Effect of catalysts on asymmetric induction cationic copolymerization of l-menthyl vinyl ether with indene

Cationic copolymerization of l-menthyl vinyl ether (l-MVE) with indene (IN) was carried out with several catalysts in toluene (Tol) at 0°C. The catalysts used were BF₃OEt₂, CH₃COClO₄, and SnCl₄. l-Menthyl residue, an optically active side chain of the copolymer obtained, was removed with dry hydrogen bromide gas by the ether cleavage reaction. Ether-cloven copolymers [vinyl alcohol(VA)–IN] also had optical rotation. The efficiency of asymmetric induction to the polymer main chain was in the order of BF₃OEt₂ > CH₃COClO₄ > SnCl₄.     

Asymmetric induction radical copolymerization of optically active l-menthyl vinyl ether with vinylene carbonate and indene

The copolymerizations of l-menthyl vinyl ether (l-MVE) with the monomers vinylene carbonate (VCA) and indene (IN) were carried out in benzene with azobisisobutyronitrile (AIBN) as an initiator to obtain optically active copolymers. The optically active l-menthyl residue from the copolymer main chain was removed using dry hydrogen bromide gas. After the ether cleavage reaction, the copolymers prepared (VA–VCA and VA–IN) were still optically active, and hence it was found that asymmetric induction had taken place in the copolymer main chain. The optical rotatory dispersion (ORD) and circular dichroism (CD) data of the original and ether-cloven copolymers were also determined.     

Asymmetric induction copolymerization. Cationic copolymerization of l-menthyl vinyl ether with indene and acenaphthylene

l-Menthyl vinyl ether (l-MVE) was homopolymerized and copolymerized with the monomers indene (IN) and acenaphthylene (ANp) by BF₃OEt₂ as a catalyst. The chiral menthyl substituent was cloven from the homopolymers and copolymers using dry-hydrogen bromide gas. After the removal of optically active menthyl group, poly(vinyl alcohol) (PVA) from l-MVE homopolymer was optically inactive, and copolymers (VA-IN, VA-ANp) from l-MVE-IN and l-MVE-ANp copolymers were still optically active. Hence, in the case of l-MVE homopolymer, it was concluded that asymmetric induction in the polymer main chain can only produce pseudoasymmetry. In the case of l-MVE-IN and l-MVE-ANp copolymers, it was found that asymmetric induction proceeded in the copolymer main chain and was caused by the influence of chiral menthyl group.     

Asymmetric induction copolymerization of optically active l-menthyl vinyl ether with styrene and N-phenylmaleimide

The copolymerizations of l-menthyl vinyl ether (l-MVE) with styrene (St) and N-phenylmaleimide (N-PMI) as comonomers were carried out in benzene with azobisisobutyronitrile (AIBN) as an initiator to give optically active copolymers. After the removal of the optically active menthyl group by use of hydrogen bromide gas, the ether-cloven l-MVE-N-PMI copolymer (VA-N-PMI) was still optically active. On the other hand, the optical activity of l-MVE-St copolymer disappeared after ether cleavage. It is thought that asymmetric induction took place in the polymer main chains. The optical rotatory dispersion and circular dichroism of the original and ether-cloven copolymers were measured in order to confirm the asymmetric induction.     

Radical copolymerization of optically active l-menthyl vinyl ether with maleic anhydride,dimethyl maleate,and dimethyl fumarate

The copolymerizations of l-menthyl vinyl ether (l-MVE) with the monomers, that is, maleic anhydride (MAn), dimethyl maleate (DMM), and dimethyl fumarate (DMFu), were undertaken to obtain optically active copolymers. The optically active l-menthyl group in the side chain of copolymers was removed by the ether cleavage reaction with dry-hydrogen bromide gas. The ethercloven copolymers were still optically active. Hence it was concluded that asymmetric carbon atoms were introduced into the copolymer main chain, the reason given being that l-MVE and comonomers (MAn, DMM, and DMFu) made the stereoselective charge-transfer complex one another and copolymerized stereospecifically. From the results of the measurements of optical rotatory dispersion (ORD) and circular dichroism (CD) for copolymers before and after the ether cleavage reaction, the mode of bond opening for α,β-substituted monomers (MAn, DMM, and DMFu) was discussed and the microstructures of copolymers were prepared.     

Studies on propagating species in cationic polymerization of styrene derivatives by acetyl perchlorate or iodine. III. Effect of salt on cationic copolymerization of styrene derivatives with vinyl ethers by acetyl perchlorate

A common-ion salt, tetra-n-butylammonium perchlorate, was found to affect the monomer reactivity ratios in the cationic copolymerization by acetyl perchlorate of styrene with p-methylstyrene and of 2-chloroethyl vinyl ether with p-methylstyrene, but not those for the copolymerization of 2-chloroethyl vinyl ether with isobutyl vinyl ether. In the copolymerization of p-methylstyrene with styrene or with 2-chloroethyl vinyl ether, the addition of the common-ion salt in a polar solvent shifted the monomer reactivity ratios to those in a less polar solvent. The molecular weight distribution analysis of the copolymer suggested that the addition of the common-ion salt depresses the dissociation of propagating species. Therefore, it was concluded that a propagating species with a different degree of dissociation shows a different relative reactivity towards two monomers. The nature of propagating species was also discussed on the basis of the common-ion effect on the monomer reactivity ratios in various solvents.     

Polymerization and reaction of tetraoxane with various olefins catalyzed by BF3O·(C2H5)2

The copolymerization of tetraoxane with various olefins by BF₃·O(C₂H₅)₂ in ethylene dichloride at 30°C has been studied. The gas chromatographic technique was employed for the determination of concentration of each compound. The rate of tetraoxane consumption was decreased by the addition of olefins in the order of; no addition > trans-stilbene > styrene > 1,1-diphenylethylene > 2-chloroethyl vinyl ether > cyclohexene ≥ indene ≥ α-methylstyrene. The formation of the methanol-insoluble copolymer of tetraoxane and olefin was not confirmed. However, 4-methyl-4-phenyl-1,3-dioxane and 4,4-diphenyl-1,3-dioxane were formed in the reaction of tetraoxane with α-methylstyrene and 1,1-diphenylethylene, respectively. 4,4-Diphenyl-1,3-dioxane was identified on the basis of the molecular weight measurement, elemental analysis and NMR and infrared spectroscopy. On the other hand, 1,3-dioxane derivatives were not formed in the reaction of tetraoxane with α,β-disubstituted olefins. Monomer composition dependence of the copolymerization of tetraoxane with 1,1-diphenylethylene or α-methylstyrene has been studied. The amount of 4,4-diphenyl-1,3-dioxane formed reached a maximum at a monomer composition of 1:1 in the reaction of tetraoxane with 1,1-diphenylethylene. The formation of cyclic dimer of α-methylstyrene was suppressed by tetraoxane.     

Radical ring‐opening copolymerization behavior of vinyloxirane: Synthesis of copolymer from 2‐isopropenyl‐3‐phenyloxirane and styrene and its functionalization

The radical ring‐opening copolymerization of 2‐isopropenyl‐3‐phenyloxirane (1) with styrene (St) was examined to obtain the copolymer [copoly(1‐St)] with a vinyl ether moiety in the main chain. The copolymers were obtained in moderate yields by copolymerization in various feed ratios of 1 and St over 120 °C; the number‐average molecular weights (M_n) were estimated to be 1800–4200 by gel permeation chromatography analysis. The ratio of the vinyl ether and St units of copoly(1‐St) was estimated with the ¹H NMR spectra and varied from 1/7 to 1/14 according to the initial feed ratio of 1 and St. The haloalkoxylation of copoly(1‐St) with ethylene glycol in the presence of N‐chlorosuccinimide produced a new copolymer with alcohol groups and chlorine atoms in the side group in a high yield. The M_n value of the haloalkoxylated polymer was almost the same as that of the starting copoly(1‐St). The incorporated halogen was determined by elemental analysis. The analytical result indicated that over 88% of the vinyl ether groups participated in the haloalkoxylation. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3729–3735, 2000     

Cationic Copolymerization of 2-Chloroethyl Vinyl Ether with Styrene Derivatives. III. Solvent and Catalyst Effects on Relative Reactivity

Abstract

The change in relative reactivity in the cationic copolymerization of 2-chloroethyl vinyl ether and styrene derivatives was investigated with various catalysts and solvents. p-Methoxystyrene, p-methylstyrene, and a-methyl-styrene were used as styrene derivatives. The styrene content in the co-polymer increased when a polar solvent and/or a strong catalyst was used. The change of relative reactivity in the copolymerization of 2-chloroethyl vinyl ether with styrene derivatives was much greater than that in the copolymerization between vinyl ethers or styrene derivatives. When nitro-ethane was used as a solvent, not only the polarity but also the nucleophilicity influenced the copolymer composition. The results were discussed by two energies, E^π and E_rs, which are measures of complex formation between monomer and carbonium ion, and stabilization energy in the transition state, respectively.     

Unzipping and scrambling reaction-induced sequence control of copolymer chains via temperature changes during cationic ring-opening copolymerization of cyclic acetals and cyclic esters

A temperature change-dependent sequence transformation of copolymer chains was demonstrated by a method based on tandem depolymerization and transacetalization reactions during the cationic ring-opening copolymerization of cyclic acetals and cyclic esters. In this study, the position of polymerization-depolymerization equilibrium was controlled by the reaction temperature rather than by the decrease in monomer concentration under vacuum conditions, as in our previous study. First, the conditions for efficient copolymerization were optimized, with a particular focus on the structures of cyclic acetals and cyclic esters. Subsequently, sequence transformation induced by temperature change was examined during the copolymerization of 2-methyl-1,3-dioxepane (generated in situ from 4-hydroxybutyl vinyl ether) and δ-valerolactone using EtSO₃H. The homosequence length of cyclic acetals decreased during depolymerization (unzipping) at the oxonium chain ends upon increasing the temperature from 30 to 90 °C, while transacetalization (scrambling) of the main chain transferred midchain cyclic acetal homosequences to the oxonium chain ends. As a result of the cycle of unzipping and scrambling reactions, an alternating-like copolymer was obtained. Interestingly, the possibility of reversible sequence transformation upon heating and cooling was also demonstrated.     

Synthesis and characterization of perfluoro‐3‐methylene‐2,4‐dioxabicyclo[3,3,0] octane: Homo‐ and copolymerization with fluorovinyl monomers

The synthesis of perfluoro‐3‐methylene‐2,4‐dioxabicyclo[3,3,0] octane (D), its radical homopolymerization, and copolymerization with fluoroolefins are presented. Fluorodioxolane (D) was synthesized through direct fluorination of the corresponding hydrocarbon precursor in a fluorinated solvent by F₂/N₂ gas. It was polymerized in bulk using perfluorodibenzoyl peroxide as the initiator. The resulting homopolymer had a limited solubility in fluorinated solvents, and its glass transition temperature (T_g) was in the range of 180–190 °C. The polymeric films prepared by casting from hot hexafluorobenzene (HFB) solution were transparent with low refractive index (1.329 at 633 nm). These films were thermally stable (T_d > 350 °C), and were hard and brittle. The copolymers of monomer (D) were prepared with fluorovinyl monomers such as chlorotrifluoroethylene (CTFE), perfluoropropyl vinyl ether, perfluoromethyl vinyl ether, and vinylidene fluoride. The kinetics of radical copolymerization of monomer (D) with CTFE led to the assessment of the reactivity ratios of both comonomers: r_D = 3.635 and r_CTFE = 0.737 at 74 °C, respectively. The copolymers obtained were soluble in HFB and perfluoro‐2‐butyltetrahydrofuran, with T_g in the range of 84–145 °C depending on the copolymer composition. The films of the copolymers were flexible and clear with a low refractive index (1.3350–1.3770 at 532 nm). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6571–6578, 2009     

Syntheses of Vinyl Sulfoxide/Vinyl Acetate-Type Copolymers

The homopolymerization of a series of alkyl vinyl sulfoxides (CH₂[dbnd]CHSOR; R = CH₃ (MVSO), C₂H₅ (EVSO), t-C₄H₉ (BVSO)) and their copolymerization with vinyl acetate (VAc) with 2,2′-azobisisobutyronitrile (AIBN) as initiator at 60°C was attempted. MVSO was found to homopolymerize radically, but EVSO and BVSO were not. Poly-MVSO is soluble in chloroform, methanol, DMSO, and water, but insoluble in acetone and benzene. MVSO and EVSO were found to copolymerize with VAc, but BVSO was not. The copolymerization parameters obtained for both systems were as follows; r₁(MVSO) = 2.23, r₂ (VAc) = 0.09, and r₁(EVSO) = 3.40, r₂ (VAc) = 0.11, respectively. MVSO/vinyl alcohol (VA) copolymers were obtained through the saponification of MVSO/VAc copolymers by sodium hydroxide in methanol. The solubility of MVSO/VAc and of MVSO/VA copolymers toward various solvents was examined, and it was observed that the sulfoxide comonomer has a tendency to give amphiphilicit to poly(vinyl acetate) and poly(vinyl alcohol). The 24 mol% MVSO containing VAc copolymer is soluble in both benzene and water.     

Fluorocyclopropanes. IV. Copolymers of perfluorocyclopropene

Perfluorocyclopropene undergoes free-radical copolymerization with ethylene, isobutylene, cis- and trans-2-butene, vinyl acetate, methyl vinyl ether, vinyl chloride, styrene, acrylonitrile, tetrafluoroethylene, vinyl fluoride, and vinylidene fluoride. The copolymerization proceeds most readily with electron-rich olefins such as methyl vinyl ether (to yield a 1:1 copolymer), but conditions were found to give copolymers with electron-deficient olefins such as tetrafluoroethylene and vinylidene fluoride. Copolymers with methyl vinyl ether, tetrafluoroethylene, vinyl fluoride, and vinylidene fluoride were examined in detail. Evidence is presented that the perfluorocycloproply ring is incorporated intact into the copolymer and can be subsequently isomerized to a perfluoropropenyl unit by heating at 200–300°C.     

Cationic copolymerization of 3,3-bis(chloromethyl) oxetane with vinyl compounds

Copolymerizations of 3,3-bis(chloromethyl)oxetane (BCMO) with some vinyl compounds were carried out with cationic catalysts in various solvents to determine what kind of vinyl compound is able to copolymerize with BCMO. p-Methylstyrene (pMS), 2-chloroethyl vinyl ether (CEVE), α-methylstyrene (αMS), and isobutene (IB) were used as comonomers. The rate of consumption of each monomer was measured by gas chromatrography. Plots of copolymer composition in the copolymerization of BCMO with pMS were characterized by S-shaped curves in several solvents. As poly-BCMO is insoluble and the vinyl polymers are soluble in benzene, the polymers obtained were separated into benzene-soluble and benzene-insoluble fractions, and the composition of each fraction was determined by elemental analysis. It was found that pMS, CEVE and IB formed a copolymer with BCMO, but αMS produced no copolymer with BCMO. Thus the formation of copolymer between a cyclic ether and some vinyl monomers was observed by a cationic mechanism. The cross-propagation mechanism is discussed on the basis of these results.     

A novel synthetic strategy for copolymers of vinyl alcohol: Radical copolymerization of alkoxyvinylsilanes with styrene and oxidative transformation of C?Si(OR)2Me into C?OH in the copolymers to afford poly(vinyl alcohol‐ran‐styrene)s

As a novel synthetic strategy for copolymers of vinyl alcohol, we propose herein copolymerization of alkoxyvinylsilanes with other vinyl monomers, followed by oxidative cleavage of the alkoxysilyl groups attached to the main chain of the resulting copolymers. Radical copolymerization of di(isobutoxy)methylvinylsilane 1 with styrene afforded poly( 1 ‐ran‐styrene)s with a variety of compositions of both repeating units, although the M_n's (<9000) and yields (<35%) were rather low. The oxidative cleavage of the alkoxysilyl groups in the copolymers with m‐chloroperbenzoic acid proceeded efficiently, giving poly(vinyl alcohol‐ran‐styrene)s, which were soluble in common organic solvents. The structures of the poly(vinyl alcohol‐ran‐styrene)s were characterized by NMR, GPC, elemental analysis, and matrix‐assisted laser desorption time‐of‐flight mass spectrometry (MALDI‐TOF‐MS). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3648–3658, 2007     

Studies on propagating species in cationic polymerization of styrene derivatives by acetyl perchlorate or iodine. II. Salt effect on the relative reactivity in the cationic copolymerization of styrene derivatives with 2-chloroethyl vinyl ether initiated by iodine

To determine the effect of the dissociation of propagating species on the relative reactivity of monomers, 2-chloroethyl vinyl ether was copolymerized with p-methoxystyrene or with p-methylstyrene by using iodine in various solvents at 0°C. A common-ion salt (tetra-n-butylammonium iodide or tetra-n-butylammonium triiodide) was added to these copolymerization systems in a polar solvent to depress the dissociation of the propagating species. The addition of a common-ion salt increased the vinyl ether content in the copolymer. The more the dissociation of propagating species was depressed, the more the vinyl ether content in the copolymer increased. This effect of common-ion salt was in agreement with that of decreasing solvent polarity which yielded vinyl ether-rich copolymer as well. Therefore, the change of the monomer reactivity ratio by the solvent polarity, which used to be explained in terms of a selective solvation, must be reconsidered from the viewpoint of varying degrees of the dissociation of propagating species.     

High Tg microspheres by dispersion copolymerization of N‐phenylmaleimide with styrenic or alkyl vinyl ether monomers

Solution and dispersion copolymerizations of N‐phenylmaleimide (PMI) with either styrenics or alkyl vinyl ethers (AVEs), systems with a tendency to give alternating polymers, were investigated with the goal of producing high glass transition particles. Equimolar solution copolymerization of PMI with styrenics gave alternating copolymers, whereas AVEs gave PMI‐rich copolymers (～65:35) except for t‐butyl vinyl ether, which gave copolymers with only a slight excess of PMI. These copolymers had glass transition temperatures (T_gs) ranging from 115 to 225 °C depending on comonomer(s). Dispersion copolymerization in ethanol‐based solvents in the presence of poly(vinylpyrrolidone) as steric stabilizer led to narrow‐disperse microspheres for many copolymers studied. Dispersion copolymeriations of PMI with styrenics required good cosolvents such as acetonitrile or methyl ethyl ketone as plasticizers during particle initiation and growth. Dispersion copolymerizations generally resulted in copolymer particles with compositions and T_gs very similar to those of the corresponding copolymers formed by solution polymerization, with the exception of t‐butyl vinyl ether (tBVE), which now behaved like the other AVEs. Dispersion terpolymerizations of PMI (50 mol %) with different ratios of either n‐butylstyrene and t‐butylstyrene or n‐butyl vinyl ether and tBVE led to polymer particles with T_gs that depended on the ratio of the two butyl monomers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Effect of solvent on the copolymerization of ethylene and vinyl acetate

The ethylene (M₁)–vinyl acetate (M₂) copolymerization at 62°C and 35 kg/cm² with α,α′-azo-bisisobutyronitrile as initiator has been studied in four different solvents, viz., tert-butyl alcohol, isopropyl alcohol, benzene, and N,N-dimethylformamide. The experimental method used was based on frequent measurement of the composition of the reaction mixture throughout the copolymerization reaction by means of quantitative gas chromatographic analysis. Highly accurate monomer reactivity ratios have been calculated by means of the curve-fitting I procedure. The observed dependence of the r values on the nature of the solvent is surprisingly large and can be correlated with the volume changes (= excess volumes) observed on mixing vinyl acetate (VAc) with the relevant solvent. An increased hydrogen bonding or dipole–dipole interaction through the carbonyl moiety of the acetate side group of VAc, induces a decreased electron density on the vinyl group of VAc, which in turn leads to a decreased VAc reactivity. The differences among the overall rates of copolymerization in the various solvents can be interpreted in terms of a variable chain transfer to solvent and the rate of the subsequent reinitiation by the solvent radical. In the case of benzene, complex formation is believed to play an important part.     

Trans-1,4-stereospecific copolymerization of ethylene and isoprene catalyzed by MgCl2-supported Ziegler–Natta catalyst

Copolymerization of ethylene and isoprene (Ip) catalyzed by TiCl₄/MgCl₂-Al(i-C₄H₉)₃ catalyst was systematically studied. Homopolymer of ethylene and Ip were synthesized under the same conditions for making comparisons. Proton nuclear magnetic resonance was employed to characterize chain structure of the copolymer. Influences of Ip concentration, molar ratio of cocatalyst to Ti and reaction temperature on the copolymerization activity and copolymer chain structure were investigated. The copolymerization activity was evidently lowered by increasing Ip concentration, and the Ip content in copolymer was rather low under reaction conditions leading to higher activity. Insertions of Ip in polymer chain showed rather high regioselectivity for 1,4-connections (>85%) and medium to high stereoselectivity for trans-1,4-isomer (>70%) under typical conditions, but the regio and stereoselectivities tended to decrease with decrease in Ip concentration and increase in Al/Ti ratio. Melting temperature of the copolymer decreased with increase of Ip content, indicating incorporation of Ip units in most of the copolymer chains. This work has proved feasibility of introducing small amount of Ip units with high trans-1,4-stereoselectivity into ethylene/isoprene copolymer chains by catalyzed copolymerization with MgCl₂-supported Ziegler–Natta catalysts. The copolymer is expected to be a promising candidate of easily degradable film or packaging materials. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2715–2722     

Photocatalyzed Hydrogen Atom Transfer Degradation of Vinyl Polymers: Cleavage of a Backbone C−C Bond Triggered by Radical Activation of a C−H Bond in a Pendant

In this work, we achieved a triggering degradation of polymers composed of carbon-carbon (C−C) bonded backbone without relying on introduction of labile heteroatom-based bond. The crucial point for the achievement is using vinyl ether (VE) as a comonomer in radical copolymerization of (meth)acrylate for introduction of the carbon-hydrogen (C−H) bonds active for photocatalyzed hydrogen atom transfer (HAT) as triggers in the pendant. Interestingly, methyl methacrylate (MMA)-n-butyl vinyl ether (NBVE) copolymer underwent degradation in acetonitrile in the presence of benzophenone (Ph₂CO) under UV irradiation at 80 °C. The degradation did not take place, when any one of UV, Ph₂CO, heat, and NBVE unit was removed or HAT-active solvent such as toluene and 1,4-dioxane was used. These control experiments strongly supported the HAT-triggering degradation. Furthermore, the degradation behaviors of the copolymers with other vinyl ethers such as tert-butyl vinyl ether and methyl isopropenyl ether indicated that the C−H bond neighboring to oxygen on the pendant is mainly responsible for the trigger leading to degradation. The HAT-triggering degradation was also demonstrated even with the acrylate-based copolymer.