Styrene polymerization with rare earth catalysts using a magnesium alkyl cocatalyst

A new highly active rare earth coordination catalyst composed of rare earth phosphonate, di-n-butylmagnesium (MgBu), and hexamethyl phosphoramide (HMPA) for the polymerization of styrene has been developed for the first time. High molecular weight polystyrene (M̄_ν = 50–70 × 10⁴) in 100% conversion could be prepared at following conditions: [Nd] = 6–8 × 10⁻⁴ mol/L, [St] = 3.0 mol/L, Mg/Nd = 11, and HMPA/Mg = 1–1.5 (molar ratio). The catalytic activity of this new catalyst is 3530 g PSt/g Nd. Kinetics study shows that the polymerization rate is of first order with respect to both monomer concentration and catalyst concentration, and activation energy of the polymerization is 40.1 kJ/mol. © 1996 John Wiley & Sons, Inc.     

Reactive surfactants in heterophase polymerization. Part XXI—kinetics of styrene dispersion polymerization stabilized with poly(ethylene oxide) macromonomers

The kinetics of styrene dispersion polymerization, using poly(ethylene oxide) macromonomers as precursors for the stabilization, has been studied. The conversions of both styrene and macromonomers have been determined. The effects of various parameters such as the polarity of the medium, the nature and the amount of macromonomer and the concentrations of the reactants have been studied. A strong gel effect was observed, the main polymerization process taking place inside the particles where the average number of radicals per particle may be more than a thousand. © 1997 John Wiley & Sons, Ltd.     

Styrene polymerization in the presence of the CpTiCl3/Al2O3–SiO2/MAO catalytic system

Syndiotactic polymerization of styrene in the presence of heterogenized hemititanocene catalysts CpTiCl₃/Al₂O₃–SiO₂/MAO (Cp = cyclopentadienyl; MAO = methylaluminoxane) showed that the yield and selectivity of this reaction depend on the support composition, i.e. on the Al₂O₃ content in the support. The most active catalysts contained Al₂O₃ in a quantity of 50 to 70 wt%. Despite a relatively lower selectivity of 75–59%, the amount of syndiotactic polystyrene in the presence of those catalysts was the greatest. Copyright © 2002 John Wiley & Sons, Ltd.     

Living radical emulsion polymerization using the nanoprecipitation technique: An extension to atom transfer radical polymerization

Living radical polymerizations of styrene were performed under emulsion atom transfer radical polymerization conditions with latexes prepared by a nanoprecipitation technique recently developed for the stable free‐radical polymerization process. Latexes were prepared by the precipitation of a solution of low‐molecular‐weight polystyrene in acetone into a solution of a surfactant in water. The resulting particles were swollen with styrene and then heated. The effects of various surfactants and hydrophobic ligands, the reaction temperature, and the ligand/copper(I) bromide ratio were studied. The best results were obtained with the nonionic surfactant Brij 98 in combination with the hydrophobic ligand N,N‐bis(2‐pyridylmethyl)octadecylamine and a ligand/copper(I) bromide ratio of 1.5 at a reaction temperature of 85–90 °C. Under these conditions, latexes with good colloidal stability with average particle diameters of 200 nm were obtained. The molecular weight distributions of the polystyrenes were narrow, although the experimental molecular weights were slightly larger than the theoretical ones because not all the macroinitiator appeared to reinitiate. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4027–4038, 2006     

Effect of phenol and derivatives on atom transfer radical polymerization in the presence of air

The various phenolic compounds in conjunction with Cu(II) or Cu(I)‐N,N,N′,N″,N″‐pentamethyl diethylenetriamine (PMDETA) complexes are used to initiate atom transfer radical polymerization (ATRP) of methyl methacrylate, styrene, and methyl acrylate in the presence of a limited amount of air at temperatures in the range of 80–110 °C. Meanwhile, an effort is directed toward the elucidation of the role of phenol and derivatives in ATRP catalyzed by Cu(II)/PMDETA. The catalytic sequence involves the formation of Cu(I) by electron transfer from phenol to Cu(II); Cu(I) so formed can then react in two distinctly different ways: with organic halide to form a propagating radical or with oxygen to form copper salt in its higher oxidation state; and regeneration of Cu(I) by excess phenol. Such regeneration of Cu(I) would be expected to lead to polymerization as a result of the consumption of oxygen and phenol as well. The phenols with electron releasing groups tended to increase the conversion of the polymerization. In this respect, sodium phenoxide, a more effective additive was found, whereas p‐nitro phenol was the least effective. The obtained polymers displayed the common features of a controlled polymerization such as molecular weight control and low polydispersity index value (M_w/M_n < 1.5). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 351–359, 2004     

Styrene polymerization with nickel complexes/methylaluminoxane catalytic system

Polymerization of styrene using β‐diketiminate nickel (II) bromide complexes CH{C(R)NAr}₂NiBr (R = CH₃, Ar = 2,6‐ⁱPr₂C₆H₃, 1 ; R = CH₃, Ar = 2,6‐Me₂C₆H₃, 2 ; R = CF₃, Ar = 2,6‐ⁱPr₂C₆H₃, 3 ; R = CF₃, Ar = 2,6‐Me₂C₆H₃, 4 ) in the presence of methylaluminoxane was studied. Compound 3 is the most active styrene polymerization catalyst of all the nickel complexes tested. The activity of these catalysts increases with increases in steric bulk of the substituents on the aryl rings. The electronic nature of the ligand backbone also affects the activity. Weight‐average molecular weight of the prepared polystyrene ranges from 21 000 to 72 000, with polydispersity indexes of 1.95–2.78. The microstructure of the obtained products is atactic polystyrenes from NMR analyses. Copyright © 2008 John Wiley & Sons, Ltd.     

Reactive surfactants in heterophase polymerization. Part XXII—incorporation of macromonomers used as stabilizers in styrene dispersion polymerization

The effect of several parameters on the incorporation yield of poly(ethylene oxide) macromonomers at the surface of the particles, for the dispersion polymerization of styrene in ethanol–water mixtures, has been studied. The reactivity of the macromonomer is a key parameter in the mechanism of stabilization of the micrometer-size polymer particles, because it partly determines the amount and the composition of the copolymer stabilizer available at any moment during the process. The polarity of the reaction medium also strongly influences the polymerization process: higher incorporation yield and grafting density were obtained in medium of lower polarity. Besides, a chain length of around 50 ethylene oxide units for the macromonomer were needed to produce stable monodisperse particles with a significant incorporation yield. Thus, an incorporation yield as high as 53% and a grafting density corresponding to a surface area of 232 Ų/molecule have been obtained in a one-step process by using a methacrylate macromonomer. In an optimized two-step process resulting in monodisperse polymer particles, 80% incorporation yield with a very high grafting density (175 Ų/molecule) were reached. The particles with high grafting density (surface area lower than 600 Ų/molecule) could be transferred in water and exposed to a freeze–thaw cycle without massive flocculation, illustrating the efficiency of the steric stabilization. © 1997 John Wiley & Sons, Ltd.     

Radical polymerization of styrene in the presence of C60

Radical polymerizations of styrene in the presence of C₆₀ have been conducted at 90°C in benzene using benzoyl peroxide (BPO) as initiator. The behaviors of C₆₀ are investigated by monitoring BPO concentration, C₆₀ content, and polymerization time. It is found that C₆₀ acts like a radical absorber which multiply absorbs primary radicals from BPO and propagating radicals. Therefore, in the presence of C the yield and molecular weight decrease significantly. However, the molecular weight distribution is narrowed down by its coupling characteristics. At the beginning of the reaction, owing to the radical-absorbing effect of C₆₀, it makes the chain-propagation restricted. However, the number of polystyrene chains added to C₆₀ increases with polymerization time. Direct dilatometric experiment proves that C₆₀ is mainly as inhibitor for radical polymerization of styrene by benzoyl peroxide. Besides, the glass transition temperature (T_g) of the copolymers increases with increasing content of C₆₀. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2969–2975, 1999     

On the emulsion polymerization of styrene in the presence of a nonionic emulsifier

The batch emulsion polymerization kinetics of styrene (St) initiated by a water-soluble peroxodisulfate in the presence of a nonionic emulsifier was investigated. The polymerization rate versus the conversion curves showed two nonstationary rate intervals, two rate maxima, and Smith–Ewart Interval 2 (nondistinct). The rate of polymerization and number of nucleated polymer particles were proportional to the 1.4th and 2.4th powers, respectively, of the emulsifier concentration. Deviation from the micellar nucleation model was attributed to the low water solubility of the emulsifier, the low level of the micellar emulsifier, and the mixed modes of particle nucleation. In emulsion polymerizations with a low emulsifier concentration, the number of radicals per particle and particle size increased with increasing conversion, and the increase was more pronounced at a low conversion. By contrast, in emulsion polymerizations with a high emulsifier concentration, the number of radicals per particle decreased with increasing conversion. This is discussed in terms of the mixed models of particle nucleation, the gel effect, and the pseudobulk kinetics. The formation of monodisperse latex particles was attributed to coagulative nucleation and droplet nucleation for the polymerizations with low and high emulsifier concentrations, respectively. The effects of the continuous release of the emulsifier from nonmicellar aggregates and monomer droplets, the close-packing structure of the droplet surface, and the hydrophobic nature of the emulsifier on the emulsion polymerization of St are discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4422–4431, 1999     

Controlled radical polymerization of styrene in the presence of cyclic 1,2‐disulfides

The thermal polymerization of styrene (St) in the presence of cyclic 1,2‐disulfides at 120 °C was investigated. In the polymerization of St in the presence of 1,2‐dithiane (DT), that is, six‐member cyclic 1,2‐disulfide, the polymer yields and molecular weights increased with the reaction time. The linear relation between the polymer yields and molecular weights was observed, and the line passed through an original point. The molecular weight distributions of the polymers remained almost constant but were not narrow. For this polymerization with a living nature, we proposed the following mechanism: the propagating St radical reacted with thiyl radicals derived from DT, leading to the formation of dormant species, and the formed C S bond of the dormant was dissociated again to give the propagating polystyryl radical and thiyl radical. Similar results were obtained in the thermal polymerization of St at 120 °C in the presence of 1,2‐dithiacycloheptane, that is, seven‐member cyclic 1,2‐disulfide. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 145–151, 2001     

Reactive surfactants in heterophase polymerization

The mechanism for the formation of polymer particles in the dispersion polymerization of methyl methacrylate and styrene in alcohol-water mixtures has been investigated. Methacrylic based poly(ethylene oxide) macromonomers and poly(vinyl-pyrrolidone) have been used as steric stabilizers. Dynamic light scattering as well as transmission electron microscopy have been applied to determine the evolution of the average particle size at the beginning of the polymerization. Stable nuclei from 80 to 400 nm in diameter size were detected. The nucleation process was quite rapid and completed within less thanca. 0.1% monomer conversion. The experimental results are compared with those predicted by the multibin kinetics model for coalescence developed by Paine [(1990) Macromolecules 23: 3109].A series of publication from the EU program Human Capital and Mobility (CHRX CT 93-0159)     

Reactive surfactants in heterophase polymerization. VIII. Emulsion polymerization of alkyl sulfopropyl maleate polymerizable surfactants (surfmers) with styrene

The copolymerization of styrene with two polymerizable surfactants (surfmers) based on maleic acid (dodecyl sodium sulfopropyl maleate and tetradecyl sodium sulfopropyl maleate) was studied in batch emulsion polymerizations. The surfmer conversion was obtained by serum replacement with water and subsequent analysis of the recovered, unreacted surfmers with two-phase titration. It was found that both surfmers copolymerized well with styrene and their partial conversion was higher than that of styrene. These results are contradictory to what was found before in the literature using ultrafiltration with methanol, and the differences are explained on the basis of oligomer formation: The oligomers formed are detected if the latices are washed with methanol. It was found that at the end of the polymerization (almost complete conversion of both styrene and surfmer) only 45% of the surfmer groups were present on the particle surface, which is in agreement with a high conversion of the surfmer at the beginning of the reaction. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2561–2568, 1997     

New azo-peroxidic initiators in the radical polymerization of styrene and methyl methacrylate

Two new azo-perester compounds, di-tert-butyl-6,6′-azobis-(6-cyanoperoxyheptanoate) (6,6-di-tBu) and di-tert-amyl-6,6′-azobis-(6-cyanoperoxyheptanoate) (6,6-di-tAm), synthesized on the basis of 6,6′-azobis-(6-cyanoheptanoic acid) (ACHpA), were investigated for their use in the radical polymerization of styrene (S) and methyl methacrylate (MMA). Their characteristics are given, including chemical (IR spectra), thermal (DSC) and kinetic, i.e., thermal decomposition studied by volumetric and gas chromatographic methods. The rate constants and activation energies of the decomposition of both the azo and perester bonds were determined. The new azo-peresters were utilized to initiate the radical solution polymerizations of S and MMA at 60 °C. The kinetic parameters of the processes, i.e., polymerization rate and overall rate constant, were determined. Subsequently, the polymerization products were characterized by IR and DSC. It was found that the perester groups were present in the obtained polymers, and hence, the polymers are “active” for further polymerization.     

Synthesis and radical polymerization of 2-vinyldibenzothiophene

A monomer having dibenzothiophene moiety, 2-vinyldibenzothiophene (1), was prepared by the Ni-catalyzed cross-coupling reaction of vinyl bromide with the Grignard reagent of 2-bromodibenzothiophene. The radical homopolymerization of 1 and the copolymerization with styrene were carried out at 60°C in toluene (1.0M) for 20 h using AIBN (5 mol %) as an initiator to obtain the corresponding polymers in high yields. Thermal analyses of the copolymers showed that both 10% weight loss and glass transition temperatures increase when increasing the content of 1 unit. The monomer reactivity ratio was evaluated as r₁ = 2.55 (1) and r₂ = 0.16 (styrene). © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2813–2819, 1997     

Effect of temperature on styrene emulsion polymerization in the presence of sodium dodecyl sulfate. II

The batch emulsion polymerization kinetics of styrene initiated by a water‐soluble peroxodisulfate at different temperatures in the presence of sodium dodecyl sulfate was investigated. The curves of the polymerization rate versus conversion show two distinct nonstationary‐rate intervals and a shoulder occurring at a high conversion, whereas the stationary‐rate interval is very short. The nonstationary‐state polymerization is discussed in terms of the long‐term particle‐nucleation period, the additional formation of radicals by thermal initiation, the depressed monomer‐droplet degradation, the elimination of charged radicals through aqueous‐phase termination, the relatively narrow particle‐size distribution and constant polydispersity index throughout the reaction, and a mixed mode of continuous particle nucleation. The maximum rate of polymerization (or the number of polymer particles nucleated) is proportional to the rate of initiation to the 0.27 power, which indicates lower nucleation efficiency as compared to classical emulsion polymerization. The low activation energy of polymerization is attributed to the small barrier for the entering radicals. The overall activation energy was controlled by the initiation and propagation steps. The high ratio of the absorption rate of radicals by latex particles to the formation rate of radicals in water can be attributed to the efficient entry of uncharged radicals and the additional formation of radicals by thermally induced initiation. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1477–1486, 2000     

Thermokinetics evaluation and simulations for the polymerization of styrene in the presence of various inhibitor concentrations

Styrene is an important commodity chemical that is globally applied in various polymerization processes. The aim of this study was to obtain integrated thermokinetics and safety parameters for polymerization of styrene. We mainly used differential scanning calorimetry (DSC), thermal activity monitor (TAM), and simulative methods to investigate thermal polymerization of styrene and styrene containing various levels of 4-tertiary-butylcatechol (TBC). The results obtained included the rate constant (k), reaction order (n), apparent activation energy (E _a), frequency factor (A), and so on, from various DSC curves and simulative methods. From DSC curves, the exothermic onset temperature (T ₀) was about 105 and 132°C for styrene and styrene containing 10 ppm TBC. On the other hand, the test results from TAM indicated that styrene polymerization displays an autocatalytic phenomenon from 50–85°C. By means of this study, the intrinsic safety of a system for styrene during transportation and storage could be established.     

Investigation of the free radical polymerization of styrene in the presence of several 1,1-disubstituted ethylenes

A variety of 1,1-disubstituted ethylenes, having an electron-withdrawing (capto) and an electron-donor (dative) substituent on the same carbon, were synthesized and added to styrene polymerizations. The dative substituents investigated were alkoxy or alkylcarbonate. After the addition of a polystyryl radical to a disubstituted ethylene, the resulting alkoxy or carbonate radicals could potentially fragment, resulting in chain termination and the formation of alkyl radicals. This process is called addition-fragmentation chain transfer (AFCT). The polymers produced during this study were examined for evidence of copolymerization and AFCT. The relative stability of the radicals generated by the fragmentation process appears to be the predominant factor controlling the ratio of copolymerization versus AFCT. © 1993 John Wiley & Sons, Inc.     

Styrene miniemulsion polymerization initiated by 2,2′-azobisisobutyronitrile

The effects of various parameters on the dodecyl methacrylate (DMA) or stearyl methacrylate (SMA) containing styrene miniemulsion polymerizations were investigated. These parameters include the type of initiators [2,2′-azobisisobutyronitrile (AIBN) vs. sodium persulfate (SPS)], the size of the homogenized monomer droplets, the AIBN concentration, and the SDS concentration. A small quantity of a water-insoluble dye was also incorporated into the polymerization system to study the related particle nucleation mechanisms. The oil-soluble AIBN promotes nucleation in the monomer droplets, whereas homogeneous nucleation predominates in the reaction system with the water-soluble SPS. Homogeneous nucleation, however, cannot be ruled out in the DMA or SMA containing polymerizations with AIBN as the sole initiator. Increasing the level of AIBN or SDS enhances formation of particle nuclei via homogeneous nucleation. The reaction kinetics is primarily controlled by the competitive events of monomer droplet nucleation and homogeneous nucleation. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2537–2550, 1999     

Influence of Cyclodextrin on the Styrene Polymerization

Cyclodextrin (CD) are oligosaccharides consisting of 6( α ), 7( β ), 8( γ ) units of1,4-linked glucose. Due to their polar hydrophilic outer shell and relatively hydrophobic cavity, theyare able to build up host-guest complexes by inclusion of suitable hydrophobic molecules. Theformation of these complexes leads to significant changes of the solubility and reactivity of the guestmolecules, but without any chemical modification. Thus, water insoluble molecules may becomecompletely water soluble simply by mixing with an aqueous solution of native CD or CD-derivatives.Hydrogen bonds or hydrophobic interactions are responsible for the stability of the complexes and itturned out that the complexed monomers could be successfully polymerized by free radicalpolymerization in water.In our present work, using styrene as monomer, potassium peroxodisulfate as radical initiator thatreacted in water in the presence ofβ-CD but without any additional surfactant, the effect ofcyclodextrin on the polymerization was described. Additionally, the acceleration mechanism ofcyclodextrin in the polymerization was also explained based on dynamic study.Table 1 Effect of CD on the monomer reactivityIt is found that β -CD could greatly accelerate the polymerization, enhance the final conversion ofmonomer. And the more the amount of β-CD was introduced, the faster the polymerization wasobtained. From Figure 1, after 5 hours reaction at 80℃, the monomer conversion in the presence of1.0g cyclodextrin reached to 95%. However, that in absence of cyclodextrin was only 60%. And themonomer conversion was not to exceed 75% even reacted for 8 hours when no CD in reactionsystem.In order to describe the acceleration of CD in the polymerization quantitatively, based onCD and without CD. As shown in Table 1, CD produced significant effect on the monomer reactivity.The relative relativities of monomer were greatly increased with the increase of the amount of CD.