Exchange reaction between epoxides and chlorohydrins

Conclusions We determined the equilibrium constant of the exchange reaction between epichlorohydrin and 1-chloro-2-hydroxy-3-phenoxypropane, which leads to the formation of phenyl glycidyl ether and glycerol 1,3-dichlorohydrin.Translated from Izvestiya Akademii Nauk SSR, Seriya Khimicheskaya, No. 2, pp. 450–451, February, 1979.     

Solvent-induced embrittlement in a crystallizable polyarylate

The effects of solvent-induced crystallization on the micromechanical properties of thin films of polyarylate (PAr) were studied. Under uniaxial extension amorphous polyarylate was observed to deform exclusively by shear deformation with no evidence of crazing. Upon exposure to methylethyl ketone, vapor, or liquid, PAr crystallizes and is subsequently embrittled. Our transmission electron microscopy results clearly show that this embrittlement results from a transition in plastic deformation mechanism from shear yielding to crazing. A detailed examination of the samples revealed that the crazes formed preferentially within the noncrystalline regions and that the craze tips followed a complex trajectory around the crystallites. In some cases the craze tip advance deviated by as much as ±30 from a direction normal to the tensile axis. Because crazes are inherently more susceptible to forming cracks than shear deformation zones, crystallization reduces the fracture toughness of the polymer. This type of embrittlement, via a transition in plastic deformation mechanism, is believed to be a general behavior for solvent-crystallizable thermoplastics.     

Miscibility of a polyarylate with a liquid crystalline copolyester

The miscibility has been investigated for binary blends of a polyarylate (PAr) with a liquid crystalline copolyester of p-hydroxybenzoate and ethylene terephthalate units in a 6/4 molar ratio (PET/PHB). The binary blends were prepared by solution precipitation. The transitions of the PET/PHB have been measured with a rheometrics dynamic spectrometer. The phases in blends have been studied with a differential scanning calorimeter, by ther-mogravimetry and with a polarizing optical microscope. The blends exhibit two glass transitions (T_gs) over the composition range 10–90 wt %. The amorphous PET phase from the PET-PHB is found to be partially miscible with PAr, which leads to a decrease of the PAr T_g. The amount of this partially miscible portion of PET has been estimated by the Couch-man equation. On heat treatment of the blends at 250 to 300°C, transesterficiation takes place, as judged by the shift of the higher of the two T_gs. © 1993 John Wiley & Sons, Inc.     

Exchange reaction of perfluoroalkyl- and perfluorooxaalkylimidoylamidines

Conclusions It was found that exchange reaction takes place between N-(perfluorobutyrylimidoyl)perfluoropropyl-amidine and N-(perfluoro-2-methyl-3-oxahexylimidoyl)perfluoro-2-methyl-3-oxahexylamidine at temperatures where their thermal condensation to triazines still does not take place.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2784–2787, December, 1977.     

Amine/anhydride reaction versus amide/anhydride reaction in polyamide/anhydride carriers

Polyamide 6 (PA6) and poly(metaxylene adipamide) (PAmXD6) were blended in a batch mixer with anhydrides such as phthalic anhydride, n-octadecyl succinic anhydride, and anhydride-grafted ethylene propylene rubber. The melt viscosity, the solution viscosity, and chain end concentration were studied during the mixing. PA was first mixed 5 min to get an homogeneous melt prior to the anhydride addition. The introduction of the anhydride to the molten polyamide resulted in large decreases of melt and solution viscosities and of amine chain end concentrations. The anhydride units react with amine chain ends to form imide groups. The resulting low amine chain end concentration causes hydrolysis reaction to maintain the condensation equilibrium. As a consequence an increased carboxylic chain end concentration is observed. The imide concentration was studied by IR. It was shown that when most of the amine chain ends are consumed, the remaining anhydride reacts with amino groups formed by polyamide hydrolysis. © 1995 John Wiley & Sons, Inc.     

Monitoring the synthetic reaction of a polyamide/peptide conjugate using electrospray ionization mass spectrometry

Recently, the chemical structures of a series of monoimidazole/polyamine conjugates were studied in this laboratory using electrospray ionization mass spectrometry (ESI-MS) combined with tandem mass spectrometry (ESI-MS/MS). The method was found to be a powerful tool for the identification of this class of compounds. During the synthesis of targeted polyamide/peptide conjugates as derivatives or analogues of netropsin and distamycin, the method was applied to analyze and track the coupling reaction for the formation of the polyamide, which was difficult to achieve using thin layer chromatography (TLC). Characteristic fragmentation pathways for a nitro-monoimidazole conjugate, an amino-monoimidazole conjugate, and the final product (a nitro-diimidazole conjugate) were explored. The fragmentations of these conjugates were strongly affected by the presence of an amino group instead of a nitro group in the molecule, and led to the identification of the three compounds in the reacting solution or in the final reaction mixture. Consequently, the reaction could be monitored successfully and the synthetic route optimized.     

Nanomorphology and reaction to fire of polyurethane and polyamide nanocomposites containing flame retardants

The reaction to fire of polymer nanocomposites (thermoplastic polyurethane and polyamide-6) containing two different nanofillers (organoclay and carbon nanotube) has been investigated. Polymer nanocomposites exhibit significant reduction of peak of heat release rate but the nanomorphology (exfoliation, intercalation and presence of tactoids) does not play any significant role, although a reasonable level of nanodispersion is necessary to achieve good flame retardancy in specific cases (mass loss calorimetry experiment). Modelling aspects for the time to ignition are also proposed in the paper. It is shown that the approach ‘nanocomposite’ gives the best results combined with conventional flame retardants (phosphinate and phosphate) and leads to synergistic effects. The aspects of nanodispersion of the nanoparticle with the flame retardant (microfiller) are fully commented in the paper using TEM and solid state NMR. Mechanisms of action are finally proposed explaining the synergy when conventional flame retardants are combined with nanoparticles.     

Solution properties of polyarylate in good and theta-solvents

Investigations have been carried out to determine the Mark-Houwink constants K and a in THF of a polyarylate based on an equimolar mixture of isophthalic and terephthalic acids and bisphenol A. An iterative method, involving intrinsic viscosities and GPC chromatograms, has been used. Molecular weight distributions and molecular weight averages are, in this way, accessible. Conformational characteristic magnitudes such as the characteristic ratio C_x and the steric factor σ have been calculated starting from data in good and θ-solvents.     

聚酰胺与稀土离子相互作用的研究

用热分析和傅里叶变换红外光谱法研究了尼龙6与稀土离子之间的相互作用。实验结果表明,当将稀土离子引入尼龙6体系后,可观察到以下几种效应：1)尼龙6的熔点显著降低。2)红外光谱结果表明,尼龙6-稀土体系熔化过程中,代表N－H伸缩振动的酰胺A带发生红移。3)尼龙6的酰胺Ⅰ和Ⅱ带区段,可观察到代表与稀土配位的酰胺基团的知,随着温度升高,尼龙6的酰胺Ⅰ,Ⅱ带吸光度降低而在1600cm^-^1附近的新峰的吸光度增加。     

Characterization of carbonyl chloride-terminated aromatic polyamide nanoparticles with carboxyl groups and their reaction

Aromatic polyamide nanoparticles with carbonyl chloride (COCl) and carboxyl (COOH) groups were obtained using a precipitation polymerization method. The morphology, number of COCl groups incorporated, and degree of polymerization of the resulting particles depended on the reaction system. The COOH group of diamine used decreased the reactivity of NH₂ groups and chemically stabilized the COCl groups existing at the ends of the molecular chains. Also, the COCl groups were retained in particles by the rapid formation of particles. Thus, the chemical structures and formation mechanism were found to play an important role in the formation of particles with COCl groups.     

Relationship between the morphology and combustibility of fluorinated polyamide composites

The effect that polyfluorinated alcohols immobilized on montmorillonite support exert on structuralmorphological characteristics and combustibility of polymer composites was studied with 1,1,9-trihydroperfluoro- 1-nonanol as example. The relationship between the flame resistance of this heterochain polymer and its morphology was revealed by X-ray diffraction analysis, electron microscopy, DSC, and Fourier IR spectroscopy. This relationship is associated with the reorganization of the crystal and molecular structure under the influence of fluorinated organoclay, ensuring increased degree of crystallinity and redistribution of the fractions of α- and γ-crystalline forms in the polymorphic composition of polycaprolactam, making its supramolecular structure more perfect, and favoring preparation of a fluorinated material of decreased combustibility.

     

Blends of poly(butylene terephthalate) and a polyarylate before and after transesterification

Blends of poly(butylene terephthalate) (PBT) and a copolyester of bisphenol-A with 50% terephthalate-50% isophthalate (PAr), before and after transesterification, have been studied by thermal and dynamic mechanical tests to determine crystallinity and phase behavior. Blends without transesterification, as prepared by solution precipitation, show a single T_g, indicating amorphous miscibility of PBT and PAr. A melting-point depression for PBT crystals is not observed; this means that PBT crystallizes excluding PAr and the entropy of melting is small. The highest fractional crystallinity for PBT is obtained at 20-35% of PAr. Transesterified blends were obtained by holding the physical blends at 250°C for up to 16 h. The transesterified systems show higher T_g's than the corresponding physical blends and also show a marked melting-point depression and lesser PBT crystallinity at the corresponding increased PAr content.     

Exchange reaction involving olefin α-oxides and diethyl-β-hydroxyalkylamines

Conclusions The feasibility was demonstrated for an exchange reaction for the olefin oxide--hydroxyalkylamine system, and a mechanism was proposed involving the formation of an ammonium salt as an intermediate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2307–2309, October, 1981.     

Fluorescence dynamics of interactions between polyamide PyPyPyβDp and DNA

The photophysical properties of the polyamide PyPyPyβDp (PPP) were investigated by means of steady-state absorption and fluorescence spectroscopies, as well as time-resolved fluorescence spectroscopy. It was found that the excited-state properties of PPP are very sensitive to solvents. In TKMC buffer PPP exhibited weak fluorescence with a decay time constant of 16 ps, while with the decrease of the solvent polarity PPP showed the blue-shifted peak position, increased intensity and lengthened life-time for its fluorescence behavior. In the presence of calf thymus DNA, it was observed that the fluorescence intensity was enhanced and the fluorescence lifetime increased from 16 to 32 ps for PPP, which verified that PPP bound into the minor groove of DNA duplex.     

A chain geometry prediction of polystyrene and polyarylate block copolymer by a kinetic simulation model

The chain geometry of polystyrene (PS) and polyarylate (PAr) block copolymer was predicted by the simulation of the kinetics of the block‐copolymerization route. The simulation model consisted of a combination of two models. In the first model, the kinetics of the free‐radical polymerization of carboxyl‐terminated telechelic PS (COOH‐PS‐COOH) was simulated for the determination of the molecular weight distribution. In the second model, the kinetics of the PS and PAr block copolymerization with COOH‐PS‐COOH was simulated by a Monte Carlo computation, with each reacting functional group assigned by an integer. The number‐average and weight‐average molecular weights and the composition of the PS‐PAr block copolymer, as calculated by the simulation models, were in good agreement with the experimental data. From this agreement, plausible predictions for the chain geometry (i.e., the type of block copolymer and length of each segment) were obtained that were practically impossible to analyze experimentally. The simulation results showed that more than 80 wt % of the block copolymer synthesized by this method was a composite of various types of multiblock copolymers and that the length of the PAr segment was almost the same as that of the homo‐PAr obtained as a by‐product. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 299–309, 2000