Hydroxyl Moieties Research Articles

Catalytic Oxidation of Primary C-H Bonds in Alkanes with Bioinspired Catalysts.

Catalytic oxidation of primary C-H bonds of alkanes with a series of iron and manganese catalysts is investigated. Products resulting from oxidation of methylenic sites are observed when hexane (S1) is used as model substrate, while corresponding primary C-H bonds remain unreactive. However, by using 2,2,3,3-tetramethylbutane (S2) as model substrate, which only contains primary alkyl C-H bonds, oxidation takes place catalytically using a combination of hydrogen peroxide, a manganese catalyst and acetic acid as co-catalyst, albeit with modest yields (up to 4.4 TON). Complexes bearing tetradentate aminopyridine ligands provide the best yields, while a related pentadentate ligand provides smaller product yields. The chemoselectivity of the reaction is solvent dependent. Carboxylic acid 2b is observed as major product when the reaction takes place in acetonitrile, because of the facile overoxidation of the first formed alcohol product 2a. Instead the corresponding primary alcohol 2a becomes dominant in reactions performed in 2,2,2-trifluoroethanol (TFE). Polarity reversal of the hydroxyl moiety arising from the strong hydrogen bond donor ability of the latter solvent accounts for the unusual product chemoselectivity of the reaction. The significance of the current results in the context of light alkane oxidation is discussed.

Effect of surface impurities on downconversion luminescence of Pr3+, Yb3+ activated SrF2 nanoparticles

Pr3+,Yb3+ activated SrF2 nanoparticles synthesized by low-temperature hydrothermal method were studied. The composition and size of nanoparticles were intentionally changed by controlling synthesis conditions. After structural and morphological characterization, the spectroscopic properties of the nanoparticles were analyzed in the visible and near infrared spectra ranges. The results show correlation between the gradual change of the amount of carboxylate and hydroxyl moieties on the nanoparticle surface, varied by the size nanoparticles and the quenching of the luminescence. The size-related amount of surface quenchers is strongly connected to the decrease of the downconversion efficiency.

Band structure, work function and interfacial diagrams of oxygen-functionalized carbon nano-onions

Carbon nano-onions (CNOs) are an emerging class of carbon nanomaterials with a wide range of applications. Few is known about their electronic structure and the factors that affect it. Here, we study for the first time the effect of two oxidation treatments on the electronic structure of CNOs using ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). CNOs were oxidized by physical (Ar/O2 radio frequency plasma) and chemical (HNO3/H2SO4) methods. It was found that the physical oxidative treatment introduced preferentially hydroxyl and carbonyl groups on the outer shells of CNOs and changed the electronic state from metallic to semiconductor with a work function of 4.3 eV and a valence band located 0.2 eV below the Fermi level. In contrast, the chemical oxidation produced CNOs with hydroxyl and carboxylic acid moieties and increased the work function from 4.3 to 4.8 eV with preservation of the metallic structure of CNO. The variations on the electronic structure were explained in terms of the elimination/generation of structural defects on the outer shells of CNO and the electronic effects that resulted from the introduction of different oxygen-containing functional groups on the graphitic layers. The interfacial energy diagrams for pristine and oxidized CNOs were constructed from the UPS data. These diagrams can be used to explain electronic interfacial properties of these materials and the design of novel electrochemical or photovoltaic devices.

Development of a bioavailable boron-containing PI-103 Bioisostere, PI-103BE

PI-103 (7) is a potent dual phosphatidylinositol 3-kinase (PI3K)/mTOR inhibitor, but its rapid in vivo metabolism hinders its further clinical development. To improve the bioavailability of PI-103, we designed and synthesized a PI-103 bioisostere, PI-103BE (9) in which the phenolic hydroxyl group of PI-103 was replaced by a boronate, a structural modification known to enhance bioavailability of molecules containing phenolic hydroxyl moieties. In cell culture, PI-103BE is partially converted to its corresponding boronic acid (10) and to a lesser extent the active ingredient, PI-103. This mixture contributes to the in vitro activity of 9 that shows reduced potency compared to the parent compound. When administered to mice by oral gavage, 9 displays a significantly improved pharmacokinetic profile compared to PI-103, which shows no oral bioavailability at the same dose. Drug exposure of 9 as measured by the area under curve (AUC) value is 88.2 ng/mL*h for 7 and 8879.9 ng/mL*h for 10. When given by intraperitoneal injection (IP), the prodrug afforded an AUC of 32.3 ng/mL*h for 7 and 400.9 ng/mL*h for 10, compared to 9.7 ng/mL*h from PI-103 injection. In plasma from both pharmacokinetic studies, 9 is fully converted to 10 and 7, with the boronic acid metabolite (10) displaying antiproliferative activities comparable to 9, but weaker than 7. The boronic bioisostere of PI-103 thus offers an improved bioavailability that could be translated to in vivo efficacy of PI-103.

Co-delivery of superfine nano-silver and solubilized sulfadiazine for enhanced antibacterial functions.

For the effective treatment of bacterial infection, it is essential to find a new strategy to deliver antibacterial agents. In the present study, the co-delivery of superfine nano-silver with solubilized sulfadiazine (SD) using cyclodextrin metal-organic frameworks (CD-MOF) as a carrier exhibited superior antibacterial efficacy to insoluble silver sulfadiazine. The abundant hydroxyl moieties in CD-MOF were utilized to reduce Ag precursor into silver nanoparticles (Ag NPs) of 4-5nm and immobilized within the nano-sized cavities. Microporous CD-MOF facilitated the inclusion of SD molecules in the hydrophobic cavities of γ-cyclodextrin (γ-CD) molecular pairs. The hydrophilic CD-MOF can easily dissolve within exudates at the wound region to release the drug. This approach improved the aqueous solubility of SD by 50 folds which subsequently enhanced SD release and their antibacterial activity. The CD framework also prevented the aggregation of nano-silver particles, stabilizing the particle size and enhancing the curative effects. Hence, the incorporation of superfine nano-silver with solubilized SD using CD-MOF could be an alternate strategy to co-deliver silver and SD with higher efficacy.

Cloning and heterologous expression of P450Lent4B11, a novel bacterial P450 gene, for hydroxylation of an antifungal agent sordaricin.

Microbial transformation is known to be one of promising options to add functional groups such as a hydroxyl moiety to active base compounds to generate their derivatives. Sordaricin, a diterpene aglycone of the natural product sordarin, is an antifungal agent to selectively inhibit fungal protein synthesis by stabilizing the ribosome/EF-2 (elongation factor 2) complex. We screened actinomycetes to catalyze hydroxylation of sordaricin on the basis that the hydroxyl moiety would make it easier to generate derivatives of sordaricin. As a result of the screening, 6-hydroxylation of sordaricin was found to be catalyzed by Lentzea sp. 7887. We found that the cytochrome P450 inhibitor metyrapone inhibited this reaction, suggesting that a cytochrome P450 may be responsible for the biotransformation. As a next step, we cloned multiple cytochrome P450 genes, one of which were named P450Lent4B11, using degenerate PCR primers. The expressed cytochrome P450 derived from the P450Lent4B11 gene provided a different absorbance spectrum pattern from original one when it was incubated with sordaricin. Moreover, in cell-free conditions, the corresponding cytochrome P450 displayed the 6-hydroxylation activity toward sordaricin. Taken together, these results indicate that P450Lent4B11, derived from Lentzea sp. 7887, should be responsible for catalyzing 6-hydroxylation of sordaricin.

Polyolefin copolymer PE-HEMA with increased metal adhesion properties

Polyethylene (PE) is a great material, but inherently is hard to functionalize. A neat way to introduce functionality is by including small quantities of a functional comonomer into the polymer. A suitable comonomer bearing hydroxyl functionality is 2-hydroxyethyl methacrylate (HEMA). PE-HEMA copolymers may combine the low cost of PE while allowing for addition of functional groups using the hydroxyl moiety. We analyze copolymers with varying amounts of HEMA by studying the influence of the increasing HEMA content on the mechanical properties, which are found to decrease due to a reduced crystallinity of higher HEMA containing samples. The varying degree of crystallinity between polymer samples was identified as the major influence on the β-transition shift of the PE-HEMA copolymers, which was not off-set by the additional hydrogen bonding in the polymers with, for instance, high HEMA content. At temperatures above 220 °C, a permanent cross-linking of the HEMA groups through trans-esterification reaction, can be observed, which can be exploited in applications where cross-linking on demand is necessary. Finally, an improved adhesion of the copolymers to steel and aluminum was demonstrated in lap shear tests, owing to the increased hydrophilicity of the copolymers.

Mild and Chemoselective Thioacylation of Amines Enabled by the Nucleophilic Activation of Elemental Sulfur.

A mild and chemoselective method for the thioacylation of amines using α-keto acids and elemental sulfur has been developed. The key to the success of this transformation is the nucleophilic activation of elemental sulfur by thiols such as 1-dodecanethiol. A variety of functional groups, including unprotected hydroxyl, carboxyl, amide, sulfide, and tertiary amine moieties, are tolerated under the applied reaction conditions. To demonstrate the advantages of this method compared with conventional O-S exchange reactions using Lawesson's reagent or P2S5, thioamide moieties were introduced site-specifically into biologically active compounds.

Synthetic bioactive olivetol-related amides: The influence of the phenolic group in cannabinoid receptor activity

Focusing on the importance of the free phenolic hydroxyl moiety, a family of 23 alkylresorcinol-based compounds were developed and evaluated for their cannabinoid receptor binding properties. The non-symmetrical hexylresorcinol derivative 29 turned out to be a CB2-selective competitive antagonist/inverse agonist endowed with good potency. Both the olivetol- and 5-(2-methyloctan-2-yl)resorcinol-based derivatives 23 and 24 exhibited a significant antinociceptive activity. Interestingly, compound 24 proved to be able to activate both cannabinoid and TRPV1 receptors. Even if cannabinoid receptor subtype selectivity remained a goal only partially achieved, results confirm the validity of the alkylresorcinol nucleus as skeleton for the identification of potent cannabinoid receptor modulators.

First Zinc Bromide Promoted Annulative Domino Reactions between Enamines and Cyclic Morita–Baylis–Hillman Alcohols: Synthesis of N,O-Ketals

A new efficient ZnBr2-mediated annulative domino reaction between enamines and cyclic Morita–Baylis–Hillman (MBH) alcohols is disclosed. The process involves a tandem sequence (intermolecular conjugate addition of enamines to MBH alcohols and intramolecular nucleophilic addition of the hydroxyl moiety to the transiently generated iminium ion), affording the corresponding N,O-ketals diastereoselectively in good yields.

Biocatalytic allylic hydroxylation of unsaturated triterpenes and steroids by Bacillus megaterium CGMCC 1.1741.

In this study, we described the microbial catalyzed allylic oxidation by Bacillus megaterium CGMCC 1.1741 of three Δ12-pentacyclic triterpenes, erythrodiol (1), uvaol (2), hederagenin (3) and of four steroids including Δ5-steroids, diosgenin (4), pennogenin (5), 25(R,S)-ruscogenin (6) and Δ4-steroid, diosgenone (7). As a result, fourteen metabolites were generated with allyl hydroxyl moiety. Ten (1a-c, 2a, 2c, 3a, 5a-b, and 6a-b) of them were new natural products and their structures were determined on the basis of 1D/2D NMR and HR-MS data. Biocatalytic allylic oxidation by B. megaterium CGMCC 1.1741 is thus a potential non-toxic and efficient alternative method toward metal-mediated oxidation procedures in the synthesis of natural products and medicines.

Revealing and comparing different excited‐state intramolecular proton transfer processes for 3‐(4‐dimethylamino‐phenyl)‐1‐(4‐fluoro‐2‐hydroxy‐phenyl)‐propenone and 3‐(4‐dimethylamino‐phenyl)‐1‐(4‐fluoro‐2‐hydroxy‐phenyl)‐3‐hydroxy‐propenon

AbstractTwo novel 2′‐hydroxychalcone derivatives (i.e., M1 and M2) are explored in this work. We mainly focus on investigating the effects of photoexcitation on hydrogen bonds and on the excited‐state intramolecular proton transfer (ESIPT) process. On the basis of calculations of electrostatic potential surface and intramolecular interactions, we verify the formation of hydrogen bond O1H2···O3 in both S0 and S1 states. Exploring the ultraviolet–visible spectra in the liquid phase, our simulated results reappear in the experimental phenomenon. Analyzing molecular geometry and infrared stretching vibrational spectra, we confirm O1H2···O3 is strengthened for both M1 and M2 in the S1 state. We further confirm that charge redistribution facilitates ESIPT tendency. Constructing potential energy curves, we find the ultrafast ESIPT behavior for M1, which is because of the deficiency of side hydroxyl moiety comparing with M2. This work makes a reasonable affiliation of the ESIPT mechanism for M1 and M2. We wish this paper could facilitate understanding these two novel systems and promote their applications.

Development of flavanone and its derivatives as topical agents against psoriasis: The prediction of therapeutic efficiency through skin permeation evaluation and cell-based assay.

Flavonoids inhibit skin inflammation. Previous study suggests that the flavonoids with flavanone backbone were beneficial to penetrate into the skin. We aimed to investigate the possibility of psoriasis treatment by topically applied flavanone and its derivatives including naringenin, hesperetin, 6-hydroxyflavanone, flavanone, and 6-bromoflavone. The skin absorption of the compounds was determined by Franz cells. Molecular modeling was used to compute the physicochemical and molecular parameters of the penetrants in order to elucidate the correlation between structure and permeation. Among the compounds tested, flavanone showed the greatest skin absorption. The in vitro skin absorption predicted efficient skin targeting of 6-bromoflavone with minimal risk of circulation absorption. The permeation of naringenin was remarkably enhanced 13-fold in the barrier-defective skin mimicking inflamed skin. The penetrants with fewer hydrogen bond number, total polarity surface, and molecular volume were advantageous for facile skin absorption. In the cell-based study, IL-1β inhibition in imiquimod (IMQ)-stimulated keratinocytes was increased following the increase in compound lipophilicity. Naringenin, a flavanone analog with three hydroxyl moieties, could suppress IL-6 overexpression to baseline control. We assessed the anti-inflammatory potency of the chemicals in comparison with tacrolimus as reference in a psoriasis-like mouse model. Flavanone was found to mitigate scaling and epidermal hyperplasia at a higher level than naringenin. Flavanone lessened IL-6 overexpression by 80% in the psoriasiform plaque. The skin barrier function recorded by transepidermal water loss (TEWL) was recovered by naringenin but not flavanone. The experimental data indicate that naringenin and flavanone are potential candidates for anti-psoriatic therapy.

Boosting electrosynthesis of ammonia on surface-engineered MXene Ti3C2

Abstract Seeking a breakthrough in the development of efficient nitrogen fixation catalysts has become the frontier of energy and chemical conversion schemes. Here, we report that the MXene Ti3C2 can serve as a promising catalyst for the electrochemical N2 reduction reaction (NRR) under ambient conditions. The electrocatalytic performance of Ti3C2 can be further optimized through surface engineering. Specifically, Ti3C2 with the increased surface hydroxyl moieties demonstrates enhanced production of NH3 with a yield rate of 1.71 μg h−1 cm−2, a Faradaic efficiency of 7.01% at −0.2 V vs. RHE at 20 °C and an even higher yield rate of 12.46 μg h−1 cm−2 together with a Faradaic efficiency of 9.03% at −0.2 V vs. RHE at 60 °C. The detailed electrochemical analysis suggests that the surface hydroxyl modification can effectively facilitate the electron transfer, surface adsorption and activation of dinitrogen. Our work sheds light on the development of efficient NRR catalysts based on earth-abundant elements.

The hydroxyl moiety on carbon one (C1) in the monoterpene nucleus of thymol is indispensable for anti-bacterial effect of thymol

BackgroundThymol, a natural monoterpene phenol is not only relevant clinically as an anti-microbial, anti-oxidant and anti-inflammatory agent but also holds the prospect as a natural template for pharmaceutical semi-synthesis of therapeutic agents. It is a major component of essential oils from many plants. Evidence abound linking overall bioactivity of thymol to its monoterpene nucleus, specifically, the hydroxyl (-OH) substituent on carbon number one (C1) on the monoterpene nucleus. Other studies have posited that the overall bioactivity of thymol is not substantially altered by chemical modification of - OH on the C1 of the monoterpene nucleus. In view of this, it is still unclear as to whether removal or modification of the –OH on C1 of the monoterpene nucleus relates generally or context-dependently to bioactivity of thymol. ObjectiveThe present study investigated anti-bacterial effects of ester-and-ether substituted derivatives of thymol on S. aureus, P. aeruginosa and E. coli. Materials and methodstwelve ester-and-ether substituted derivatives of thymol (6TM1s and 6TM2s) were synthesized and characterized by using HPLC, Mass spectrometry, and IR techniques. Anti-bacterial activity of the 12 thymol derivatives was evaluated using broth macrodilution and turbidimetric methods against pure clinical isolates (S. aureus, P. aeruginosa and E. coli). Standard anti-biotics used were Thymol Streptomycin and flucloxacillin, while DMSO was used as vehicle for thymol derivatives. MIC and MBC were determined. ResultsThymol produced broad-spectrum growth inhibition on all isolates. At equimolar concentrations, thymol and reference drugs produced concentration-dependent growth inhibition against the isolates (Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli) compared to DMSO. Although the growth inhibitory effects of the ester-and-ether derivatives of thymol was significant (P ≤ 0.05) compared to DMSO, it was however insignificant (P ≥ 0.05) compared to thymol and reference antibiotics. Comparatively, at equimolar concentrations, ester-substituted derivatives of thymol, particularly the branched chain derivative (TM1C) produced more effective growth inhibition on the isolates than the ether-substituted derivatives of thymol. Thymol was twice as potent (MIC and MBC, 500 μg/ml) than both ester-and-ether substituted derivatives of thymol (MIC and MBC, > 1000 μg/ml) on all the three clinical isolates. Increase in side chain bulkiness of –OH moiety on the monoterpene nucleus of thymol decreased growth inhibition on isolates. ConclusionThymol has demonstrated broad-spectrum anti-bacterial effects attributable to the hydroxyl moiety on C1 of the monoterpene nucleus. Structural modification of the hydroxyl moiety on C1 of the monoterpene nucleus of thymol with either ether-or-ester substitutions yielded no significant anti-bacterial effects.

Synthesis, properties and biodegradability of cross-linked amphiphilic Poly(vinyl acrylate)-Poly(tert-butyl acrylate)s by photo-initiated radical polymerization

The novel amphiphilic poly(vinyl acrylate)-poly(tert-butyl acrylate) based networks are produced by light-induced photo-initiated radical polymerization between poly(vinyl acrylate) (PVAcr), obtained by using hydroxyl moieties of poly(vinyl alcohol) (PVA), and tert-Butyl acrylate (tBA) monomer. PVA is modified by acryloyl chloride to obtained the corresponding acrylate functionalities (PVAcr). The achieved PVAcr is crosslinked with different amount of tBA (PVAcr:tBA = 0.005:1 and 0.005:2 by mole) to give desired structures (PVAcr-PtBA-1 and PVAcr-PtBA-2) in the presence of 2,2-Dimethoxy-2-phenylacetophenone (DMPA) at λ = 350 nm under nitrogen atmosphere. The structure, wettability, thermal and biodegradability properties of the pristine PVA and achieved networks are evaluated as a function of tBA loading by Fourier transform infrared (FT-IR) spectroscopy, water contact angle (WCA) measurement, thermogravimetric (TGA) and differential scanning calorimetry (DSC) analyses and biodegradation test, respectively. The results indicate that PVAcr-PtBA-2 obtained by higher tBA loading is less hydrophilic and biodegradable, but have improved thermal properties compared to pure PVA, and PVAcr-PVAcr control sample and PVAcr-PtBA-1.

Design, Synthesis, Molecular Modeling and Anti-HIV Assay of Novel Quinazolinone Incorporated Coumarin Derivatives.

The emergence of drug-resistant viral strains has created the need for the development of novel anti-HIV agents with a diverse structure that targets key enzymes in the HIV lifecycle. Considering the pharmacophore of integrase inhibitors, one of the validated targets for anti-HIV therapy, we designed a quinazolinone incorporated coumarin scaffold to affect HIV. Coumarin is a beta enol ester and also a well-known drug scaffold. Designed structures were prepared using a one-pot three-component reaction from 3-amino-4-hydroxycoumarin, isatoic anhydride and benzaldehyde derivatives. In vitro anti-HIV and cytotoxicity assay indicated that more than half of the compounds had EC50 values lower than 50 µM. Unsubstituted phenyl derivative showed the highest activity and selectivity with an EC50 value of 5 µM and a therapeutic index of 7. Compounds were docked into the integrase active site to investigate the probable mechanism of action. Accordingly, the hydroxyl moiety of coumarin along with the carbonyl of the quinazolinone ring could function as the metal chelating group. Quinazolinone and phenyl groups interact with side chains of IN residues, as well. Here, a novel anti-HIV scaffold is represented for further modification and in-vivo studies.

A Schiff base colorimetric chemosensor for CN‐ ion and its dioxidomolybdenum (VI) complexes: Evaluation of structural aspects and optoelectronic properties

Six new cis‐dioxidomolybdenum(VI) complexes featured with a tridentate ONO donor Schiff base derived from salicylidene‐2‐aminophenolato backbone have been synthesised and characterised by elemental analysis, spectroscopic techniques (like IR, UV‐vis and 1H‐NMR) and cyclic voltammetry. Suitable single crystals of the parent complex [MoO2L(MeOH)]2·H2O (1) was obtained by the slow evaporation of the mother liquor, whereas the crystals of the complexes 2‐6 were grown in coordinating solvents like ethanol, DMF, DMSO etc. and were characterised by single crystal X‐ray diffraction as monomers stabilised by the solvent molecules used for the recrystallization purpose. The structures of the complexes were further quantified using Hirshfeld surface analysis. The Schiff base acts as a colorimetric chemosensor for CN‐ ions in DMSO solution. The receptor‐CN‐ ion interaction and the sensing mechanism of the chemosensor were verified by colorimetric, UV‐vis, 1H‐NMR and FT‐IR spectroscopic studies. Hydroxyl moiety present in the receptor function as the binding site for cyanide ion thereby leading to its optical discrimination in presence of other anions by producing a visible colour change from colourless to yellow. Therefore the Schiff base sensor portrays estimable selectivity and sensitivity towards CN‐ ion. Additionally the Schiff base as well as the molybdenum complexes exhibit good third order non‐linear optical properties and optical power limiting when analysed by the Z‐scan technique.

Carbamoylethyl locust bean gum: Synthesis, characterization and evaluation of its film forming potential

The synthesis of carbamoylethyl locust bean gum (CLBG) was optimized using Plackett-Burman design. The generated model showed high significance (p < 0.05) to all the response variables which justifies the authenticity of the designed model. The optimal conditions i.e. acrylamide (5.12 mM), sodium hydroxide (3.00 mM), reaction temperature (50.97 °C) and reaction time (2.00 h) supported maximum -CONH2 content (5.44%), –COOH content (3.04%), degree of substitution (0.85) and product yield (7.25%, w/w). Carbamoylethylation of locust bean gum (LBG) involved substitution of its hydroxyl (-OH) moieties with amide group (-CH2CH2CONH2). FTIR and NMR spectroscopy confirmed the addition of amide group to CLBG. Scanning electron microscopy assured the slight rough surface of CLBG particles. Differential scanning calorimetry showed that carbamoylethylation of LBG lowered its melting temperature range (205.60–272.45 °C). However, the amorphous nature, non-Newtonian flow and shear-thinning behaviour of pure LBG were retained in CLBG. Further, CLBG films prepared with glycerol (1%, w/w, plasticizer) showed partially smooth surface and have clear transversal cross-sections. CLBG-glycerol films were highly water resistant and almost transparent. Further, CLBG-glycerol films showed good tensile strength (18.55 ± 0.02 MPa) and higher percentage elongation (6.11 ± 0.01%). Water vapor transmission rate of CLBG-glycerol film was quite lower (0.211 ± 0.001 g.mm/h.m2.kPa) which verified its higher resistance towards water.

Thermal properties of polyurethane-based composites modified with chitosan for biomedical applications

The thermal properties of chitosan and hydroxyapatite (HAp)-crosslinked polyurethanes (PU) prepared in a two-step bulk polymerization were investigated. Synthesis of PU was carried out using 1,6-hexamethylene diisocyanate, poly(ethylene glycol) 2000 and dibutyltin dilaurate as a catalyst. Various molar ratios of chitosan and 1,4-butanediol were applied, and the effects of incorporating different HAp amounts and the chitosan-to-BDO ratio were studied. It was found that the thermal properties of PU materials depend on polysaccharides and bioceramics load, which was confirmed by differential scanning calorimetry and thermogravimetry. The glass transition temperature increases with increasing chitosan fraction. Similarly, the onset temperature of degradation increased with chitosan addition. On the other hand, the presence of ceramics did not show a significant impact on the thermal properties of PU composites. Successful polymerization and chain extension of the isocyanate groups with hydroxyl moieties from chitosan and HAp were confirmed by Fourier transform infrared spectroscopy, and the morphology was examined using scanning electron microscopy.