swelling in DMSO depends on index, pH of precipitation and catalyst utilization for PU preparation. According to AFM studies, surface roughness is between 10 and 28 nm.

Synthesis and Application of Nonisocyanate Polyurethanes

The latest published achievements in the research and developments of non-isocyanate polyurethanes on the base of five-membered cyclic carbonates and amines are briefly presented. Preparations of hybrid epoxy-amine hydroxyurethane-grafted polymers with a controlled number of cross-links are described. Examples of the use of hydroxyurethanes of different nature for modification of the oligomeric compositions are also given.

Synthesis and application of a novel poly-l-phenylalanine electroactive macromonomer as matrix for the biosensing of ‘Abused Drug’ model

The synthesis and biosensing application of a novel poly-l-phenylalanine-bearing electroactive macromonomer has been carried out.