Amine-epoxide Reactions Research Articles

A Curable Underwater Adhesive Based on Poly(propylene oxide) and Tannic Acid Coacervate

Coacervation of poly(propylene oxide) and tannic acid, driven by hydrogen bonding, renders a tacky viscous material that provides an underwater adhesion strength of ∼350–550 kPa on aluminum substrates and also can bond other wet surfaces such as glass, metal, plastic, and porcelain. A curing functionality is achieved by designing a two-component system, using epoxidized poly(propylene oxide)/tannic acid coacervate as part A and amine-terminated poly(propylene oxide) as part B. Aside from underwater bonding, this adhesive can cure underwater through amine-epoxide reactions providing a commercially competitive and waterproof bonding.

Novel cross-linked films from epoxy-functionalized conjugated polymer and amine based small molecule for the interface engineering of high-efficiency inverted polymer solar cells

The modification of metal/metal oxide electrode is of great importance to the performance of inverted organic optoelectronic devices. Cross-linked films provide good chance to modify the metal/metal oxide electrode and enable the fabrication of high-performance multi-layer organic optoelectronic devices due to its superior ability to resist solvent erosion. However, most of the reported methods to prepare cross-linked films are suffering from harsh processing conditions such as high-temperature thermal treatment or long-time UV radiation. Here, we develop novel robust cross-linked thin films which are prepared from an epoxy-functionalized conjugated polymer (PFEX) and an amine-based small molecule (TAA). The cross-linking processing can be realized under mild heating due to the highly-efficient amine-epoxide reaction, and the resulting cross-linked films show good solvent resistibility. Moreover, the cross-linked films showed large tolerance with the composition of PFEX and TAA, which provides opportunity to modify the metal/metal oxide electrodes in a wide range using the cross-linked films. The modified indium tin oxide (ITO) using the cross-linked films show much lowered work function and hydrophobic property than pristine ITO, which indicates great potential application in inverted organic optoelectronic devices. Inverted polymer solar cells (IPSCs) using the modified ITO show remarkable enhanced power conversion efficiency (9.4%) than those with pristine ITO (6.8%). Our design and preparation of the novel cross-linked films and the finding on the correlation between cross-linked film and photovoltaic performance will be useful to design and prepare high-performance cross-linked films for inverted organic optoelectronic devices.

Assessing the Potential for the Reactions of Epoxides with Amines on Secondary Organic Aerosol Particles.

Nuclear magnetic resonance techniques were used to study the kinetics and products of the reaction of a variety of epoxides with various amines under varying pH conditions. In agreement with a previous finding, the amine-epoxide reactions were found to be water-catalyzed and not directly dependent on the pH of the reaction environment. At pH values higher than the pK(a) of the particular amine, the amine-epoxide reactions were extremely efficient, outcompeting hydrolysis reactions even for conditions where water was the solvent and the amine was a relatively low-concentration solute. This finding was rationalized by measurements that showed that the relative nucleophilic strength of amines relative to water was on the order of 1000, while the nucleophilic strength of protonated amines (which are predominant when pH < pK(a)) was negligible. The epoxide carbon substitution environment was found to have a large effect on the measured rate constants (more substituted epoxides had slower rate constants), while the amine carbon substitution environment had a much more limited effect. While the amine-epoxide rate constants are large enough such that amine-epoxide reactions may be kinetically feasible for isoprene-derived epoxides and high amine secondary organic aerosol (SOA) concentrations, most atmospheric amines are expected to be present in protonated form on the largely acidic SOA found in the atmosphere and thus are expected to be largely unreactive toward epoxides.

Fabrication, Morphology and Cure Behavior of Triethylenetetramine-Grafted Multiwalled Carbon Nanotube/Epoxy Nanocomposites

Multiwalled carbon nanotubes (MWCNTs) were first treated by a 3:1 (v/v) mixture of concentrated H2SO4/HNO3, and then triethylenetetramine (TETA) grafting was carried out. X-Ray photoelectron spectroscopy and Raman spectroscopy analyses proved the effectiveness of this kind of chemical functionalization method. The TETA thin layer was formed on the MWCNT surface, which contributes to good dispersion of MWCNTs in epoxy matrix. Cure behaviors of MWCNT/epoxy systems were studied with non-isothermal differential scanning calorimetry. MWCNTs have the retarding effect on the cure reaction owing to their steric hindrance, while TETA functional groups on the MWCNT surface can accelerate the primary amine-epoxide reaction and weaken the inhibition effect on the process of cure. A qualitative analysis of the degree of vitrification in different epoxy systems was performed. The activation energy of the cure reactions was obtained by the Flynn-Wall-Ozawa method.

Promotion effect of bifunctional five‐membered cyclic dithiocarbonate on curing of one‐component epoxy resin by imines as latent initiator

AbstractThis article deals with curing of a one‐component epoxy resin containing a bifunctional five‐membered cyclic dithiocarbonate 1 with an imine 2 as a latent initiator. When 1 was added to a mixture of epoxy resin and 2, the curing rate and initial adhesive strength increased higher than that without 1. It was supposed that the reaction of 1 and an amine released from 2 was much faster than the amine–epoxide reaction, and a thiol group formed by the reaction of 1 with the amine accelerated the amine–epoxide reaction. The adhesive strength of the one‐component epoxy resin containing 10 mol % of 1 exhibited the highest value. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 961–964, 2004

MIT process promises jump in efficiency

The modification of metal/metal oxide electrode is of great importance to the performance of inverted organic optoelectronic devices. Cross-linked films provide good chance to modify the metal/metal oxide electrode and enable the fabrication of high-performance multi-layer organic optoelectronic devices due to its superior ability to resist solvent erosion. However, most of the reported methods to prepare cross-linked films are suffering from harsh processing conditions such as high-temperature thermal treatment or long-time UV radiation. Here, we develop novel robust cross-linked thin films which are prepared from an epoxy-functionalized conjugated polymer (PFEX) and an amine-based small molecule (TAA). The cross-linking processing can be realized under mild heating due to the highly-efficient amine-epoxide reaction, and the resulting cross-linked films show good solvent resistibility. Moreover, the cross-linked films showed large tolerance with the composition of PFEX and TAA, which provides opportunity to modify the metal/metal oxide electrodes in a wide range using the cross-linked films. The modified indium tin oxide (ITO) using the cross-linked films show much lowered work function and hydrophobic property than pristine ITO, which indicates great potential application in inverted organic optoelectronic devices. Inverted polymer solar cells (IPSCs) using the modified ITO show remarkable enhanced power conversion efficiency (9.4%) than those with pristine ITO (6.8%). Our design and preparation of the novel cross-linked films and the finding on the correlation between cross-linked film and photovoltaic performance will be useful to design and prepare high-performance cross-linked films for inverted organic optoelectronic devices.

Fourier transform infrared analysis of polycarbonate/epoxy mixtures cured with an aromatic amine

In our previous article, we established that polycarbonate (PC) can react with the diglycidyl ether of bisphenol-A (DGEBA) at 200°C through transesterification and addition reactions, resulting in degraded PC chains with phenolic end groups and also in PC/DGEBA copolymers. However, these reactions can be minimized or eliminated at lower temperatures, below 160°C. In this article, Fourier transform infrared analysis (FTIR) was used to study the curing kinetics of epoxies in the presence of PC. The curing agent was an aromatic amine, diaminodiphenyl methane (DDM). FTIR results showed that the presence of a small amount of PC promoted the amine–epoxide reactions, probably due to the catalytic effect of the phenolic end groups in the PC chains. However, the PC did not alter the epoxy cure reaction mechanism. Two different blending processes were used to premix the PC and DGEBA, namely, solution-blending and melt-blending processes, in order to give different extents of prereactions. If a solution-blending process was used, PC tended to undergo crystallization during an early stage of cure. When a melt-blending process was used, no melting peak was observed in the thermograms of the differential scanning calorimeter (DSC) for the modified epoxies; PC chains bonded to DGEBA during prereaction at 200°C, thus inhibiting the crystallization of PC during cure. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2395–2407, 1998

Fourier transform infrared analysis of polycarbonate/epoxy mixtures cured with an aromatic amine

In our previous article, we established that polycarbonate (PC) can react with the diglycidyl ether of bisphenol-A (DGEBA) at 200°C through transesterification and addition reactions, resulting in degraded PC chains with phenolic end groups and also in PC/DGEBA copolymers. However, these reactions can be minimized or eliminated at lower temperatures, below 160°C. In this article, Fourier transform infrared analysis (FTIR) was used to study the curing kinetics of epoxies in the presence of PC. The curing agent was an aromatic amine, diaminodiphenyl methane (DDM). FTIR results showed that the presence of a small amount of PC promoted the amine–epoxide reactions, probably due to the catalytic effect of the phenolic end groups in the PC chains. However, the PC did not alter the epoxy cure reaction mechanism. Two different blending processes were used to premix the PC and DGEBA, namely, solution-blending and melt-blending processes, in order to give different extents of prereactions. If a solution-blending process was used, PC tended to undergo crystallization during an early stage of cure. When a melt-blending process was used, no melting peak was observed in the thermograms of the differential scanning calorimeter (DSC) for the modified epoxies; PC chains bonded to DGEBA during prereaction at 200°C, thus inhibiting the crystallization of PC during cure. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2395–2407, 1998

Kinetic modelling studies of amine–epoxide reactions: application of radiochemical and numerical techniques

The reaction between phenyglycidyl ether and a series of primary aromatic amines has been studied under conditions where [epoxide][amines](conditions which we categorise as ideal) using a radio-high-performance liquid chromatography (HPLC) method that is shown to be very versatile and capable of wide application. The results show that the small amounts of water present in the reaction medium possess a catalytic role as do the hydroxylated species formed during the course of the reaction. The detailed information so obtained makes it possible to use numerical techniques so that a comparison can be made between a theoretical model and the actual experimental behaviour.

Steric hindrance in the amine–epoxide reaction

AbstractThe effect of steric hindrance on the reaction of silicon‐containing aliphatic amines with phenylglycidyl ether (PGE) has been studied using 13C‐NMR, a technique described by Sojka and Moniz [J. Appl. Polym. Sci., 20, 1977 (1976)]. It was found that steric hindrance produced a large change in the reaction rate of the primary and secondary amine hydrogens, thus leading to a separation of the polymerization and cross‐linking reactions.

Cure kinetics of epoxy formulations of the type used in advanced composites

An analysis of the cure kinetics of three different formulations composed of tetraglycidyl 4,4′-diaminodiphenyl methane (TGDDM) epoxy resin and diaminodiphenyl sulfone (DDS) was performed. A series of isothermal tests was run, and the experimentally obtained results were checked against the proposed kinetic model. An autocatalyzed mechanism with the overall reaction order of 2 was found to adequately describe the cure kinetics. An increase in reaction rate was observed at higher temperature and higher DDS concentration. For a given formulation, the extent of reaction corresponding to the maximum reaction rate was independent of temperature. A secondary exotherm was detected, particularly in formulations with low DDS concentration, at approximately 40% conversion. At that point, the rate of primary amine–epoxide reaction decreases, and other reactions dominate the curing process. Such a mechanism is likely to cause a formation of an inhomogeneous thermoset morphology.

An analysis of the substitution effects involved in diepoxide‐diamine copolymerization reactions

AbstractThe relative reactivity of the functional groups present in aromatic amine and diepoxide monomers has been investigated by gel permeation chromatography. The ratio of rate constants for the consumption of the secondary and primary amine hydrogens involved in the reaction between aniline and phenyl glycidyl ether has been calculated to equal approximately 0.5. In the case of the reaction between N‐methy aniline and diglycidyl ether of bisphenol A (DGEBA) the rate constant ratio for the consumption of the first and second epoxide groups in the DGEBA molecule is also approximately 0.5. In contradiction to previously published data these results suggest that substitution effects are unimportant for aromatic amines as well as DGEBA. Furthermore, etherification side reactions, consuming epoxide groups at the expense of the amine–epoxide reaction, also appear to be insignificant.

New Aspects of the Nucleophilic Opening of Epoxide Rings

Abstract The mechanism of nucleophilic opening of epoxide rings has been investigated by studying the kinetics of (i) amine-epoxide reactions both in the absence and presence of hydroxyl-containing catalysts, (ii) reactions of commercial epoxydiane oligomers of different molecular weights with aromatic diamines ( m -phenylene diamine), and (iii) reactions of epoxides with phenols in the absence and presence of alkali.

Effect of stoichiometric concentration of hardener and percentage styrene oxide diluent on the crosslinking and mechanical properties of an epoxy resin cured with DEAPA

AbstractEpoxy resin was cured with diethylaminopropylamine (DEAPA) in amounts ranging from 10% to 50% of stoichiometric amount. The yield strength of resulting thermosets formed by heat curing at 75°C is found to increase with decreasing amount of hardener. This is attributed to a more densely crosslinked structure resulting from increased tertiary amine‐initiated epoxide–epoxide chain reaction and decreased primary and secondary amine–epoxide reaction. Infrared analysis and swelling data are also presented. Styrene oxide diluent is found to have a moderate effect on mechanical properties in the range from 10 to 25 parts per hundred (phr).

The mechanism of the crosslinking of epoxide resins by amines

Previous work on the kinetics and mechanism of the reaction between amines and epoxides is reviewed, and it is considered that a termolecular mechanism is to be preferred to a bimolecular mechanism. The hypothesis that these reactions proceed via a termolecular hydrogen-bonded transition state is treated kinetically, and is shown to be consistent with previously published work. Energies of activation and entropies of activation of some amine-epoxide polymerizations have been studied by isothermal gel-point measurements, and by the observation of temperature changes during crosslinking. The results are consistent with the conclusion that the transition state is hydrogen bonded. This mechanism, it is concluded, applies to amine-epoxide reactions under all conditions previously studied, and the second-order kinetics reported from studies on dilute aqueous and dilute alcoholic solutions may therefore not be regarded as diagnostic of a bimolecular reaction mechanism.