Cyclo- and cyclized diene polymers. XII. Cationic polymerization of isoprene

Polymerization of isoprene with Lewis acids in n-heptane is a process leading to a quasiequilibrium which is characterized by very low conversions. Polymerization rates in aromatic solvents are much higher due to extensive chain transfer with solvent with regeneration of the original active centers. The rate of monomer disappearance in benzene or toluene when aluminum bromide is the catalyst is second order with respect to monomer concentration. The reaction order with respect to the catalyst depends on the reaction conditions; at constant monomer concentration it is approximately one. Polymerization rates in halogenated solvents with the use of syringe techniques are much higher than those in aromatic solvents. Polymers obtained with various cationic catalysts ranged from oils to white powders having molecular weights up to more than 100,000 depending on reaction conditions. All polymers exhibited infrared spectra characteristic of cyclopolydienes, and the content of linear structures usually did not exceed 20%, irrespective of the nature of the catalyst or solvent. In solvents of higher polarity, such as o-dichlorobenzene, more linear structures were detected. Among residual linear forms the trans-1,4 addition was found to prevail. Residual unsaturation in polymers did not exceed 30%.     

Cyclo- and cyclized diene polymers. XIII. γ-Ray-initiated polymerization of 1,3-dienes

The γ-ray-initiated polymerization of butadiene, isoprene, and 2,3-dimethylbutadiene-1,3 was carried out at temperatures of 20°C. and ?78°C. Polymers of butadiene and isoprene with mixed linear and cyclic structure were proved to result from the polymerization at ?78°C. A monocyclic structure was found for the 2,3-dimethylbutadiene-1,3 polymers initiated either at ?78°C. or in the thiourea canal complex at 20°C.     

An improved method for the diimide hydrogenation of butadiene and isoprene containing polymers

The hydrogenation of unsaturated polymers with diimide generated in-situ by thermolysis of p-toluenesulfonyl hydrazide (TSH) is a commonly used method for preparing laboratory scale quantities of saturated diene based polymers. The by-products from TSH, particularly p-toluenesulfinic acid, can attack at olefinic sites, adding p-tolylsulfone functionality and degrading polymer molecular weight. The addition of tri-n-propyl amine has been found to eliminate these side reactions in butadiene containing polymers and copolymers, enabling the preparation of polymers devoid of backbone unsaturation. No detectable sulfur-containing impurities were indicated by IR, NMR, or elemental analysis, and no chain degradation was observed via GPC analysis of the hydrogenated polymers. cis-Polybutadiene and butadiene containing random and block copolymers with styrene were hydrogenated cleanly using this technique. A ratio of 2 mol TSH and 2 mol amine/mol of olefin was necessary to assure > 99% hydrogenation, and a w/v ratio of 2 parts butadiene/100 parts o-xylene gave the most efficient hydrogenation. Polymers prepared from isoprene were only partially hydrogenated when treated with TSH in the presence of tri-n-propyl amine, and gave evidence of slight degradation of the polymer structure.     

Organometallic polymers. XVI. Copolymerization of styrenetricarbonylchromium and the reaction of polystyrene with chromium hexacarbonyl

Styrenetricarbonylchromium (IV) has been synthesized. Monomer IV did not homopolymerize with free-radical initiation but copolymerized with styrene, methyl acrylate, and vinylcymantrene. The copolymerizations were carried out in benzene solutions at 70°C with azobisisobutyronitrile as the initiator. The relative reactivity ratios were determined for the styrene and methyl acrylate copolymerizations. They were (defining M₁ as monomer IV) r₁ ? 0, r₂ ? 1.39 for styrene copolymerizations and r₁ ? 0, r₂ ? 0.75 for methyl acrylate copolymerization. Polystyrene reacted with chromium-hexacarbonyl in refluxing DME to produce a polymer in which about 32% of the benzene rings were complexed with ? Cr(CO)₃ units. The use of a polystyrene of narrow molecular weight distribution in this reaction demonstrated that no decomposition of the polystyrene chains occurred.     

Synthesis and electrochemical properties of novel redox‐active polymers with anthraquinone moieties by Pd‐catalyzed cyclopolymerization of dienes

Redox‐active polymers enhanced the focus of attention in the field of battery research in recent years. Anthraquinone is one of the most generic redox‐active functional compounds for battery applications, because the quinonide structure undergoes a redox reaction involving two electrons and features stable electrochemical behavior. Although various redox‐active polymers have been developed, the polymer backbone is mostly based on linear alkyl chains [e.g., poly(methacrylate)s, poly(ether)s]. Polymers featuring ring structures in the backbone are limited due to the restricted availability of suitable polymerization techniques [e.g., poly(norbornene)s by ROMP]. The cyclopolymerization of dienes with pendant redox‐active anthraquinone moieties by Pd catalysis represents a novel approach to synthesize redox‐active polymers featuring cyclic structures in the backbone. Electrochemical investigations, in particular cyclic voltammetry, of these new diene monomer, polymers and the corresponding polymer supported carbon paper composites were conducted in different organic electrolytes. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2184–2190     

Influence of a diene impurity on the molecular structure of phosphate-containing polymers with medical applications

We have demonstrated that the unacknowledged presence of almost 30% diene impurity in some commercial phosphate monomers had not only a significant effect on the molecular structure (topology) of a series of synthesized polymers but the instability of the ester functionalities during these polymerizations resulted in unexpectedly complex co-polymer chemistry.     

Syntheses and reactions of optically active polymers. II. Preparations of optically active polymers containing quinine,L-ephedrine,and L-histidine residues and their reactions with α-cyanoethylaquocobaloxime

Preparations of polymers with bis(dimethylglyoximato)cobalt (cobaloxime) were investigated. 4-Vinylpyridine was reacted with α-cyanoethylaquocobaloxime to produce α-cyanoethyl-4-vinylpyridinatocobaloxime (I) in 72% yield. It did not, however, polymerize by the use of azobisisobutyronitrile (AIBN) as an initiator. Polymers containing α-cyanoethylcobaloxime were obtained by reactions of polymers with α-cyanoethylaquocobaloxime (II). Poly(9-O-methacryloylquinine) (III), poly(O-methacryloyl-N-methyl-L -ephedrine) (IV), poly[N^α-(o-vinylbenzyl)-L -histidine] (V), and poly(4-vinylpyridine) (VI) were prepared and used in these reactions. Polymers V and VI were reacted with II to give polymers X, XI, XII, and XIII containing α-cyanoethylcobaloxime.     

The synthesis of diene and of vinyl copolymers containing predetermined quantities of polynuclear hydrocarbon or heterocyclic adducts—IV. Copolymers of butadiene or isoprene,anthracene and a linking agent

Evidence is given that, when solutions of diene monomers and anthracene in tetrahydrofuran are reacted with alkali metal and subsequently titrated with linking agents such as alkyl dihalides, copolymers are formed; they contain the 9,10-dihydroanthracene adduct and the diene in the same proportion as in the original solution. The structures of these copolymers have been elucidated by NMR spectroscopy and the mechanism of formation is discussed.     

Study of photopolymers. XVI. Novel syntheses of the polymers with azidonitrobenzoyl groups and their photochemical and thermochemical reactions

Poly-2-(2-azido-5-nitrobenzoyloxy)ethylmethacrylate (P-II-A) and poly-2-(4-azido-3-nitrobenzoyloxy)ethylmethacrylate (P-II-B) were synthesized from the reactions of 2-hydroxyethylmethacrylate with 2-chloro-5-nitrobenzoic acid and 4-chloro-3-nitrobenzoic acid, respectively, by substitution reactions of sodium azide with the corresponding chloronitrobenzoyl group. In addition, the degradation reaction of the 2-azido-5-nitrobenzoyl group in P-II-A and the transformation of the 4-azido-3-nitrobenzoyl group to 5-carboxylbenzofurazane-1-oxide ring in P-II-B by irradiation with ultraviolet (UV) light or by heating were investigated in detail. In the photochemical reaction the reaction of the azide group in P-II-A was affected by the presence of a spacer in the polymer chain. Moreover, in the thermochemical reaction the rates of the reactions of azide groups in P-II-A and P-II-B were controlled by the facility of molecular motion and the conformation of polymer chains.     

Electrochemically generated tungsten‐based active species as catalysts for metathesis‐related reactions: 1. Acyclic diene metathesis polymerization of 1,9‐decadiene

The application of the WCl₆–e^?–Al–CH₂Cl₂ system to acyclic diene metathesis polymerization of 1,9‐decadiene is reported. The polyoctenamer formed is of a weight‐average molecular weight of 9000 with a polydispersity of 1.92. IR and NMR spectral analyses indicate the retention of the double bonds in the polymer structure with high trans content as expected from a step condensation reaction. This relatively stable catalytic system, however, also activates the competing vinyl addition reactions while being inactive in ring‐closure metathesis reactions. Copyright © 2002 John Wiley & Sons, Ltd.     

Polymerization of coordinated monomers. XVI. Stereoregulation in the alternating copolymerization of methyl methacrylate with styrene in the presence of metal halides

Triad cotacticities of alternating copolymers of methyl methacrylate with styrene prepared in the presence of zinc chloride, ethylaluminium sesquichloride, and ethylboron dichloride are investigated from the mechanistic point of view by means of ¹H- and ¹³C-NMR. The cotacticities from ¹H-NMR spectra are obtained accurately by using α-d-styrene in the place of styrene and by measuring the spectra on the copolymer in o-dichlorobenzene at 170°C. The relative intensities of three peaks of the splitting signal for the methoxy protons in the nonalternating copolymers obtained by the use of benzoyl peroxide in the absence of metal halides agree well with the cotacticity distribution calculated theoretically by the Lewis-Mayo mechanism with the stereoregulation following Bernoullian statistics. The splitting signals in the ¹H- and ¹³C-NMR spectra of the alternating copolymers prepared in the presence of metal halides cannot be explained by the same mechanism. The relative intensities of three peaks of the splitting signals for the methoxy protons and for the carbonyl carbon in the methyl methacrylate unit (the contents of cotactic triads centered by the methyl methacrylate unit) are not equal to those for the aromatic C₁ carbon in the styrene unit (the contents of cotactic triads centered by styrene unit). The value of f²Y - 4fxfz is not equal to zero, where fx, fy, and fz are the cosyndiotactic, coheterotactic, and coisotactic triad contents, respectively, in the alternating copolymer. Copolymers obtained in the presence of zinc chloride are not exactly equimolar alternating but always contain a methyl methacrylate unit in excess, and the relative intensities of the three peaks for the aromatic C₁ carbon change with the copolymer composition. These results are explained by a proposed mechanism: the alternating copolymerization proceeds through the homopolymerization of a ternary molecular complex composed of a metal halide, methyl methacrylate, and styrene, accompanied with the stereoregulation following first-order Markovian statistics; the increase of methyl methacrylate content in the copolymer prepared in the presence of zinc chloride is caused by the participation of the binary molecular complex composed of a metal halide and methyl methacrylate in addition to the ternary molecular complex.     

The synthesis of diene and of vinyl copolymers containing predetermined quantities of polynuclear hydrocarbon or heterocyclic adducts—II. The reaction of alkali metal salts of anthracene with alkyl halides

The reactions of alkali metal salts of anthracene with alkyl halides result in the formation of 9,10-dialkyl 9,10-dihydroanthracenes as the principal product, although appreciable quantities of other adducts, notably the 1,2- and 1,4-dialkyl compounds, are also formed.When the disodium salt is used, these adducts account for the total anthracene consumed, but with the dilithium salt appreciable quantities of 9,(4-hydroxybutyl) anthracene compounds are produced; they resulted from additive reaction of the salt with the tetrahydrofuran solvent. In the present experiments, these adducts account for about 20 per cent of the anthracene, but this proportion may be increased by prolonging the standing of the dilithium anthracene solution before reacting with alkyl halide.     

Change in the selectivity of the action of catalysts during the hydrogenation of the diene group. Communication 2. Modification of a nickel catalyst with cadmium

Russian Chemical Bulletin -     

Side-chain liquid crystalline polymers with silphenylene-siloxane main chains. II. Preparation and characterization of polymers containing biphenyl mesogens

Side-chain liquid crystalline polymers with poly(silphenylene-siloxane) backbones and 4,4′-biphenyl-containing pendant mesogenic groups have been prepared and characterized. Polymers with spacers having only three methylene groups were not liquid crystalline, LC, but those with spacers having eight methylene groups or more and a long terminal substituent were LC as indicated by an isotropization peak on the shoulder of the melting peak in the DSC thermogram and the appearance of a Schlieren texture on examination by polarized light microscopy. However, the LC behavior could not be confirmed by wide-angle X-ray diffraction, WAXD, because the crystalline pattern apparently remained up to the isotropization temperature, presumably because the melting transition and isotropization are too close. In contrast, polymethylsiloxanes with the same mesogenic side-chains revealed the presence of well-defined smectic phases by WAXD as well as by polarized light microscopy.     

Development and evaluation of a detailed mechanism for the atmospheric reactions of isoprene and NOx

A detailed photochemical mechanism for the atmospheric reactions of isoprene and its major oxidation products in the presence of NO_x, which incorporates the most recent laboratory results and our current understanding of the system, is described. It is evaluated by comparing its predictions against results of NO_x-air irradiations of isoprene and its two major products, methacrolein, and methyl vinyl ketone (MVK), in five different types of environmental chambers at two different laboratories. In most cases it simulated experimental results within the uncertainty of the data and the chamber and run characterization model. However, the photodecomposition quantum yields of methacrolein and MVK and the organic nitrate yield from the OH + isoprene reaction had to be adjusted to obtain satisfactory simulations of the data. The major discrepancy observed was that the model tended to underpredict PAN by ca. 40% in the isoprene experiments, despite the fact that the model predicted PAN from methacrolein and MVK reasonably well. The uncertainties and additional data needed to completely characterize the isoprene atmospheric photooxidation system are discussed. © 1996 John Wiley & Sons, Inc.