Copolymerization of acrylonitrile. I. Copolymerization with styrene derivatives containing nitrile groups in the side chain

Acrylonitrile was copolymerized in bulk with cinnamonitrile (I), ethyl benzylidenecyanoacetate (II), and benzylidenemalononitrile (III) by radical initiation up to low conversions. The conventional scheme of copolymerization fitted all the three copolymer pairs.     

Characterization of water-soluble oligomers formed during the emulsion polymerization of styrene by means of isotachophoresis

The concentrations and probable nature of charged oligomers formed by aqueous-phase termination in the persulfate-initiated emulsion polymerization of styrene were measured by isotachophoresis. Isotachophoresis has some advantages over other techniques (e.g., GPC, UV spectroscopy) in that it separates species according to their molecular weight, geometry, and charge. The charged water-soluble oligomeric species were detected in experiments in which particles were nucleated in a surfactant-free environment. Identification of the moieties present was made by comparison with model compounds. Evidence was found for bimolecular combination as a major mechanism of termination in the aqueous phase, although the possibility of disproportionation could not be ruled out. The species formed in the aqueous phase under saturated monomer conditions were found to be subject to further reaction towards the end of polymerization. The surface adsorption characteristics of the compounds formed were compared with those of known surfactants and showed good agreement with the assumptions in the model of Maxwell et. al. [Macromolecules, 24 , 1629 (1991)] for initiator efficiencies in emulsion polymerization. The relatively large concentrations of nonradical aqueous–soluble oligomeric compounds demonstrate conclusively that initiator efficiencies are not 100%, as is often assumed in such systems. © 1993 John Wiley & Sons, Inc.     

Quantitative analysis of (styrene/acrylonitrile/methyl methacrylate) co-polymer systems by infrared resonance spectroscopy

A detailed careful analysis of the infrared resonance (IR) spectra of polystyrene (PSt), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN) and their co-mixtures were performed. Through this study the absorption peak area to weight ratios as well as working curves were obtained to test for their reliability as well as their suitability. Satisfactory results were achieved and these working curves were then used to measure the polymerized components of binary and ternary co-polymers. By investigating the acquired data we conclude that the monomer preferential polymeric sequence is St > MMA > AN. A quantitative method to measure P (St/AN/MMA) concentrations by IR spectroscopy is proposed in this work.     

Copolymerizations mechanochemically initiated—I. Influence of some factors on the copolymerization of acrylonitrile with styrene

The possibility of initiating copolymerization mechanochemically is studied. Acrylonitrile and styrene were used as monomers; the mechanical energy was supplied by vibratory milling in metallic equipment. No additives were introduced to activate the reaction. The process was carried out at 18 ± 2° and study was made of the following parameters: duration, rate of wear of the grinding media, comonomer ratio. The reaction probably proceeds through radical-anions and catalysis by the apparatus walls. The copolymers thus synthesized are crystalline, thermostable compounds resistant to chemical agents.     

Copolymerization of acrylonitrile. II. Physical and mechanical properties of copolymers with styrene derivatives containing nitrile groups in the side chain

Copolymers of acrylonitrile with cinnamonitrile (I), ethyl benzylidenecyanoacetate (II), and benzylidenemalononitrile (III) were prepared in suspension up to high conversions. Films and molded specimens were made from the copolymers and their basic physical and mechanical properties, such as solubility, viscosity, glass transition temperature, and tensile and compressive strength were determined. Further, treatment by heat and ultraviolet light, the permeability of water vapors, and the behavior of films in a weathering tester were studied.     

Thermal degradation of copolymers of styrene and acrylonitrile. III. Chain-scission reaction

The chain-scission reaction which occurs in copolymers of styrene and acrylonitrile has been studied at temperatures of 262, 252, and 240°C. Under these conditions volatilization is negligible, and chain scission can be studied in virtual isolation. At 262°C three kinds of chain scission are discernible, namely, at weak links which are associated with styrene units, “normal” scission in styrene segments of the chain and scission associated with the acrylonitrile units. The rate constants for normal scission and scission associated with acrylonitrile units are in the ratio of approximately 1 to 30. The molecular weight of the copolymer has no effect on the rates of scission. At 252°C the same general behavior is observed for the copolymers containing up to 24.9% acrylonitrile. The 33.4% acrylonitrile copolymer is anomalous, however. At 240°C the trends observed at 262°C appear to break down completely although individual experiments are quite reproducible. This behavior at the lower temperatures is believed to be associated with the fact that the melting points of the various copolymers are in this temperature range. Thus the viscosity of the medium, which should be expected to have a strong influence on the chain scission reaction, will be changing rapidly with temperature, copolymer composition, and molecular weight in this temperature range.     

Study of n-butene isomerization and polymerization on CaNaY-type zeolites by means of 13C-N.M.R. spectroscopy

With highly resolved carbon-13 n.m.r. spectroscopy, the isomerization and polymerization of but-1-ene sorbed in CaNaY-type zeolites have been investigated. The application of molecules partially enriched with carbon-13 nuclei allowed a detailed study of the transformtion of labelled groups.At lower temperatures (290 – 350 K) only the double bond isomerization of butenes proceeds in CaNaY-type zeolites with 65 – 70% of their sodium ions replaced by calcium. Within the limits of experimental error an enrichment of ¹³C nuclei was found in the CH₃ and CH groups of but-2-ene molecules if the but-1-enes were enriched in the positions CH₂ and CH, respectively. Relative equilibrium concentrations as determined from n.m.r. line intensities were in fair agreement with known data for the thermal equilibrium of the n-butene isomers in the gas phase. Thus, possible differences between Overhauser factors of the different carbon-13 resonance lines were so small that they did not give rise to significant errors in determining concentrations via the enchanced resonance line intensities.Polymerization reactions occurred at higher temperatures. They gave rise to mutually overlapping lines of saturated carbons which were difficult to detect unless carbon-13 enriched butene molecules were applied. Using pore filling factors of ≈ ≈ 0.6, partly branched octanes were formed. This is at variance with investigations at low pore filling factors of ≈ ≈ 0.1 where predominantly octenes were found. These experimental results are explained by a different availability of hydrogen as an important controlling factor in these reactions.     

Investigation of polycarbonate/acrylonitrile butadiene styrene/multiwall carbon nanotube nanocomposites under impact loading

In this study, the effect of polycarbonate (PC)/acrylonitrile butadiene styrene (ABS)‐reinforced multiwall carbon nanotube (MWCNT) nanocomposites under a high‐velocity impact was investigated. PC/ABS (70/30 w/w)/MWCNT nanocomposites containing 1, 2, and 4 wt% were used to manufacture samples for this study. The samples were fabricated in sheet form with 100 × 100 mm dimensions and tested by gas gun for high‐velocity impact tests. The experimental results indicate that the energy absorption, limit velocity, and tensile modulus of the nanocomposite samples increased by approximately 121%, 52%, and 103% for the PC/ABS (70/30 w/w)/2 wt% MWCNT samples respectively. These results were confirmed by a transmission electron microscopy analysis test that was conducted for the state of dispersion of MWCNTs in the nanocomposite samples. The transmission electron microscopy results show that the best morphological structure of carbon nanotube at the interface of PC and ABS is that for the nanocomposite containing 2 wt% MWCNTs, which led to improved interface of the nanocomposites and higher mechanical properties. Copyright © 2016 John Wiley & Sons, Ltd.     

Distinguishing and identifying hydrogens in an NH3 group by I.R. spectroscopy

Combined low temperature isotopic dilution and polarized i.r. measurements have been performed on single crystal specimens of sulfamic acid, ⁺H₃NSO₃⁻, containing 5% D with respect to H. The three isotropically isolated νND bands observed in these spectra at 2302.5, 2313 and 2324 cm⁻¹ were polarized along different crystallograpkic axes, which allowed to assign them to specific hydrogen positions in the crystal and in the NH₃ groups. Comparison of neutron diffraction and vibrational frequency data shows that, despite the differences in NHO hydrogen angles, of all the geometric parameters the N⋯O distance only seems to correlate with the isolated N-D stretching frequencies.     

Thermal degradation of copolymers of styrene and acrylonitrile. II. Reaction products

Hydrogen cyanide is a minor product of degradation of copolymers of styrene and acrylonitrile. The liquid products have been separated and identified by combined gas chromatography and mass spectrometry (GC-MS), as styrene, acrylonitrile, toluene, and benzene. The ratio of styrene to acrylonitrile monomers in the products is approximately twice that of the monomer units in the copolymers, and the ratios of styrene to toluene and benzene are the same as are obtained from pure polystyrene. These ratios were determined by using infrared spectral methods. The fraction of products volatile at the temperature of degradation but involatile at ambient temperature was also analyzed by using GC-MS. A series of four dimers and four trimers were fairly reliably identified. The residual material from copolymers containing up to 33.4% acrylonitrile is always soluble in toluene. The 50/50 copolymer and its residues are insoluble in toluene. Yellow coloration develops in the residues from high acrylonitrile copolymers at advanced stages of degradation. Infrared and ultraviolet spectra suggest that this is due to conjugated unsaturation in the polymer chain backbone which may be associated with the liberation of hydrogen cyanide from the acrylonitrile units.     

In vivo Investigation of Plant-Cell Metabolism by means of natural-abundance 13C-NMR spectroscopy

Based on the natural abundance of ¹³C, in vivo ¹³C-NMR was used for the first time to monitor the metabolism of sucrose and hydroquinone ( 1 ) in cell suspensions of the plant Rauwolfia serpentina (L.) BENTH . ex KURZ . Cells converted sucrose extracellularly into α-D - and β -D -glucose as well as into β -D -fructofuranose and β -D -fructopyranose, respectively. The sugar mixture was completely taken up by the cells after 4 days. Hydroquinone fed at that time resulted in optimum conversion into its β -D -glucoside arbutin ( 2 ) within 10 h. A further metabolite, the primeveroside ( 3 ) of hydroquinone, appeared as a trace compound after 10 h. The formation of this diglycoside can be increased by further addition of sucrose.     

Conformational investigations on cyclic dipeptides containing a proline residue by means of 13C n.m.r. spectroscopy

The amounts of boat (A) and planar (B) forms for the equilibrium state in D₂O and CD₃OD/d₆-DMSO (1:1) were calculated for seven proline-containing cyclic dipeptides from their ¹³C n.m.r. spectra. For c-Pro-Val the thermodynamic functions for the conversion between the boat and planar forms have been obtained from measurements of equilibrium constants at different temperatures.     

Flexibility of phenylene oligomers revealed by single molecule spectroscopy

The rigidity of a p-phenylene oligomer (p-terphenyl) has been investigated by single molecule confocal fluorescence microscopy. Two different rylene diimide dyes attached to the terminal positions of the oligomer allowed for wavelength selective excitation of the two chromophores. In combination with polarization modulation the spatial orientation of the transition dipoles of both end groups could be determined independently. We have analyzed 597 single molecules in two different polymer hosts, polymethylmethacrylate and Zeonex. On average we find a 22 degrees deviation from the linear gas phase geometry (T = 0 K), indicating a rather high flexibility of the p-phenylene oligomer independent of the matrix. To substantiate our experimental results, we have performed quantum chemical calculations at the density functional theory level for the molecular geometry and the electronic excitations. Our findings are in agreement with former experiments on the persistence length of poly(p-phenylenes).     

Investigation of electronic structure of allenyl ethers by means of photoelectron and UV spectroscopy

A study of the photoelectron spectra of alkyl allenyl ethers has demonstrated their similarity to spectra of alkyl vinyl ethers, with the exception of a band in the 10.0–10.3 eV interval due to ionization of the -orbital of the allenyl fragment C=C. According to data obtained by photoelectron spectroscopy and MNDO quantum-chemical calculations, alkyl allenyl ethers with straightchain substituents exist primarily in the s-cis conformation. The stable conformation of allenyl tert-butyl ether is the s-trans form. The long-wave absorption bands in the UV spectra of alkyl allenyl ethers at 255–275 and 208–213 nm are assigned to electronic transitions of the ^* and ^{* *} types; these are quite insensitive to s-cis/s-trans isomerism.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 81–88, January, 1990.The authors are extremely grateful to V. K. Turchaninov for assistance in interpreting the spectra.     

Hybrid organosilazane/organosilylamine telechelic oligomers—I. Two-dimensional NMR spectroscopy characterization of dimethylsilylethylenediamine oligomers

The detailed characterization of multifunctional hybrid organosilazane/organosilylamine telechelic oligomers by IR and ¹H, ¹³C and ²⁹Si NMR spectroscopy in one and two dimenions has been undertaken. The specific multifunctional oligomers, comprising NH/NH₂ or SiCl functionalities depending on the monomer feed-ratio, were prepared from mono- and di-functionally reacted dichlorodimethylsilane (DDS) and mono-, di-, tri- and tetra-functionally reacted ethylenediamine (EDA). Varying the feed-ratio afforded control of the microstructures of the oligomers and the preparation of oligomers with, in some cases, conterminously located silicon–chlorine (SiCl) groups. The combination of the NMR methods with the IR technique has enabled the detailed microstructural characterization of the oligomers and the identification of the functionalities therein. This approach and the knowledge gained from the DDS/EDA system has been applied to the microstructural characterization of other hybrid organosilazane/silylamine preceramic telechelic oligomers.