Anionic polymerization of vinyl monomers with xanthates

The polymerization of vinyl monomers with various xanthates (potassium tert-butylxanthate, potassium benzylxanthate, zinc n-butylxanthate, etc.) were carried out at 0°C in dimethylformamide. N-Phenylmaleimide, acrylonitrile, methyl vinyl ketone, and methyl methacrylate were found to undergo polymerization with potassium tert-butylxanthate; however, styrene, methyl acrylate, and acrylamide were not polymerized with this xanthate. In the anionic polymerization of methyl vinyl ketone with potassium tert-butylxanthate, the rate of the polymerization was found to be proportional to the catalyst concentration and to the square of the monomer concentration. The activation energy of methyl vinyl ketone polymerization was 2.9 kcal/mole. In the polymerization, the order of monomer reactivity was as follows: N-phenylmaleimide > methyl vinyl ketone > acrylonitrile > methyl methacrylate. The initiation ability of xanthates increased with increasing basicity of the alkoxide group and with decreasing electronegativity of the metal ion in the series, lithium, sodium, and potassium tert-butylxanthate. The relative effects of the aprotic polar solvents on the reactivity of potassium tert-butylxanthate was also determined as follows: diethylene glycol dimethyl ether > dimethylsulfoxide > hexamethylphosphoramide > dimethylformamide > tetrahydrofuran (for methyl vinyl ketone); dimethyl sulfoxide > hexamethylphosphoramide > dimethylformamide ? diethylene glycol dimethyl ether (for acrylonitrile).     

Polymerization of vinyl monomers by alkali metal–thiobenzophenone complexes

The polymerization of vinyl monomers by use of alkali metal (Li, Na, K)–thiobenzophenone complexes was studied. Monoalkali metal complexes of thiobenzophenone (thioketyls) induced the polymerization of vinyl monomers such as acrylonitrile (AN) and methyl methacrylate (MMA), and dialkali metal complexes of thiobenzophenone (dianion) induced the polymerization of styrene (St), butadiene (Bd), and isoprene (Ip) as well as AN and MMA. The polymerization of MMA with the dianion was initiated by both the mercaptide and the carbanion of the dianion, but that of styrene was initiated by the carbanion alone. In the case of polymerization of MMA by the thioketyl, the initial rate of polymerization depended on the catalyst concentration and the square of the monomer concentration. Similar results were obtained in the case of the dianion. The polymer yield increased with increasng polarity of sovents. In the copolymerization of AN with MMA, the copolymer obtained consisted almost of AN units. From these results, it was concluded that the polymerization proceeded by anionic mechanisms.     

Metal-Containing Initiator Systems. XXIX. Selective Initiation of Vinyl Polymerizations with Cobaltocene

The polymerizations of acrylonitrile (AN), acrolein (AL), butadiene (BD), and isobutyl vinyl ether (EBVE) with cobaltocene were investigated. It was found that both AN and AL could polymerize in dimethyl sulfoxide through a coordination mechanism, but AN and BD polymerized by a radical mechanism in the presence of some organic halides, such as carbon tetrachloride, benzyl bromide, and allyl bromide. The initiator system of cobaltocene and organic halide also induced cationic polymerization of IBVE. On the basis of the results obtained, a mechanism for the selective initiation of polymerization is proposed and discussed.     

Effect of temperature and solvents on stereospecific polymerization of vinyl alkyl ethers catalyzed by aluminum sulfate–sulfuric acid complex

The effect of polymerization temperature and solvents was determined on the crystallinity of polymers of vinyl isobutyl ether and of vinyl n-butyl ether prepared with aluminum sulfate–sulfuric acid complex catalyst. Principally, the methyl ethyl ketone (MEK)-insoluble fractions of these polymers were used for characterization. Density, per cent crystallinity by x-ray diffraction, infrared ratio, and dilatometric volume contraction of these polymer fractions were used as criteria of crystallinity. The MEK-insoluble fractions of poly(vinyl n-butyl ethers) prepared in carbon disulfide in the temperature range of ?30 to +25°C did not show any significant difference in the values of the above crystallinity parameters. The polymer obtained at 50°C. was less crystalline than the rest of the polymers. The MEK-insoluble fractions of poly(vinyl isobutyl ethers) prepared at 0–50°C. in carbon disulfide and n-heptane solvents also did not significantly differ in their degree of crystallinity. They were, however, decidedly less crystalline than the MEK-insoluble fractions of the corresponding polymers obtained at ?20°C. These data a indicate that on increasing the temperature of polymerization the crystallinity of the polymers was either unchanged or decreased slightly. The polymerizations of vinyl n-butyl ether and vinyl isobutyl ethers were also carried out in binary mixtures of carbon disulfide with n-heptane, chlorobenzene, and MEK. Generally, increasing the concentration of carbon disulfide increased the inherent viscosities of polymers as well as the weight percentage of their MEK-insoluble fractions. The MEK-insoluble fraction of poly(vinyl isobutyl ether) prepared in carbon disulfide-MEK mixture (volume ratio 2:1) was isotactic and highly crystalline. Likewise, the MEK-insoluble fractions of two polymers of vinyl n-butyl ether prepared in MEK itself were also isotactic and highly crystalline. Compared to poly(tetramethylene oxide), these latter fractions exhibited less dependence of rate of crystallization upon temperature. Consequently, at low degrees of supercooling they crystallize much more rapidly than does poly(tetramethylene oxide).     

Modified copolymers of bifunctional vinyl ethers with methyl vinyl sulfide as active matrices of solid superbases

Reactive linear and crosslinked copolymers of diethylene glycol divinyl ether and ethylene glycol vinyl glycidyl ether with methyl vinyl sulfide have been synthesized in the presence of 2,2′-azobis(isobutyronitrile) (2%, 60 °C, 45–55 h) in ∼53% yield. The hydrolyzed at the residual vinyloxy and epoxy groups and oxidized at the methylthio groups copolymers upon treatment with KOH afford alkoxide (complex) and crown-like superbases. They are capable of catalyzing the acetone ethynylation, as well as the prototropic isomerization of methyl propargyl ether to allenyl methyl ether and vinylation of ethylene and diethylene glycols with acetylene.     

Copolymerization of 2-methylene-4-phenyl-1,3-dioxolane with electrophilic vinyl monomers through zwitterionic mechanism

Spontaneous copolymerization of cyclic ketene acetal, 2-methylene-4-phenyl-1,3-dioxolane ( I ) with common electrophilic vinyl monomers, such as methyl α-cyanoacrylate (MCA), acrylonitrile (AN), and methyl methacrylate (MMA) were investigated to further explore zwitterion polymerization method with cyclic ketene acetals. In the reaction of I with MCA and AN, spontaneous copolymerization took place at ambient temperature. The copolymers of I with MCA gave low molecular weight polymers, but copolymers obtained with I and AN were high molecular weight polymers. In the reaction of I and MMA, high molecular weight copolymer was obtained only at temperatures above 80°C. Thus, obtained polymers were not the alternating copolymers and possessed high I content in all the cases. From the above results, macrozwitterionic mechanism was suggested as discussed.     

Polymerization of vinyl monomers initiated by organoaluminium compounds/benzoyl peroxide systems

The free-radical polymerization of methyl methacrylate (MMA) initiated by systems comprizing benzoyl peroxide (BPO) and different organoaluminium compounds (OACs) has been studied. The influence of the type of OAC, concentration of components of the initiation system, temperature, and time on the reaction yield have been determined. Systems containing BPO and diethylaluminium chloride (Et₂AlCl) have been found to enable us to obtain, in high yields at room temperature, of homopolymers of MMA, methyl acrylate, acrylonitrile (AN), vinyl acetate, and the alternating AN/styrene (St) copolymer; they are, however, not very active in the homopolymerization of St and vinyl chloride. Factors affecting the polymerization yield have been discussed in terms of the mechanism of the reaction between BPO and OACs, reactivity of alkyl radicals formed in these systems, and catalytic effect of OAC in the propagation step.     

Polymerization of vinyl monomers with salts of bronsted acids

The polymerization of vinyl monomers (N-phenylmaleimide, acrylamide, acrylonitrile, methyl vinyl ketone, methyl methacrylate, vinyl chloride, and styrene) with sodium salts of Brønsted acids (sodium cyanide, sodium nitrite, sodium hydroxide, etc.) were investigated at 0°C in dimethylformamide. N-Phenylmaleimide, acrylonitrile, and methyl vinyl ketone were found to undergo polymerization with sodium cyanide, however the other monomers were not polymerized with this salt. In the polymerizations of acrylonitrile and N-phenylmaleimide with sodium cyanide, the rates of the polymerizations were found to be proportinal to the initiator concentration and to the square of the monomer concentration. The activation energy of acrylonitrile polymerization was 3.7 kcal/mole, and that of N-phenylmaleimide ws 3.0 kcal/mole. The results of the copolymerization of acrylonitrile with methyl methacrylate at 0°C in dimethyl-formamide with sodium cyanide confirm that these polymerizations proceeded by an anionic mechanism initiated by the Michael addition reaction of the monomers with the salts. In these polymerizations, the monomer reactivity increased with increase in the e values. The initiation ability of sodium salts increased with increasing pK_a of the conjugate acids and with decreasing electronegativity of metal ion in the series of lithium, sodium, and potassium cyanide. The polymerizations took place only in aprotic polar solvents, and did not occur in weak polar solvents and in protonic solvents.     

EFFECTS OF VINYL ETHERS UPON RADICAL POLYMERIZATIONS

Various vinyl ethers have been examined as additives during radical polymerizations initiated by azobisisobutyronitrile at 60°C; the monomers were methyl methacrylate (MMA), styrene (STY) and acrylonitrile (AN). For MMA and STY, the vinyl ethers were incorporated to only small extents but they caused reductions in rate of polymerization and chain length of the resulting polymer; the effects can be attributed to the low reactivities in growth reactions of radicals to which a vinyl ether unit was last added. Copolymerization of the vinyl ethers with AN was more evident but, in many cases, it was accompanied by increased rate of consumption of AN and increased chain length of the polymer. These changes can be explained in terms of a physical effect which can be likened to that believed to be responsible for the gel effect. It is considered that polymer radicals are rather tightly coiled in an indifferent solvent so that the normal bimolecular termination is impeded.     

Formation of diethylene glycol as a side reaction during production of polyethylene terephthalate

Polymers of poly(ethylene terephthalate) (PET) always contain a certain amount of incorporated diethylene glycol (DEG), substituting the incorporated glycol. DEG is formed in a side reaction during the ester interchange of dimethyl terephthalate (DMT) with ethylene glycol or during direct esterification of terephthalic acid with ethylene glycol, and to a smaller extent during the polycondensation of the low-molecular material. DEG is formed via an unusual type of reaction: ester + alcohol → ether + acid. Some evidence of this type of reaction is given by the formation of dioxane in low molecular PET and of methyl Cellosolve and methyl carbitol during the ester interchange of DMT with ethylene glycol and diethylene glycol, respectively. The strongest support for this type of reaction, however, was obtained from kinetic data. Polyesters of low molecular weight with OH group contents ranging from 3 to 0.5 mole/kg were heated at 270°C in sealed tubes for 1–7 hr. The kinetic equation for the proposed reaction is: d[DEG]/dt = k[OH] [ester]. With the aid of one rate constant the formation of DEG in all esters could be described.     

Functional polymers. III. Asymmetric Michael reactions catalyzed by cinchona alkaloid–acrylonitrile copolymers

The enantio-differentiating abilities of cinchona alkaloid–acrylonitrile copolymers (AN–CA) in the Michael reactions were studied. The reaction of methyl indan-1-one-2-carboxylate (I) with methyl vinyl ketone in toluene at room temperature yielded product (II) in 24–42% optical yield, depending on the type and frequency of the alkaloid units on the polymeric skeleton. The catalysts were recovered from the reaction mixture by filtration and with retention of their stereoselectivities. Modification of the amino or hydroxyl group of the alkaloid moiety greatly reduced the reaction rate and optical yield. The asymmetric reactions of other donors (III–VII) with methyl vinyl ketone were also studied.     

<Emphasis Type="Italic">P. psyllium</Emphasis>-<Emphasis Type="Italic">g</Emphasis>-polyacrylonitrile: synthesis and characterization

P. psyllium mucilage, an anionic natural polysaccharide consisting of pentosan and uronic acid obtained from the seeds of Plantago psyllium (Plantago family), was grafted with acrylonitrile (AN). Graft copolymers were prepared by grafting acrylonitrile onto P. psyllium mucilage (PSY) using ceric ion initiated solution polymerization technique for the very first time. The influence of varying concentration of (AN) and ceric ammonium nitrate (CAN) on graft copolymerization was studied. The percent grafting was found to be affected by the concentrations of AN and CAN in the reaction mixture. The prepared copolymers were not soluble in any common solvent or mixture of solvents. The prepared copolymers were characterized by FTIR.     

Cobalt-mediated radical polymerization of acrylonitrile: kinetics investigations and DFT calculations

The successful controlled homopolymerization of acrylonitrile (AN) by cobalt-mediated radical polymerization (CMRP) is reported for the first time. As a rule, initiation of the polymerization was carried out starting from a conventional azo-initiator (V-70) in the presence of bis(acetylacetonato)cobalt(II) ([Co(acac)(2)]) but also by using organocobalt(III) adducts. Molar concentration ratios of the reactants, the temperature, and the solvent were tuned, and the effect of these parameters on the course of the polymerization is discussed in detail. The best level of control was observed when the AN polymerization was initiated by an organocobalt(III) adduct at 0 degrees C in dimethyl sulfoxide. Under these conditions, poly(acrylonitrile) with a predictable molar mass and molar mass distribution as low as 1.1 was prepared. A combination of kinetic data, X-ray analyses, and DFT calculations were used to rationalize the results and to draw conclusions on the key role played by the solvent molecules in the process. These important mechanistic insights also permit an explanation of the unexpected "solvent effect" that allows the preparation of well-defined poly(vinyl acetate)-b-poly(acrylonitrile) by CMRP.     

Synthesis of functional polymers bearing cyclic carbonate groups from (2-oxo-1,3-dioxolan-4-yl) methyl vinyl ether

(2-Oxo-1,3-dioxolan-4-yl) methyl vinyl ether (OVE) was synthesized with high yield by addition reaction of glycidyl vinyl ether with carbon dioxide using tetrabutylammonium bromide (TBAB) as a catalyst. OVE was also prepared by reaction with β-butyrolactone or sodium hydrogencarbonate in the presence of TBAB as the catalyst. Poly [(2-oxo-1,3-dioxolan-4-yl) methyl vinyl ether] [P(OVE)] was obtained with high yield by cationic polymerization of OVE catalyzed using boron trifluoride diethyl ether complex in dichloromethane. Polymers bearing pendant 5-membered cyclic carbonate groups were also prepared by radical copolymerization of OVE with some electron-accepting monomers. Furthermore, addition reaction of P(OVE) with alkyl amines yielded the corresponding polymer having pendant 2-hydroxyethyl carbamate residue with high conversions. © 1994 John Wiley & Sons, Inc.     

Vinyl monomers bearing chromophore moieties and their polymers. IV. Fluorescence and photosensitizing behavior of 8-acryloyloxyquinoline and its polymer

Acrylic monomers bearing electron-donating quinolyl moiety, i.e., 8-acryloyloxyquinoline (AQ) was prepared and polymerized. It was found that the fluorescence intensity of AQ was much lower than that of P(AQ) at the same chromophore concentration. The fluorescence of P(AQ) could be quenched by electron-deficient vinyl monomers, such as acrylonitrile (AN) and methyl methacrylate (MMA). This is another example of the “fluorescence structural self-quenching effect” termed by us previously, and demonstrates again that this phenomenon is not an accidental but a general one for acrylic monomers bearing electron-donating chromophores. The photopolymerization of acrylonitrile (AN) sensitized by AQ and P(AQ) as well as combining with carbon tetrabromide (CBr₄) was studied kinetically. From the rates of the polymerization (R_p) and overall activation energies obtained for these four systems, it was found that R_p sensitized by the binary systems was much higher than by AQ or P(AQ) alone, while the molecular weights of the resulting P(AN) were lower. The fluorescent analysis of the resulting P(AN) in solution showed that the sensitizers also entered into the P(AN) chains. A mechanism of charge transfer complex (CTC) formation was tentatively suggested for the photopolymerization of AN initiated by these four systems. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1087–1093, 1997     

Thermophysical properties of binary liquid mixtures of polyether and n-alkane at 298.15 and 323.15 K: heat of mixing,heat capacity,viscosity, density and thermal conductivity

An apparatus for a rapid and simultaneous determination of the thermophysical properties excess enthalpy, isobaric heat capacity, kinematic viscosity, density and thermal conductivity has been developed. The experimental setup is subject of this paper. At 298.15 and 323.15 K, the systems ethylene glycol dimethyl ether–n-dodecane, diethylene glycol dimethyl ether–n-dodecane, triethylene glycol dimethyl ether–n-dodecane, tetraethylene glycol dimethyl ether–n-dodecane and diethylene glycol dibutyl ether–n-dodecane have been investigated. The experimental results are correlated and the macroscopic properties are interpreted.     

Effect of reaction medium on copolymerization of acrylonitrile and methyl acrylate

The copolymerization of acrylonitrile (AN) with methyl acrylate (MEA) has been investigated in three types of polymerization, i.e., emulsion polymerization in water with a water-soluble initiator, suspension polymerization in water with an oil-soluble and water-insoluble initiator, and solution polymerization in dimethyl sulfoxide (DMSO). Monomer reactivity ratios at 50°C. for AN and MEA are found to be r₁ = 0.78 ± 0.02, r₂ = 1.04 ± 0.02 in emulsion polymerization; r₁ = 1.02 ± 0.02, r₂ = 0.70 ± 0.02 in DMSO solution polymerization; r₁ = 0.75 ± 0.05, r₂ = 1.54 ± 0.05 in suspension polymerization. The large differences found in the reactivity ratios may be attributed to the different ratio of concentration of two monomers in the loci of polymerization. Chemically, AN is somewhat more reactive than MEA as shown by the reactivity ratios in DMSO. In the case of the suspension polymerization, the MEA/AN ratio in the polymer particles in which polymerization occurs may be higher than that in the total phase. Experimental results of the emulsion polymerization show that the emulsion polymerization of AN occurs both in the particles and in water. In addition, rates of the copolymerization of AN with MEA have also been investigated.     

The location of olefinic bonds in mono- and di-unsaturated compounds

The use of vinyl methyl ether as a chemical ionization reagent gas for the location of olefinic bonds is limited by reactions of various ion with vinyl methyl ether molecules. A 75: 20: 5 mixture of nitrogen/carbon disulphide/vinyl methyl ether suggested by Harrison and Chai gives much cleaner spectra and has been used to study octenes and octadienes. Evidence is presented to indicate the formation of two reaction complexes with octenes and four reaction complexes with unconjugated octadienes. Elimination of olefins from these complexes allows one to infer the positions of the carbon-carbon double bonds in each type of molecule.     

Syntheses and Surface Properties of Polyacrylonitrile-based Copolymer Membranes Containing Sugar Moieties

Introduction Asatypeofwidelyusedmembranematerials, polyacrylonitrile(PAN)hasbeeninvestigatedby manyresearchersinthefieldsofpervaporation,ul- trafiltration,anddialysis[1_4].However,PAN- basedmembranesarerelativelyhydrophobicwitha lowbiocompatibility.Thesepropertieslimittheir furtherapplicationsinaqueoussolutionseparation andtheirusageasbiomedicaldevices.Muchatten- tionhasbeenpaidtoimprovingthecharacteristics ofPAN-basedmembranes.Thecopolymerization ofANwithhydrophilicmonomersisconsideredas…     

Sodium hydride-initiated polymerizations of vinyl monomers in aprotic solvents

Polymerizations of several vinyl monomers at 25°C in aprotic solvents (dimethyl sulfoxide, N,N-dimethylacetamide, and hexamethylphosphoric triamide) using sodium hydride dispersion as initiator yield low to intermediate molecular weight polymers. The molecular weight of the resulting polymer as well as the mode of initiation depends on the monomer and aprotic solvent used. Initiation of polymerization of monomers with available α hydrogens (methyl acrylate, acrylonitrile) involves monomer anion, while initiation of a monomer with no α hydrogen (methyl methacrylate) proceeds by a more complex mechanism. In contrast, initiation of styrene and α-methylstyrene proceeds by dimsyl anion addition to monomer in dimethylsulfoxide. Although the triad tacticities and number-average molecular weights of poly(methyl methacrylate) samples obtained from all three aprotic solvents are nearly the same, poly(methyl methacrylates) prepared in dimethyl sulfoxide and N,N-dimethylacetamide give polymers having polydispersities of ～3, while a very polydisperse polymer is obtained in hexamethylphosphoric triamide.