Saponification Kinetics of Acrylonitrile Terpolymer and Polyacrylonitrile

Saponification kinetics of acrylic terpolymer and polyacrylonitrile were studied. The influence of alkali concentration and the time of hydrolysis on the degree of saponification were determined by the residual nitrogen content. The order of reaction was graphically determined and the rate of saponification was found to be faster in the terpolymer than in the homopolymer. Chemical and infrared spectroscopy methods reveal that the reaction is initiated through cyclization of nitrile groups, followed by hydrolysis to amide and carboxylic groups of the [sbnd](C[dbnd]N)_n[sbnd] segments produced.

The saponification of nitrile groups in the terpolymer initially yields amide groups, then slows down to yield carboxylic groups.     

On the modification of the nitrile groups of acrylonitrile/butadiene/styrene into oxazoline in the melt

Oxazoline functionality is well known to be highly reactive toward a lot of other functional groups like carboxyls, hydroxyls, mercaptans, and amines. In this work we report the possibility to modify the nitrile groups of an acrylonitrile/butadiene/styrene (ABS) copolymer into oxazoline in the molten state in the presence of aminoethanol as modifier agent and zinc acetate as a catalyst. The reaction has been carried out in a batch mixer and in a corotating twin screw extruder. The conversion of the nitrile groups into oxazoline has been verified by infrared spectroscopy, NMR analysis microanalysis and confirmed by thermomechanical characterization. The results indicate that the kinetic of grafting is fast and the conversion of the nitrile groups into oxazoline relatively high, encouraging the use of this modified polymer in the reactive compatibilization of ABS‐based blends. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1795–1802, 2000     

Graft copolymerization of acrylonitrile onto polystyrene

It is possible to graft vinyl monomers, such as acrylonitrile, onto polystyrene via anionic processes but not by a radical process. Both homopolymerization of the added acrylonitrile and graft copolymerization in which acrylonitrile units are added to the para position on the benzene ring in styrene occur; the conversion of acrylonitrile into polymer depends upon the time and temperature of the reaction and on the concentration of the anionic initiator, butyllithium. A constant 15–20% of the acrylonitrile is converted to graft copolymer while the remainder is homopolymerized; graft copolymer may be separated from homopolymer by selective precipitation from either N,N′-dimethylformamide or aqueous potassium thiocyanate. Treatment of the mixed graft and homopolymer with aqueous sodium hydroxide converts the nitrile into an acid salt and one may conveniently separate homopolymer from graft copolymer in this way. Each polystyrene chain is grafted with acrylonitrile units. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1275–1282, 1997     

Enantioselective nitrile anion cyclization to substituted pyrrolidines. A highly efficient synthesis of (3S,4R)-N-tert-butyl-4-arylpyrrolidine-3-carboxylic acid

[reaction: see text] A practical asymmetric synthesis of N-tert-butyl disubstituted pyrrolidines via a nitrile anion cyclization strategy is described. The five-step chromatography-free synthesis of (3S,4R)-1-tert-butyl-4-(2,4-difluorophenyl)pyrrolidine-3-carboxylic acid (2) from 2-chloro-1-(2,4-difluorophenyl)-ethanone achieved a 71% overall yield. The cyclization substrate was prepared via a catalytic CBS asymmetric reduction, t-butylamine displacement of the chlorohydrin, and a conjugate addition of the hindered secondary amine to acrylonitrile. The key nitrile anion 5-exo-tet cyclization concomitantly formed the pyrrolidine ring with clean inversion of the C-4 center to afford 1,3,4-trisubstituted chiral pyrrolidine in >95% yield and 94-99% ee. Diethyl chlorophosphate and lithium hexamethyldisilazide were shown to be the respective optimum activating group and base in this cyclization. The trans-cis mixture of the pyrrolidine nitrile undergoes a kinetically controlled epimerization/ saponification to afford the pure trans-pyrrolidine carboxylic acid target compound in >99.9% chemical and optical purity. This chemistry was also shown to be applicable to both electronically neutral and rich substituted phenyl substrates.     

Hydrolysis of polyacrylonitrile in aqueous solution of sodium carbonate

The kinetics of homogeneous hydrolysis of polyacrylonitrile in an aqueous solution of sodium carbonate and the chemical structure of the resulting copolymer are studied by FTIR spectroscopy, ¹³C NMR analysis, and titration methods. It is found that hydrolysis in the presence of sodium carbonate does not include the stage of amidine formation and does not result in the complete exhaustion of nitrile groups in a polymer. The designed partial-hydrolysis method permits the use of polyacrylonitrile for the synthesis of the copolymer with a predominant unit alternation; this copolymer is identical in terms of chemical structure to the Rohacell copolymer obtained through block copolymerization of acrylonitrile and methacrylic acid.     

The ritter reaction of poly(acrylonitrile) with tert.-butyl alcohol

The course of the Ritter reaction has been investigated for poly(acrylonitrile) with tert.-butyl alcohol in the presence of sulphuric acid in tetramethylene sulphone. From the rate constants, activation parameters and their dependence on molecular mass, tacticity, concentration of the reaction mixture and extent of the reaction, and from composition of the reaction products, it was concluded that the reaction proceeded by a non-acceleration mechanism with formation of a random copolymer acrylonitrile—N-tert.-butylacrylamide. At about 55% conversion of nitrile groups, the reaction is considerably slowed down, obviously due to a conformational change of the chain.     

Electrochemical properties of hydrophilic weak-acid membranes from hydrolysed polyacrylonitrile—I. Effect of cross-linking and chemical composition

Gels cross-linked to various degrees and containing various amounts of nitrile, amide and carboxylic groups were prepared by polymerizing acrylonitrile at various concentrations in aqueous 70 per cent ZnCl₂ solution and by hydrolysis of polymers for various times in HCl vapours. Chemical characteristics of gels, concentration membrane potentials, membrane functions and permselectivities in KCl solutions were determined. It was proved that under the conditions used (pH close to 7, content of acrylic acid in the copolymer only 1·4–3·9 mole %). cross-linking is the decisive factor for permselectivity and ideality of the membrane functions. Cross-linking yielded almost 100 per cent permselectivity values and a slope of the membrane function of about 55 mV/decade. Further hydrolysis impairs the ideality of membranes, since the increase in swelling outweighs the effect of the increase in concentration of the active groups. Variability of the density of the ionizable groups is not sufficient to explain differences in the behaviour of the membranes under investigation.     

The uranium recovery from aqueous solutions using amidoxime modified cellulose derivatives. III. Modification of hydroxypropylmethylcellulose with amidoxime groups

Grafting of acrylonitrile on hydroxypropyl methylcellulose films has been carried out by means of ⁶⁰Co-γ radiation, using a constant amount of hydroxypropyl methylcellulose films, at different concentrations of acrylonitrile in dimethylformamide. Grafting percentage—dose curves were obtained. 63 % of grafting yield were reached at around 3 kGy dose. Conversion of nitrile groups to amidoxime groups were achieved by aqueous solutions of NH₂OH·HCl–NaOH at 50 °C. The amidoxime conversion was followed by using FTIR spectrophotometer and determined as percentage. 98 % amidoxime conversion was achieved within 50 h. The structural, morphological and thermal evaluations of acrylonitrile grafted hydroxypropyl methylcellulose films, before and after amidoxime conversion, were performed using FTIR, AFM, Contact Angle, SEM and TGA analyses.     

Synthesis of Acid Dyeable Acrylonitrile Copolymer

In this paper, a unique and updated technique was applied to obtain an acid dyeable copolymer of acrylonitrile by solution polymerization of acrylonitrile, and a kind of alkaline monomer F (N,N‐dialkylaminoethylacrylate). Azodiisobutyronitrile (AIBN) was used as initiator to prepare the copolymer in sodium sulfocyanate aqueous solution. The effect of initiator concentration on the polymer's molecular weight and conversion during polymerization was studied. The relation between concentration of the alkaline monomer F and the polymer conversion, as well as the relation between concentration of the alkaline monomer F and the % dye‐uptake of the copolymer are discussed. The influence of pH was also researched. The structure of the copolymer was characterized by IR and NMR. The copolymer has excellent acid dyeable characteristics.     

Polymérisation et copolymérisation radiochimique du bromure de vinyle

The kinetics of the radiation induced polymerization of vinyl bromide (V Br) were investigated in bulk and in acetonitrile solutions. The reaction proceeds with precipitation. In bulk the conversion curves exhibit slight auto-acceleration and the order with respect to chain initiation is 0.78. The molecular weight of the resulting polymer lies between 110.000 and 120.000: it depends very little on the rate of initiation. This fact, as well as the very high values calculated for the radiolytic yield of chain initiation, indicate efficient chain transfer to the monomer. The addition of acetonitrile strongly reduces the polymerization rate and the conversion curves become auto-retarded. It is assumed that this effect is caused by an unreactive radical resulting from the addition of a growing chain to the nitrile group. The rate of copolymerization of V Br with acrylonitrile exhibits a minimum for a mole fraction of 0.88 of V Br. The reactivity ratios are calculated and the solubilities of the various copolymers are measured.     

Complex formation and degradation in poly(acrylonitrile‐co‐vinyl acetate) containing copper nitrate

The pyrolysis of polymers containing metal nitrates may provide a relatively simple, rapid, and advantageous method of producing high‐temperature superconductors (HTSCs). The advantage lies in the ability to use conventional polymer processing or microlithographic patterning before pyrolysis. A copolymer of acrylonitrile and vinyl acetate [P(AN‐VA)], a well‐known fiber‐forming polymer, was investigated as a potential HTSC precursor. Complex formation with the highly polar acrylonitrile groups was expected to enhance atomic‐level mixing and hinder nitrate recrystallization. The metal nitrates were found to have a profound effect on P(AN‐VA) pyrolysis. P(AN‐VA) containing copper nitrate (CuN) exhibited complex formation and an exothermic decomposition that began at about 170 °C (reaction 1‐CuN). Reaction 1‐CuN had a heat of about 3.5 kJ/g_NO3 and a mass loss of about 0.99 g/g_NO3. As reaction 1‐CuN also involved the nitrile groups, it disrupted the nitrile cyclization reaction at about 290 °C. For a P(AN‐VA)/CuN ratio of 2/1, there was no nitrile cyclization, and the thermooxidative degradation temperature was reduced by approximately 200 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1023–1032, 2004     

A Phosphoric Acid Treated Reactive GLC Column for the Analysis of Long Chain Amides

Abstract

The conversion of nonvolatile amides to more volatile nitriles on a reactive column was studied. It was found that pyrophosphoric acid was necessary for the conversion, that the amide reacts 100% on the first 6 inches of the column to produce one nitrile and 3 carboxylic acid groups for every 4 amide groups injected and that a quantitative analytical procedure is possible.     

Polyamide synthesis from 6-aminocapronitrile, part 2: heterogeneously catalyzed nitrile hydrolysis with consecutive amine amidation

To test the potential of heterogeneous catalysts for the nylon-6 synthesis from 6-aminocapronitrile, a number of zeolites, aluminum silicate, and metal oxides were tested as catalysts for the model reaction of pentanenitrile with water and hexylamine to N-hexylpentanamide. All zeolitic and aluminum silicate systems showed an insufficient performance, while the metal oxides (TiO(2), ZrO(2), Nb(2)O(5)) showed very promising results. The kinetic behavior of the metal oxides was further investigated. First the nitrile was catalytically hydrolyzed to the terminal amide and subsequently the amidation of the hexylamine occurred. To polymerize 6-aminocapronitrile into nylon-6, more than 99 % nitrile conversion was required to obtain a high-molecular-weight polymer. Pentanenitrile conversions larger than 99 % can be obtained within six hours, at 230 degrees C, by using ZrO(2) as the catalyst. A kinetic study (by using IR spectroscopy) on the behavior of the metal oxides demonstrated that the adsorbed nitrile was catalytically hydrolyzed at the surface, but remained tightly bound to the surface. Zirconia-catalyzed polymerizations of 6-amino-capronitrile demonstrated that high-molecular-weight nylon-6 is feasible by using this route.     

Process Development of the Copper(II)-Catalyzed Dehydration of a Chiral Aldoxime and Rational Selection of the Co-Substrate

The access towards chiral nitriles remains crucial in the synthesis of several pharmaceuticals. One approach is based on metal-catalyzed dehydration of chiral aldoximes, which are generated from chiral pool-derived aldehydes as substrates, and the use of a cheap and readily available nitrile as co-substrate and water acceptor. Dehydration of N-acyl α-amino aldoximes such as N-Boc-l -prolinal oxime catalyzed by copper(II) acetate provides access to the corresponding N-acyl α-amino nitriles, which are substructures of the pharmaceuticals Vildagliptin and Saxagliptin. In this work, a detailed investigation of the formation of the amide as a by-product at higher substrate loadings is performed. The amide formation depends on the electronic properties of the nitrile co-substrate. We could identify an acceptor nitrile which completely suppressed amide formation at high substrate loadings of 0.5 m even when being used with only 2 equivalents. In detail, utilization of trichloroacetonitrile as such an acceptor nitrile enabled the synthesis of N-Boc-cyanopyrrolidine in a high yield of 92 % and with full retention of the absolute configuration.     

Adsorption of polymers at the solution–solid interface. IX. Solution adsorption of nitrile rubbers on silicas

The adsorption of three acrylonitrile–butadiene random copolymers from two solvents has been studied: two pyrogenic silicas of differing surface areas, which had received several surface modifications, were used as adsorbents. Infrared spectroscopic studies confirm that the nitrile groups bond to the silica surface. The amount of copolymer adsorbed is related to the acrylonitrile content, which also controls the copolymer solubility: adsorptions are higher from benzene than from a better solvent, trichloroethylene. Vapor sorption of model compounds indicate how the adsorbent surface area and surface composition affect monolayer capacities: heats of adsorption are not markedly altered by the adsorbent modifications.     

Self-assembled hybrid polymer-TiO2 nanotube array heterojunction solar cells

Films comprised of 4 microm long titanium dioxide nanotube arrays were fabricated by anodizing Ti foils in an ethylene glycol based electrolyte. A carboxylated polythiophene derivative was self-assembled onto the TiO2 nanotube arrays by immersing them in a solution of the polymer. The binding sites of the carboxylate moiety along the polymer chain provide multiple anchoring sites to the substrate, making for a stable rugged film. Backside illuminated liquid junction solar cells based on TiO2 nanotube films sensitized by the self-assembled polymeric layer showed a short-circuit current density of 5.5 mA cm-2, a 0.7 V open circuit potential, and a 0.55 fill factor yielding power conversion efficiencies of 2.1% under AM 1.5 sun. A backside illuminated single heterojunction solid state solar cell using the same self-assembled polymer was demonstrated and yielded a photocurrent density as high as 2.0 mA cm-2. When a double heterojunction was formed by infiltrating a blend of poly(3-hexylthiophene) (P3HT) and C60-methanofullerene into the self-assembled polymer coated nanotube arrays, a photocurrent as high as 6.5 mA cm-2 was obtained under AM 1.5 sun with a corresponding efficiency of 1%. The photocurrent action spectra showed a maximum incident photon-to-electron conversion efficiency (IPCE) of 53% for the liquid junction cells and 25% for the single heterojunction solid state solar cells.     

Sur un “effet de matrice” dans la polymerisation de l'acrylonitrile en masse

The kinetics of the radiation initiated polymerization of acrylonitrile at 20° have been investigated in the presence of a highly divided polyacrylonitrile obtained by polymerizing the crystalline monomer. This polymer catalyses the reaction to a much larger extent than polymer formed at 20°. The analogy between the kinetic features of the polymerizations of acrylic acid and acrylonitrile in bulk leads to extending to this last monomer the assumption of a “matrix effect” in its polymerization. This effect is believed to result from the dipole interaction of the nitrile groups which lead to the formation of a complex in which the double bonds are favourably oriented for the propagation. If the matrix-polymer is produced with a pre-irradiation dose at low temperature exceeding a critical value, inhibition occurs perhaps resulting from the addition of growing chains to the CN double bonds present in the matrix-polymer.     

Radiation-Induced Copolymerization of Trioxane with Styrene Oxide

Copolymerization of trioxane (TOX) and styrene oxide (STO) induced by gamma radiation was studied under varying operating conditions to see the effects of radiation dose, STO concentration, postpolymerization temperature, and duration on the polymer yield. Charging 5% STO with TOX STO conversion was 65% but yield was only 23% compared with 62% for the homopolymer. Molecular weight, melting point, density, and thermal stability of the copolymer samples were determined.     

Thermal behaviour of binary and ternary copolymers containing acrylonitrile

Three types of acrylonitrile copolymers (acrylonitrile-styrene-butadiene copolymer (ABS¹), acrylonitrile-styrene random copolymer (SAN²) and acrylonitrile-butadiene random copolymer (BAN³) were studied by thermogravimetry (TG/DTG⁴) and by pyrolysis in a semi-batch process at 450 °C in order to find structure–thermal behaviour relationships. The overlapped thermo-oxidative degradation processes were separated and the corresponding kinetic parameters were calculated. The TG/DTG studies have evidenced that the styrene-acrylonitrile interactions stabilize the nitrile groups reacting by chain scission rather than cyclization and destabilize the styrene units. Also, the cyclization of the acrylonitrile units in ABS is favoured by interactions with the styrene and butadiene units. The pyrolysis behaviour evidenced that the styrene-acrylonitrile interactions in SAN and ABS lead to the formation of 4-phenylbutyronitrile as the most important decomposition compound. ABS shows similar composition of the degradation oil with SAN copolymer therefore in the ABS the styrene-butadiene interactions are less important than those between styrene and acrylonitrile units.     

Synthesis of 2-propyloxazole and 2-propyloxazole-4-carboxylic acid derivatives

2-Propyloxazole (VI) was obtained in a number of steps starting from butyronit rile. The hydrazide and amide were obtained from ethyl 2-propyloxazole-4-carboxylate; the amide was converted to the nitrile, from which the thioamide and amidoxime were obtained by the usual method. Attempts to convert VI to 2-propylisonicotinic acid or its nitrile by the reaction of VI with acrylic acid or acrylonitrile did not give positive results.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 7–9, January, 1972.