Intramolecular Friedel-Crafts Acylation of [11C]Isocyanates Enabling the Radiolabeling of [carbonyl-11C]DPQ.

α,ß-aromatic lactams are highly abundant in biologically active molecules, yet so far they cannot be radiolabeled with short-lived (t1/2=20.3 min), ß+-decaying carbon-11, which has prevented their application as positron emission tomography tracers. Herein, we developed, optimized, and applied a widely applicable, one-pot, quick, robust and automatable radiolabeling method for α,ß-aromatic lactams starting from [11C]CO2 using the reagent POCl3⋅AlCl3. This method proceeds via intramolecular Friedel-Crafts acylation of in situ formed [11C]isocyanates and shows a broad substrate scope for the formation of five- and six-membered rings. We implemented our developed labeling method for the radiosynthesis of the potential PARP1 PET tracer [carbonyl-11C]DPQ in a clinical radiotracer production facility following the standards of the European Pharmacopoeia.

Design of 3D-Photoprintable, Bio-, and Hemocompatible Nonisocyanate Polyurethane Elastomers for Biomedical Implants.

Polyurethanes (PUs) have adjustable mechanical properties, making them suitable for a wide range of applications, including in the biomedical field. Historically, these PUs have been synthesized from isocyanates, which are toxic compounds to handle. This has encouraged the search for safer and more environmentally friendly synthetic routes, leading today to the production of nonisocyanate polyurethanes (NIPUs). Among these NIPUs, polyhydroxyurethanes (PHUs) bear additional hydroxyl groups, which are particularly attractive for derivatizing and adjusting their physicochemical properties. In this paper, polyether-based NIPU elastomers with variable stiffness are designed by functionalizing the hydroxyl groups of a poly(propylene glycol)-PHU by a cyclic carbonate carrying a pendant unsaturation, enabling them to be post-photo-cross-linked with polythiols (thiol-ene). Elastomers with remarkable mechanical properties whose stiffness can be adjusted are obtained. Thanks to the unique viscous properties of these PHU derivatives and their short gel times observed by rheology experiments, formulations for light-based three-dimensional (3D) printing have been developed. Objects were 3D-printed by digital light processing with a resolution down to the micrometer scale, demonstrating their ability to target various designs of prime importance for personalized medicine. In vitro biocompatibility tests have confirmed the noncytotoxicity of these materials for human fibroblasts. In vitro hemocompatibility tests have revealed that they do not induce hemolytic effects, they do not increase platelet adhesion, nor activate coagulation, demonstrating their potential for future applications in the cardiovascular field.

Relief of Residual Stress in Bulk Thermosets in the Glassy State by Local Bond Exchange.

The covalently cross-linked network gives thermosets superior thermal, mechanical, and electrical properties, which, however, squarely makes the large residual stress that is inevitably induced during preparation hardly relieved in the glassy state. In this work, an incredible reduction in residual stress is successfully achieved in bulk thermosets in the glassy state through introducing highly dynamic thiocarbamate bonds by "click" reactions of thiols and isocyanates. Due to the excellent dynamic behaviors of thiocarbamate bonds, local network rearrangement is achieved through thermal stimulation, while the strong 3D cross-linked network is well maintained. Ultimately, a decrease by 44% in residual stress is detected by simply annealing samples at 30 °C below glass transition temperature (Tg), during which they could well maintain more than 98.4% of the storage modulus. After the annealing, more uniform residual stress distribution is also observed, showing a 32% decline in sample standard deviation. However, the residual stress of epoxy resin, a typical thermoset as a reference, changes little even after annealing at Tg. The results prove it a feasible strategy to reduce residual stress in bulk thermosets in the glassy state by introducing proper dynamic covalent bonds.

Konjac Glucomannan Aerogels Modified by Hydrophilic Isocyanate and Expandable Graphite with Excellent Hydrolysis Resistance, Mechanical Strength, and Flame Retardancy.

At present, biomass foamlike materials are a hot research topic, but they need to be improved urgently due to their defects such as large size shrinkage rate, poor mechanical strength, and easy hydrolysis. In this study, the novel konjac glucomannan (KGM) composite aerogels modified with hydrophilic isocyanate and expandable graphite were prepared by a facile vacuum freeze-drying method. Compared with the unmodified KGM aerogel, the volume shrinkage of the KGM composite aerogel (KPU-EG) decreased from 36.36 ± 2.47% to 8.64 ± 1.46%. Additionally, the compressive strength increased by 450%, and the secondary repeated compressive strength increased by 1476%. After soaking in water for 28 days, mass retention after hydrolysis of the KPU-EG aerogel increased from 51.26 ± 2.33% to more than 85%. The UL-94 vertical combustion test showed that the KPU-EG aerogel can achieve a V-0 rating, and the limiting oxygen index (LOI) value of the modified aerogel can reach up to 67.3 ± 1.5%. To sum up, the cross-linking modification of hydrophilic isocyanate can significantly improve the mechanical properties, flame retardancy, and hydrolysis resistance of KGM aerogels. We believe that this work can provide excellent hydrolytic resistance and mechanical properties and has broad application prospects in practical packaging, heat insulation, sewage treatment, and other aspects.

Polyurethane films formation from microcrystalline cellulose as a polyol and cellulose nanocrystals as additive: Reactions favored by the low viscosity of the source of isocyanate groups used.

To simultaneously form films while synthesizing solvent-free and catalyst-free bio-based polyurethanes, hexamethylene diisocyanate trimer was selected as an isocyanate group source to produce a low-viscosity reaction medium for dispersing high contents of microcrystalline cellulose (MCC, polyol) and cellulose nanocrystals (CNC). Castor oil was used as an additional polyol source. Up to 80 % of the MCC was dispersed, producing a film exhibiting the highest Tg (72 °C), tensile strength (18 MPa), and Young's modulus (522.4 MPa). 12.5 % (30 % MCC) and 7.5 % (50 % MCC) of CNC dispersed in the reaction medium formed films stiffer than their counterparts. All the films exhibited transparency and high crystallinity. The contact angle/zeta potential (ζ) indicated hydrophobic film surfaces. At pH 7.4, ζ suggested that the films interacted with physiological fluids favorably. The films were non-cytotoxic, and the composites exhibited cell growth compared with the control. The reported results, as far as it is known, are unprecedented.

New Method to Biomonitor Workers Exposed to 1,6-Hexamethylene Diisocyanate.

Isocyanates such as 1,6-hexamethylene diisocyanate (HDI), 4,4'-methylenediphenyl diisocyanate, and toluene diisocyanate are highly reactive compounds that have a variety of commercial applications, including manufacturing polyurethane foam, elastomers, paints, adhesives, coatings, insecticides, and many other products. Their primary route of occupational exposure is through inhalation. Due to their high chemical reactivity, they are toxic and have adverse effects at the cellular and subcellular levels, leading to irritative and immunological reactions associated with lung disease. High concentrations of isocyanates are strong respiratory irritants. Bronchial sensitization and asthma are among the major adverse clinical reactions associated with low-level chronic exposure to isocyanates. Albumin adducts have been linked to the mechanism of occupational asthma caused by isocyanates. Isocyanates react in vivo with albumin, which is recognized by the immune system. Albumin adducts of isocyanates trigger immune responses and are probably the antigenic basis for isocyanate asthma. Sensitization to isocyanates is the main pathway for adverse health effects. Therefore, markers for the biologically effective dose such as albumin adducts of HDI are needed. A new isocyanate adduct of HDI with lysine─Nε-[(6-amino-hexyl-amino)carbonyl]-lysine (HDI-Lys)─was synthesized and characterized by 1H-NMR, 13C-NMR, and mass spectrometry (MS). Appropriate internal standards─HDI-Lys-4,4'-5,5'-d4 (HDI-d4-Lys) and Nε-[(7-amino-heptyl-amino)carbonyl]-lysine (Hep-Lys)─were synthesized to establish a LC-MS/MS method for the analysis of HDI adducts in in vitro modified albumin and in workers. The presence of HDI-Lys was found after pronase digestion of albumin and confirmed by two independent chromatographic approaches: with a C8 reversed-phase column and with a hydrophilic interaction liquid chromatography column. Quantification was performed with positive electrospray ionization (ESI)-MS. The adduct peak found in vivo was confirmed with the less sensitive negative ESI-MS. In summary, these are new compounds and methods to determine isocyanate-specific adducts with albumin in workers exposed to HDI.

Water-Induced Self-Blown Non-Isocyanate Polyurethane Foams.

For 80 years, polyisocyanates and polyols were central building blocks for the industrial fabrication of polyurethane (PU) foams. By their partial hydrolysis, isocyanates release CO2 that expands the PU network. Substituting this toxic isocyanate-based chemistry by a more sustainable variant-that in situ forms CO2 by hydrolysis of a comonomer-is urgently needed for producing greener cellular materials. Herein, we report a facile, up-scalable process, potentially compatible to existing infrastructures, to rapidly prepare water-induced self-blown non-isocyanate polyurethane (NIPU) foams. We show that formulations composed of poly(cyclic carbonate)s and polyamines furnish rigid or flexible NIPU foams by partial hydrolysis of cyclic carbonates in the presence of a catalyst. By utilizing readily available low cost starting materials, this simple but robust process gives access to greener PU foams, expectedly responding to the sustainability demands of many sectors.

Preparation of Biobased Nonisocyanate Polyurethane/Epoxy Thermoset Materials Using Depolymerized Native Lignin.

Polyurethane polymers are found in a wide range of material applications. However, the toxic nature of isocyanates used in their formulation is a major concern; hence, more environmentally friendly alternatives are of high interest in the search for new sustainable polymer materials. In this work, we present the preparation of isocyanate-free polyurethane/epoxy hybrid thermosets with a high biobased content (85-90 wt %). The isocyanate-free polyurethanes were based on polyhydroxyurethanes (PHUs) prepared from depolymerized native lignin, which we refer to as lignin hydrogenolysis oil (LHO). The LHO was functionalized with epichlorohydrin to yield the epoxidized structure (LHO-GE), which was in turn reacted with CO2 to form the cyclocarbonated species (LHO-CC). Blends of the LHO-CC and glycerol diglycidyl ether (GDGE) were cured to produce hybrid PHU/epoxy (LHO-CC/GDGE) thermosets. Thermosetting materials with flexural moduli of 4.5 GPa and flexural strengths of 160 MPa were produced by optimizing the mass ratio of the two main components and the triamine hardener. These novel biobased hybrid materials outperformed the corresponding epoxy-only thermosets and comparable hybrid PHU/epoxy materials produced from petrochemicals.

Friedel-Crafts-Type Acylation and Amidation Reactions in Strong Brønsted Acid: Taming Superelectrophiles.

In this review, we discuss Friedel-Crafts-type aromatic amidation and acylation reactions, not exhaustively, but mainly based on our research results. The electrophilic species involved are isocyanate cation and acylium cation, respectively, and both have a common +C=O structure, which can be generated from carboxylic acid functionalities in a strong Brønsted acid. Carbamates substituted with methyl salicylate can be easily ionized to the isocyanate cation upon (di)protonation of the salicylate. Carboxylic acids can be used directly as a source of acylium cations. However, aminocarboxylic acids are inert in acidic media because two positively charged sites, ammonium and acylium cation, will be generated, resulting in energetically unfavorable charge-charge repulsion. Nevertheless, the aromatic acylation of aminocarboxylic acids can be achieved by using tailored phosphoric acid esters as Lewis bases to abrogate the charge-charge repulsion. Both examples tame the superelectrophilic character.

Glutathione reactivity with aliphatic polyisocyanates.

Isocyanate chemicals known to cause adverse health effects when inhaled are essential to making important products and are used in multiple industries. Glutathione (GSH), a major antioxidant of the lower airways with a well described role in xenobiotic metabolism, is a primary reaction target for di-isocyantes. However, GSHs reactivity with poly-isocyanates which have largely replaced diisocyanates (particularly aliphatic) in most end-user settings remains uncertain. We hypothesized aliphatic polyisocyanates would readily react with glutathione under physiologic conditions and the products could be identified using liquid chromatography (LC) coupled-mass spectrometry (MS) and tandem MS/MS. The data identified (tris)GSH-isocyanate adducts as the major reaction product of GSH with the most commonly used contemporary polymeric (tri-isocyanate) formulations of hexamethylene diisocyanate (HDI), the isocyanurate and biuret, as [M+H]+ ions of 1426.53 and 1400.55 m/z respectively in reverse phase LC-MS using electrospray in positive ion mode. The uretdione form of HDI, a stabilized dimer, formed two reaction products with GSH, a tris(GSH)-isocyanate reaction product recognized as a 1258.44 m/z [M+H]+ ion, and a bis(GSH)-isocyanate product identified as a 951.36 m/z [M+H]+ ion. Predicted structures for the newly described GSH-polyisocyanate reaction products, modeled based on collision induced dissociation (CID) fragmentation patterns in tandem MS/MS, support S-linkage of the GSH to N = C = O groups. In summary, industrially-used aliphatic polyisocyanates readily react with GSH to form primarily S-linked tris(GSH)-conjugates, a process that may play an important role in response to respiratory tract exposure.

Synthesis of Sucrose-HDI Cooligomers: New Polyols for Novel Polyurethane Networks.

Sucrose-1,6-hexamethylene diisocyanate (HDI) cooligomers were synthesized and used as new polyols for poly(ε-caprolactone) (PCL)-based polyurethanes. The polyaddition reaction of sucrose and HDI was monitored by MALDI-TOF MS. It was found that by selecting appropriate reaction conditions, mostly linear oligomer chains containing 16 sucrose units could be obtained. For the synthesis of polyurethane networks, prepolymers were prepared by the reaction of poly(ε-caprolactone) (PCL, 10 kg/mol) with HDI or 4,4'-methylene diphenyl diisocyanate (MDI) and were reacted with sucrose-HDI cooligomers. The so-obtained sucrose-containing polyurethanes were characterized by means of attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FT IR), swelling, mechanical (uniaxial tensile tests) and differential scanning calorimetry (DSC).

In silico predictions of absorption of MDI substances after dermal or inhalation exposures to support a category based read-across assessment.

Methylenediphenyl diisocyanate (MDI) substances used polyurethane production can range from their simplest monomeric forms (e.g., 4,4'-MDI) to mixtures of the monomers with various homologues, homopolymer, and prepolymer derivatives. The relative dermal or inhalation absorption of 39 constituents of these substances in human were predicted using the GastroPlus® program. Predicted dermal uptake and absorption of the three MDI monomers from an acetone vehicle was 84-86% and 1.4-1.5%, respectively, with lower uptake and absorption predicted for the higher MW analogs. Lower absorption was predicted from exposures in a more lipophilic vehicle (1-octanol). Modeled inhalation exposures afforded the highest pulmonary absorption for the MDI monomers (38-54%), with 3-27% for the MW range of 381-751, and <0.1% for the remaining, higher MW derivatives. Predicted oral absorption, representing mucociliary transport, ranged from 5 to 10% for the MDI monomers, 10-25% for constituents of MW 381-751, and ≤3% for constituents with MW > 900. These in silico evaluations should be useful in category-based, worst-case, Read-Across assessments for MDI monomers and modified MDI substances for potential systemic effects. Predictions of appreciable mucociliary transport may also be useful to address data gaps in oral toxicity testing for this category of compounds.

Lignin-enriched residues from bioethanol production: Chemical characterization, isocyanate functionalization and oil structuring properties.

Lignin-enriched waste products from bioethanol production of agriculture residues were tested as structuring agents in castor oil once functionalized with hexamethylene diisocyanate. Cane bagasse, barley and wheat straw were processed through steam explosion, pre-saccharification and simultaneous saccharification and fermentation (PSSF). Alternatively, cane bagasse was submitted to steam explosion and enzymatic hydrolysis (EH). Several Nuclear Magnetic Resonance techniques were used to characterize both residues and NCO-functionalized counterparts. The ß-O-4'/resinol/phenylcoumaran content and hydroxyphenyl/guaiacyl/syringyl distribution depend on biomass source, pretreatment, and enzymatic hydrolysis. Total hydroxyl content (from 1.23 for cane bagasse to 1.85 for wheat straw residues), aromatic/aliphatic hydroxyl ratio (0.78 for cane bagasse and 0.61 and 0.49 for barley and wheat straw residues, respectively) and S/G ratio (ranging from 0.25 to 0.86) influence the NCO-functionalization and oleogel rheological response. Oleogels obtained with barley straw residues exhibited the highest values of the storage modulus; around 2 × 105 Pa and 104 Pa for 25% and 20% contents, respectively. PSSF process showed weaker modification, leading to softer viscoelastic response compared to EH. These oleogels exhibited rheological properties similar to lubricating greases of different NLGI grades. Therefore, we herein show an integrative protocol for the valorization of lignin-enriched residues from bioethanol production as potential thickeners of lubricating greases.

Viability of cultured human skin cells treated with 1,6-hexamethylene diisocyanate monomer and its oligomer isocyanurate in different culture media.

The isocyanate monomer 1,6-hexamethylene diisocyanate (HDI) and one of its trimers, HDI isocyanurate, are airway and skin sensitizers contained in polyurethane paint. The toxic response of cultured skin cells to these compounds was measured by evaluating the isocyanate concentrations at which 50% of the cells die (i.e., lethal concentration 50%, LC50) because the relative toxicity of each form of HDI should be considered when exposure limits of HDI-based paints are set. By using a luminescent ATP-viability assay, we compared the cytotoxic effects of HDI monomer and HDI isocyanurate on cultured human skin cells (keratinocytes, fibroblasts, and melanocytes) after 4-h isocyanate exposures using culture media with varying levels of nutrients in order to also determine the effects of media composition on isocyanate toxicity. Before analysis, experimental wells were normalized to controls containing cells that were cultured with the same vehicle and media. The measured mean LC50 values ranged from 5 to 200 µM across the experimental conditions, in which HDI isocyanurate in protein-devoid media was the most toxic to cells, producing the lowest LC50 values. For HDI monomer, keratinocytes were the most resistant to its toxicity and melanocytes were the most susceptible. However, when exposed to HDI isocyanurate, the opposite was observed, with melanocytes being the most resilient and the keratinocytes and fibroblasts were more susceptible. Depending on the type of skin cells, dose-response data indicated that HDI isocyanurate was 2-6 times more toxic than HDI monomer when using protein-devoid media whereas HDI isocyanurate was 4-13 times more toxic than HDI monomer when protein-rich media was used. Therefore, if the protein-devoid saline medium alone were used for these experiments, then a significant under-estimation of their relative toxicities in protein-rich environments would have resulted. This difference is because HDI monomer toxicity was more attenuated by the presence of protein in the culture media than HDI isocyanurate toxicity. Thus, conclusions based on comparative toxicity studies and consequent inference applied to potential human toxicity can be affected by in vitro culture media conditions. The physiochemical difference in reactivity of the two forms of HDI to biological molecules most likely explains the observed toxicity differences and may have implications for skin penetration, adverse effects like skin sensitization, and systemic responses like asthma. Future studies are warranted to investigate differences in the biological availability, cellular toxicity, and immunologic sensitization mechanisms for HDI monomer and HDI isocyanurate.

Multigram synthesis of N-alkyl bis-ureas for asymmetric hydrogen bonding phase-transfer catalysis.

Fluorine is a key element present in ~35% of agrochemicals and 25% of marketed pharmaceutical drugs. The availability of reliable synthetic protocols to prepare catalysts that allow the efficient incorporation of fluorine in organic molecules is therefore essential for broad applicability. Herein, we report a protocol for the multigram synthesis of two representative enantiopure N-alkyl bis-urea organocatalysts derived from (S)-(-)-1,1'-binaphthyl-2,2'-diamine ((S)-BINAM). These tridentate hydrogen bond donors are highly effective phase-transfer catalysts for solubilizing safe and inexpensive metal alkali fluorides (KF and CsF) in organic solvents for enantioselective nucleophilic fluorinations. The first catalyst, characterized by N-isopropyl substitution, was obtained by using a two-step sequence consisting of reductive amination followed by urea coupling from commercially available starting materials (14 g, 48% yield and 5-d total synthesis time). The second catalyst, featuring N-ethyl alkylation and meta-terphenyl substituents, was accessed via a novel, scalable, convergent route that concluded with the coupling between N-ethylated (S)-BINAM and a preformed isocyanate (52 g and 52% overall yield). On this scale, the synthesis requires ~10 d. This can be reduced to 5 d by performing some steps in parallel. Compared to the previous synthetic route, this protocol avoids the final chromatographic purification and produces the desired catalysts in very high purity and improved yield.

Heterogenous hydrogel mimicking the osteochondral ECM applied to tissue regeneration.

Inspired by the intricate extracellular matrix (ECM) of natural cartilage and subchondral bone, a heterogenous bilayer hydrogel scaffold is fabricated. Gelatin methacrylate (GelMA) and acryloyl glucosamine (AGA) serve as the main components in the upper layer, mimicking the chondral ECM. Meanwhile, vinylphosphonic acid (VPA) as a non-collagen protein analogue is incorporated into the bottom layer to induce the in situ biomineralization of calcium phosphate. The two heterogenous layers are effectively sutured together by the inter-diffusion between the upper and bottom layer hydrogels, together with chelation between the calcium ions and alginate added to separate layers. The interfacial bonding between the two different layers was thoroughly investigated via rheological measurements. The incorporation of AGA promotes chondrocytes to produce collagen type II and glycosaminoglycans and upregulates the expression of chondrogenesis-related genes. In addition, the minerals induced by VPA facilitate the osteogenesis of bone marrow mesenchymal stem cells (BMSCs). In vivo evaluation confirms the biocompatibility of the scaffold with minor inflammation and confirms the best repair ability of the bilayer hydrogel. This cell-free, cost-effective and efficient hydrogel shows great potential for osteochondral repair and inspires the design of other tissue-engineering scaffolds.

Design, Synthesis, Antibacterial, and Antitumor Activity of Linear Polyisocyanide Quaternary Ammonium Salts with Different Structures and Chain Lengths.

The development of organic polymer materials for disinfection and sterilization is thought of as one of the most promising avenues to solve the growth and spread of harmful microorganisms. Here, a series of linear polyisocyanide quaternary ammonium salts (L-PQASs) with different structures and chain lengths were designed and synthesized by polymerization of phenyl isocyanide monomer containing a 4-chloro-1-butyl side chain followed by quaternary amination salinization. The resultant compounds were characterized by 1H NMR and FT-IR. The antibacterial activity of L-PQASs with different structures and chain lengths against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was evaluated by determining the minimum inhibitory concentrations (MICs). The L-POcQAS-M50 has the strongest antimicrobial activity with MICs of 27 µg/mL against E. coli and 32 µg/mL against S. aureus. When the L-PQASs had the same polymerization degree, the order of the antibacterial activity of the L-PQASs was L-POcQAS-Mn > L-PBuQAS-Mn > L-PBnQAS-Mn > L-PDBQAS-Mn (linear, polyisocyanide quaternary ammonium salt, monomer, n = 50,100). However, when L-PQASs had the same side chain, the antibacterial activity reduced with the increase of the molecular weight of the main chain. These results demonstrated that the antibacterial activity of L-PQASs was dependent on the structure of the main chain and the length of the side chain. In addition, we also found that the L-POcQAS-M50 had a significant killing effect on MK-28 gastric cancer cells.

Screening of dicyanoisophorone-based probes for highly sensitive detection of viscosity changes in living cells and zebrafish.

Herein, seven viscosity-sensitive probes were developed via simple structural modification of dicyanoisophorone (DCO)-derived dyes. Among them, DCO-5 significantly enhances (180-fold) the response signal in highly viscous aqueous media while showing insensitivity to polarity changes or pH variations, and enables the successful detection of viscosity changes in nystatin-treated HepG2 cells, PC 12 cells and zebrafish.

DABCO catalyzed [4+2] annulations of Morita-Baylis-Hillman carbonates with isocyanates.

A highly concise method for 1,4-diazabicyclo[2.2.2]octane (DABCO) catalyzed [4+2] annulations of o-amino-acylation of aryl MBH carbonates with isocyanates has been developed. For the first time, MBH carbonates served as 1,4-dipoles, providing functionalized 3,4-dihydroquinazolinones in mild conditions with good to excellent yields. The density functional theory calculations of the mechanism supports our hypothesis.

Preparation and characterization of guar gum based polyurethanes.

Guar gum (plant-based polysaccharide) is a promising candidate with immense potential. It is used as emulsifier, thickener, stabilizer, and as binding agent in many industries. In the present project, it was planned to synthesize guar gum based polyurethanes by varying the amount of guar gum. Guar gum (GG) was used along with hydroxyl-terminated polybutadiene (HTPB) as soft segment, which was then reacted with isophorone diisocyanate (IPDI) to form PU pre-polymers. In last step, these -NCO terminated pre-polymers were extended with 1,4 butane diol as chain extender. The prepared polyurethane samples were then characterized by using FTIR, solid-state 1HNMR and X-ray diffraction (XRD). Thermal behavior of the samples was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results indicated that the incorporation of guar gum in PU backbone improved its thermal behavior and crystallinity.