Epoxy-amine polymers obtained upon curing with adamantane diamines

The versions of modification of epoxy polymers upon curing of epoxy-diane oligomers with adamantane diamines and adamantane-containing imidazolines that are close in basicity to aliphatic amines are considered. The parameters of their manufacturability, life and curing times, and parameters that characterize the adhesion strength are defined. The effect of an increase in the functionality of epoxy compounds on the thermal stability of epoxy adamantane-containing polymers is established.     

Kinetics of curing of epoxy oligomers with adamantane diamines

The kinetics of curing of diglycidyl ester of diphenylolpropane (the first homolog of epoxy-diane oligomers) with diaminomethyladamantane is studied. It is shown that, at the initial stage, the autocatalytic polycondensation is developed which is characterized by an increase in viscosity, branching of a macromolecule, and increasing intermolecular interactions.     

Mechanism of formation,structure, and properties of heat-resistant network polymers prepared by thermal curing of Rolivsans

The mechanism of structural transformation of divinylaromatic formulations containing methacrylates of secondary aromatic alcohols and diols into heat-resistant and strong glassy network polymers was examined. The structure and properties of the products were studied. The Rolivsans prepared demonstrate the possibility of chemical construction of high-temperature thermosets in which molecules with thermally stable ether groups and labile ester groups, providing excellent process properties of the formulation in the low-temperature step of the reactive forming, are capable of transforming into heat-resistant network polymers.     

Arylation of adamantanamines: V. Palladium-catalyzed amination of isomeric chloroquinolines with diamines of the adamantane series

Palladium-catalyzed arylation of diamines of the adamantane series with isomeric 2-, 4-, and 6-chloroquinoline was studied, and optimal conditions for the synthesis of the corresponding N,N′-diaryl derivatives were found. N,N-Diarylation products of primary amino groups in the diamines bearing 2-aminoethyl and 4-aminophenyl substituents were readily formed.     

Formation,structure, and elasticity of loosely crosslinked epoxy-amine networks. I. Statistics of formation

Using the theory of branching processes based on cascade substitution, relations are derived for structural parameters characterizing network formation from diepoxide, monoepoxide, and diamine for various initial compositions. The different reactivities of the hydrogen atoms of the primary and secondary amino groups (the latter being formed in the reaction) and possibly different reactivities of epoxy groups in diepoxide and monoepoxide are taken into account. Relations are derived for the critical conversion at the gel point and for changes as a function of conversion in the average molecular weight in the pregel stage, changes in the sol and gel contents, effective functionality of the crosslinks, and concentration of elastically active network chains. The derivation includes the trapping factor that appears in the theory of permanent interchain interactions (trapped entanglements) of the Langley type. An analysis of the approximation usually employed in the statistical theory based on network formation from dyads of structural units shows that this approach is quite satisfactory for small differences in the reactivities of epoxy groups in diepoxide and monoepoxide.     

Investigation of kinetics of curing of triglycidyl-p-aminophenol with aromatic diamines by differential scanning calorimetry

The kinetics of curing of triglycidyl-p-aminophenol with four different diamines in stoichiometric amounts were investigated by means of differential scanning calorimetry. The results indicated that the curing reaction follows first-order Arrhenius kinetics with an activation energy in the range 40–70 kJ · mol^–1. The effect of the structure of the curing agent on the curing characteristics is discussed on the basis of the curing characteristics and the kinetic parameters. An epoxy fortifier was observed to lower the curing temperature of an epoxy-amine system when incorporated prior to curing.

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Zusammenfassung Mittels Differential-Scanning-Kalorimetrie wurde die Kinetik der Vernetzung von Triglycidyl-p-aminophenol mit stöchiometrischen Mengen vier verschiedener Amine untersucht. Laut den Ergebnissen verläuft die Vernetzungsreaktion mit einer Arrhenius-Kinetik erster Ordnung, wobei die Aktivierungsenergie im Bereich von 40–70 kJ/mol liegt. Auf Grundlage der Vernetzungscharakteristika und der kinetischen Parameter wird der Einfluss der Struktur des Vernetzungsreagenz auf die Vernetzungskenndaten beschrieben. Mit einem vor der Vernetzung eingebrachten Epoxyfortifyers konnte die Vernetzungstemperatur eines Epoxy-Amin-Systemes heruntergesetzt werden.

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One of the authors (R.D.P.) is grateful to the University Grants Commission, New Delhi, for the award of a Research Associateship under the Special Assistance Programme.     

Flexibility of macromolecules and structure formation in amorphous polymers

The reflection indicating the presence of nanostructures with a coherence length of ~10 nm is found for the first time on the wide-angle X-ray diffraction patterns of amorphous polymers. It is shown that the structural organization in the amorphous polymers is formed much more rapidly and effectively if macromolecules contain regions with increased local flexibility or short spacings with another mechanism of hindered internal rotation around single bonds than that in the chain. Average intermolecular distances in the polymers with nanostructures are substantially smaller than those in the structureless ones. The temperature range of existence of the structural organization in the amorphous polymers above their glass-transition temperature becomes narrower with an increase in the kinetic rigidity of macromolecules.     

Arylation of adamantanamines: VI. Palladium-catalyzed arylation of amines and diamines of the adamantane series with 3-bromopyridine

Palladium-catalyzed amination of 3-bromopyridine with amines of the adamantane series in the presence of Pd(dba)₂/L [L = 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl or 2-dimethylamino-2′-dicyclohexylphosphinobiphenyl] gave the desired N-(pyridin-3-yl)-substituted amines in 74–97% yields. Diamines of the adamantane series reacted with 2 equiv of 3-bromopyridine in a complicated fashion to produce mono- and triaryl-substituted derivatives as by-products, while the yields of N,N′-diarylation products were 18–56%.     

Effect of vibration in processes of structure formation in polymers

It was shown that the strength characteristics of the samples produced from thermoplastics (low density polyethylene, polyamide 6, Armamid, and polyethylene terephthalate) increase as a result of short vibration treating with a frequency close to that of natural vibrations of the structural elements.     

Unconventional multiple ring structure formation from evaporation-induced self-assembly of polymers

The formation of multiring deposits of poly(2-vinylpyridine) (P2VP) from the evaporation of a P2VP-(2,6-lutidine + water) drop on a glass substrate does not conform to the conventional pinning-depinning mechanism. Instead, ringlike deposits are formed when the droplet undergoes several cycles of spreading and receding where, for each spreading event, a P2VP ridge is formed at the contact line when the polymer flows toward the outward advancing edge. The complex interplay between an outward solutal-Marangoni flow due to a higher concentration of the polymer at the contact line and an inward solvent-Marangoni flow arising from the differences in volatilities and surface tensions of the pure solvent components plays an important role in enhancing the droplet spreading rate. The newly discovered surface patterning mechanism has important implications in the development of novel techniques for inducing self-assembly of functional materials from evaporating drops.     

Differences in structure growth in amine curing of diglycidyl ether of bisphenol a and N,N-diglycidylaniline epoxy resins: Bifunctional models

The reaction of diepoxides, diglycidylaniline (DGA), or diglycidyl ether of Bisphenol A (DGEBA) with aniline was followed using HPLC and SEC. The effect of molar ratio of reagents, dilution of the system, reaction temperature, and the difference between the reaction mechanisms for DGA and DGEBA systems on the reaction kinetics and molecular weight evolution is discussed. Molecular weights of the DGA-aniline polymers were by an order of magnitude lower than those of the DGEBA-aniline polymers due to the formation of small cyclic products in the former case. Also, a reduction in M_n with increasing temperature, dilution, and diluent polarity is brought about by a greater tendency toward cyclization under these conditions. Theoretically calculated molecular weight evolution during the reaction is in satisfactory agreement with the experiment. © 1995 John Wiley & Sons, Inc.     

Effect of molecular structure of curing agents on cyclic creep in highly cross-linked epoxy polymers

Ratcheting behavior of highly–cross-linked epoxy polymers was investigated considering the effect of molecular structure of curing agents by molecular dynamics simulations. Cyclic loading–unloading simulations at two different frequencies were conducted using atomistic models for epoxies cured by aliphatic and aromatic curing agents, triethylenetetramine (TETA) and diethyltoluenediamine (DETDA), respectively. Different ratcheting strain evolutions, dihedral angle stress accumulations, and stiffness variations were observed during the cyclic deformation simulations depending on the molecular structure of curing agents. The epoxy cured by DETDA exhibited a more rapid increase of ratcheting strain and a decrease of the stiffness toward the loading direction. Structural analyses were carried out by observing the orientation order parameter of the monomers, radius of gyration, and free volume evolution to understand the ratcheting strain behaviors and stiffness variations at atomistic scale. The structural analyses revealed that irreversible dihedral angle transitions near the benzene ring of the curing agent DETDA were responsible for low ratcheting resistance and stiffness degradation during the cyclic deformations. Whereas, the aliphatic curing agent TETA, which does not exhibit any stress possession by the irreversible dihedral angle change, was revealed to be advantageous for the ratcheting resistance and stiffness variation of the epoxy polymers.     

Syntheses of optically active polymers by condensation polymerization of d-tartaric acid with some diamines

In order to synthesize optically active polymers which have asymmetric carbon atoms in the polymer main chain, polyamides were synthesized at high temperatures by the condensation of the salt prepared from d-tartaric acid with diamines, such as hexamethylenediamine, o-, m-, and p-phenylenediamine. Effects of the solvent, polymerization time, intrinsic viscosity, and pH on the degree of the specific rotation of polyhexamethylene-d-tartaramide, were investigated. From the results of hydrolyses of the polymers, it was found that d-tartaric acid is not racemized during condensation polymerization.     

Study of the processes of epoxyallyl polymer formation of IPN type upon curing of oligomer-oligomer mixtures

The process of epoxyallyl polymer formation upon curing of oligomers, proceeding simultaneously in independent directions, was studied. A significant mutual influence of epoxy and allyl groups on the level of transformation was established.     

Structure of tetracarbonylethyleneosmium: ethylene structure changes upon complex formation

Rotational spectra of seven isotopomers of tetracarbonylethyleneosmium, Os(CO)4(eta2-C2H4), were measured in the 4-12 GHz range using a Flygare-Balle-type pulsed-beam Fourier transform microwave spectrometer system. Olefin-transition metal complexes of this type occur extensively in recent organic syntheses and serve as important models for transition states in the metal-mediated transformations of alkenes. Three osmium ((192)Os, (190)Os, and (188)Os) and three unique 13C isotopomers (13C in ethylene, axial, and equatorial positions) were observed in natural abundance. Additional spectra were measured for a perdeuterated sample, Os(CO)4(eta2-C2D4). The measured rotational constants for the main osmium isotopomer ((192)Os) are A = 929.3256(6), B = 755.1707(3), and C = 752.7446(3) MHz, indicating a near-prolate asymmetric top molecule. The approximately 140 assigned b-type transitions were fit using a Watson S-reduced Hamiltonian including A, B, C, and five centrifugal distortion constants. A near-complete r0 gas-phase structure has been determined from a least-squares structural fit using eight adjustable structural parameters to fit the 21 measured rotational constants. Changes in the structure of ethylene on coordination to Os(CO)4 are large and well-determined. For the complex, the experimental ethylene C-C bond length is 1.432(5) A, which falls between the free ethylene value of 1.3391(13) A and the ethane value of 1.534(2) A. The angle between the plane of the CH2 group and the extended ethylene C-C bond ( angleout-of-plane) is 26.0(3) degrees , indicating that this complex is better described as a metallacyclopropane than as a pi-bonded olefin-metal complex. The Os-C-C-H dihedral angle is 106.7(2) degrees , indicating that the ethylene carbon atoms have near sp3 character in the complex. Kraitchman analysis of the available rotational constants gave principal axis coordinates for the carbon and hydrogen atoms in excellent agreement with the least-squares fit results. The new results on this osmium complex are compared with earlier work on the similar complex, tetracarbonylethyleneiron (Fe(CO)4(eta2-C2H4)). The ethylene structural changes upon coordination to the metal are found to be larger for the ethylene-osmium complex than for the analogous ethylene-iron complex, consistent with the expected greater pi donation for the osmium atom.     

Ring formation during the reaction of aromatic diamines with acetoacetic acid esters

It is shown that the reaction of aromatic o-diamines having a nitro group in the para position relative to one of the amino groups with acetoacetic esters under mild conditions gives arylaminocrotonates, which are isomerized to ketimines under the influence of acid, are cyclized to dihydro-1,5-benzodiazepinones on heating, and are converted to 1-isopropenylbenzimidazolones under more severe conditions. If the condensation of the nitrodiamine with the acetoacetic acid esters is carried out under severe conditions, the isomeric dihydro-1,5-benzodiazepinone is obtained. Splitting out of an alkylacetate ester to give the corresponding 2-methylbenzimidazole occurs in the condensation of various o-diamines with 2-alkylacetoacetic esters.     

Effects of liquid crystalline structure formation on the curing kinetics of an epoxy resin

The curing kinetics of a system containing 4,4′-diglycidyloxy-α-methylstilbene (DOMS) and different functionality amines, N-ethylaniline (NEA), aniline, benzenesulfonamide (BSA), and sulfanilamide (SAA), have been studied by differential scanning calorimetry (DSC) under isothermal conditions. The phase transformations during curing of the systems have been monitored by a crosspolarized optical microscope equipped with a hot-stage and photo detector. It has been found that the growth of a nematic liquid crystal structure does not cause a discrepancy from the autocatalytic model for the reactions between aniline and epoxy. There is no liquid crystalline structure formed for the systems containing NEA or BSA, which follow the autocatalytic kinetic models within the temperature range of 120–150°C. For the curing reactions between DOMS and SAA, there is a big deviation from the autocatalytic model when the liquid crystals transfer from a nematic structure to a smectic structure. Unlike the usual decrease of reaction rate resulting from diffusion in a heterogeneous reaction, the reaction rate is enhanced. A modified kinetic model has been constructed for this reaction system by introducing a pseudoconcentration term caused from the liquid crystalline structure formation. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1105–1124, 1997     

Peculiarities of flow and viscoelastic properties of solutions of polymers with a narrow molecular-weight distribution

The concepts developed for flexible-chain linear high-molecular-weight polymers of narrow molecular weight distribution, according to which transition from the fluid to the highelastic state at increased shear rates is accompanied by loss of fluidity, have been extended to concentrated solutions of these polymers. The change of principal viscoelastic characteristics, in a concentration range which can be associated with the effect of formation of an entanglement network in polymer solution, is considered. On the basis of the parameters characterizing the viscous properties of dilute polymer solutions (the intrinsic viscosity and the Martin constant), a generalized representation of the dependence of the initial viscosity of polybutadiene solutions on concentration over the entire range up to bulk polymer has been derived.     

Analysis of curing of diglycidyl ether of bisphenol A (BADGE n = 0) with 2‐adamantylethanamine

The epoxy resin diglycidyl ether of Bisphenol A (BADGE n = 0) has been cured with a new synthesized hardener (2‐adamantylethanamine) and the crosslinking reaction was characterized by DSC. Values of 413.3 J/g and 95°C have been obtained for the enthalpy of the reaction and the glass transition temperature, respectively. The experimental results obey Kamal's model over all conversion range of temperatures (70°C‐100°C). The activation energies of the mechanisms involved in the curing reaction have been determined for both the autocatalytic and the n‐order mechanism, the values being 63.3 and 29.8 kJ/mol, respectively. The value for T_g is 23°C higher than the one for (BADGE n = 0)/amantadine, while the activation energy for the n‐order mechanism is around 13 kJ/mol lower. This is consistent with a higher steric effect of the adamantyl group in the second hardener since it will hinder the opening the oxirane ring by the nitrogen atom of the amino group. As the polymerization reaction progress, this effect will disappear as the distance adamantyl‐oxirane increase when new oxirane groups react with the hydroxyl groups (autocatalyzed reaction). Consequently, by selecting the appropriate cross‐linking agent, it is possible to simultaneously increase T_g while reducing theactivation energy, two effects which may be desirable for some industrial applications of the material.