Alternative copolymerization of vinyl sulfides with maleic anhydride. III. Alternative copolymerization

Ethyl vinyl sulfide (EVS) and phenyl vinyl sulfide (PVS) were found to undergo alternative copolymerization with maleic anhydride (MAn) even in the absence of radical initiators. It is noted that both the rates and the reduced viscosities in these alternative copolymerization show a maximum at 50 mole-% comonomer mixture, anticipating that a 1 : 1 charge transfer complex is formed preceding polymerization. From spectroscopic studies, it was also observed that the formation of such a complex between vinyl sulfide and MAn was confirmed, but their equilibrium constants were quite small, i.e. 0.090 l./mole for PVS-MAn in CHCl₃ and 0.035 l./mole for EVS-MAn in CH₂Cl₂ at room temperature. The mechanism of these alternative copolymerizations is discussed.     

Radical copolymerization of cyclic acetals derived from acrolein, 2. Alternating copolymerization

Copolymerizations of 2-vinyl-l,3-dioxane ( 1a ), 5,5-bis(hydroxymethyl)-2-vinyl-1,3-dioxane ( 1b ), and 5,5-dimethyl-2-vinyl-1,3-dioxane ( 1c ) with maleic anhydride (MA) and N-vinyl-2-pyrrolidone (NVP) were investigated. Copolymerization of the cyclic acetals 1 with MA yielded copolymers with perfectly alternating sequences independent of the initial monomer feed composition. Terpolymerization of 1a , MA, and styrene, also despite of monomer composition, yielded terpolymers with a molar composition of 50% in MA which confirms the participation of transfer complexes in these copolymerizations. The composition of the 1 /NVP copolymers (mole fraction) F₁(NVP) ≈ 0,6–0,8 also varied little with the feed. The copolymerization rates passed through a maximum when the monomer mixture contained a mole fraction f₁ (NVP) of ca. 0,7.     

Copolymer-monomer miscibility during copolymerization

Significant drift in the compositions of copolymer and of unreacted monomer mixture is predicted to occur during the bulk copolymerization of N-vinyl-2-pyrrolidone (VP) with butyl acrylate (BA), when the inital feed mixture contains 75 wt.-% VP. The drift in copolymer composition has been confirmed by 1 the optical appearance and glass transition (T_g) behaviour of the products of the γ-ray initiated copolymerization at various fractional conversions (C) and 2 the T_g behaviour of low-conversion samples of poly(VP-co-BA) blended in propertions so as to simulate the overall composition of material that would be present cumulatively at selected values of C during an actual copolymerization. The compositions of unreacted monomer mixtures co-existing with copolymer at selected conversions have been calculated and intrinsic viscosities [η] of blends dissolved in these VP/BA mixtures have been measured. Theta conditions for the blends have been established turbidimetrically in chloroform/heptane and the corresponding values of [η]_Θ measured. The chain expansion factors thereby derived from [η] and [η]_Θ show a decreasing affinity of copolymer for residual monomer during the course of copolymerization.     

High conversion copolymerization, 1. Kinetics of the copolymerization of styrene and maleic anhydride

The copolymerization of styrene (S) with maleic anhydride (MAn) in 1,4-dioxane at 60, 70 and 80°C up to high conversion (≈ 98%) was followed by differential scanning calorimetry. The rate of copolymerization increases up to 20 – 40% conversion of both monomers and then gradually decreases to zero. The increase in the copolymerization rate is more pronounced for equimolar ratios [S]/[MAn] as compared to ratios with an excess of S. For a given mole ratio of S and MAn the copolymerization rate in 1,4-dioxane is higher at higher total monomer concentrations and/or at higher temperatures. The heat of copolymerization is 81,6 kj · mol^?1 for the equimolar [S]/[MAn] mixture. For mixtures with [S]/[MAn] > 1 the heat of reaction is between 70 and 80 kj · mol^?1. The limitingconversion of styrene for [S]/[MAn] = 1 is about 98%, and for [S]/[MAn] > 1 it is a function of the [S]/[MAn] ratio. Assuming exclusively the formation of an alternating S/MAn copolymer the following relation is derived. for the ratio of the apparent rate constants of propagation k?_p, and termination k?</_t.     

Reversible copolymerization at equilibrium

The relationships for copolymer composition and microstructure in reversible copolymerization at equilibrium are derived. They allow to predict the comonomer equilibrium concentrations and the structure of the copolymer at equilibrium if the initial state and equilibrium constants are known and provided that [I] ? [M₁]₀ + [M₂]₀ - [M₁]_e - [M₂]_e.     

Ring-opening copolymerization of anhydroalditols with tetrahydrofuran

By ring-opening copolymerization of 1,4-anhydro-2,3-di-O-ethyl-D-erythritol (cis-3,4-diethoxyoxolane, 1 ) or 1,4:2,5:3,6-trianhydro-D-mannitol ( 3 ) with tetrahydrofuran carbohydratecontaining copolyether polyols were obtained. Using trifluoromethanesulfonic acid as catalyst the molecular weights were in a range from M?_w = 13 000 up to 25 000 with about 10% of carbohydrate constituent. The novel copolyethers were studied by polymer analytical procedures, their structures 4 and 5 tentatively assigned and compared to the homopolymerization products of the monomers. The present procedure features an approach to novel partially functionalized high molecular weight copolymer polyols based on carbohydrate-derived materials.     

Cationic copolymerization of dioxolan and tetroxan

The cationic copolymerization of dioxolan (DOL) and tetroxan (TEX) at a mole-ratio of 9/1 with BF₃OEt₂ in toluene was studied by gas chromatography and NMR. The very reactive TEX was consumed at an early stage, whereas DOL was consumed slowly until an equilibrium conversion was reached. Correspondingly, the fraction of formal units in the copolymers decreased gradually with conversion. Therefore TEX is both kinetically and thermodynamically more reactive than DOL. As a by-product, a significant amount of trioxepan was found, which indicates a rather facile back-biting reaction.     

Cationic polymerization and copolymerization of vinylferrocene

Vinylferrocene was shown to undergo readily cationic polymerization by FRIEDEL-CRAFTS and other cationic catalysts. The polymers obtained possessed rather low molecular weights, the highest being 3500. In spite of the high reactivity of the ferrocene nucleus towards electrophilic substitution, no mode of propagation other than vinyl addition was detected when the infrared spectra of polymers prepared by cationic and free radical reactions were compared. The electronic spectra of polyvinylferrocene and its oxidized form were similar to those of ferrocene and ferricinium ion, respectively. In the cationie copolymerization with styrene, the latter was incorporated into the polymer only when the styrene content in the monomer feed exceeded 90%. The copolymerization with vinyl isobutyl ether (M₂) by BF₃OEt₂ in toluene at 0°C gave the reactivity ratios: r₁ = 0.1 ± 0.1, r₂ = 9.7 ± 1.0. The high cationic reactivity of vinylferrocene is consistent with the stability of the α-ferrocenylearbonium ion inferred from solvolysis and other reactions.     

Anionic copolymerization of acrolein with aldehydes

Unsaturated copolyacetals have been prepared by anionic copolymerization of acrolein with aldehydes, such as, acetaldehyde, benzaldehyde, propionaldehyde, pivaldehyde and others. The dependence of the structure of the copolymers on the dielectric constant of the solvent, and on the temperature, the aldehyde, the catalyst and the extension of the reaction has been studied.     

Anionic homo- and block copolymerization of vinylferrocene

Vinylferrocene was polymerized by means of anionic initiators such as n-BuLi, s-BuLi and distyryl disodium in tetrahydrofuran as solvent. In all cases the polymerization shows the characteristics of a living polymerization. Depending on the sequence of the monomer addition, either block copolymers of the ABA or the AB type were synthesized.     

Polymerization and copolymerization of cyclic unsaturated sulfides

The polymerization and copolymerization behaviour of the unsaturated cyclic sulfides 2,3-dihydrothiophene ( 1 ), 2,3-dihydrothiopyran ( 2 ) and p-Dithiene ( 3 ) was studied. With cationic initiators such as borontrifluoride etherate, all three monomers were transformed into polymers. The five-membered ring compound 1 gave quantitative yields, the two six-membered ring compounds 2 and 3 gave limited conversions. This was attributed to the advantageous geometrical position of the pen-penultimate sulfide function toward the growing chain-end to form a sulfonium ion. Radical homopolymerization was impossible for all three monomers but copolymerization with different vinyl monomers yielded copolymers with various sulfide unit contents. From the copolymerization reactivity parameters of the copolymerization with methyl acrylate, the reactivity of the different monomers towards a growing polymer chain ending with a methyl acrylate radical could be compared. The sequence was 1 ≥vinyl sulfides ? 2>3 . Copolymerization with maleic anhydride yielded alternating copolymers independent of the monomer feed composition. This copolymerization is believed to occur via the formation of a charge-transfer complex between the two comonomers. The association constants of complex formation in chloroform were measured.     

Determination of copolymerization parameters in steady state

In the proposed method copolymerization is carried out in an agradient flow reactor where a steady state is established. For the homogenous radical process the following copolymerization equation holds where r₁ and r₂ are the reactivity ratios; a₀, b₀ and a, b are the feed (with index) and steady mole ratios of monomers to an internal standard. Experimentally the relative substance quantities in the reaction system can be measured with the help of gas-chromatography. It is possible to calculate statistically the most probable values for r₁ and r₂ as parameters of the linear form of the above equation. As an example the reaction of styrene and methyl methacrylate in toluene initiated by benzoyl peroxides at 100°C was used. The results are r₁ =0,582±0,044 and r₂ =0,530±0,004; they agree well with literature values.     

On the copolymerization of acrylonitrile with styrene in the presence of Lewis acid, 3. Photoinitiated copolymerization

The rate of the acrylonitrile (AN)-styrene (St) copolymerization (R_p) photoinitiated (λ=365 nm) by the St? AN? ZnCl₂ complex at 30°C is proportional to the square root of the intensity of radiation. The limiting viscosity number [η] of alternating copolymers increases with the intensity of radiation. The 1/[η] vs. R_p relationship for the St? AN copolymers is similar as has been found for the initiation of copolymerization by thermal decomposition of 2,2-azoisobutyronitrile. Provided benzophenone combined with 2-propanol is used as a photosensitizer, the rate of the St? AN copolymerization in acetone—at constant concentrations of both comonomers, zinc chloride, and benzophenone—decreases with 2-propanol concentration in the reaction mixture. If benzophenone alone (e.g. without 2-propanol) is used as a photosensitizer under equal conditions, the observed values of the rate of copolymerization are lower in comparison with the system where the ternary molecular complex is empolyed as a photosensitizer. Moreover, R_p decreases with increasing concentration of benzophenone in the system. These findings are interpreted as a result of the termination reactions of ketyl radicals (hydroxydiphenylmethyl radicals) with macroradicals of copolymer.     

Free radical copolymerization of butadiene and vinylferrocene

The free radical copolymerization of butadiene and vinylferrocene was studied at 60°C in 1,4-dioxane. Copolymerization occurs readily to give low molecular weight random copolymers. The reactivity ratios are r₁ (butadiene) = 3,5±0,5 and r₂ (vinylferrocene) = 0,30±0,10 and the Q and e values for vinylferrocene are 0,68 and ?1,05, respectively. The copolymers are shown to contain a paramagnetic species which is identified as a high spin Fe(III) complex.     

Graft copolymerization of methyl methacrylate onto cellulose

Methyl methacrylate has been grafted onto cellulose pulp using manganic ion as the initiator. The variable parameters studied are initiator and monomer concentrations, temperature and reaction time. The grafting efficiency, degree of grafting and frequency of grafting are found to be dependent on the above mentioned variables.     

Photo-induced copolymerization of cyclohexene with maleic anhydride

Kinetics and mechanism of photo-induced copolymerization of cyclohexene with maleic anhydride in chloroform were studied. The UV spectra suggested the formation of a chargetransfer complex between the comonomers. This complex was excited under irradiation and then underwent hydrogen abstraction to produce two kinds of radicals for initiation. The polymerization produces an alternating copolymer in the composition range of 25 to 75 mol-% of either comonomer. The chain-transfer role of cyclohexene was also investigated.     

Asymmetric copolymerization of styrene homologues with oxygen

Styrene homologues (styrene, α-methylstyrene, and β-methylstyrene) were copolymerized with oxygen to produce optically active copolymers in the presence of a chiral Co(II) (Schiffbase) complex. The absolute configuration of the carbon atom in the copolymer chain was determined by hydrogenolysis of the copolymer to phenylethanediol derivatives. In the cases of styrene and α-methylstyrene, (R)-(+)-1-phenylethanediol and (R)-(+)-2-phenyl-1,2-propanediol were preferentially formed, respectively. In the reaction of β-methylstyrene, the preferential formation of (1S, 2R)-(?)- and/or (1R, 2R)-(?)-1-phenyl-1,2-propanediol was observed. The chiral Co(II) (Schiff-base) complex seems to stabilize both the peroxy-and the peroxyalkyl radical.     

Cationic copolymerization of 1,3-dioxolane with styrene

Cationic copolymerization of 1,3-dioxolane with styrene was performed in toluene solution at 25°C. using boron fluoride etherate as catalyst. Determination of formaldehyde units in the copolymer showed that the two monomer units formed somewhat longer sequences in the copolymer chain than calculated on the assumption that these monomer units are statistically distributed in the copolymer chain according to their copolymerization parameters.