The kinetics of styrene emulsion polymerization

A study has been carried out on the kinetics of persulfate-initiated emulsion polymerization of styrene in the presence of an anionic (oleate) or mixed anionic-nonionic emulsifier. In both cases it appears that Smith-Ewart kinetics are obeyed, i.e., there is a constant-rate period up to 40–50% conversion, during which there is a concomitant constant molecular weight development. The sharp increases in molecular weight with conversion reported by Grancio and Williams appear to be an artifact resulting from the use of an impure emulsifier (Triton X-100), which acts as a chain transfer agent to reduce the molecular weight by approximately an order of magnitude. Hence there does not appear to be any kinetic justification for assuming an inhomogeneous swollen latex particle (“core-shell” morphology), and normal thermodynamic considerations should still apply to this swelling phenomemon.     

Branching kinetics in copolymerization of styrene with a chain-transfer monomer

In an earlier work it was shown that a random long-chain branching structure can be incorporated in polystyrene by copolymerizing styrene with a small amount of monomer that contains a chain transfer group. The use of vinylbenzylthiol as the chain transfer monomer produced a polystyrene with low number-average molecular weight and a degree of branching lower than expected. In this study polymerization kinetics were used to compute the theoretical molecular weight and degree of branching. The results show that if the chain-transfer constant of the chain transfer monomer is as high as that for vinylbenzylthiol the expected molecular weight and degree of branching will indeed be as low as those found experimentally. The theory also predicts that if the chain transfer constant is near one a highly branched bushy structure will result.     

Study of the kinetics of styrene copolymerization with divinyl sulfide and the structure of macromolecules

The kinetics of the free-radical copolymerization of styrene with divinyl sulfide in the presence of N,N′-bis(vinyloxyethyl)thiuram disulfide as an iniferter has been studied. The rate of polymerization is shown to decrease with increasing iniferter concentration. The structure of the copolymers isolated in the course of copolymerization has been investigated by electron microscopy and compared with that of the copolymers synthesized using AIBN as an initiator. Evolution in the morphology of the polymer phase during the process, which consists in self-organization of the secondary supramolecular structure into spheroids with diameters of 0.1–10 μm, has been revealed. The stages of the formation of polymer particles of various structures are described by the scheme of morphogenesis.     

Excluded volume effects on the intrachain reaction kinetics

On the basis of the recently developed optimized Rouse-Zimm theory of chain polymers with excluded volume interactions, we calculate the long-time first-order rate constant k(1) for end-to-end cyclization of linear chain polymers. We first find that the optimized Rouse-Zimm theory provides the longest chain relaxation times tau(1) of excluded volume chains that are in excellent agreement with the available Brownian dynamics simulation results. In the free-draining limit, the cyclization rate is diffusion-controlled and k(1) is inversely proportional to tau(1), and the k(1) values calculated using the Wilemski-Fixman rate theory are in good agreement with Brownian dynamics simulation results. However, when hydrodynamic interactions are included, noticeable deviations are found. The main sources of errors are fluctuating hydrodynamic interaction and correlation hole effects as well as the non-Markovian reaction dynamic effect. The physical natures of these factors are discussed, and estimates for the magnitudes of required corrections are given. When the corrections are included, the present theory allows the prediction of accurate k(1) values for the cyclization of finite-length chains in good solvents as well as the correct scaling exponent in the long-chain limit.     

Influence of allyl ethers on free radical polymerization of styrene

The effect of allyl ethers on the free radical polymerization of styrene has been studied with respect to chain transfer, copolymerization, and conversion. The studies have been performed in an inert atmosphere or in air. Six different allyl ethers have been used as model substances in order to show the effect of structural differences of the ethers on the polymerization. Contrary to what was expected, no chain transfer through hydrogen abstraction was found. Nor did any copolymerization occur. When the polymerization was performed in air, the allyl ethers had a retarding effect on the polymerization rate, due to oxidation of the allyl ethers. The oxidation rate of the allyl ethers was found to be related to their structure, where the functionality and presence of intramolecular hydrogen bonding are the main factors.     

Emulsifier-free emulsion copolymerization of styrene and sodium styrene sulfonate

The kinetics of the emulsifier-free emulsion copolymerization of styrene and sodium styrene sulfonate have been examined over a range of comonomer compositions. The rate of polymerization was found to increase dramatically in the presence of small amounts of sodium styrene sulfonate. This increase is attributed to the increased number of particles formed when sodium styrene sulfonate was present and to a gel effect enhanced by ion association. At low concentrations of functional comonomer, where a monodisperse product was obtained, a homogeneous nucleation mechanism of particle generation is proposed. At higher concentrations, broader and then bimodal size distributions were obtained, and this is ascribed to significant aqueous phase polymerization of sodium styrene sulfonate. The water-soluble homopolymer is supposed to act as a locus of polymerization. The occurrence of this aqueous phase side reaction and the generation of secondary particles makes impossible the preparation of highly sulfonated polystyrene latexes by batch or seeded batch emulsion copolymerization.     

The emulsion copolymerization of styrene and sodium styrene sulfonate

The emulsion copolymerization of styrene and sodium styrene sulfonate has been shown to be a feasible preparative route to ionomeric sulfonated polystyrene. The properties of these copolymers are reported elsewhere. The copolymerization rate was found to be dramatically enhanced when compared to that for the emulsion copolymerization of styrene under identical conditions. This copolymerization was studied in detail and two mechanisms were proposed to account for these rate differences. An increase in the number of polymerizing particles in the copolymerization with consequent rate enhancement was substantiated by electron microscopy. However, the data indicate that the rate differences cannot be fully accounted for by this effect. In addition, a gel effect is proposed as a second contributor to the enhanced rate. This gel effect is believed to result from the intermolecular association of the incorporated metal sulfonate units in the growing polymer particles. When a third monomer that plasticizes the ionic interactions is used the polymerization rate decreases. This supports the gel effect hypothesis.     

Determination of reactivity ratios and kinetics of free radical copolymerization of linalool with styrene

Copolymerization of acyclic monoterpenoid, namely linalool (LIN), with styrene (STY) initiated by benzoyl peroxide (BPO) p‐acetyl benzylidene triphenyl arsonium ylide (p‐ABTAY) in xylene separately at 80°C for 180 min under inert atmosphere of nitrogen was performed. The results give a nearly alternating copolymer as evidenced from reactivity ratios (r₁ = 0.016, r₂ = 0.057) w.r.t. BPO; (r₁ = 0.017, r₂ = 0.052) w.r.t. p‐ABTAY (i.e. r₁ = 0.0165 ± 0.0005 and r₂ = 0.0545 ± 0.0025 per initiator set) using Kelen–Tudos method. The FT‐IR spectrum shows a band at 3026 cm^?1 due to the aromatic ring of polystyrene and an alcoholic band of linalool at 3408 cm^?1. ¹H‐NMR spectrum shows peaks at δ 7.0–7.7 ppm of ? OH protons and peaks at δ 7.5–8.0 ppm due to phenyl protons of styrene. The system follows ideal kinetics i.e. Rp ∝ [LIN]^1.0[STY]^1.0[BPO]^0.5/[p‐ABTAY]^0.5. The overall energy of activation in the temperature range 75–85°C is 77.0 kJ mol^?1 and 90.0 kJ mol^?1, respectively. The values for Mark–Houwink constants for the functional copolymer has been evaluated as a = 0.40 and K = 1.60 × 10^?4 with the help of gel permeation chromatography (GPC). Alfrey–Price, Q and e parameters for linalool have been evaluated as Q₂ = 0.80; e₂ = 1.25 w.r.t. BPO and Q₂ = 0.90; e₂ = 1.54 w.r.t. p‐ABTAY. Thermal properties of copolymers were investigated by thermogravimetric analysis (TGA) techniques. Copyright © 2004 John Wiley & Sons, Ltd.     

Kinetic model-based experimental design of the polymerization conditions in suspension copolymerization of styrene/divinylbenzene

The use of a mechanistic model-based experimental design technique to determine the polymerization conditions and polymer properties in suspension copolymerization of styrene and divinylbenzene is reported. The technique consists of using a mathematical model to design the polymerization conditions of a copolymer with characteristics specified beforehand. The properties (conversion, gel content, molecular weight averages, and copolymer composition) of the copolymer synthesized using this approach agree very well with the calculated properties for the pregelation period, but accurate prediction of properties during the postgelation period is still uncertain. It is demonstrated that the use of mechanistic modeling for experimental design purposes can be more adequate (when the model is sound, yet simple to solve) than other design techniques (e.g., factorial designs). © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2081–2094, 1998     

反应性乳化剂存在下半连续苯丙乳液共聚合表观动力学

研究了在反应性乳化剂SE-10N存在下,采用半连续滴加工艺进行苯丙乳液共聚合的表观动力学.首先利用间歇法研究了引发剂、乳化剂用量、单体总量和温度对聚合反应速率的影响,得到了相应的聚合反应速率方程为Rp =k[M]0.30[I]0.18[E]0.97,并计算得到聚合反应的表观活化能为90.8 kJ·mol-1.然后采用半连续滴加法,讨论了不同滴加速率对聚合表观速率Rp的影响,结果表明,随滴加速率Ra 的增加,反应速率Rp也增加,但增加的幅度逐渐减少,且聚合过程的状态不断远离饥饿态.要使该聚合过程的状态保持在稳定的饥饿态,单体滴加时间应控制在140 min 以上.     

Alternating copolymerization of 2,3-dichloro-5,6-dicyano-p-benzoquinone with styrene and polymerization behavior with vinyloxy compounds

2,3-Dichloro-5,6-dicyano-p-benzoquinone (DDQ) was found to copolymerize alternatingly with styrene (St). DDQ–isobutyl vinyl ether and DDQ–2-chloroethyl vinyl ether systems gave homopolymers of vinyl ethers, while DDQ–phenyl vinyl ether and DDQ–vinyl acetate systems gave oligomers containing both monomer units. In the terpolymerization of DDQ, p-chloranil (pCA), and St, terpolymers obtained were found to have about 50 mole % of St units regardless of monomer feed ratio and DDQ was incorporated much more rapidly into the terpolymer than pCA. The difference in the reactivity of the acceptor monomers could be attributed to that in their electron-accepting character.     

Effect of styrene oligomers on syndiospecific polymerization of styrene

Styrene oligomers, preferentially consisting of styrene dimers and trimers, are formed by a free radical mechanism at the thermal polymerization of stabilizer-free styrene during storage and at higher polymerization temperatures. The identity of several dimer and trimer fractions formed in such a free radical polymerization, their influence on a coordinative polymerization reaction, the syndiospecific polymerization of styrene, as well as their effect on the properties of the resulting polymers has been investigated.Styrene dimers and styrene trimers reduce the polymerization activity of the transition metal catalyst significantly, especially at low amounts of oligomers added to the styrene. This behavior is discussed with respect to a proposed mechanism involving complexation of the active transition metal species with the specific oligomer instead of the styrene monomer, resulting in increased steric hindrance towards insertion of a styrene molecule to the active site.Both oligomers reduce the molecular weight of the syndiotactic polystyrene, by acting as chain-transfer agents. The constancy of the polydispersity over the whole concentration range of added dimer or trimer indicates that the uniformity of the active sites of the coordinative polymerization is not significantly influenced by the presence of the oligomers.The thermal properties of the polymers demonstrate that the oligomers do not affect the high syndiospecificity of the active catalytic sites, whereas the increase in crystallization temperature with increasing amounts of styrene dimer or trimer is comparable to effects observed by the addition of crystallization nucleators to semicrystalline polymers.     

Anionic copolymerization of styrene and 1,1-diphenylethylene

Kinetics of anionic copolymerization of styrene (S) and 1,1-diphenylethylene (D) were investigated in THF. The rate constant of addition of D to living polystyrene was found to be k_{1,2 ±} = 250 l./mole-sec. for , Na⁺ ion-pair, and that for the free , Na⁺ ion is k_1,2?～400,000 l./mole-sec. Both values refer to 25°C. The addition of styrene to ? D^?, Na⁺ was found to be reversible: and k_2,1 was determined by three different methods to be ～0.5–0.7 l./mole-sec. Studies performed in a stirred-flow reactor led to k-₂₁ = 13 sec. ^?1 and K₂₁ ～ 5 × 10^?2 l./mole. An alternating copolymer is obtained in the presence of a large excess of 1,1-diphenylethylene.     

Emulsion copolymerization of styrene and methyl methacrylate

Chain transfer constants to monomer have been measured by an emulsion copolymerization technique at 44°C. The monomer transfer constant (ratio of transfer to propagation rate constants) is 1.9 × 10^?5 for styrene polymerization and 0.4 × 10^?5 for the methyl methacrylate reaction. Cross-transfer reactions are important in this system; the sum of the cross-transfer constants is 5.8 × 10^?5. Reactivity ratios measured in emulsion were r₁ (styrene) = 0.44, r₂ = 0.46. Those in bulk polymerizations were r₁ = 0.45, r₂ = 0.48. These sets of values are not significantly different. Monomer feed compcsition in the polymerizing particles is the same as in the monomer droplets in emulsion copolymerization, despite the higher water solubility of methyl methacrylate. The equilibrium monomer concentration in the particles in interval-2 emulsion polymerization was constant and independent of monomer feed composition for feeds containing 0.25–1.0 mole fraction styrene. Radical concentration is estimated to go through a minimum with increasing methyl methacrylate content in the feed. Rates of copolymerization can be calculated a priori when the concentrations of monomers in the polymer particles are known.     

Synthesis of 2-formyl-1-(p-vinylphenyl)cyclopropane and its polymerization and copolymerization with styrene

2-Formyl-1-(p-vinylphenyl)cyclopropane was prepared, and its homopolymerization and copolymerization with styrene were performed. The effect of the substituent on the monomer reactivity and the photosensitivity of the copolymer obtained were examined. Original Russian Text K.G. Guliev, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 4, pp. 636 639.     

Investigation of the radical copolymerization of styrene and divinylbenzene

A kinetic investigation of the early steps of the radical copolymerization of styrene and divinylbenzene (DVB) has been performed in the presence of a transfer agent, meant to delay the onset of the gel point. It is confirmed that the consumption of DVB is faster than that of styrene. However, in the early stages of the reaction, pendant double bonds are formed to a large extent as a result of DVB incorporation. In later stages, the probability for these pendant unsaturations to be involved in intermolecular linking increases as the concentration of the monomers decreases. This process is responsible for gelation and it continues after the gel point, to build more and more crosslinks. This effect can be followed by measurements of the equilibrium swelling degree, which decreases and reaches a limiting value, depending upon the DVB content of the monomer mixture. The results prompt us to reconsider some of the commonly accepted ideas about the structure of crosslinked polymers synthesized by radical copolymerization.     

Coupled single-particle growth and kinetics modeling for styrene polymerization over silica-supported metallocene catalyst

A comprehensive mathematical model for styrene stereoregular polymerization was carried out. This model was generated by coupling the single particle growth model (SPGM) with kinetics model, to predict the effect of intraparticle mass transfer resistance and initial catalyst size on the polymerization kinetics. SPGM was derived based on a modified multigrain model (MMGM) to calculate the spatial-time evolution of styrene concentration under intraparticle mass transfer limitations. Then, the SPGM was solved simultaneously with kinetics model to estimate the polymerization rate and molecular weight distribution (MWD) under the above mentioned limitations. The results show that a significant radial distribution of styrene concentration across polymer growing. Moreover, the diffusion resistance was most intense at the early step of the polymerization and the effects of the polymerization rate are more strongly. Additionally, it is appear that increasing the initial catalyst size leads to a decrease in the rate of polymerization. For MWD, the model simulation show that the diffusion resistance led to have an increase in the molecular weight within a period of time similar to the one needed in the catalyst decay. The validation of the model with experimental data given a agreement results and shows that the model is able to predict monomer profile, polymerization rate, and MWD of syndiotactic polystyrene.