Epoxy Ring Research Articles

Talaketides A−G, linear polyketides with prostate cancer cytotoxic activity from the mangrove sediment-derived fungus Talaromyces sp. SCSIO 41027

Seven novel linear polyketides, talaketides A−G (1−7), were isolated from the rice media cultures of the mangrove sediment-derived fungus Talaromyces sp. SCSIO 41027. Among these, talaketides A−E (1−5) represented unprecedented unsaturated linear polyketides with an epoxy ring structure. The structures, including absolute configurations of these compounds, were elucidated through detailed analyses of nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HR-MS) data, as well as electronic custom distributors (ECD) calculations. In the cytotoxicity screening against prostate cancer cell lines, talaketide E (5) demonstrated a dose-dependent inhibitory effect on prostate cancer PC-3 cell lines, with an IC50 value of 14.44 μmol·L−1 . Moreover, compound 5 significantly inhibited the cloning formation of PC-3 cell lines and arrested the cell cycle in S-phase, ultimately inducing apoptosis. These findings indicate that compound 5 may serve as a promising lead compound for the development of a potential treatment for prostate cancer.

Vegetable oil-derived polyether-polyester thermosets: Solvent-free synthesis and mechanical properties

Vegetable oils differing in the number and kind of reactive chemical sites were investigated as potential feedstock in reactions involving epoxy rings to produce sustainable polymeric thermosets. Sustainable polyether-polyester matrices were synthesized through the mixing of three different vegetable oils (castor, tung and sunflower oil) with maleic anhydride to promote their chemical activation, and subsequently induce the reaction with polyethylene glycol diglycidyl ether (PEGDGE). The interactions between double bonds and/or hydroxyl groups present in vegetable oils, anhydrides and epoxy rings within a solvent-free medium promote the expected chemical crosslinking, yielding polymeric thermosets that encompass the Green Chemistry tenets. Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry tests were employed to validate the chemical reactions taken place during the synthesis, as well as to monitor the kinetics of curing. Moreover, a rheological characterization was conducted to assess the influence of both the vegetable oil and the ratio of reactive components on the ultimate mechanical properties. Although chemical crosslinking was suitably attained in all the systems studied, a more reinforced network with values of the storage modulus (G’) of 54·105 Pa was obtained in those based on tung oil possessing the higher quantity of reactive functional sites; meanwhile, the presence of hydroxyl groups within the vegetable oil structure led to the production of more flexible thermosets (G’ of 6.2·105 Pa).

Facile preparation of fluorine-containing 2,3-epoxypropanoates and their epoxy ring-opening reactions with various nucleophiles.

We describe herein a facile method to access 2,3-epoxyesters with fluorine-containing substituents at their 3-position starting from the corresponding enoates by utilization of the low-costed and easy-to-handle reagent, NaOCl·5H2O. Because very little has been disclosed about the reactivity of such 2,3-epoxyesters, their epoxy ring opening by a variety of nucleophiles was carried out and we succeeded in clarifying these chemo- as well as regioselective processes proceeding via the SN2 mechanism to mainly afford 2-substituted 3-hydroxyesters usually in a highly anti selective manner.

A Cytochrome P450 Enzyme Catalyses Oxetane Ring Formation in Paclitaxel Biosynthesis

AbstractOxetane synthase (TmCYP1), a novel cytochrome P450 enzyme from Taxus×media cell cultures, has been functionally characterized to efficiently catalyse the formation of the oxetane ring in tetracyclic taxoids. Transient expression of TmCYP1 in Nicotiana benthamiana using 2α,5α,7β,9α,10β,13α‐hexaacetoxytaxa‐4(20),11(12)‐diene (1) as a substrate led to the production of a major oxetane derivative, 1β‐dehydroxybaccatin IV (1 a), and a minor 4β,20‐epoxide derivative, baccatin I (1 b). However, feeding the substrate decinnamoyltaxinine J (2), a 5‐deacetylated derivative of 1, yielded only 5α‐deacetylbaccatin I (2 b), a 4β,20‐epoxide. A possible reaction mechanism was proposed on the basis of substrate‐feeding, 2H and 18O isotope labelling experiments, and density functional theory calculations. This reaction could be an intramolecular oxidation‐acetoxyl rearrangement and the construction of the oxetane ring may occur through a concerted process; however, the 4β,20‐epoxide might be a shunt product. In this process, the C5‐O‐acetyl group in substrate is crucial for the oxetane ring formation but not for the 4(20)‐epoxy ring formation by TmCYP1. These findings provide a better understanding of the enzymatic formation of the oxetane ring in paclitaxel biosynthesis.

A Cytochrome P450 Enzyme Catalyses Oxetane Ring Formation in Paclitaxel Biosynthesis.

Oxetane synthase (TmCYP1), a novel cytochrome P450 enzyme from Taxus×media cell cultures, has been functionally characterized to efficiently catalyse the formation of the oxetane ring in tetracyclic taxoids. Transient expression of TmCYP1 in Nicotiana benthamiana using 2α,5α,7β,9α,10β,13α-hexaacetoxytaxa-4(20),11(12)-diene (1) as a substrate led to the production of a major oxetane derivative, 1β-dehydroxybaccatin IV (1 a), and a minor 4β,20-epoxide derivative, baccatin I (1 b). However, feeding the substrate decinnamoyltaxinine J (2), a 5-deacetylated derivative of 1, yielded only 5α-deacetylbaccatin I (2 b), a 4β,20-epoxide. A possible reaction mechanism was proposed on the basis of substrate-feeding, 2H and 18O isotope labelling experiments, and density functional theory calculations. This reaction could be an intramolecular oxidation-acetoxyl rearrangement and the construction of the oxetane ring may occur through a concerted process; however, the 4β,20-epoxide might be a shunt product. In this process, the C5-O-acetyl group in substrate is crucial for the oxetane ring formation but not for the 4(20)-epoxy ring formation by TmCYP1. These findings provide a better understanding of the enzymatic formation of the oxetane ring in paclitaxel biosynthesis.

Experimental and Theoretical Study on Electron Ionization and Fragmentation of Propylene Oxide─the First Chiral Molecule Detected in the Interstellar Medium.

Propylene oxide, CH3CHOCH2, is the first chiral molecule detected in space and the third C3 oxide detected toward the Sagittarius B2 (Sgr B2 (N)) molecular cloud, the others being propanal, CH3CH2CHO, and acetone, (CH3)2CO. With homochirality being ubiquitous in the building blocks of living matter, the formation and decay paths of propylene oxide in space are of specific interest. Motivated by the significant role of photo- and secondary electrons in astrochemistry, we have studied electron ionization and fragmentation of propylene oxide. Ion appearance energies are determined and compared to threshold values for the respective processes calculated at the G4MP2 level of theory, and potential reaction pathways are computed at the DFT level of theory. Electron ionization is found to destabilize propylene oxide, leading to barrierless opening of the C1-C2 bond of the epoxy ring, hydrogen transfer, and fragmentation over the methyl vinyl ether or rupture of the C2-O bond of the epoxy ring and fragmentation of the allyl alcohol cation as an intermediate, rather than direct bond ruptures.

PH‐responsive polyurethane‐acrylate from palm olein and sunflower oil: Sustainable synthesis, enhanced lovastatin solubility, and potential drug carrier for targeted delivery

AbstractA pH responsive non‐isocyanate polyurethane‐acrylate (NIPUA) is synthesized through utilizing palm olein and sunflower oil as feedstock. The unsaturated acyl chains of both vegetable oils are converted into epoxy rings through epoxidation and subjected to carbonation with binary catalytic system under a solventless and mild condition to produce the cyclic carbonates. The cyclic carbonates were reacted with 1,4‐butanediamine and itaconic acid to produce the NIPUA. The intermediates and product were characterized by FTIR spectroscopy, NMR spectroscopy and gel permeation chromatography. The NIPUA was incorporated with poly(vinyl pyrrolidone) (PVP) to form a polymer carrier system loaded with a hydrophobic model drug, lovastatin (LOV). All NIPUA/PVP preformulations demonstrated pH responsiveness, with 1 to 2‐folds enhanced solubility at pH 7.4 compared to pH 2.0. NIPUA/PVP exhibited solubility enhancer effect by significantly enhanced solubility (2–4 times) compared to pure LOV, LOV‐loaded PVP, and Medostatin tablets at both pH levels. LOV‐loaded NIPUA/PVP exhibited lower enthalpy energy in DSC thermogram than LOV‐loaded PVP, indicating disruption of LOV's crystalline structure. In MTT assay, IC50 values were 30.76 μg mL−1 for pure LOV and 273.53 μg mL−1 for NIPUA/PVP, demonstrating the potential of NIPUA as an environmentally friendly, pH responsive drug carrier for controlled release of poorly water‐soluble drugs.

Cationic UV-curing of bio-based epoxidized castor oil vitrimers with electrically conductive properties

The growing appeal of carbon nanotube composites in the contemporary market derives from their exceptional thermal and chemical stability, coupled with electrical conductivity. In this study, we combined these salient features with a biobased epoxy matrix having vitrimeric properties, hence being reprocessable and resheapable, to obtain a biobased conductive coating. Epoxidised castor oil (ECO) was chosen as a monomer precursor for the straightforward synthesis. The synthesis relied on a cationic UV-curing process, embedding the conductive carbon nanotubes in the matrix. Photo DSC and transmission FTIR analysis were conducted to determine the final conversion of the epoxy rings in the cationic photocuring process. Thermo-mechanical properties were evaluated by tensile tests, and DMTA. Thermal stability was assessed by TGA. Dielectric spectroscopy confirmed increased electrical conductivity in the presence of increasing CNT content, reaching a percolation threshold at 0.5 phr of CNTs. Vitrimeric properties were proved by stress relaxation experiments, and the UV-cured composite underwent a thermo-activated transesterification reaction starting from 70 °C, catalysed by dibutyl phosphate. Overall, the ECO-CNT composite showed high thermal resistance (up to 400 °C) electrical conductivity with 0.5 phr CNT concentration, and vitrimeric properties. The study can be, therefore, considered a promising starting point to obtain sustainable biobased and electrically conductive vitrimers.

Evaluation of the curing reaction of epoxy resins by electrochemical measurement and molecular orbital method

Epoxy resin is a thermosetting resin with excellent mechanical properties. It has been pointed out that there are problems on its mechanical properties due to poor polymerization of the epoxy ring caused by water and chlorine impurities during resin production. In this study, we focused on the electrochemical behavior during curing reaction of epoxy resin. To investigate the electrochemical reaction, galvanostat meter was used to measure the voltage behavior during chemical reaction. Molecular Orbital (MO) method was used to understand the mechanisms of voltage behavior during curing reaction. Furthermore, the effect of water existence during curing reaction was investigated by experimentally and analytically. As a result of experimental electrochemical reaction, we successfully measured the voltage behavior associated with the curing reaction. In the case of MO analysis, the epoxy and curing agent models were prepared. Before the reaction, each molecule had zero charge, but after the reaction, it was confirmed that the epoxy had a positive charged and the amine had a negative charged. It is thought that the voltage could be observed due to the movement of this charge during curing reaction. It has been also demonstrated through experimentation and analysis that water accelerates the curing reaction. It was observed that the accelerating effect amplifies as the quantity of water increases. Building upon these results, it was confirmed that the factor leading to the increase in voltage is due to the amount of water. To examine the presence of chlorine impurities during the production of epoxy resin, MO analysis was conducted on the production reaction of epoxy prepolymers. The findings indicated that as the water content increases, the reaction that results in the production of by-products is amplified. This outcome suggested that by-products were already incorporated during the formation of the epoxy. In conclusion, this study provides significant insights into the electrochemical behavior during the curing reaction of epoxy resin, the role of water in accelerating the reaction, and the impact of chlorine impurities during resin production. The findings pave the way for further research to optimize the production process and enhance the mechanical properties of epoxy resin.

Enhancing Volumetric Stability of Metakaolin-Based Geopolymer Composites with Organic Modifiers WER and SCA

Shrinkage during hardening and curing is one of the largest challenges for the widespread application of metakaolin-based geopolymers (MKGs). To solve this problem, a silane coupling agent (SCA) and waterborne epoxy resin (WER) were used to synthesize MKG composites. The individual and synergistic effects of the SCA and WER on chemical, autogenous, and drying shrinkage were assessed, the modification mechanisms were investigated by microstructural characterization, and shrinkage resistance was evaluated by the chloride ion permeability of MKG composite coatings. The results showed that the SCA and WER significantly decreased the chemical shrinkage, autogenous shrinkage, and drying shrinkage of the MKG, with the highest reductions of 46.4%, 131.2%, and 25.2% obtained by the combination of 20 wt% WER and 1 wt% SCA. The incorporation of the organic modifiers densified the microstructure. Compared with the MKG, the total volume of mesopores and macropores in MKG-WER, MKG-SCA, and MKG-WER-SCA decreased by 11.5%, 8.7%, and 3.8%, respectively. In particular, the silanol hydrolyzed from the SCA can react with the opened epoxy ring of the WER and the aluminosilicate oligomers simultaneously to form a compact network and resist shrinkage during the hardening and continuous reaction of the geopolymer. Furthermore, the apparently lowered chloride ion diffusion coefficient of concrete (i.e., reduction of 51.4% to 59.5%) by the WER- and SCA-modified MKG coatings verified their improved shrinkage resistance. The findings in this study provide promising methods to essentially solve the shrinkage problem of MKGs at the microscale and shed light on the modification mechanism by WERs and SCAs, and they also suggest the applicability of MKG composites in protective coatings for marine concrete.

Aromatic amination of refined rice bran oil previously epoxidized with Novozym 435

Objective: To aromatically aminate refined rice bran oil (RBO), a by-product of the rice agro-industry,through a chemical-enzymatic epoxidation based on Novozym 435 and p-xylylenediamine insertion.Design/Methodology/Approach: Refined RBO was epoxidized with H2O2/Novozym 435. The resultingepoxidized rice bran oil (eRBO) was functionalized with the p-xylylenediamine aromatic diamine via epoxyring-opening (X-eRBO), using ZnCl2 as catalyst. Iodine value (IV), saponification value (SV), and oxiraneoxygen content (OOC) were determined to evaluate structural changes in oils. The RBO, the eRBO, and theX-eRBO were identified using FTIR, 1H, and 13C NMR.Results: The IV, the SV, and the OOC suggest that the synthesis of eRBO and X-eRBO were effective. Theincrease of molecular weight in eRBO point to the formation of 6 epoxy rings per original triglyceride. TheOOC value of X-eRBO was 22% lower than the OOC value of eRBO, implying that an effective aromaticamination was achieved. The FTIR, 1H and 13C NMR spectroscopy analysis confirmed the epoxidation andamination of the RBO.Study Limitations/Implications: X-eRBO may be a feasible precursor for value-added products, such ascrosslinked polymers or corrosion inhibitors.Findings/Conclusions: Refined rice bran oil was aromatically aminated after two stages under mild thermal conditions. This result was achieved with an epoxidation sequence with H2O2/Novozym 435, followed byfunctionalization with p-xylylenediamine.

Quantum Mechanical/Molecular Mechanical Elucidation of the Catalytic Mechanism of Leukotriene A4 Hydrolase as an Epoxidase.

Leukotriene A4 hydrolase (LTA4H) functions as a mono-zinc bifunctional enzyme with aminopeptidase and epoxidase activities. While the aminopeptidase mechanism is well understood, the epoxidase mechanism remains less clear. In continuation of our prior research, we undertook an in-depth exploration of the LTA4H catalytic role as an epoxidase, employing a combined SCC-DFTB/CHARMM method. In the current work, we found that the conversion of LTA4 to leukotriene B4 (LTB4) involves three successive steps: epoxy ring opening (RO), nucleophilic attack (NA), and proton transfer (PT) reactions at the epoxy oxygen atom. Among these steps, the RO and NA stages constitute the potential rate-limiting step within the entire epoxidase mechanism. Notably, the NA step implicates D375 as the general base catalyst, while the PT step engages protonated E271 as the general acid catalyst. Additionally, we delved into the mechanism behind the formation of the isomer product, Δ6-trans-Δ8-cis-LTB4. Our findings debunked the feasibility of a direct LTB4 to iso-LTB4 conversion. Instead, we highlight the possibility of isomerization from LTA4 to its isomeric conjugate (iso-LTA4), showing comparable energy barriers of 5.1 and 5.5 kcal/mol in aqueous and enzymatic environments, respectively. The ensuing dynamics of iso-LTA4 hydrolysis subsequently yield iso-LTB4 via a mechanism akin to LTA4 hydrolysis, albeit with a heightened barrier. Our computations firmly support the notion that substrate isomerization exclusively takes place prior to or during the initial substrate-binding phase, while LTA4 remains the dominant conformer. Notably, our simulations suggest that irrespective of the active site's constrained L-shape, isomerization from LTA4 to its isomeric conjugate remains plausible. The mechanistic insights garnered from our simulations furnish a valuable understanding of LTA4H's role as an epoxidase, thereby facilitating potential advancements in inhibitor design.

The Synthesis and Application of Novel, Star-Shaped Surfactants for the Destabilization of Water in Arabian Heavy Crude Oil Emulsions

Water in heavy crude oil (W/O) emulsions, which are stubborn mixtures of immiscible heavy crude oil and brine, are a ubiquitous challenge in the petroleum industry. They cause serious corrosion problems, increase the viscosity of petroleum and make the production cost very high. This phenomenon appears during the production of crude oil and should be treated to maximize the overall profitability of oil production and meet transportation requirement. Surfactants are some of the most useful demulsifiers and play a pivotal role in breaking brine/oil emulsions. Herein, we aimed to combine ethyleneamine units and ethyleneoxide units to prepare star-shaped surfactants and test the effect of this combination on the demulsification performance. First, diethylenetriamine reacted with glycidyl 4-nonyl ether (GNE) through an epoxy ring opening to prepare trinonyl phenoxy diethylenetriamine (TNDT). Then, ethylene oxide units were introduced via the interaction of hydroxyl groups with 2-(2-chloroethoxy)ethanol to form ethoxylated trinonyl phenoxy diethylenetriamine (ETNDT). The chemical structures of the surfactants were verified via FTIR and NMR characteristic techniques. The surfactants were applied as demulsifiers for W/O emulsions. It was found that the introduction of the ethyleneoxide units enhanced the solubility of the water and the demulsification performance of the prepared surfactants. The demulsification efficiency was enhanced via ethoxylation and reached 100% for ETNDT for most of the W/O emulsions.

Synthesis of androstane derivatives fused with polyheterocycles at the D ring

An unusual reaction of 16α,17α-epoxypregn-5-en-20-one with 3-amino-5-mercapto-1,2,4-triazole is accompanied by the heterocyclization involving epoxy ring opening and results in a mixture of new androstane derivatives fused with polyheterocycles at the D ring. Such polyheterocycles belong to 3-thia-1,2,8,8b-tetraazaacenaphthylene and 1,2a,7,7b-tetraazacyclopenta[cd]indene-2-thione families incorporating isomeric [1,2,4]triazolopyrimidine systems

Utilization of dry-method styrene-butadiene-styrene and epoxy polymer to enhance the aged asphalt binder: Properties evaluation and cost discussion

To reduce the cost of epoxy asphalt mixture (EAM) pavement and increase the performance of mixture with high reclaimed asphalt pavement (RAP) content, three different dry-method styrene-butadiene-styrene (SBS) modifiers and an epoxy polymer (EP) were employed in this study to enhance the properties of aged asphalt binder and prepare SBS-modified epoxy reclaimed asphalt (SERA) binders. The chemical interaction between the dry-method SBS and EP was analyzed, and the microscopic structure and mechanical properties of the SERA binder were evaluated. Additionally, a discussion on the initial material cost of the newly proposed SERA mixture (SERAM) was conducted. Results indicated that the degraded products generated by the oxidization of dry-method SBS undergo interactive reactions with the epoxy rings present on the epoxy resin molecules. Phase separation occurred both between EP and SBS-containing aged asphalt binder, and between SBS and aged asphalt binder. The addition of dry-method SBS to epoxy reclaimed asphalt (ERA) increased the size of the asphalt binder phase in the fluorescence images. At EP contents ranging from 30% to 50%, the incorporation of dry-method SBS led to notable improvements in the elongation at peak, low-temperature properties, and fatigue resistance of ERA binder. The SERA binder exhibited comparable or even superior properties in terms of tensile strength, low-temperature behavior, and fatigue properties when compared to virgin epoxy asphalt (EA) binder. However, dry-method SBS may have a negative impact on the high-temperature properties and curing time of the binder. Dry-method SBS with rejuvenation capacity exhibited the greatest improvement in elongation at peak, low-temperature properties, and fatigue properties of ERA. Compared to EAM, the utilization of SERAM results in material cost-savings of approximately 46 USD (9%) per ton of mixture.

Chemistry of new polyfluorinated oxiranyl anions and epoxy silanes

The reaction of partially fluorinated epoxides with strong, hindered bases in the presence of electrophiles resulted in functionalization of the epoxy ring. For example, the reaction of hexafluoroisobutene epoxide with LDA and trimethyl- or triethychlorosilanes at low temperature led to the formation of the corresponding epoxy silanes. In the case of the E- and Z-epoxides of 1,1,1,3,3,3-hexafluorobutene-2, the deprotonation step can be successfully carried out using i-PrMgCl.LiCl (Turbo Grignard reagent), and the reaction with chlorosilanes can be carried out at ambient temperature, which significantly simplifies the synthetic protocol. The process was found to be stereospecific, proceeding with complete retention of configuration of the epoxide ring and giving access to pure E- or Z-isomers of the corresponding epoxy silanes. Using this protocol, the corresponding epoxy silanes were also prepared from the epoxides of E-3,3,3,1-tetrafluoropropene-1 and 3,3,3-trifluoropropene-1.The new silanes were demonstrated to be convenient reagents for the transfer of a fluorinated epoxy moiety to carbonyl compounds under fluoride anion catalysis. This process was shown to proceed with complete retention of the geometry of the epoxy ring.

Computational Study on Radical-Mediated Thiol-Epoxy Reactions.

Radical-mediated thiol-epoxy reactions were elucidated for analyzing the overlap problem of the thiol-ene/thiol-epoxy systems using computational approaches. Nine epoxy model molecules were evaluated to mimic the chemical structures and reactivity of some industrial epoxy molecules. Modeling reaction mechanisms was conducted through density functional theory (DFT) calculations using the M06-2X/6-31+G(d,p) level at 1.0 atm and 298.15 K. An analog thiol-ene mechanism was proposed for radical-mediated thiol-epoxide reactions. Unlike the thiol-ene reactions, the addition reaction to epoxides is relatively slow (rate constants <10-4 M-1 s-1). However, the chain transfer, which paves the way for the overlapping of dual curing systems, is quite fast (rate constants >101 M-1 s-1). High stability of thiyl radicals, epoxy ring strain, and the instability of formed alkoxy radical from addition reaction were emphasized as the main driving forces for the reaction energetics and kinetics. Control of temperature and using certain thiols are strongly recommended to avoid curing step overlap based on the findings in this study.

Ceramic bodies without warping using epoxide–acrylate hybrid ceramic slurry for photopolymerization‐based 3D printing

AbstractTo be able to produce ceramic bodies with complex shapes without interlayer delamination and warping through vat photopolymerization‐based 3D printing techniques, photosensitive ceramic slurries should be studied to prepare 3D printed green and sintered bodies. In this study, we developed dual curable acrylate–epoxide ceramic slurries for digital light processing (DLP) 3D ceramic printing. The dual curing process of the slurries is a combination of photo‐radical polymerization of acrylate and thermal cationic polymerization of cyclo‐aliphatic epoxide. The green bodies prepared by dual curing of the slurries showed higher fracture strength and better adhesion between layers and between starting particles and binder polymer in comparison to acrylate‐based green body. These advantages were due to higher crosslinking density of the binder matrix and hydrogen bonding by hydroxyl groups from epoxide ring opening. The green and sintered bodies printed with improved slurry and DLP 3D printer had flat shape without warping unlike those from acrylate‐based bodies. Moreover, the distribution of inter‐particle necking in the sintered body was uniform and the interface boundary between layers was not observed. This is because of excellent uniformity of the dual cured acrylate–epoxide polymer matrix (uniform crosslinking density in layers) in the green body and hydroxyl groups generated by epoxy ring opening.

Synthesis of 22- and 23-dehydroxybrassinosteroids of the stigmastane series

The synthesis of previously undescribed 22- and 23-deoxyanalogues of homocastasterone has been carried out, which makes it possible to obtain target compounds without replacing the carbon skeleton of the side chain. The key reactions in their synthesis were epoxy ring opening and radical debromination.

Interfacial bond characterization of epoxy adhesives to aluminum alloy and carbon fiber-reinforced polyamide by vibrational spectroscopy

Vibrational spectroscopic technique has been utilized to investigate interfacial bonding chemistry of two epoxy adhesive products, XP0012 and XP5005F, on plasma-treated AA6061 and carbon fiber-reinforced polyamide 66 (CFRP-PA66) surfaces. The change in vibrational peak ratios was measured by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy to deduce bonding mechanisms. Both adhesives showed strong crosslinking polymerization of hydroxyl- and amine-initiated epoxy ring opening on AA6061 surface, but on CFRP surface XP0012 formed a simple amide linkage by the reaction of surface hydroxyl groups and nitrile groups of curing agent, and XP5005F formed a crosslinked network by hydroxyl-initiated epoxy ring opening polymerization. The different interfacial bonding formation of two adhesives on CFRP-PA66 surface is attributed to additive effect. Addition of additives to epoxy adhesives (XP5005F) changed the interfacial bonding mechanism on CFRP-PA66 surface, rather forming hydroxyl-initiated epoxy opening crosslinking polymerization than a simple amide bond formation (XP0012). The interfacial bonding chemistry was also proved by addition of bisphenol A (BA) to a simplified model diglycidyl ether of bisphenol A/dicyandiamide (DGEBA/DICY) epoxy system. When BA was added to the model DGEBA/DICY system, epoxy ring gradually decreased on CFRP-PA66 surface, while without BA, DGEBA/DICY showed only decrease in a nitrile peak intensity in ATR-FTIR. The foregoing different types of interfacial chemical bonds at the adhesive/CFRP-PA66 interfaces can affect the lap shear behavior of the joint.