Urethane Groups Research Articles

Transparent self-healing luminescent elastomer with superior stretchability achieved via dynamic hard domain design

High mechanical performance versatile materials exhibiting rapid self-healing and luminescence ability are highly desired and present tremendous prospects in various fields. However, it is still a huge challenge to concurrently integrate all the above capacities into individual polymer materials, since these capabilities stem from different molecular mechanisms. Here, a dynamic hard domains strategy is reported for fabricating transparent luminescent self-healing elastomers featuring unprecedented stretchability (4333 ± 36%), high toughness (42.25 ± 0.19 MJ m−3) enabled by hydrogen-bonding (single and double) and lanthanide-bipyridine (Ln-Bpy) coordination interactions in the polymer chains. The dynamic rigid domains containing hydrogen-bonds constructed by urea and urethane groups and Ln-Bpy coordination also lead to a very dynamic system for fast self-healing at room temperature. Besides, excellent luminescence performance was obtained via the efficient energy transfer from the Bpy component to Ln3+ (Eu3+ and /or Tb3+). This strategy of dynamic rigid domains as building blocks applied in this study provides an alternative approach for preparing self-healing luminescence materials with superior stretchability and high toughness.

Role of NF-κB/ICAM-1, JAK/STAT-3, and apoptosis signaling in the anticancer effect of tangeretin against urethane-induced lung cancer in BALB/c mice

Lung carcinoma is one of the most prevalent and deadly neoplasia worldwide. Numerous synthetic medications have been used in the treatment of cancer. However, there are several drawbacks, such as side effects and inefficiency. The current study focused on the potential anti-cancer effectiveness of tangeretin, an antioxidant flavonoid, on lung cancer induced experimentally in BALB/c mice and explored the involvement of NF-κB/ICAM-1, JAK/STAT-3, and caspase-3 signaling in its anti-cancer effect. BALB/c mice were injected with urethane (1.5 mg/kg) twice; on the first day and on the 60th day of the experiment, then treated with 200 mg/kg tangeretin orally once daily for the last 4 weeks of the experiment. Compared with urethane group, tangeretin normalized oxidative stress markers; MDA, GSH, and SOD activity. Moreover, it had an anti-inflammatory effect by decreasing lung MPO activity, ICAM-1, IL-6, NF-қB, and TNF-α expressions. Interestingly, tangeretin decreased cancer metastasis by reducing p-JAK, JAK, p-STAT-3, and STAT-3 protein expression levels. Furthermore, it increased the apoptotic marker, caspase-3, indicating enhanced apoptosis of cancer cells. Finally, histopathology confirmed the anti-cancer effect of tangeretin. In conclusion, tangeretin could have a promising effect in counteracting lung cancer via modulation of NF-κB/ICAM-1, JAK/STAT-3, and caspase-3 signaling.

Preparation and characterization of non-isocyanate polyurethane resins derived from tannin of Acacia mangium bark for the modification of ramie fibers

Abstract The purpose of this research was to create bio-based non-isocyanate polyurethane (Bio-NIPU) resins derived from the tannin of Acacia mangium Willd. bark for the impregnation of ramie fibres (Boehmeria nivea L.) and to investigate the properties of impregnated fibres. Tannin was extracted from the bark of A. mangium using hot water. Tannin-bio-NIPU resin was created using dimethyl carbonate and hexamine. Based on the findings, it is possible to conclude that tannin extract from the bark of Acacia mangium can be used effectively as a renewable alternative to toxic polyols in the development of tannin-Bio-NIPU resins. FTIR spectroscopy was used to confirm the urethane bond formed on the tannin-Bio-NIPU resins. Thermal and mechanical analysis were used to investigate the properties of tannin-Bio-NIPU resins and ramie fibres before and after impregnation. This study shows that the impregnation time of ramie fiber using tannin-Bio-NIPU resins is 30 minutes. The reaction between tannin-Bio-NIPU resins with ramie fiber forms the C=O urethane group as confirmed by FTIR Spectroscopy. The characterization results show that tannin-Bio-NIPU resins has ability to modify ramie fiber via impregnation in order to increase its mechanical properties, thus enhancing its potential for wider industrial application as a functional material.

Determination of End-Group Functionality of Propylene Oxide-Based Polyether Polyols Recovered from Polyurethane Foams by Chemical Recycling.

Chemical recycling of polyurethane foams (PUFs) leads to partially aromatic, amino-functionalized polyol chains when the urethane groups in the PUF structure are incompletely degraded. Since the reactivity of amino and hydroxyl groups with isocyanate groups is significantly different, information on the type of the end-group functionality of recycled polyols is important to adjust the catalyst system accordingly to produce PUFs from recycled polyols of suitable quality. Therefore, we present here a liquid adsorption chromatography (LAC) method using a SHARC 1 column that separates polyol chains according to their end-group functionality based on their ability to form hydrogen bonds with the stationary phase. To correlate end-group functionality of recycled polyol with chain size, LAC was coupled with size-exclusion chromatography (SEC) to form a two-dimensional liquid chromatography system. For accurate identification of peaks in LAC chromatograms, the results were correlated with those obtained by characterization of recycled polyols using nuclear magnetic resonance, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and SEC coupled with a multi-detection system. The developed method allows the quantification of fully hydroxyl-functionalized chains in recycled polyols using an evaporative light scattering detector and appropriate calibration curve.

Comparison of the effects of two anesthetics, isoflurane and urethane, on bladder function in rats

We compared the effects of two anesthetics, isoflurane and urethane on bladder function in rats. Arterial pressure, cystometry (CMG), and rhythmic bladder contractions (RBCs) under isovolumetric conditions, mechanosensitive single-unit afferent activities (SAAs), bladder compliance and bladder myogenic microcontractions (bladder microcontractions), and bladder blood flow, and blood and urine biochemical tests were investigated in isoflurane- or urethane-anesthetized female rats. In results of the CMG, 3/8 rats in the isoflurane group and 7/7 rats in the urethane group showed constant bladder neurogenic contractions for micturition, whereas 5/8 rats in the isoflurane group showed unstable contractions or overflow incontinence. The RBCs appeared in the urethane group but not in the isoflurane group, and SAAs in both the Aδ- and C-fibers, bladder compliance, and bladder microcontractions in the isoflurane group were higher than those in the urethane group during bladder distension. The blood biochemical test showed that the serum calcium level was higher in the isoflurane group. The mean arterial pressure and bladder blood flow were not different between the groups. The results showed that urethane anesthesia more retains bladder neurogenic contractions for micturition compared to isoflurane. In contrast, isoflurane anesthesia more retains bladder function during the storage phase compared to urethane.

The size effects of micron particles on the physico-mechanical properties of resinous composites containing inorganic-organic dual fillers

In this study, thermal polymerized resinous composites containing inorganic-organic dual fillers were developed. The size effects of micron particles on the physico-mechanical properties of composites were investigated. According to the standard BS EN ISO 4049, the degree of transformation, hardness, three-point flexural strength, water absorption and water solubility of the prepared composite materials were determined. Contrary to expectations, the degree of transformation of the composites increased as the micron particle size increased. It has been deduced that this increase is directly related to the varying surface areas depending on the particle sizes and the modification rates that can vary depending on the surface areas. The hardness values did not show a general trend with increasing particle size. When the flexural strengths of composites containing varying micron size particles were examined, their strengths differed in relation to the degree of transformation and the rate of modification, which is also effective in hardness. As with other properties, the effects of competing particle size and rate of modification had an effect on the absorption behavior. When the resolutions of the composites are examined, the values of all are positive. It was concluded that this situation may be due to the absence of polar groups in the main monomer structure other than ester, hydroxyl and urethane groups, which will keep the absorbed water in the structure, and the release of unreacted monomers with the absorbed water.

Eco-Friendly Tannin-Based Non-Isocyanate Polyurethane Resins for the Modification of Ramie (Boehmeria nivea L.) Fibers.

This study aimed to develop tannin-based non-isocyanate polyurethane (tannin-Bio-NIPU) and tannin-based polyurethane (tannin-Bio-PU) resins for the impregnation of ramie fibers (Boehmeria nivea L.) and investigate their mechanical and thermal properties. The reaction between the tannin extract, dimethyl carbonate, and hexamethylene diamine produced the tannin-Bio-NIPU resin, while the tannin-Bio-PU was made with polymeric diphenylmethane diisocyanate (pMDI). Two types of ramie fiber were used: natural ramie without pre-treatment (RN) and with pre-treatment (RH). They were impregnated in a vacuum chamber with tannin-based Bio-PU resins for 60 min at 25 °C under 50 kPa. The yield of the tannin extract produced was 26.43 ± 1.36%. Fourier-transform infrared (FTIR) spectroscopy showed that both resin types produced urethane (-NCO) groups. The viscosity and cohesion strength of tannin-Bio-NIPU (20.35 mPa·s and 5.08 Pa) were lower than those of tannin-Bio-PU (42.70 mPa·s and 10.67 Pa). The RN fiber type (18.9% residue) was more thermally stable than RH (7.3% residue). The impregnation process with both resins could improve the ramie fibers' thermal stability and mechanical strength. The highest thermal stability was found in RN impregnated with the tannin-Bio-PU resin (30.5% residue). The highest tensile strength was determined in the tannin-Bio-NIPU RN of 451.3 MPa. The tannin-Bio-PU resin gave the highest MOE for both fiber types (RN of 13.5 GPa and RH of 11.7 GPa) compared to the tannin-Bio-NIPU resin.

Understanding the Reaction of Hydroxy-Terminated Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Random Copolymers with a Monoisocyanate

This work investigates the reaction kinetics of relatively high molecular weight poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymers containing primary and secondary hydroxyl groups (1°OH and 2°OH) as well as terminal carboxylic acid groups (COOH) with a monoisocyanate. To facilitate their end use in block copolymer synthesis, effects of molecular weight (24–194 kDa), [NCO]/[OHtotal] (1.2–8), and reaction time (4–17 h) were studied. The results show that 1°OH reacted faster than 2°OH, as expected, while the COOH did not react with isocyanate at all under these conditions. Both urethane and allophanate groups were formed. A further reaction of a hydroxy-terminated PHBV (Mn of 27 kDa) with monoisocyanate was undertaken at a ratio of 2.2, with more detailed analysis over time showing the complete reaction of 1°OH and 95 mol % reaction of 2°OH within 4 h at 65 °C. This work is a basis for the potential for controlled PHBV-based block copolymer synthesis.

Synthesis and properties of oligodiuretane diisocyanates and oligotetraurethanes based on a mixture (2.4÷2.6) of toluene diisocyanate

By the reaction of a mixture of isomers (2.4-2.6) of toluene diisocyanate with aliphatic, individual or oligomeric diols (such as polyoxypropylene glycols of different molecular weight) in cyclohexanone, oligodiurethane diisocyanates with the diol component of different nature and length in their structure are synthesized in the first stage. In the second stage, the synthesized oligodiurethane diisocyanates were blocked by monofunctional aliphatic alcohols of normal structure with different lengths of fatty radical. The structure of the latter is confirmed by the absence of absorption bands characteristic of free –NCO groups in the IR spectra. Both series of isolated oligodiureta diisocyanates and oligotetraurethanes are characterized by refractive index and Ubellode drop temperature, molecular weights, content of free –NCO groups, and IR spectra. They are well soluble in esters, ethers, chlorinated and aromatic hydrocarbons, ketones, and aprotic solvents; they are poorly soluble in aliphatic hydrocarbons. The presence in the structure of such compounds of polar urethane groups simultaneously with relatively high molecular weight suggests that they will be useful not only as plasticizers, but also as modifiers of the properties of polymers and composite materials.

N-Sulfonyl Urethanes to Design Polyurethane Networks with Temperature-Controlled Dynamicity

(Re)processing of cross-linked polyurethanes (PUs) is often energy intensive and inefficient since dissociation of urethane linkages at elevated temperatures generates highly reactive isocyanate moieties that can react with a wide range of nucleophiles. In this study, we first show with a small molecule study that the introduction of N-sulfonyl urethane bonds leads to dynamic covalent exchange reactions under much milder conditions compared to regular urethane groups. Then, these exchangeable N-sulfonyl urethane motifs have been introduced, in relatively small amounts (5, 10, and 20%), in a cross-linked PU matrix in an attempt to facilitate plastic flow at lower temperatures. Rheological analysis of the elastomeric dissociative networks revealed an interesting double relaxation behavior, even for temperatures between 150 and 100 °C, which could be described by a Maxwell model with two elements, which can be related to the activated and less activated urethane bonds. Finally, the (re)processability of these sulfonyl urethanes containing PUs was demonstrated through multiple cutting and hot pressing cycles and the corresponding materials showed a good retention of thermal properties.

Physicochemical fundamentals of processing solutions of thermoplastic poly(ether urethane)s to obtain fibrous-porous polymer composite materials

Objectives. To study the structure and properties of solutions of thermoplastic poly(ether urethane)s (PEUs) to inform their potential use in the production of fibrous-porous polymer composite materials with a given structure and set of performance properties depending on the field of practical application.Methods. The composition of PEUs was studied by attenuated total reflection infrared (ATR-IR) spectroscopy using a program for correcting the spectra on an IR Fourier spectrophotometer, as well by differential scanning calorimetry (DSC) using a heat flow calorimeter. The viscosity of PEU solutions was determined on a rotational viscometer.Results. The chemical composition of PEUs and the nature of the formation of hydrogen bonds were studied. An analysis of the spectra demonstrates the almost complete identity of the PEUs synthesized from the same 4,4'-diphenylmethane diisocyanate. In the studied PEUs of the Vitur and Desmopan® brands, as well as Sanpren, pronounced absorption bands characteristic of urethane groups involved in the formation of hydrogen bonds are visible in the region from 1702 to 1730 cm−1. The temperature transitions and thermal stability of the investigated PEUs were determined by DSC. The influence of the ratio of rigid and flexible blocks, as well as the nature of hydrogen bonds on the melting temperatures of polymers, was shown. Analysis of the DSC curves demonstrated all the studied PEUs to have high melting points ranging from 159 to 215°C. From the studied temperature dependences of the structural viscosity of thermoplastic PEUs solutions, all solutions were established to have a minimum viscosity anomaly; the value of the logarithm of viscosity depends on the chemical composition and structure of the initial PEUs. It is shown that the viscosity anomaly of PEU solutions can be reduced with increasing temperature.Conclusions. A comparison of the chemical composition, structure, thermal and rheological characteristics of thermoplastic PEUs with PEU solutions widely used for the production of fibrous-porous materials and coatings of Sanpren LQ-E-6 and Vitur R 0112 grades demonstrates their practicability as production materials and coatings having a predetermined structure and a set of properties depending on the requirements and operating conditions of finished products.

Hydrogen Bonds under Stress: Strain-Induced Structural Changes in Polyurethane Revealed by Rheological Two-Dimensional Infrared Spectroscopy.

The remarkable elastic properties of polymers are ultimately due to their molecular structure, but the relation between the macroscopic and molecular properties is often difficult to establish, in particular for (bio)polymers that contain hydrogen bonds, which can easily rearrange upon mechanical deformation. Here we show that two-dimensional infrared spectroscopy on polymer films in a miniature stress tester sheds new light on how the hydrogen-bond structure of a polymer is related to its viscoelastic response. We study thermoplastic polyurethane, a block copolymer consisting of hard segments of hydrogen-bonded urethane groups embedded in a soft matrix of polyether chains. The conventional infrared spectrum shows that, upon deformation, the number of hydrogen bonds increases, a process that is largely reversible. However, the 2DIR spectrum reveals that the distribution of hydrogen-bond strengths becomes slightly narrower after a deformation cycle, due to the disruption of weak hydrogen bonds, an effect that could explain the strain-cycle induced softening (Mullins effect) of polyurethane. These results show how rheo-2DIR spectroscopy can bridge the gap between the molecular structure and the macroscopic elastic properties of (bio)polymers.

Physical and Mechanical Properties of Cross-Laminated Timber Made of a Combination of Mangium-Puspa Wood and Polyurethane Adhesive

This study aimed to evaluate the physical and mechanical properties of cross-laminated timber (CLT) characteristics from mangium (Acacia mangium) and puspa (Schima wallichii) woods and their combination using polyurethane (PU 1.2) adhesives. The manufacture of CLT began with basic adhesive characterization and thermo-mechanical analysis. Wood material’s physical and chemical properties were also tested with its response to the PU 1.2 wettability. The CLT (100 ´ 30 ´ 3.60) cm3 was manufactured with 160 g/m2 glue spread at a pressure of 0.80 MPa for 200 minutes. The CLT panels were characterized refers to the JAS 3079 standard. The results show that PU 1.2 had a gelatination time of 182.1 minutes at 25°C, was able to form urethane groups, and experienced an increase in storage modulus at 35°C. Mangium and puspa woods have different physical and chemical properties, but they interact similarly with PU 1.2 wettability. Puspa CLT panel has a higher density than mangium but lower dimensional stability. The bending mechanical properties of hybrid puspa-mangium-puspa CLT were able to match puspa CLT and have one sample of shear strength that met the JAS 3079 standard in both grain directions. Therefore, hybrid puspa-mangium-puspa CLT has the potential to be developed to improve its dimensional stability and mechanical properties. Keywords: Acacia mangium, cross-laminated timber, layer combination, polyurethane adhesive, Schima wallichii

Development and Characterization of Eco-Friendly Non-Isocyanate Urethane Monomer from Jatropha curcas Oil for Wood Composite Applications

The aim of this research work was to evaluate the potential of using renewable natural feedstock, i.e., Jatropha curcas oil (JCO) for the synthesis of non-isocyanate polyurethane (NIPU) resin for wood composite applications. Commercial polyurethane (PU) is synthesized through a polycondensation reaction between isocyanate and polyol. However, utilizing toxic and unsustainable isocyanates for obtaining PU could contribute to negative impacts on the environment and human health. Therefore, the development of PU from eco-friendly and sustainable resources without the isocyanate route is required. In this work, tetra-n-butyl ammonium bromide was used as the activator to open the epoxy ring with 3-Aminopropyltriethoxisylane as a catalyst to yield urethane of JCO (UJCO). The UJCO were characterized by Fourier Transform Infra-Red spectroscopy (FTIR) and their oxirane, and hydroxyl values were measured. The result showed that a decrease in oxirane value was found while the hydroxyl value was increased during the time, confirming that the urethane group was formed. The presence of functional groups in FTIR spectra at wave numbers 1732.08, 1562.34, and 3348.42 cm−1 indicates the functional groups of C = O (urethane carbonyl), –NH, and –OH, respectively confirmed this finding. The potential applications of NIPU in the wood composite were also outlined.

Protection of threaded connections against corrosion

The paper presents data on the effect of the addition of D-10TM oligomer in the composition of standard lubricants for processing threaded connections on the degree of corrosion damage, the value of the torque for unscrewing and the value of friction coefficient in threaded connections. The addition of D-10TM oligomer 5% by weight in Litol-24 helps to reduce the torque for unscrewing threaded joints by 1.5-1.7 and 1.3-1.4 times in comparison with G-SKa 2/6-2 Grease and Lithol-24 respectively, therefore, reduces the coefficient of friction in threaded connections by the same amount. When examining the threaded part of fasteners after disassembling the joints pre-treated with the developed composition, traces of corrosion appear only after 720 hours, and in joints treated with G-SKA 2/6-2 Grease and Lithol-24 – after 96 hours. Production tests showed that the developed composition improves the disassembly of the threaded connection by 1.3-1.4 times in comparison with factory processing. The improvement of the protective properties of the composition with the addition of the D-10TM oligomer is explained by the fact that the D-10TM oligomer, having polar urethane groups in the chain and a high molecular weight, exhibits strong intermolecular interactions due to the formation of hydrogen bonds. Its three-dimensional spatial structure provides better filling of cracks and gaps in the threaded joint, seals them, isolates them from aggressive environments and thus provides better protection against corrosion.

Effects of Ketamine/Xylazine and Urethane Anesthesia on Compound Muscle Action Potential Latency of Gastrocnemius Muscle in Rats

ABSTRACT Objective: Anesthetic agents, which are used in appropriate doses for the application of the experimental procedure in animals, relieve pain when applied in sufficient amounts as well as muscle relaxation. However, many anesthetics can alter the dynamics of neuromuscular systems. We aimed to compare the effects of two frequently used anesthetic agents on electromyographic parameters in rats. Materials and Methods: This study was performed on male Wistar albino rats aged 22–24 months. The animals were divided into two groups: urethane (1.5 gkg−1, i.p; n = 6) and ketamine+xylazine (K+X) (80 mg/kg, i.p; n = 6). Under general anesthesia, rats were electrically stimulated with bipolar hook electrodes from both legs, and compound muscle action potential (CMAP) was recorded from the needle electrode of the gastrocnemius muscle. Motor nerve action potential latency (MNAPL) was measured from the sciatic nerve of the rats. Results: The results of electrodiagnostic findings related to two different anesthetics in the animals were compared, and CMAP parameters were found to differ between the groups. MNAPL in both the right and left legs was significantly reduced in the urethane group compared to the K+X group (P < 0.05). Conclusion: Urethane anesthesia may be a better choice than K+X anesthesia to evaluate nerve and muscle functions in animal electromyography studies.

Upgrading Polyurethanes into Functional Ureas through the Asymmetric Chemical Deconstruction of Carbamates.

The importance of systematic and efficient recycling of all forms of plastic is no longer a matter for debate. Constituting the sixth most produced polymer family worldwide, polyurethanes, which are used in a broad variety of applications (buildings, electronics, adhesives, sealants, etc.), are particularly important to recycle. In this study, polyurethanes are selectively recycled to obtain high value-added molecules. It is demonstrated that depolymerization reactions performed with secondary amines selectively cleave the C-O bond of the urethane group, while primary amines unselectively break C-O and C-N bonds. The selective cleavage of C-O bonds, catalyzed by an acid:base mixture, led to the initial polyol and a functional diurea in several hours to a few minutes for both model polyurethanes and commercial polyurethane foams. Different secondary amines were employed as nucleophiles to synthesize a small library of diureas obtained in good to excellent yields. This study not only targets the recovery of the initial polyol but also aims to form new diureas which are useful building blocks for the polymerization of innovative materials.

The effect of Moringa oleifera leaf extracts against urethane-induced lung cancer in rat model.

Lung cancer is one of the most common malignancies in the world, and chemotherapy can have unfavorable side effects. The aim of the present study is to evaluate the therapeutic anticancer role of Moringa oleifera leaf extracts (MLE) in urethane-induced lung cancer in adult male albino rats as compared to standard chemotherapy. Rats were categorized into four groups (10 rats/group), including negative control rats, urethane lung cancer model rats, MLE-treated lung cancer rats, and cisplatin-treated rats. Estimation of lung index, some biochemical markers of oxidative stress, quantitative real-time polymerase chain reaction (qRT-PCR), and histopathology and transmission electron microscopy were performed. The lung index was significantly increased about one-fold in urethane lung cancer model rats, but it decreased after MLE treatment. Also, MLE was able to improve the induced changes in glutathione, superoxide dismutase, and malondialdehyde concentration to be 3.8 ± 0.4mg/g, 900.6 ± 58 U/g, and 172 ± 24nmol/g, respectively. Additionally, after MLE treatment, the expression of EGFR-mRNA increased by about 50%. Our light and electron microscopic examination revealed that urethane group showed abnormally distributed excessive collagen fibers and the development of papillary adenocarcinoma from hyperplastic Clara cells in the lumen of terminal bronchiole with bronchiolar wall thickening, alveolar collapse, and inflammation. MLE group has moderate amount of collagen fiber and absence of tumor mass and provided more or less restoration of normal lung histology. Moreover, MLE was able to ameliorate the induced changes in mucin and PCNA positive cells in the lung by 10.8 ± 2.3%. Collectively, the current study showed that MLE could be used as anticancer agents alleviating changes associated with lung cancer in a urethane-induced lung cancer bearing rats thereby representing alternative options to toxic chemotherapy.

Phase-Change Microcapsules with a Stable Polyurethane Shell through the Direct Crosslinking of Cellulose Nanocrystals with Polyisocyanate at the Oil/Water Interface of Pickering Emulsion.

Phase-change materials (PCMs) attract much attention with regard to their capability of mitigating fossil fuel-based heating in in-building applications, due to the responsive accumulation and release of thermal energy as a latent heat of reversible phase transitions. Organic PCMs possess high latent heat storage capacity and thermal reliability. However, bare PCMs suffer from leakages in the liquid form. Here, we demonstrate a reliable approach to improve the shape stability of organic PCM n-octadecane by encapsulation via interfacial polymerization at an oil/water interface of Pickering emulsion. Cellulose nanocrystals are employed as emulsion stabilizers and branched oligo-polyol with high functionality to crosslink the polyurethane shell in reaction with polyisocyanate dissolved in the oil core. This gives rise to a rigid polyurethane structure with a high density of urethane groups. The formation of a polyurethane shell and successful encapsulation of n-octadecane is confirmed by FTIR spectroscopy, XRD analysis, and fluorescent confocal microscopy. Electron microscopy reveals the formation of non-aggregated capsules with an average size of 18.6 µm and a smooth uniform shell with the thickness of 450 nm. The capsules demonstrate a latent heat storage capacity of 79 J/g, while the encapsulation of n-octadecane greatly improves its shape and thermal stability compared with bulk paraffin.

The characteristics and mechanism of hydrogen bonding assembly in linear polyurethane with multiple pendant 2‐ureido‐4[1H]‐pyrimidone units

Abstract2‐Ureido‐4[1H]‐pyrimidone (UPy) can form strong quadruple hydrogen bonding (H‐bonding) and is widely used to construct supramolecules. Though the H‐bonding assembly of UPy‐containing polymers has been widely reported, little attention is paid to the H‐bonding characteristics and mechanism of UPy‐containing polyurethanes. Here, by using UPy‐p‐PDLLA‐SMPU, a linear polyurethane with multiple pendant UPy units as the model polymer, the H‐bonding assembly characteristics in solution, solid film and melt are systematically investigated. It is found that the UPy units mainly exist as free monomers in DMSO, UPy dimers in CHCl3, and both free monomers and dimers in DMF. The dimerization of UPy can promote the H‐bonding of urea and urethane groups and thus the formation of hard segment aggregates. Thereby, the thermal resistance and reversibility of the H‐bonds are significantly enhanced in both UPy‐p‐PDLLA‐SMPU film and melt. UPy‐p‐PDLLA‐SMPU can transition from a rubber state (70°C–85°C) to a viscous flow state (≥120°C), presenting the characteristics of both chemically crosslinked and linear polyurethanes. This work provides a clear picture on the H‐bonding assembly of UPy units together with urea and urethane groups in UPy‐p‐PDLLA‐SMPU. The obtained assembly characteristics and mechanism are beneficial for the design and processing of UPy‐based physically crosslinked polyurethanes.