Radical copolymerization of alkyl cyclobutenecarboxylates fused with cycloaliphatic framework with alkyl (meth)acrylates

Radical copolymerization behavior of alkyl cyclobutenecarboxylate‐derivatives 4‐6 and related norbornene‐derived compounds 7–9 is described. A variety of alkyl cyclobutenecarboxylates fused with cycloaliphatic framework ( 4–6 ) were prepared by [2 + 2] cycloaddition of five, six, and eight‐membered cycloolefins with alkyl propiolates [alkyl = Me, 2‐hydroxyethyl, and 3‐γ‐butyrolactonyl (γ‐BL)]. The fused cyclobutenecarboxylates 4–6 were radically copolymerized with n‐butyl acrylate (nBA) to afford random copolymers, and terpolymerized with alkyl methacrylates with bulky ester groups [alkyl = γ‐BL and 3‐(3‐methyladamantyl)]. The cyclobutane‐containing bicyclic framework incorporated in the resulting polymer backbone contributes to raising T_g of resulting copolymers. Similar results were obtained when a mixture of related norbornene‐derived compounds were used as monomers with an apparently enhanced T_g‐raising effect in the copolymerization with nBA. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2716–2724     

Kinetic and thermodynamic aspects of miniemulsion copolymerization

Miniemulsion polymerization involves initiation of polymerization in preformed stable monomer emulsion droplets with average droplet diameter of 50–500 nm. At the end of the polymerization, only a fraction of the initial number of monomer droplets become polymer particles. The emulsifier system used for the preparation of such emulsions comprises a mixture of ionic surfactant and a fatty alcohol or long chain alkane (termed cosurfactant). The cosurfactant is essential for the formation of stable emulsion droplets and in addition it plays an important role in the interparticle monomer transport. Kinetic results are presented on conventional emulsion and miniemulsion copolymerization of different pairs of monomers, showing the main differences for both processes. These differences were related to the particle formation mechanism and the influence of the cosurfactant in the miniemulsion process. A theoretical model was developed, based on mass balances and equilibrium thermodynamics, which was found to describe accurately the experimentally generated data on comonomer distribution during the course of the copolymerization process and the interdroplet mass transport process.     

The effect of alkyl substituents in nickelocenes on the catalytic dimerization of ethylene

(C₅H₄ i-Pr)₂Ni exhibits the highest catalytic activity in the dimerization of ethylene among the nickelocenes, (C₅H₄R)₂Ni (R = H, Et,n-Pr,i-Pr, ori-Bu) and their analogs (C₅H₄R)Ni(C₃H₅) (R = H,i-Pr). The higher activity is accompanied by lower selectivity with respect to 1-butene and with higher yields of 1-hexene. It is suggested that the introduction of an alkyl substituent in the cyclopentadienyl ring of nickelocene favors the generation of hydride sites involving the nickel atom. These sites participate in the process of ethylene dimerization.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 970–972, May, 1993.     

Radical copolymerization of acrylic monomers. IV. Effect of substituents on the radical polymerization and copolymerization of phenyl acrylates

The kinetics of radical polymerization of phenyl, ortho-chlorophenyl, and para-chlorophenyl acrylates, as well as their copolymerization with methyl methacrylate, have been studied dilatometrically. The results obtained indicate that the overall rate of polymerization is affected by the flexibility of the growing radicals. However, the copolymerization of these monomers with methyl methacrylate gives overall rates rather similar for all three systems, being fundamentally regulated by the formation of reversible π complexes between the donor aromatic rings and the acceptor methacrylic double bonds. Dilatometric methods for the study of the copolymerization reactions have been tested and the corresponding binary bonding frequencies B_ij and conversion factors K_ij have been calculated for the copolymerization of ortho- and para-chlorophenyl acrylates with methyl methacrylate.     

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.     

Alternating copolymers of propylene and alkyl acrylates

High-molecular-weight alternating and acrylate-rich copolymers of propylene and ethyl acrylate were prepared by using boron trifluoride to complex the acrylate ester. The polymerizations were run at room temperature and autogeneous pressures with free-radical initiation. The polymers were characterized by their nuclear magnetic resonance (NMR) and infrared (IR) spectra, differential scanning calorimetry, and gel permeation chromatography. The proton and ¹³C NMR spectra show that the equimolar copolymers are alternating to a high degree.     

Effect of protic agents on the catalytic activity of supported palladium catalysts in the copolymerization of ethylene with carbon monoxide

The influence of the addition of different amounts of MeOH, H₂O, and HCOOH on the activity of supported palladium catalyst in the copolymerization of CO with ethylene and the kinetic regularities of this reaction were studied for the first time. The maximum yield of the copolymer is attained when MeOH and H₂O or HCOOH and H₂O are simultaneously introduced into the reaction medium (toluene). The results obtained are consistent with the concepts about the role of protic agents in the formation of active intermediates and polymer molecules in the copolymerization of CO with ethylene in the presence of the homogeneous catalytic systems.     

Effect of catalyst partitioning in Co(II) mediated catalytic chain transfer miniemulsion polymerization of methyl methacrylate

The effect of catalyst partitioning over the organic and water phases in the catalytic chain transfer mediated miniemulsion polymerization was investigated and a mathematical model developed to describe the instantaneous degree of polymerization of the formed polymer. Experimental and predicted instantaneous degrees of polymerization prove to be in excellent agreement. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5839–5849, 2008     

SHOP-type nickel complexes with alkyl substituents on phosphorus, synthesis and catalytic ethylene oligomerization

The beta-keto phosphorus ylides (n-Bu)3P=CHC(O)Ph 6, (t-Bu)2PhP=CHC(O)Ph 7, (t-Bu)Ph2P=CHC(O)Ph 8, (n-Bu)2PhP=CHC(O)Ph 9, (n-Bu)Ph2P=CHC(O)Ph 10, Me2PhP=CHC(O)Ph 11 and Ph3P=CHC(O)(o-OMe-C6H4) 12 have been synthesized in 80-96% yields. The Ni(II) complexes [NiPh{Ph2PCH...C(...O)(o-OMeC6H4)}(PPh3)] 13, [NiPh{Ph(t-Bu)PCHC(O)Ph}(PPh3)] 15, [NiPh{(n-Bu)2PCH...C(...O)Ph}(PPh3)] 16 and [NiPh{Ph(n-Bu)PCH...C(...O)Ph}(PPh3)] 17 have been prepared by reaction of equimolar amounts of [Ni(COD)2] and PPh3 with the beta-keto phosphorus ylides 12 or 8-10, respectively, and characterized by 1H and 31P{1H} NMR spectroscopy. NMR studies and the crystal structure determination of 13 indicated an interaction between the hydrogen atom of the C-H group alpha to phosphorus and the ether function. The complexes [NiPh{Ph2PCHC(O)Ph}(Py)] 18, [NiPh{Ph(t-Bu)PCHC(O)Ph}(Py)] 19, [NiPh{(n-Bu)2PCH...C(...O)Ph}(Py)] 20, [NiPh{Ph(n-Bu)PCH...C(...O)Ph}(Py)] 21 and [NiPh{Me2PCH...C(...O)Ph}(Py)] 22 have been isolated from the reactions of [Ni(COD)2] and an excess of pyridine with the -keto phosphorus ylides Ph3PCH=C(O)Ph 3 or 8-11, respectively, and characterized by 1H and 31P{1H} NMR spectroscopy. Ligands 3, 8, 10 and 12 have been used to prepare in situ oligomerization catalysts by reaction with one equiv. of [Ni(COD)2] and PPh3 under an ethylene pressure of 30 or 60 bar. The catalyst prepared in situ from 12, [Ni(COD)2] and PPh3 was the most active of the series with a TON of 12700 mol C2H4 (mol Ni)-1 under 30 bar ethylene. When the beta-keto phosphorus ylide 8 was reacted in situ with three equiv. of [Ni(COD)2] and one equiv. of PPh3 under 30 bar of ethylene, ethylene polymerization was observed with a TON of 5500 mol C2H4 (mol Ni)-1.     

Effect of the nature of an organoaluminum activator on catalytic properties of phenoxyimine zirconium complexes in homo- and copolymerization reactions of ethylene

Catalytic properties of the phenoxyimine zirconium complexes, viz., bis[N-(3,5-di-tert-butylsalicylidene)anilinato]zirconium(IV) dichloride (1) and its fluorinated analog, bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6-tetrafluoroanilinato]zirconium(IV) dichloride (2), were studied. Ethylene homopolymerization and copolymerization of ethylene with α-olefins were chosen as catalytic reactions, and various organoaluminum compounds served as activators: commercial polymethylalumoxane (MAO) containing ∼35 mol.% of trimethylaluminum (TMA), MAO purified from TMA (“dry” MAO), and “classical” organoaluminum compounds, namely, TMA and triisobutylaluminum (TIBA). Complex 1 is not activated by “dry” MAO but is efficiently transformed into the catalytically active state by commercial MAO, “conventional” TMA, and TIBA. These processes give low-molecular-weight polyethylenes (PE) characterized by high values of polydispersity indices and by polymodal curves of gel permeation chromatography (GPC). The order of decreasing the efficiency of activation for the cocatalysts is MAO > TIBA > TMA. Fluorinated complex 2 exhibits a high activity after its treatment with MAO and “dry” MAO, the activity is much lower upon mixing with TIBA, and complex 2 is inactive when using TMA. In the copolymerization of ethylene with hex-1-ene and dec-1-ene, complex 1 treated with MAO is highly active but gives a low level of insertion of the comonomer (1–2 mol.% in the copolymer). Complex 2 activated with “dry” MAO is more efficient in the copolymerization of ethylene with propylene or hex-1-ene but, like complex 1, it does not produce copolymers with a high content of the comonomer. The both catalysts provide the insertion of α-olefin as isolated units separated by extended sections of the chain consisting of ethylene units.     

Enthalpy relaxation in polymethyl(α-n-alkyl)acrylates: Effect of length of alkyl chain

In this work, we have investigated by DSC the structural relaxation of amorphous polymethyl(α-n-alkyl)acrylates in which it is possible to change the length of the alkyl chain. We have evaluated the Narayanaswamy parameter, x, which controls the relative contribution of temperature and of structure to the relaxation time, the apparent activation energy, Δh*, and the nonexponentiality parameter, β, of the stretched exponential response function. The results suggest that x increases while Δh* decreases and β remains constant as the length of the side chain increases. This allows us to comment on the effect of chemical modification on the relaxation kinetics. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 583–593, 1998     

Miniemulsion copolymerization of vinyl acetate and butyl acrylate. I. Differences between the miniemulsion copolymerization and the emulsion copolymerization processes

Differences between the emulsion copolymerization and miniemulsion copolymerization processes, in terms of emulsifier adsorption, emulsion stability, polymerization kinetics, copolymer composition and dynamic mechanical properties were studied for the comonomer mixture of 50:50 molar ratio vinyl acetate (VA+)—butyl acrylate (BuA), using sodium hexadecyl sulfate (SHS) as a surfactant and hexadecane (HD) as a co-surfactant. The use of hexadecane with the appropriate SHS initial concentration led to a higher adsorption of surfactant, smaller droplet size, higher stability of the emulsions, lower polymerization rates, and larger latex particle size. The copolymer composition during the initial 70% conversion was found to be less rich in Vac monomer units for the miniemulsion process. The dynamic mechanical properties of the copolymer films showed less mixing between the BuA-rich core and the VAc-rich shell in the miniemulsion latexes compared to the conventional latex films.     

On the copolymerization of acrylates in the modified microemulsion process

Copolymerization of methyl methacrylate, methyl acrylate, butyl methacrylate, and butyl acrylate in turn was performed in the modified microemulsion polymerization process, i.e., continuous addition of monomer to a preemulsified system. It was found that the particle size of the copolymer microlatex did not change distinctly with the monomer composition. The estimation of emulsifier coverage on the microlatex particles indicated that the process switched from a traditional microemulsion to a normal seeded emulsion polymerization very soon after monomer dropping began. Therefore, a longer dropping time is needed to produce a microlatex with narrow dispersed particle size. Besides, in the modified microemulsion polymerization less emulsifier is needed to produce a stable microlatex. This behavior is related to the mechanism of normal seeded emulsion polymerization during monomer dropping.     

Preparation and polymerization of difluoramino-substituted alkyl acrylates and methacrylates

Several difluoramino-substituted alkyl acrylic acid esters were conveniently prepared by the debromination of difluoramino-substituted alkyl-2,3-dibromopropionates and 2,3-dibromoisobutyrates. The polymerization character of difluoramino-substituted alkyl acrylates and methacrylates was found to be similar to that displayed by other alkyl acrylic esters.     

Copolymers of vinyl and vinylidene chlorides with alkyl acrylates

High-molecular-weight copolymers of vinyl chloride and ethyl or butyl acrylate were prepared in high conversion and yield in the presence of boron trifluoride as the acrylate ester complexing agent. When the vinyl chloride monomer is in excess of equimolar amounts, the resulting copolymers are alternating; and when the alkyl acrylates are in excess, acrylate-rich copolymers are obtained. Ethylene–vinyl chloride–ethyl acrylate and propylene–vinyl chloride–ethyl acrylate terpolymers were also obtained with an ethyl acrylate content of 50 mole %. The relative reactivities of propylene, vinyl chloride, and ethylene in these polymerizations were 5.4, 3.8, and 1.0, respectively. Vinylidene chloride–ethyl acrylate copolymers that are nearly alternating and rich in acrylate or in vinylidene chloride have also been prepared. The monomer reactivity ratios for vinylidene chloride and ethyl acrylate in the presence of boron trifluoride are considerably lower than in its absence.     

Mathematical modeling of seeded miniemulsion copolymerization for oil-soluble initiator

A mathematical model of seeded miniemulsion copolymerization of styrene-methyl methacrylate for oil-soluble initiator is presented. The mathematical model includes the mass transfer, from the miniemulsion droplets to the polymer particles, by both molecular diffusion and collision between miniemulsion droplets and the polymer particles. The mathematical model also includes the calculation of both the distribution of partices with i radicals and the average number of radicals per particle in the miniemulsion copolymerization using oil-soluble initator. Studies were carried out on the mass transfer coefficients of monomers across the interface between the miniemulsion droplet and the aqueous phase, hexadecane concentration in the miniemulsion droplets, the miniemulsion droplet sizes, and the collision between miniemulsion droplets. The results indicated that the copolymerization of styrene-methyl methacrylate was not a mass transfer controlled process. The mass transfer by collision between miniemulsion droplets and polymer particles plays an important role and was included in the model in order to predict the experimental data of seeded miniemulsion copolymerization.     

Copolymerization of 2-hydroxyethyl methacrylate with alkyl acrylates

Copolymerization of 2-hydroxyethyl methacrylate (HEMA) with methylacrylate (MA), ethylacrylate (EA), n-butylacrylate (BA) and methylmethacrylate (MMA) were studied in bulk at 60° using benzoyl peroxide as initiator. The monomer reactivity ratios were determined using several methods and are briefly discussed.     

Synthesis and copolymerization of new phosphorus‐containing acrylates

Two phosphorus‐containing acrylate monomers were synthesized from the reaction of ethyl α‐chloromethyl acrylate and t‐butyl α‐bromomethyl acrylate with triethyl phosphite. The selective hydrolysis of the ethyl ester monomer with trimethylsilyl bromide (TMSBr) gave a phosphonic acid monomer. The attempted bulk polymerizations of the monomers at 57–60 °C with 2,2′‐azobisisobutyronitrile (AIBN) were unsuccessful; however, the monomers were copolymerized with methyl methacrylate (MMA) in bulk at 60 °C with AIBN. The resulting copolymers produced chars on burning, showing potential as flame‐retardant materials. Additionally, α‐(chloromethyl)acryloyl chloride (CMAC) was reacted with diethyl (hydroxymethyl)phosphonate to obtain a new monomer with identical ester and ether moieties. This monomer was hydrolyzed with TMSBr, homopolymerized, and copolymerized with MMA. The thermal stabilities of the copolymers increased with increasing amounts of the phosphonate monomer in the copolymers. A new route to highly reactive phosphorus‐containing acrylate monomers was developed. A new derivative of CMAC with mixed ester and ether groups was synthesized by substitution, first with diethyl (hydroxymethyl)phosphonate and then with sodium acetate. This monomer showed the highest reactivity and gave a crosslinked polymer. The incorporation of an ester group increased the rate of polymerization. The relative reactivities of the synthesized monomers in photopolymerizations were determined and compared with those of the other phosphorous‐containing acrylate monomers. Changing the monomer structure allowed control of the polymerization reactivity so that new phosphorus‐containing polymers with desirable properties could be obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2207–2217, 2003     

Palladium(II) beta-agostic alkyl cations and alkyl ethylene complexes: investigation of polymer chain isomerization mechanisms.

A series of stable dialkyl complexes of Pd, (alpha-diimine)PdR2 (alpha-diimine = aryl-substituted diimine, R = n-Pr, n-Bu, i-Bu), have been prepared via Grignard alkylation of the corresponding (alpha-diimine)PdCl2 complexes. Protonation of these dialkyl species at low temperature results in loss of alkane and formation of cationic Pd beta-agostic alkyl complexes, which have been observed as intermediates in the polymerization of ethylene and propylene by these Pd catalysts. Studies of the structure and dynamic behavior of these alkyl complexes are presented, along with the results of trapping reactions of these species with ligands such as NCMe, CO, and C2H4. Trapping with ethylene results in formation of cationic alkyl ethylene complexes which model the catalyst resting state in these systems. These complexes have been used to obtain mechanistic details and kinetic parameters of several processes, including isomerization of the alkyl ethylene complexes, associative and dissociative exchange with free ethylene, and migratory insertion rates of both primary and secondary alkyl ethylene species. These studies indicate that the overall branching observed in polyethylenes produced by these Pd catalysts is governed both by the kinetics of migratory insertion and by the equilibria involving the alkyl ethylene complexes.     

Living/controlled copolymerization of acrylates with nonactivated alkenes

The living/controlled copolymerization of methyl acrylate with 1‐alkenes and norbornene derivatives through several radical polymerization techniques has been achieved. These techniques include atom transfer radical polymerization, reversible addition–fragmentation transfer polymerization, nitroxide‐mediated polymerization, and degenerative transfer polymerization. These systems display many of the characteristics of a living polymerization process: the molecular weight increases linearly with the overall conversion, but the polydispersity remains low. Novel block copolymers have been synthesized through the sequential addition of monomers or chain extension. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6175–6192, 2004