Coumarin Concentration Research Articles

Application of coumarin concentrations and number of nodes on induction potato (Solanum tuberosum L.) micro tuber in vitro

Potato is a horticultural commodity with good prospects for development. Potato tissue culture technology is one of the efforts to produce virus- and disease-free potato seeds. The aim of this experiment was to see if there was an interaction between the administration of multiple coumarin concentrations and the number of nodes and at what concentration of coumarin and at what number of nodes gives optimal results for induction of potato micro tuber. This experiment was arranged according to a two-factor factorial Completely Randomized Design with 3 replications. The 1st factor was multiple coumarin concentrations with 4 levels (30, 60, 90, 120 mg/l) and the 2nd factor was the number of nodes with 3 levels (1 node, 2 nodes, and 3 nodes). The results showed that there was an interaction between the administration of multiple concentrations of coumarin and the number of nodes, showing the best interaction when the coumarin concentration was 120 mg/l with 2 nodes that could form tubers with a percentage of 94.44%. The 120 mg/l coumarin concentration gave the highest of plantlets forming micro-tubers, the highest number of micro tuber and the largest micro-tuber diameter. The two-node treatment increased the percentage of plantlets forming micro tubers, the number of micro tubers, and the diameter of the micro tuber.

Efficacy of Young Cinnamomum zeylanicum Blume Bark on Hyperglycemia and PTPase Activity in Type 2 Diabetes.

Diabetes is a major public health concern and natural easy-going remedies are being searched. Since Cinnamomum zeylanicum Blume has a low coumarin concentration and possibleinsulin-enhancing properties, it is preferred over all other cinnamon species. Although similar research has been done on humans, there have been very few studies on this particular species, and none among South Asians. Moreover, no human trial that properly described their intervening agent (C. zeylanicum) and checked its efficacy at the molecular level along with clinical variables was conducted. Therefore, the current research aimed to explore the effects of C. zeylanicum on the glycemic index, lipid profile, and expression of the protein tyrosine phosphatase 1 B (PTP1B) enzyme in the peripheral blood mononuclear cells (PBMC) in type 2 diabetes. We examined the presence of bioactive compounds in young C. zeylanicum bark (Alba grade) from native Sri Lanka using gas chromatography-mass spectrometry, high-performance thin-layer chromatography, and thin-layer chromatography before introducing it in the clinical study where trans-Cinnamaldehyde was found to be a major chemical constituent (>60%). Then, from January 2020 to March 2022, a randomized double-blinded placebo-controlled trial was carried out in the Diabetic Clinic at AIIMS Rishikesh. A total of 154 diabetic patients were enrolled and were taken either cinnamon or placebo capsules (1.5 g/day) for 120 days on an empty stomach with warm water along with their conventional treatment. Reduction in fasting blood glucose levels in the cinnamon group was found -35.50% (95% CI, -173 to 58.4), whereas in the placebo group change was 5.00% (95% CI, -165 to 224). For glycosylated hemoglobin, it differed -0.85% (95% CI, -8.2 to 1.6) in the cinnamon group compared to the placebo where it was found 0.15% (95% CI, -6.1 to 5.5).PTP1B expression in PBMC was determined from pre- and post-trial blood samples using the Western Blot, and significant inhibition was also observed (p=0.039).The study result depicts, C. zeylanicum is emerging as a beneficial plant for type 2 diabetes in Northern India and could be used as an adjunctive treatment rather than as a standalone managerial remedy.

Effect of Aspergillus niger extract on production of coumarins in cell suspension cultures of Angelica archangelica

Abstract. Nadir DS. 2022. Effect of Aspergillus niger extract on production of coumarins in cell suspension cultures of Angelica archangelica. Biodiversitas 23: 5132-5138. Aspergillus niger is one of the most significant microbes employed in biotechnology and has been used for many years to make citric acid and extracellular enzymes. It is also utilized for waste treatment and biotransformation. In the last 20 years, A. niger has become a crucial transformational host to overexpress food enzymes. Different concentrations of A. niger extract were used to investigate their effects on the production of coumarin, both in the liquid medium and the cells, of batch cultures of Angelica archangelica L. Liquid Murashige and Skoog (MS) medium enriched with 2.0 mg.L-1 2,4-dichlorophenoxyacetic acid (2,4-D) combined with 0.5 mg.L-1 Kinetin (Kin), was used as growth medium for batch cultures of A. archangelica incubated for different incubation periods (7, 14 and 21 days). The results showed that 3.053 mg.g-1 was the highest coumarin concentration, obtained from the nutritional medium drawn from cultures treated with 2.0 mL.L-1 of A. niger after 21 days of incubation. However, 2.055 mg.g-1 was the maximum coumarin concentration reached in the harvested cells after 21 days of incubation when the cultures were treated with 2.0 mL.L-1 of A. niger extract. This study was aimed at performing extraction, identification, and estimation of coumarins from cell suspension cultures of A. archangelica and also investigating the effects of A. niger extract, at different concentrations, for various incubation periods on the production of coumarins. The concluded that A. niger extract affected coumarin accumulation, both in the medium and cells, from the cultures of A. archangelica. A dose of 2.0 mL.L-1 of A. niger extract as a biotic elicitor was found to have the best elicitor concentration, and that 21 days of incubation was the optimum period for the elicitor concentration to produce the highest coumarin content in batch cultures. Therefore, these results may contribute to increasing coumarin production by using different fungal extracts as biotic elicitors in cell suspension cultures.

Degradation of emerging contaminant coumarin based on anodic oxidation, electro-Fenton and subcritical water oxidation processes

The degradation of emerging contaminant coumarin was separately investigated in anodic, electro-Fenton and subcritical water oxidation processes. With respect to the anodic and electro-Fenton oxidation, the influence of constant current, treatment time and initial concentration of coumarin was studied. Regarding subcritical water oxidation, the effect of the oxidant concentration, temperature, treatment time and initial coumarin concentration was investigated. In anodic and electro-Fenton oxidation processes, coumarin degradation proceeded in a similar manner, achieving 99% degradation, after 180 min at a constant current of 200 mA. In both set-ups, further increasing the applied current lowered the degradation efficiency due to the formation of by-products and the increasing occurrence of side-reactions. The highest degradation of 88% was achieved in subcritical conditions, specifically at 200 °C, using 150 mM H2O2 and after 37.5 min of treatment. Under subcritical conditions, temperature was the most prominent parameter, followed by the H2O2 concentration. Under all methodologies, increasing treatment time had a small positive effect on coumarin degradation, indicating that time is not the most influential parameter. A comparison of the three methodologies in terms of performance as well as energy consumption and simplicity of operation highlighted the advantages of subcritical water oxidation.

Two Biotechnological Approaches to the Preparative Synthesis of Natural Dihydrocoumarin

In this work, we describe two different biotechnological processes that provide the natural flavour dihydrocoumarin in preparative scale. Both the presented approaches are based on the enzyme-mediated reduction of natural coumarin. The first one is a whole-cell process exploiting the reductive activity of the yeast Kluyveromyces marxianus, a Generally Recognized As Safe (GRAS) microorganism that possesses high resistance to the substrate toxicity. Differently, the second is based on the reduction of natural coumarin by nicotinamide adenine dinucleotide phosphate (NADPH) and using the Old Yellow Enzyme reductase OYE2 as catalyst. NADPH is used in catalytic amount since the co-factor regeneration is warranted employing an enzymatic system based on glucose oxidation, in turn catalysed by a further enzyme, namely glucose dehydrogenase (GDH). Both processes compare favourably over the previously reported industrial method as they work with higher coumarin concentration (up to 3 g/L for the enzymatic process) yet allowing the complete conversion of the substrate. Furthermore, the two approaches have significant differences. The microbial reduction is experimentally simple but the isolated dihydrocoumarin yield does not exceed 60%. On the contrary, the enzymatic approach requires the use of two specially prepared recombinant enzymes, however, it is more efficient, affording the product in 90% of isolated yield.

Coumarin as a green inhibitor of chloride-induced aluminum corrosion: theoretical calculation and experimental exploration.

In the present work, the adsorption mechanism and corrosion inhibition effect of coumarin as a green inhibitor was characterized. Quantum chemical calculation and molecular dynamics simulation of the coumarin molecule were performed to get insight into the adsorption model by assessing the frontier orbital parameters and adsorption configuration. The theoretical calculation disclosed that coumarin exhibited a higher adsorption reactivity in the water phase than that in the gas phase, and the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O structure in coumarin was the most favorable site for adsorption occurring. Coumarin could adsorb spontaneously on an aluminum surface in a parallel manner, where electron donation occurred from the aluminum surface to the inhibitor. Additionally, the experimental investigation determined that coumarin decreased the aluminum dissolution by suppressing both the anodic and cathodic reactions. The optimal coumarin concentration of 0.5 wt% resulted in a maximum inhibition efficiency (89.6%), but coumarin at a higher concentration would lead to the competitive and unstable adsorption of inhibitor molecules, thus decreasing the inhibition effect. Moreover, surface chemical characterization confirmed the formation of Al–coumarin complexes, which was in accordance with the theoretical calculation.

Effect of Friction Velocity on Tribological Behavior of Coumarin as Mineral Oil Additive

Abstract The tribological behavior of lubricants, prepared with a mineral base oil, lauryl alcohol, and different concentrations of coumarin, was examined using a four-ball tester under constant and variable friction velocity conditions. At constant friction velocity, the maximum non-seizure load (PB) increased from 304 N to 392 N at a coumarin concentration of 0.5 wt%. Lubricants with 0.7 wt% coumarin exhibited optimum lubricating properties, and the maximum reductions in friction coefficient (FC) and wear scar diameter (WSD) were 20.0% and 11.88%, respectively. Further investigation of the tribological mechanism implied that the ester group in the coumarin molecule established a connection with the surface atom, resulting in the formation of a tribofilm, which further restricted the adhesion wear regime. Additionally, under variable friction velocity conditions, increasing the coumarin concentration had an obvious effect on the mixed lubrication (ML) and elasto-hydrodynamic lubrication (EHL) regions but not on other lubrication regions. Moreover, a mathematical model was proposed to show the relationship between FC and friction velocity. Importantly, the present work clarifies the effect of friction velocity on the tribological behavior of coumarin and also supports the use of coumarin as a novel additive in mineral oils.

Exploration on tribological behaviour of coumarin as copper rolling oil additive through surface characterization

Tribological performance of coumarin in copper rolling oil was studied by four-ball tests and cold rolling tests. Then a systemic investigation on surface topography and surface chemistry of rolled strips was performed by field emission scanning electron microscope (FE-SEM), laser scanning confocal microscopy (LSCM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and Raman spectroscopy (Raman). Results showed that coumarin was a kind of potential lubrication additive. The average friction coefficient (AFC) and wear scar diameter (WSD) were reduced by 30.2% and 30.1%, respectively, when the optimum concentration of coumarin (2.0 wt%) was added in copper rolling oil. Meanwhile, as the formation of tribofilm during rolling process, the nonuniform deformation and adhesive wear were effectively inhibited. Thinner copper strips with fine surface quality were obtained. The surface average roughness (Sa) of rolled copper strips was reduced by up to 68.8%. Surface characterization showed that the carbonyl group in coumarin molecule connected to Cu atoms with its molecular plane vertical or tilted to the metal surface. Besides, thermal analysis disclosed that this tribofilm had negligible surface residuals, especially when coumarin concentration was lower than 3.0 wt%.

The effect of coumarin addition on the electrical characteristics of Al/Coumarin:CdO/p-Si/Al photodiode prepared by drop casting technique

In this study, cadmium oxide thin films deposited on p-Si with different weight ratio of coumarin were prepared by drop casting technique. The effect of coumarin addition in different weight ratios was investigated on the electrical and photosensivity properties of Al/Coumarin:CdO/p-Si organic-inorganic hybrid photodiodes. The current-voltage (I–V) and capacity-conductivity-voltage (C-G–V) characteristics of the diodes were determined in the dark and under various illumination intensities. It is concluded that all samples have excellent rectification properties due to good rectifying ratios found from I–V characteristics of the devices. All photodiodes produced with different coumarin weight ratios were found to have higher photo-current under illuminated conditions than dark conditions. In addition, the highest Iphoto/Idark photosensitivity value was found as 448.78 for the device with a 5% coumarin doping rate under 5 V and 100 mW/cm2 light intensity. Transient photo-current measurements showed that all devices are sensitive to light intensity. Furthermore, capacitance/conductivity-voltage measurements were performed at frequencies ranging from 10 kHz to 1 MHz. The fact that the capacity decreases and conductivity increases with the increasing frequency values was explained with the presence of interface states. The ideality factors of Al /Coumarin:CdO/p-Si/Al photodiodes, prepared with various coumarin doping ratios, are between 4.39 and 7.83. Additionally, the interfacial density (Dit) and serial resistance (Rs) values of the devices were determined to be dependent on the frequency and the coumarin concentration. As a result, produced Al/Coumarin:CdO/p-Si/Al organic-inorganic hybrid devices can be used as photocapacitors and/or photodiodes in electro-optic applications.

Biocatalytic Synthesis of Natural Dihydrocoumarin by Microbial Reduction of Coumarin

Dihydrocoumarin is a natural product of great relevance for the flavour industry. In this work, we describe a study on the biotransformation of the toxic compound coumarin into natural dihydrocoumarin, recognized as safe for food aromatization. To this end, we screened a variety of yeasts and filamentous fungi, isolated from different sources, in order to evaluate their ability to reduce selectively the conjugated double bond of coumarin. Moreover, since coumarin induces cytotoxicity and therefore inhibits cell growth as well as the cell metabolic activity, we tested out different substrate concentrations. All strains were able to convert the substrate, although showing very different conversion rates and different sensitivity to the coumarin concentration. In particular, the yeasts Torulaspora delbrueckii, Kluyveromyces marxianus and the fungus Penicillium camemberti displayed the higher activity and selectivity in the substrate transformation. Among the latter strains, Kluyveromyces marxianus presented the best resistance to substrate toxicity, allowing the biotransformation process even with coumarin concentration up to 1.8 g/L.

Cinnamon Shows Antidiabetic Properties that Are Species-Specific: Effects on Enzyme Activity Inhibition and Starch Digestion

Despite considerable research the evidence around the antidiabetic properties of cinnamon remains equivocal, and this may be due to varietal differences which is an aspect that is understudied. This study systematically compared the anti-hyperglycaemic properties of the four major commercial cinnamon types used around the world (Chinese; Cinnamomum cassia [CC], Indonesian; C. burmanii [IC], Vietnamese; C. loureirii [VC], and Ceylon; C. zeylanicum [SC]). LC-MS analysis showed distinct diffrences in the phytochemical profiles of cinnamon with SC showing the lowest coumarin concentration. CC and IC had the highest polyphenol levels and antioxidant potential, and all four types differed significantly in their content (P < 0.001). All cinnamon types showed potent species-specific effects on starch digestion enzyme activity inhibition (P < 0.001), CC was most effective against α-amylase and all four strongly inhibited α-glucosidase compared to acarbose. Cinnamon significantly reduced starch breakdown during oral (P = 0.006) and gastric (P = 0.029) phases of gastro-intestinal digestion with IC and SC showing consistent effects. No effects of cinnamon were seen in the intestinal phase. IC, VC and SC showed the greatest potential to inhibit formation of advanced glycation endproducts (AGEs) during digestion. In conclusion, cinnamon demonstrates anti-hyperglycaemic properties, however effects are species-specific with best overall properties seen for Ceylon cinnamon.

Sucrose and coumarin effect on the growth and development of micro-cutting potato plant (Solanum tuberosum) variety Granola Kembang

Abstract. Manjaswari A, Pitoyo A, Sari SLA. 2018. Sucrose and coumarin effect on the growth and development of micro-cutting potato plant (Solanum tuberosum) variety Granola Kembang. Cell Biol Dev 2: 55-62. This research aimed to determine the effect of various concentrations of sucrose and coumarin on the micro-cutting potato plant's growth and development. A completely Randomized Design (CRD) with a single concentration combination factor of sucrose and coumarin was treated well. Five levels of sucrose concentrations were 0, 30, 50, 70, and 90 g/L. While coumarin concentrations were 0, 20, 40, 60, 80 mg/L. Observation and data collection was made in the second month after the explant planting. Some parameters observed were morphological changes in explant characteristics, i.e., the percentage of explants response, the emergence of the shoot, shoot height, shoot number, leaf emergence time, number of leaves, the emergence of the root, root number, and root length. The data obtained were analyzed using ANOVA followed by DMRT at level test 5 % to determine if there is a significant difference between the treatments. The result showed that the higher sucrose concentration added into the media could increase the micro-cut growth and development of shoots and leaves; otherwise, it would negatively influence root development. The addition of coumarin in high concentration inhibited all the parameters of growth and development observed. Both combinations of sucrose and coumarin could increase the micro-cut development of shoot at 50 g/L of sucrose and 20 mg/L of coumarin concentration. Those concentrations could produce the best amount and higher shoot for micro-cut multiplications.

Influence of tetrabutylammonium cations on phase transition within adsorbed adlayer and lifting of reconstruction at Au(111) electrode in sulfate solution and in presence of coumarin

The effect of tetrabutylammonium (TBA) cations on phase transition within adsorbed adlayer and lifting of reconstruction at Au(111) electrode in sulfate solution and in presence of coumarin (CUM) has been studied by means of the cyclic voltammetry and differential capacity measurements. TBA cations retard the adsorption of sulfate anions which is responsible for the lifting of the reconstruction. Next, the presence of TBA cations in sulfate solution induces the appearance of phase transition in CUM adlayer for twice lower coumarin concentration and at much more negative potentials. Moreover, the protection against the sulfate anions adsorption which lifts the reconstruction is higher for CUM molecules than for TBA cations.

Inhibitory Effect of Coumarin on Syntrophic Fatty Acid-Oxidizing and Methanogenic Cultures and Biogas Reactor Microbiomes.

Coumarins are widely found in plants as natural constituents having antimicrobial activity. When considering plants that are rich in coumarins for biogas production, adverse effects on microorganisms driving the anaerobic digestion process are expected. Furthermore, coumarin derivatives, like warfarin, which are used as anticoagulating medicines, are found in wastewater, affecting its treatment. Coumarin, the structure common to all coumarins, inhibits the anaerobic digestion process. However, the details of this inhibition are still elusive. Here, we studied the impact of coumarin on acetogenesis and methanogenesis. First, coumarin was applied at four concentrations between 0.25 and 1 g · liter-1 to pure cultures of the methanogens Methanosarcina barkeri and Methanospirillum hungatei, which resulted in up to 25% less methane production. Acetate production of syntrophic propionate- and butyrate-degrading cultures of Syntrophobacter fumaroxidans and Syntrophomonas wolfei was inhibited by 72% at a coumarin concentration of 1 g · liter-1 Coumarin also inhibited acetogenesis and acetoclastic methanogenesis in a complex biogas reactor microbiome. When a coumarin-adapted microbiome was used, acetogenesis and methanogenesis were not inhibited. According to amplicon sequencing of bacterial 16S rRNA genes and mcrA genes, the communities of the two microbiomes were similar, although Methanoculleus was more abundant and Methanobacterium less abundant in the coumarin-adapted than in the nonadapted microbiome. Our results suggest that well-dosed feeding with coumarin-rich feedstocks to full-scale biogas reactors while keeping the coumarin concentrations below 0.5 g · liter-1 will allow adaptation to coumarins by structural and functional community reorganization and coumarin degradation.IMPORTANCE Coumarins from natural and anthropogenic sources have an inhibitory impact on the anaerobic digestion process. Here, we studied in detail the adverse effects of the model compound coumarin on acetogenesis and methanogenesis, which are two important steps of the anaerobic digestion process. Coumarin concentrations lower than 0.5 g · liter-1 had only a minor impact. Even though similar inhibitory effects can be assumed for coumarin derivatives, little effects on the anaerobic treatment of wastewater are expected where concentrations of coumarin derivatives are lower than 0.5 g · liter-1 However, when full-scale reactors are fed with coumarin-rich feedstocks, the biogas processes might be inhibited. Hence, these feedstocks should be utilized in a well-dosed manner or after adaptation of the microbial community.

Coumarin variation in Iranian biennial Melilotus genetic resources and its relationship with agro-morphophenological traits

Most of Melilotus Miller species, a forage legume, contain coumarin, an unfavorable component in their shoot. There is no information concerning coumarin on Iranian Melilotus germplasms. It is crucial for plant breeders to know the concentration of this component in the breeding materials, its relationship with other traits and with genotype geographic origin. In a two-year field study a total of 196 accessions of biennial Melilotus were planted in two replications in March 2014. Thirty-nine agro-morphobiochemical traits were recorded according to standard descriptors. Fluorescencemetery assay was applied to detect free, conjugated, and total coumarin concentrations in plant leaves. The data were subjected to correlation, path, regression, factor, and cluster analyses. Total coumarin concentration varied from 0.09 to 5.27% of leaf dry weight (LDW) with a mean of 1.63 ± 0.08% of LDW among accessions. In M. officinalis, correlation analysis showed no significant correlation between coumarin concentration and cotyledon, hypocotyl, and stem colors. Therefore, no early predicting trait was determined to estimate coumarin concentration in the early growth phases of the germplasms. A positive linear relationship between leaf area and total coumarin concentration was observed by path and regression analyses. Based on factor analysis and extracted bi-plot, the scatter of accessions with low coumarin and high forage yield was determined. Materials were divided into three groups by k-means cluster analysis. There was no clear pattern between coumarin concentration and genotype geographic origin. The findings could be utilized by Melilotus breeders to apply in their breeding programs.

UV-assisted electrochemical degradation of coumarin on boron-doped diamond electrodes

A combined treatment based on electrochemical oxidation on boron-doped diamond (BDD) anodes and UV-C irradiation was used to degrade the emerging contaminant coumarin, an ingredient of many personal care products. The efficiency of the process was assessed by monitoring the coumarin concentration decay and the total organic carbon (TOC). The effect of chloride was evaluated and the occurrence of inorganic chlorinated products was quantified.The photo-assisted electrochemical degradation resulted in a faster removal and mineralization of the pollutant, compared to the treatment without UV irradiation. The observed synergistic effect was mainly ascribed to the ability of UV light to activate the peroxides electrogenerated during the electrolysis on BDD. An additional contribution was due to the photolysis of electrogenerated hypochlorite/hypochlorous acid in the presence of chloride. UV irradiation reduced the amount of residual active chlorine but not of chlorates. TOC analysis showed that mineralization occurred together with coumarin removal from the solution, indicating that no persistent organic by-products were formed during the treatment.The possibility of reducing the energy consumption of the process by shortening the exposure time of the solution to UV light was also investigated.

PVA-Coumarin Films: Materials for Optical Applications

Pure Poly(vinylacohol) (PVA) and PVA-coum films with different concentrations were prepared by a casting technique. Optical absorption and mechanical properties were measured. The UV–Vis absorption spectra gave the same band positions but the absorption intensity increases with increasing coumarin concentration. The dependence of the absorption coefficient on the photon energy has been determined and the energy gaps and band tails were calculated. The topography of the surface was measured by atomic force microscope (AFM). It was found that Young’s modulus, the strength at the break and the band tail increase while the optical gaps for PVA-coum films decrease. RMS roughness of the surface for prepared films decreases as the coumarin concentration is increased. The obtained results illustrated that this material has promising applications in optical industries.

Hydrogenation of coumarin to octahydrocoumarin over a Ru/C catalyst

The production of octahydrocoumarin, which can serve as a replacement for toxic coumarin, was investigated using 5% Ru on active carbon (Ru/C) as the catalyst for the hydrogenation of coumarin. The hydrogenation was studied by optimizing the reaction conditions (pressure, solvent and coumarin concentration). The activity and selectivity of the Ru/C catalyst were compared for different solvents. The mechanism of coumarin hydrogenation was deduced. The formation of side products was explained. The optimal hydrogenation reaction conditions were: 130 °C, 10 MPa, 60 wt% coumarin in methanol, and 0.5 wt% (based on coumarin) of Ru/C catalyst. At the complete conversion of coumarin, the selectivity to the desired product was 90%.

The effects of coumarin additive on the properties of CdS thin films grown by chemical bath deposition

CdS thin films have been obtained on glass substrates by using chemical bath deposition technique. Different concentrations of coumarin were used as an additive in the growth solutions, for the first time. The effects of coumarin on the properties of the as-deposited and annealed CdS thin films were investigated. It was found that increasing coumarin concentration in the growth solution remarkably affects the crystallinity and uniformity of the films. The 1% and 2% presence of coumarin enhanced the surface morphology while higher concentrations decreased surface uniformity. In the optical band gap values of both as-deposited and annealed films, a decrease has been observed with increasing additive concentration. Through temperature dependent resistance measurements of the films, impurity levels׳ electrical activation energies for each film have been estimated by means of the obtained discrete linear regions indicating different conduction mechanisms.

Effect of molecular weight of PEG soft segments on photo-stimulated self-healing performance of coumarin functionalized polyurethanes

Polyurethanes consisting of tri-functional homopolymer of hexamethylene diisocyanate (tri-HDI) and polyethylene glycol (PEG) are synthesized, in which photo-reversible coumarin moieties act as pendant groups. Accordingly, the polyurethanes can be repeatedly self-healed under UV lights at room temperature by taking advantages of the photodimerization and photocleavage habits of coumarin. Molecular weight of the soft segment, PEG, is found to be closely related to the healing performance of the polyurethanes. Lower molecular weight PEG that corresponds to higher initial coumarin concentration in the polymer is critical for obtaining higher healing efficiency in the case of the first healing action. Nevertheless, it does not guarantee high reversibility of the photo-remendability during the repeated healing events. In contrast, the polyurethane with moderate molecular weight PEG has achieved balanced performance. Reaction kinetics is less important for the healing effect.