High-performance Polyurethane Research Articles

Controllable Design and Synthesis of Polyurethane Elastomers Containing Polar Dangling Chains with High Mechanical Properties and Wide Damping Temperature Range.

Vibration and noise severely affect the operation of mechanical equipment and is also detrimental to human health. Therefore, the development of high performance damping materials is crucial. However, current methods to improve damping properties often come at the expense of mechanical properties, resulting in inferior mechanical performance of materials. In order to address the issue of imbalance between damping properties and mechanical properties in polyurethane damping elastomers. In this study, polyester dangling chains containing polar groups are synthesized and introduced into polyurethane. The obtained polyurethane exhibited an effective damping temperature range of 154 °C (-54 °C to 100 °C) and a tensile strength of 15.82 MPa. Furthermore, dynamic mechanical analysis and broadband dielectric relaxation spectroscopy are combined to investigate the influence of polar dangling chains on the structure and properties of polyurethane. The degree of microphase separation increases after the introduction of polar dangling chains, indicating enhances intermolecular interaction forces, facilitating the formation of hydrogen bond between the main chain and dangling chains, thereby increasing molecular chain friction and energy dissipation. This work overcomes the challenge of balancing the damping and mechanical properties of polyurethane, providing a new strategy for designing high performance polyurethane damping elastomers.

Research Status of Lignin-Based Polyurethane and Its Application in Flexible Electronics.

Polyurethanes (PU) have drawn great attention due to their excellent mechanical properties and self-healing and recyclable abilities. Lignin is a natural and renewable raw material in nature, composed of a large number of hydroxyl groups, and has a great potential to replace petroleum polyols in PU synthesis. This review summarizes the recent advances in modification methods such as the liquefaction, alkylation, and demethylation of lignin, and a systematic analysis of how to improve the reactivity and monomer substitution of lignin during polyurethane synthesis for the green manufacturing of high-performance polyurethanes was conducted. Polyurethane can be used in the form of films, foams, and elastomers instead of conventional materials as a dielectric or substrate material to improve the reliability and durability of flexible sensors; this review summarizes the green synthesis of polyurethanes and their applications in flexible electronics, which are expected to provide inspiration for the wearable electronics sector.

Exploring the Barrier Property of High-Performance Polyurethane-Silica-Lignin Coatings on Carbon Steel

The use of lignin in anticorrosive coatings has provided efficient corrosion protection to metallic alloys.1,2 We have combined lignin-based polyurethane (PU) with silica to produce eco-friendly anticorrosive coatings with high anticorrosive performance, mechanical strength and bactericidal action.3 The PU was synthesized from methyl diphenyl diisocyanate (MDI), glycerol and lignin; the PU pre-polymer was functionalized with APTES to later form a hybrid with the polysilanol network from TEOS. The reference coating4 was prepared using 100% glycerol (PU-Si-0Lig) as the polyol source, while the other two specimens contain glycerol and 0.2 g (Pu-Si-0.2Lig) or 0.4 g (Pu-Si-0.4Lig) of lignin, keeping the predetermined proportion NCO:OH = 1.16. The incorporation of lignin into the polymer matrix led to an increase in the thermal stability (295 to 304 °C), smoothness of the coating surface (4.3 to 1.7 nm) and improvement of the coating mechanical properties, such as coating hardness (362 to 376 MPa). In addition, the lignin-containing coatings present bactericidal activity against Escherichia coli. The corrosion protection of the PU-Si-Lignin hybrid coatings deposited on carbon steel was analyzed by electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl at room temperature. The tests were conducted in a three-electrode cell, consisting of the coated carbon steel substrate as the working electrode, a platinum mesh as a counter electrode, and an Ag|AgCl|KClsat as the reference electrode. PU-Si-0Lig and PU-Si-0.2Lig present fair corrosion protection with low-frequency impedance |Zlf| values around 106 Ω.cm2 after immersion for up to 14 days. Conversely, PU-Si-0.4Lig presents |Zlf| ~ 1010 Ω.cm2, phase angle near -90 ° over seven frequency decades, and a lifespan of 100 days immersed in seawater. The equivalent electric circuit (EEC) used to fit the PU-Si-0.4Lig revealed that the EIS data of the initial 14 days can be represented by a model containing only one time constant. This means the coating has a highly capacitive behavior with insignificant water uptake in the first two weeks. Altogether, these results demonstrated the potential of PU-Si-Lig coating to be applied as an efficient anticorrosive barrier with enhanced mechanical and antibacterial properties.Acknowledgements: This work was supported by the Brazilian funding agencies CNPq, FAPESP, CAPES and PROPe UNESP.Keywords: Renewable feedstock, green coating, PU-silica, lignin, corrosion protection.(1) Harb, S. V.; Cerrutti, B. M.; Pulcinelli, S. H.; Santilli, C. V.; Hammer, P. Siloxane–PMMA Hybrid Anti-Corrosion Coatings Reinforced by Lignin. Surf Coat Technol 2015, 275, 9–16. https://doi.org/http://dx.doi.org/10.1016/j.surfcoat.2015.05.002.(2) Cao, Y.; Liu, Z.; Zheng, B.; Ou, R.; Fan, Q.; Li, L.; Guo, C.; Liu, T.; Wang, Q. Synthesis of Lignin-Based Polyols via Thiol-Ene Chemistry for High-Performance Polyurethane Anticorrosive Coating. Compos B Eng 2020, 200, 108295. https://doi.org/https://doi.org/10.1016/j.compositesb.2020.108295.(3) Alinejad, M.; Henry, C.; Nikafshar, S.; Gondaliya, A.; Bagheri, S.; Chen, N.; Singh, S. K.; Hodge, D. B.; Nejad, M. Lignin-Based Polyurethanes: Opportunities for Bio-Based Foams, Elastomers, Coatings and Adhesives. Polymers (Basel) 2019, 11 (7). https://doi.org/10.3390/polym11071202.(4) Braz, Á. G.; Pochapski, D. J.; Pulcinelli, S. H.; Santilli, C. V. Effects of Curing Temperature and Silica Content on the Structure and Properties of a Sol–Gel PU-Silica Hybrid Coating for Corrosion Protection. ACS Applied Engineering Materials 2023, 1 (7), 1739–1751. https://doi.org/10.1021/acsaenm.3c00148.

Eco-Friendly and High-Performance Bio-Polyurethane Adhesives from Vegetable Oils: A Review.

Current petrochemical-based adhesives adversely affect the environment through substantial volatile organic compound (VOC) emissions during production, contributing to air pollution and climate change. In contrast, vegetable oils extracted from bio-resources provide a compelling alternative owing to their renewability, abundance, and compatibility with adhesive formulation chemistry. This review aimed to critically examine and synthesize the existing scholarly literature on environmentally friendly, sustainable, and high-performance polyurethane adhesives (PUAs) developed from vegetable oils. The use of PUAs derived from vegetable oils promises to provide a long-term replacement while simultaneously maintaining or improving adhesive properties. This quality renders these adhesives appropriate for widespread use in various sectors, including construction, automotive manufacturing, packaging, textile, and footwear industries. This review intended to perform a comprehensive assessment and integration of the existing research, thereby identifying the raw materials, strengths, weaknesses, and gaps in knowledge concerning vegetable oil-based PUAs. In doing so, it responded to these gaps and proposes potential avenues for future research. Therefore, this review accomplishes more than merely evaluating the existing research; it fosters the advancement of greener PUA technologies by identifying areas for improvement and innovation towards more sustainable industrial practices by showcasing vegetable oil-based PUAs as viable, high-performance alternatives to their petroleum-based counterparts.

Tuning of molecular weight and chemical composition of polyols obtained from Poly(ethylene terephthalate) waste recycling through the application of organocatalysts in an upcycling route

High molecular weight liquid polyols were produced from complex Poly (ethylene terephthalate) (PET) waste (low molecular weight PET waste, monolayer compounds, and coloured PET bottles) in one-step synthesis using mild reaction conditions. For the first time, a wide range of upcycled polyols were obtained by modulating the reaction conditions to control the chemical composition and molecular weight, in order to revalorize the same PET waste in different polyols.A new versatile, efficient, selective and sustainable chemical recycling method was developed, employing cheap reagents (ethylene carbonate) and basic organocatalysts, under mild reaction conditions (moderate temperatures and atmospheric pressure). Chemically, the polyols showed a singular composition, consisting of three types of repeating units, two coming from PET and one belonging to the ethylene carbonate ring-opening. Depending on the depolymerisation conditions of the PET waste and the catalyst used, the ratio between these moieties varied considerably, giving rise to a wide portfolio of liquid polyols. In addition, the ability of the organocatalyst to introduce the carbonate unit into the polyol chain was analysed as a function of the number of ethylene carbonate units used.As a proof of concept, these new liquid secondary raw materials served as a starting point for the synthesis of polyurethanes under standard conditions. Ultimately, the final objective of this upcycling process will be the application of a wide range of high-quality polyols as soft segments to produce more sustainable and high-performance polyurethanes (flexible foams, coatings, sealants, adhesives, elastomers).

Research on lignin-modified flexible polyurethane foam and its application in sound absorption

Lignin is a sustainable biomass resource with abundant hydroxyl groups that holds great promise for use as a feedstock for polyurethane foam production. Therefore, the flexible polyurethane foams (FPUFs) were prepared using the oxidized alkali lignin (OAL) as the matrix to enhance its compatibility. The OAL was obtained under the following conditions of 60 °C, 80 min treatment, a ratio of hydrogen peroxide to lignin of 1.2:1, and a ratio of iron hydroxide to lignin of 0.01. It was demonstrated that incorporating OAL enhanced the density, compressive strength, sound-absorbing performance and degradability of foam composites. The compressive strength was also improved by more than five times than that of blank foam under the optimal conditions, reaching 0.11 MPa. The thermogravimetric analysis (TGA) revealed that the foam composite containing 30 % modified lignin content exhibited the highest thermal stability. The results of solvent resistance testing demonstrated the durability of the foam composites in both water and solvents. Lignin-modified polyurethane foam exhibited an acoustic absorption coefficient above 0.2 across a wide frequency range, with the highest value reaching 0.84, meeting the conventional requirements for sound absorption materials (α > 0.2). The results suggested that this environmentally friendly preparation method was feasible for producing high-performance polyurethane foams, which was appropriate for the production of sound absorption boards for industry, transportation by train and automobile.

High performance polyurethane nanocomposite coatings based on 2D materials for improved anticorrosion and flame-retardant applications

Cobalt disulphide (CoS2), 3-amino-5-ethoxy-1,2,4-triazole (AET), and graphene oxide, also known as GO, were added to polyurethane (PU) coatings to improve their anticorrosion and fire-retardant properties. To analyze the structural and morphological behaviours of the films of pure CoS2, AET/CoS2, GO/CoS2, and GO/AET-CoS2, SEM/EDX, TEM, TGA, XPS, and XRD techniques were used. The peak heat release rate (PHRR) and total heat release (THR) of polyurethane-graphene oxide/AET-CoS2 were significantly lower than those of polyurethane, with differences of 64.7% and 52.8%, respectively, demonstrating better flame retardancy. The anticorrosive, hydrophobic, and flame-retardant characteristics of the PU-GO/AET-CoS2 nanocomposite were confirmed using mechanical testing and electrochemical methods. Impedance studies confirmed that the corrosion protection performance of PU-GO/AET-CoS2 in seawater was much greater (22,481 kΩ cm2) than that of the plain polymer (157 kΩ cm2). The PU-GO/AET-CoS2 nanocomposite coated AA7039 aluminium alloy had the lowest aluminium ion dissipation as evidenced by SECM investigations. The PU-GO/AET-CoS2 coating had superior hydrophobic properties (WCA: 164°). Therefore, PU-GO/AET-CoS2 could be exploited as a potential material for coatings in industrial processes.

Filler effects inspired high performance polyurethane elastomer design: segment arrangement control.

Elastomers with high strength and toughness are in great demand. Previous research on elastomers focused mainly on the design of new chemical structures, but their complicated synthesis process and expensive monomers have restricted the practical application of these materials. Inspired by general filler effects, a strategy is proposed to remarkably enhance the mechanical properties of thermoplastic polyurethane (TPU) elastomers by designing the arrangement of hard/soft segments using traditional chemical compositions. By utilizing the synergetic effect of weak hard segments, normal TPU elastomers are upgraded into advanced elastomers. Combining experiments and simulations, it is demonstrated that a suitable sequence length can achieve considerably enhanced strength and toughness by maximizing the relative surface area of hard domains. Mixing the obtained elastomer with an ionic liquid can result in a durable ionogel sensor with balanced mechanical strength and ionic conductivity. This easy-to-implement strategy offers a new dimension for the development of high-performance elastomers.

Dispersion engineering of cellulose nanofibres in polyols: for controlled microstructure of high-performance polyurethane foam

An efficient control over the microstructure and physical properties of polyurethane foam is demonstrated through dispersion engineering of cellulose nanofibre, a biosourced nanoadditive, in polyols with a broad range of rheological characteristics.

High-performance polyurethane composite elastomers with coral reef-like hierarchical heterostructures for electromagnetic wave absorption and flexible sensing

With the rapid development of electronic technology and the wide application of 5G networks, flexible electronic devices with a single function can't meet the needs of daily life or military fields. Inspired by the structure of coral reefs, a high-performance polyurethane composite elastomer was designed for multifunctional applications, which was enhanced by multi-dimensional coral reef-like hierarchical heterostructures consisting of MXene, carbon nanotubes (CNTs), and Fe3O4via a solvothermal method. The composite elastomer reached a minimum reflection loss (RLmin) of −54.81 dB and worked effectively from −20 to 100 °C, which could meet the needs of year-round electromagnetic protection. Also, it showed a good sensitivity with a high GF value of 608, which could be widely used in flexible sensing and human motion monitoring. More importantly, its thermal diffusion capability was 155.9 % higher than that of pure polyurethane, and it remained stable at 200 °C and was not easy to decompose, showing outstanding thermal transmission and thermal stability. Such a novel functional composite material will provide an effective guidance solution for electromagnetic protection, flexible sensing, and thermal management under complex working conditions.

Simultaneous robustness, reprocessing and self-healing of castor oil-based polyurethane vitrimers enabled by supramolecular nitrogen-coordinated dynamic covalent boronic ester

Striving for high-performance polyurethanes from renewable resources has attracted increasing attention, due to the continuously increased environmental concerns and resource crisis related to traditional fossil-based materials. Castor oil is a renewable raw material, while the traditional castor oil-based polyurethane chains are highly flexible and permanently cross-linked, resulting in poor mechanical strength and toughness that cannot be reprocessed. To obtain robust and reprocessable castor oil-based polyurethane materials, herein we report the utilization of supramolecular nitrogen-coordinated boronic ester crosslinking. A series of castor oil-based polyurethane (COPUX) vitrimers with different amounts of dynamic covalent boronic ester crosslinking and boron-nitrogen (B-N) coordination were designed and synthesized by a solvent- and catalyst-free two-step method. The permanent crosslinking degree decreases while the strength, moduli, ductility and heat resistance significantly increase accordingly with increasing boronic ester content. The B-N coordination can further improve the mechanical properties of materials due to supramolecular interactions. The tensile behaviors are tunable over a broad range (either as elastomers or as plastics) depending on the compositions. The tensile strength of COPU4 was improved by 9 times from 1.9 to 17.1 MPa compared to COPU0. The Young's modulus for COPU3 was improved by 119 times from 2.9 to 345.1 MPa and the yield strength reaches 18.3 MPa. Boron-nitrogen coordination enhances mechanical strength without loss of material self-healing properties. COPU3 and COPU4 exhibit excellent self-healing as well as reprocessability. The investigation provides the feasibility of future shifts from traditional fossil-based thermosets to bio-based reprocessable vitrimers, offering new hints for the design and manufacture of high-value sustainable polymer materials.

Short-chain polyols from bio-based carboxylic acids for high-performance polyurethane coatings

Emerging bioengineering methods have created an opportunity to introduce a range of novel sustainable raw materials into industrial chemical processes. Among others, a multitude of bio-based acids can become available on the market on a commercial scale. These functional molecules can be useful as reagents for manufacturing sustainable high-performance materials. To this end, we evaluated a series of seven bio-based carboxylic acids as starting materials in the development of cross-linked 2K polyurethane (PU) coatings. By reacting the acids with propylene oxide (PO), seven short-chain polyols were synthesized. The synthesized polyols, consisting of mixtures of polyfunctional hydroxy-terminated products, were cross-linked with two isocyanate trimers (hexamethylene diisocyanate (HDI) trimer and isophorone diisocyanate (IPDI) trimer) to produce polyurethane coatings. The thermal, mechanical, and coating properties of PU films can be varied depending on the polyol and isocyanate used. Thus, coatings formulated using IPDI trimer were hard and brittle, whereas films made with the aliphatic HDI trimer offered a valuable combination of excellent hardness and extraordinary flexibility. Using polyols made from several isomeric carboxylic acids resulted in a significant variation of properties in the PU coatings. The results illustrate the applicability of novel bio-based acids as starting materials in the coatings industry and highlight the necessity to explore their potential application as components of sustainable materials.

Supported Catalyst Enables Synthesis of Colorless CO2-Polyols with Ultra-Low Molecular Weight.

Ultra-low molecular weight (ULMW) CO2-polyols with well-defined hydroxyl end groups represent useful soft segments for the preparation of high-performance polyurethane foams. However, owing to the poor proton tolerance of catalysts towards CO2/epoxide telomerization, it remains challenging to synthesize ULMW yet colorless CO2-polyols. Herein, we propose an immobilization strategy of constructing supported catalysts by chemical anchoring of aluminum porphyrin on Merrifield resin. The resulting supported catalyst displays both extremely high proton tolerance (~8000 times than equivalent of metal center) and independence of cocatalyst, affording CO2-polyols with ULMW (580 g mol-1) and high polymer selectivity (> 99%). Moreover, the ULMW CO2-polyols with various architectures (tri-, quadra-, and hexa-arm) can be obtained, suggesting the wide proton universality of supported catalysts. Notably, benefiting from the heterogeneous nature of the supported catalyst, colorless products can be facilely achieved by simple filtration. The present strategy provides a platform for the synthesis of colorless ULMW polyols derived from not only CO2/epoxides, but also lactone, anhydrides et al. or their combinations.

Chemically Recyclable and Upcyclable Epoxy Resins Derived from Vanillin

Epoxy resins constitute a very significant portion of all high-performance plastics due to their excellent thermal and mechanical properties that appear in a wide range of applications. Nevertheless, traditional epoxy networks show limitations regarding chemical recycling due to their covalently crosslinked structures. The current methods to recycle epoxy resins are not indeed through sustainable ways, but this issue could be solved by developing smart monomers with functional groups, which can be switched between polymerized and depolymerized states. Herein, we developed two bio-based liquid monomers based on vanillin structures containing aldehyde, acetal, and oxirane-ring functionalities. These monomers were polymerized in solvent-free conditions using commercially available diamines, resulting in double-dynamic imine-acetal-containing thermosets. These networks combine the excellent properties of the traditional epoxy systems and dynamic polymers. Most importantly, such thermosets were fully depolymerized into vanillin, which can be reused for the preparation of original epoxy monomers, and a mixture of well-defined polyols, which was upcycled into high-performance polyurethane.

Colorless, Transparent, and High-Performance Polyurethane with Intrinsic Ultraviolet Resistance and Its Anti-UV Mechanism

Polyurethane (PU) is a widely used polymer material that will age under prolonged exposure to ultraviolet (UV) light, shortening the service life. Several methods have been used to prepare the anti-UV PU, including adding nonreactive anti-UV additives, functional fillers, and biological antioxidant molecules. However, the nonreactive anti-UV additives may migrate during long-term use, the functional fillers may damage the mechanical properties and seriously reduce the light transmittance of the sample, and the biological antioxidant molecules will inevitably color the sample. To solve these problems, in this work, a benzotriazole UV absorber (Chiguard R-455) was introduced into the PU molecular chains by in situ polymerization to prepare the nonmigrating intrinsic anti-UV PU sample with high performance and colorless transparency. The anti-UV PU samples exhibit light transmittance of over 88% in the visible range and superior mechanical properties with tensile strength higher than 65 MPa and elongation at break higher than 900%. After 24 h UV irradiation (200 W, 365 nm), the tensile strength and elongation at break of pure PU sample are significantly reduced to only 8.9 and 15.8% of the original one, respectively. On the contrary, the addition of Chiguard R-455 will endow the PU sample with excellent anti-UV performance. After 24 h UV irradiation, the tensile strength (67.2 ± 1.6 MPa) and elongation at break (917.4 ± 30.0%) of PU-0.5% (the content of Chiguard R-455 is only 0.5 wt %) have changed little compared with the sample without irradiation (67.4 ± 3.5 MPa and 919.4 ± 26.5%). Additionally, the anti-UV mechanism of the PU sample is systematically studied. This work provides a feasible method for preparing colorless, transparent, high-performance, nonmigrating intrinsic UV-shielding PU samples, which can be used as a UV light-shielding material in various fields with visible and aesthetic requirements, such as protection fields and wearable products.

Tailoring crosslinking networks to fabricate photocurable polyurethane acrylate (PUA) dielectric elastomer with balanced electromechanical performance

The trade-off between high dielectric permittivity and low Young's modulus is always a challenge for fabricating high-performance polyurethane acylate (PUA) based dielectric elastomers (DEs). In this work, networks with scattered crosslinking points (type-I) and domains of concentrated crosslinking points (type-II) that being prepared by different functional telechelic ends, were mainly introduced into the photocured PUA elastomers. As the increasing of chain length between crosslinking points (Ne), the Young's modulus (Y) of the PUA was restrained below 1.2 MPa while the elongation at break (EB) markedly increased. Compared to type-I network, a longer Ne in type-II network can lower the overall crosslinking density, which endows the materials with a relatively low Y (ca. 0.83 MPa) and a large EB (389%). In addition, the concentrated crosslinking points in type-II network enhanced the polarization effect between entangled long chains and crosslinking domains, which further upraised the dielectric permittivity of the elastomer up to 74.17 @ 103 Hz. The actuation strain of the PUA elastomer with type II network can reach utmost 13.88% @ 45.41 V∙μm−1 without any pre-strain. This work offers a new strategy to fabricate photocurable dielectric elastomer actuators (DEAs) with balanced electromechanical performance.

Towards high-performance polyurethanes: a mechanism of amine catalyzed aromatic imide formation from the reaction of isocyanates with anhydrides

The mechanism of aromatic imide formation from reaction between isocyanate and anhydride using secondary amine as a pre-catalyst is driven by deprotonated urea, which is obtained from the reaction of isocyanate and amine with the help of bases.

High-performance castor oil-based polyurethane thermosets: Facile synthesis and properties

With the growing concern on the shortage of fossil resources and the environmental problems associated with their use, vegetable oils as renewable resources are important alternatives to fossil resources. Here, we used castor oil to synthesize 1-thioglycerol modified castor oil polyol with ultra-high hydroxyl value up to 463 mg KOH g−1 via a solvent-free thiol-olefin click reaction. The cross-linked polyurethanes were prepared from this polyol in a solvent-free and catalyst-free manner, and exhibited high tensile strength of ∼83 MPa and Tg of ∼124 °C, much higher than other reported vegetable oil-based polyurethanes. Besides, the obtained polyurethanes exhibited excellent coating and optical properties, much better than the polyurethane from the unmodified castor oil. This work provides a green and high-efficient method of synthesizing vegetable oil-based polyol with ultra-high hydroxyl value to construct high-performance polyurethanes, which will expand the application of vegetable oil-based polymers.

Solvent-free synthesis of high-performance polyurethane elastomer based on low-molecular-weight alkali lignin

Using cheap and green lignin as a partial substitute for petroleum-based polyols is highly attractive for sustainable development of polyurethane elastomers (LPUes). However, the traditional synthesis process of LPUes inevitably uses toxic solvents that are difficult to remove or carcinogenic. Here, we reported a solvent-free synthesis method to prepare lignin-containing polyurethane elastomers (SF-LPUes) with high strength, high toughness and high elasticity. Most of the hydroxyl groups of lignin reacted with isocyanates to form a strong chemical cross-linking network, while the unreacted ones formed a dynamic hydrogen bond network with polyurethane matrix, contributing to the in-situ formation of lignin nanoparticles to build a nano-micro phase separation structure. Consequently, a dual-crosslinking network structure was formed and endowed SF-LPUes with excellent mechanical properties. Especially, the SF-LPUes prepared from low molecular alkali lignin possessed a tensile strength as high as 38.2 MPa, a maximum elongation at break of 1108 %, and an elastic recovery ratio of up to 98.7 %. Moreover, SF-LPUes showed impressing reprocessing performance and aging resistance. This work provides an industrial application prospect for the synthesis of lignin-containing polyurethane elastomers via a solvent-free synthesis process.

Polymeric aluminum porphyrin: Controllable synthesis of ultra-low molecular weight CO2-based polyols

Carbon dioxide-based polyols with ultra-low molecular weight (ULMW, Mn < 1000 g/mol) are emergent polyurethane precursors with economic and environmental benefits. However, the lack of effective proton-tolerant catalytic systems limits the development of this field. In this work, the polymeric aluminum porphyrin catalyst (PAPC) system was applied to the copolymerization of CO2 and propylene oxide, where sebacic acid, bisphenol A, poly(ethylene glycol), and water were used as chain transfer agents to achieve the controlled synthesis of CO2-polyols. The molecular weight of the resulting CO2-polyols could be facilely regulated in the range of 400–930 g/mol at low catalyst loadings, fully demonstrating its catalytic advantages of high activity, high product selectivity, and excellent proton tolerance of PAPC. Meanwhile, the catalytic efficiency of PAPC could reach up to 2.1–5.2 kg/g under organic CTA conditions, even reaching 1.9 kg/g using water as the CTA. The cPC content could be controlled within 1.0 wt% under the optimized conditions, indicating the excellent controllability of the PAPC system. ULMW CO2-polyols combines the advantages of low viscosity (∼3000 mPa s at 25 °C), low glass transition temperature (∼−73 °C), and high carbonate unit content (∼40%), which is important for the development of high-performance polyurethanes.