Kinetics of free-radical copolymerization of α-methylstyrene and styrene

The free-radical copolymerization of α-methylstyrene and styrene has been studied in toluene and dimethyl phthalate solutions at 60°C. Gas chromatography was used to monitor the rate of consumption of monomers. For styrene alone, the measured rate of polymerization R_p and M?_n of the polymer coincided with values expected from previous studies by other workers. Solution viscosity η affected R_p and M?_n of styrene homopolymers and copolymers as expected on the basis of an inverse proportionality between η^1/2 and termination rate. The rate of initiation by azobisisobutyronitrile appears to be independent of monomer feed composition in this system. Molecular weights of copolymers can be accounted for by considering combinative termination only. The effects of radical chain transfer are not significant. A theory is proposed in which the rate of termination of copolymer radicals is derived statistically from an ideal free-radical polymerization model. This simple theory accounts quantitatively for R_p and M?_n data reported here and for the results of other workers who have favored more complicated reaction models because of the apparent failure of simple copolymer reactivity ratios to predict polymer composition. This deficiency results from systematic losses of low molecular weight copolymer species in some analyses. Copolymer reactivity ratios derived with the assumption of a simple copolymer model and based on rates of monomer loss can be used to predict R_p values measured in other laboratories without necessity for consideration of depropagation or penultimate unit effects. The 60°C rate constants for propagation and termination in styrene homopolymerization were taken to be 176 and 2.7 × 10⁷ mole/l.-sec, respectively. The corresponding figures for α-methylstyrene are 26 and 8.1 × 10⁸ mole/l.-sec. These constants account for the sluggish copolymerization behavior of the latter monomer and the low molecular weights of its copolymers. The simple reaction scheme proposed here suggests that high molecular weight styrene–α-methylstyrene copolymers can be produced at reasonable rates at 60°C by emulsion polymerization. This is shown to be the case.     

The formation of radical cations of styrene and α-methylstyrene in the irradiation of mixtures of these monomers with TiCl4 and SnCl4 in a semicrystalline heptane matrix

The formation of paramagnetic intermediates following the irradiation of styrene, α-methylstyrene, and their mixtures at ?90°C in the presence of TiCl⁴ and SnCl⁴ in the polycrystalline heptane matrix was investigated. The effect of light on vinyl aromatic monomers leads to the formation of radical cations of styrene and α-methylstyrene, which subsequently initiate the polymerization. The polymerization of styrene and α-methylstyrene supposedly proceeds via the cationic mechanism.     

Anionic Polymerization of New Dual-Functionalized Styrene and α-Methylstyrene Derivatives Having Styrene or α-Methylstyrene Moieties

Anionic polymerizations of four new dual-functionalized styrene and α-methylstyrene derivatives, 3-(4-(4-isopropenylphenoxy)butyl)styrene ( 4 ), 3-(4-(2-isopropenylphenoxy)butyl)-α-methylstyrene ( 5 ), 4-(4-(4-isopropenylphenoxy)butyl)-α-methylstyrene ( 6 ), and 4-(4-(2-vinylphenoxy)butyl)styrene ( 7 ), were carried out in THF at -78 °C with sec-BuLi as an initiator. Both 4 and 5 underwent anionic polymerization in a living manner to quantitatively afford functionalized polystyrenes and poly(α-methylstyrene)s having α-methylstyrene moiety in each monomer unit and precisely controlled chain lengths. On the other hand, insoluble polymers were obtained by the anionic polymerization of 6 and 7 under the same conditions. The positional effect of substituent on anionic polymerization was discussed.     

Cationic Polymerization with Boron Halides. VIII. Synthesis of (CH3)2C = CHCH2-Polyisobutylene-CI Prepolymer and Subsequent Preparation of (CH3)2C = CHCH2-Poly(isobutylene-b-styrene) and (CH3)2C = CHCH2-Poly(isobutylene-b-α-methylstyrene)

Asymmetric telechelic polyisobutylene, α-PIB-ω), carrying the olefinic head group α = (CH₃)₂ C[dbnd]CHCH₂- and tertiary chlorine endgroup ω = -C(CH₃)₂Cl has been synthesized by the use of the (CH₃)₂C[dbnd]CHCH₂Cl/BCl₃ initiating system. Highest yields were obtained by using methylene chloride diluent at about ?50°C. The presence and position of the olefinic head-group was proven by epoxidation/titration and epoxidation/cleavage. The presence and position of a tertiary chlorine endgroup was proven by initiating block polymerization of a second monomer, such as styrene or α-methylstyrene, by using the asymmetric telechelic polyisobutylene prepolymer in conjunction with Et₂AlCl coinitiator. According to I/DP versus 1/[M] plots obtained in model block copolymerization experiments, with the use of the tert-BuCl/Et₂AlCl initiating system at ?30°C, significant chain transfer to monomer occurs during blocking of styrene; however, monomer transfer is negligible during blocking of α-methylstyrene. Thus, under suitable conditions head-functionalized block copolymers (CH₃)₂C[dbnd]CHCH₂-PIB-b-PαMeSt virtually free of homopolymer contaminants can be obtained.     

Photodegradation behavior of tert-butyl vinyl ketone polymers and copolymers with styrene and α-methylstyrene

Photodegradation behavior of atactic and isotactic polymers of tert-butyl vinyl ketone (t-BVK) and its copolymers with styrene and α-methylstyrene was studied in dioxane as a solvent at room temperature. The quantum yield of main-chain scission of atactic poly(t-BVK) was found to be larger than that of isotactic poly(t-BVK) and atactic poly(methyl vinyl ketone). From the Stern-Volmer plots on the quenching study of atactic poly(t-BVK) with naphthalene and 2,5-dimethyl-2,4-hexadiene, it was found that 60–70% of its photochemical reaction underwent main-chain scission from the triplet state. It was also found that the increase in t-BVK contents of both copolymers accelerated the photodegradation, and the copolymer with styrene was more photodegradable than that with α-methylstyrene. These results seemed to suggest that the main-chain scission of these vinyl ketone polymers and copolymers proceeded through a Norrish type II photoelimination mechanism.     

Molecular weight distribution studies. I. Radiation-induced polymerization of liquid α-methylstyrene

The concentration of water in purified and BaO-dried α-methylstyrene was found to be 1.1 × 10^?4M. The radiation-induced bulk polymerization of the α-methylstyrene thus prepared was studied in the temperature range of ?20°C to 35°C. The polymerization rate varied as the 0.55 power of the dose rate. The theoretical molecular weights and molecular weight distribution were calculated from a proposed kinetic scheme and these values were then compared with those found experimentally. The agreement between these two was reasonably close, and therefore it was concluded that, from the molecular weight distribution point of view, the proposed kinetic scheme for the cationic polymerization of α-methylstyrene is an acceptable one. The rate constant for chain transfer to monomer k_f changed with temperature and was found to be responsible for the decrease in the molecular weight of the polymer with increase in temperature. k_f and k_p at 20°C were found to be 0.95 × 10⁴ l./mole-sec and 0.99 × 10⁶ l./mole-sec, respectively.     

Effect of zinc salts on the spontaneous copolymerization of 4-vinylpyridine with various electron-rich vinyl monomers

The spontaneous copolymerization of 4-vinylpyridine (4-VP) complexed with three different zinc salts (chloride, acetate, and triflate) with various electron-rich vinyl monomers (p-methoxystyrene, MeOSt; p-methylstyrene, MeSt; α-methylstyrene, α-MeSt; p-tert-butylstyrene, BuSt; styrene, St) was investigated in methanol at 75°C. Increasing the zinc salt concentration or the nucleophilicity of the electron-rich monomer increased the copolymer yields. All obtained copolymers are characterized by high molecular weight (10⁵) and broad molecular weight distribution. Both ¹H-NMR and elemental analyses confirmed the almost 1 : 1 copolymer structure. Changing the anion of the zinc salt does not have a considerable effect either on the copolymerization rate or on the molecular weight. The proposed mechanism exhibits the formation of a σ-bond between the β-carbons of the two donor–acceptor monomers. This creates the 1,4-tetramethylene biradical intermediate which can initiate the copolymerization reaction. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2787–2792, 1997     

Olefin polymerization in liquid sulfur dioxide initiated by m-chloroperbenzoic acid. I. Homopolymerization of styrene and α-methylstyrene

Homopolymerizations of styrene (Sty) and α-methylstyrene (AMS) in liquid sulfur dioxide were carried out in the temperature range from ?10°C to ?78°C, using m-chloroperbenzoic acid as initiator. It is shown, through the effect of initiator concentration, temperature, and times of reaction on the conversion and molecular weight of the polymers, that AMS is more reactive than Sty because it requires a smaller amount of initiator for the same conversion to be reached, although the molecular weight of the resulting polymer is lower. A linear relationship has been observed for Sty between the degree of polymerization and the initiator concentration. Within the experimental conditions employed, the presence of polysulfones has been discarded by elemental analysis. The polymerization reactions are considered to be cationic in mechanism.     

Composition and Microstructure Determination of the Syndiotactic Copolymer of para-Methylstyrene and Styrene by Pyrolysis Gas Chromatography

The composition and microstructure of syndiotactic para-methylstyrene/styrene copolymer was determined by a pyrolysis gas chromatography (Py-GC) method. This method uses the styrene and para-methylstyrene monomer peak intensities to determine the styrene and para-methylstyrene composition in the copolymer. The number average sequence length of styrene was calculated by using the triad peak intensities. Because of the low concentration of para-methylstyrene in the copolymer, the number average sequence length of para-methylstyrene was determined with formulas that incorporate the copolymer composition and the number average sequence length of styrene. The distribution of para-methylstyrene defined by the terms “percent of single units” and “percent of desired distribution” was calculated by the number average sequence of para-methylstyrene. This method has been tested with copolymers containing up to 24 mole% of para-methylstyrene. The composition results from Py-GC of para-methylstyrene and styrene copolymers used in this study were in excellent agreement with ¹H-NMR results.     

Pulse radiolysis study on the initial processes of radiation-induced cationic polymerization of styrene and α-methylstyrene

Initial processes of radiation-induced cationic polymerization of styrene and α-methylstyrene have been studied by means of microsecond pulse radiolysis. For styrene, absorption bands caused by the monomer cation radical St⁺? appear at 630 and 350 nm in a mixture of isopentane and n-butyl chloride at about ?165°C. In parallel with the decay of St⁺?, three absorption bands appear in the near-infrared (IR) region, and at 600 and 450 nm. The IR and 600 nm bands are assigned to the associated dimer cation radical St₂⁺?, and the 450 nm band to the bonded dimer cation radical St-St⁺?. The kinetic behavior of these species shows that reaction of St⁺? with styrene monomer forms both St₂⁺? and St-St⁺?. With the decay of St-St⁺?, another absorption band appears at 340 nm, and the lifetime of this band is relatively long. The 340 nm band may be due to carbonium ions of the growing polystyrene. For α-methylstyrene, the monomer cation radical (at 690 and 350 nm), the associated dimer cation radical (in the near-IR region and at 620 nm) and the bonded dimer cation radical (at 480 nm) behave in a manner similar to that of the corresponding styrene species. The absorption band caused by carbonium ions of growing poly(α-methylstyrene) appears at 340 nm.     

Determination of coisotacticities of some alternating styrene–acrylic copolymers by NMR spectra

Coisotacticities σ for some alternating copolymers were determined through the analyses of their CH₃O, CH₃ and CH₂ proton NMR spectra; styrene–methyl methacrylate (σ = 0.56), styrene-methyl acrylate (σ = 0.53), styrene–methyl α-chloroacrylate (σ = 0.69), styrene–methacrylonitrile (σ = 0.19), styrene–methacrylamide (σ = 0.16), α-methylstyrene–methyl methacrylate (σ = 0.21), and α-methylstyrene–methyl acrylate (σ = 0.53) were studied. It was found that a terminal model or Bernoullian trial prevails in these complexed copolymerizations with diethylaluminum chloride. The influence of monomer structure on σ values is discussed.     

Synthesis of methyl methacrylate,styrene, and isobutylene multiblock copolymers using atom transfer and cationic polymerization

ABCBA‐type pentablock copolymers of methyl methacrylate, styrene, and isobutylene (IB) were prepared by the cationic polymerization of IB in the presence of the α,ω‐dichloro‐PS‐b‐PMMA‐b‐PS triblock copolymer [where PS is polystyrene and PMMA is poly(methyl methacrylate)] as a macroinitiator in conjunction with diethylaluminum chloride (Et₂AlCl) as a coinitiator. The macroinitiator was prepared by a two‐step copper‐based atom transfer radical polymerization (ATRP). The reaction temperature, ?78 or ?25 °C, significantly affected the IB content in the resulting copolymers; a higher content was obtained at ?78 °C. The formation of the PIB‐b‐PS‐b‐PMMA‐b‐PS‐b‐PIB copolymers (where PIB is polyisobutylene), prepared at ?25 (20.3 mol % IB) or ?78 °C (61.3 mol % IB; rubbery material), with relatively narrow molecular weight distributions provided direct evidence of the presence of labile chlorine atoms at both ends of the macroinitiator capable of initiation of cationic polymerization of IB. One glass‐transition temperature (T_g), 104.5 °C, was observed for the aforementioned triblock copolymer, and the pentablock copolymer containing 61.3 mol % IB showed two well‐defined T_g's: ?73.0 °C for PIB and 95.6 °C for the PS–PMMA blocks. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3823–3830, 2005     

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.     

Cationic polymerization of α-methylstyrene in dichloromethane initiated with system 2,5-dichloro-2,5-dimethylhexene-BCl3. II. Continuous addition of monomer into initiator,quasiliving polymerization

A slow continuous addition of dichloromethana solutions of α-methylstyrene (α-MeSt) into a dichloromethane solution of 2,5-dichloro-2,5-dimethylhexane (DDH) with BCI₃ (initiating system II) prepared in advance resulted, in the temperature range between ?20 and ?40°, in a quasilving polymerization of α-MeSt. At ?20°C and a 100% conversion a polymer with a very narrow molecular weight distribution is formed, M?_w/M?_n - 1.1. Quasiliving polymerization of α-MeSt has not been achieved with freshly prepared dischloromethane solutions of DDH with BC₃ (initiating sytem I), or with solutions of BCI₃ alone (initiating system III). Polarity of the polymerization medium affected molecular weight distribution (MWD) of the polymer, and the polydispersity index decreased with decreasing polarity. MWD of the polymer samples were studied by the GPC method, the structure of poly (α-methylstyrene) (Pα-MeSt) was investigated by the ₁H-NMR analysis     

Interaction of organo-alkali compounds with unsaturated hydrocarbons

The stability of disodium tetramer of α-methylstyrene (“living” polymer) in THF and in a THF-α-methylstyrene mixture has been investigated by spectrophotometry. It was found that at 25°C and at concentrations lower than the equilibrium concentration α-methylstyrene greatly stabilizes the process leading to disappearance of the main absorption band (λ_max = 340 mμ) of “living” polymer. In this case isomerization of “living” polymer is accompanied by quantitative conversion of the compound having λ_max = 340 mμ into a new compound with λ_max = 430 mμ. The constants of the disappearance rate D₃₄₀ and the activation energies of the process were determined in THF and in a THF-α-methylstyrene mixture. The introduction of small amounts of α-methylstyrene into living polymer at 25°C markedly increases its activity in the course of propagation. The experimental results are considered from the standpoint of formation of complexes of living polymer with α-methylstyrene.     

The synthesis of diene and of vinyl copolymers containing predetermined quantities of polynuclear hydrocarbon or heterocyclic adducts—V. Copolymers formed from styrene or α-methylstyrene,anthracene and alkyl dihalide

When a tetrahydrofuran solution of styrene or α-methylstyrene (M) and anthracene (A) is reacted with alkali metal, anionic species are produced which can be titrated with alkyl dibromides (RBr₂) to produce copolymers. These copolymers have been analysed structurally by NMR spectroscopy and by a model compound approach.With styrene as monomer, the copolymers have been shown to consist of two types of repeat units [AM_nAR] and [AR] linked together in a random manner: at equimolar styrene to anthracene ratios, n ～ 10 and 75 per cent of the anthracene is linked directly to the alkyl ligand as in the second repeat unit. When α-methylstyrene is used, the repeat units are predominantly [M_nR] and [AR] with n ～ 5. Production of copolymers of α-methylstyrene in particular is more efficient for decane dibromide than for butane dibromide, where formation of bridged anthracene derivatives by a cyclization and regeneration of anthracene competes with the copolymerization.The reasons for the structural differences between the copolymers of the two vinyl monomers are discussed.     

Syntheses and polymerization of (meth)acrylates containing spiro ortho ester moieties

Acrylates and methacrylates bearing pendant spiro ortho ester groups ( 3 ) were prepared by the reaction of (meth)acrylic acid with bromomethyl spiro ortho esters ( 2 ) in the presence of 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU). These monomers were copolymerized with styrene (St) at 60°C in the presence of α,α'-azobisisobutyronitrile (AIBN) to give the corresponding copolymers with M?_n 6000-17000 and their compositions were in proportion to the feed ratios. Similarly, the copolymerization of 3 with acrylonitrile (AN) was carried out at 60°C to obtain the corresponding copolymers with the similar compositions to the feed ratios. Two kinds of 3 -St copolymers with different compositions were treated with BF₃OEt₂ in refluxing methylene dichloride affording the crosslinked polymers quantitatively. Slight expansion in volume was observed during the crosslinking.     

n-Butyllithium/α-methylstyrene/benzene/diethyl ether: A suitable initiation system for anionic syntheses of model co- and homopolymers of styrene and isoprene

An initiation system of the anionic polymerization, intended for the syntheses of homopolymers and block copolymers with narrow molar mass distribution, was tested with styrene and isoprene. The actual initiating species, viz., the oligomeric α-methylstyryl anion, originates by the reaction of n-butyllithium with α-methylstyrene in a benzene/diethyl ether 1:1 (v:v) solvent mixture at room temperature. The homopolymers and two-block copolymers of styrene and isoprene, prepared by using this system, were characterized by light scattering, membrance osmometry, GPC, and ¹H NMR spectroscopy. By using the suggested initiation system, it is possible to synthesize well-defined homopolymers and block copolymers with low polydispersity (as judged by the shape of the GPC peaks and by the values of the polydispersity index), especially in a molar mass region between 4 × 10⁴ and 1.5 × 10⁵ g/mol. Above the upper limit of this interval, an appropriate decrease of the diethyl ether/benzene volume ratio is recommended, though the polymerization time must then be prolonged.     

Grafting polymerization of styrene onto alternating terpolymers based on chlorotrifluoroethylene,hexafluoropropylene, and vinyl ethers,and their modification into ionomers bearing ammonium side‐groups

The grafting polymerization of styrene initiated by the alkyl chloride groups of poly(CTFE‐alt‐VE) and poly[(CTFE‐alt‐VE)‐co‐(HFP‐alt‐VE] copolymers (where CTFE, HFP, and VE stand for chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), and vinyl ether (VE), respectively) followed by the chemical modification of the polystyrene grafts are presented. First, the fluorinated alternating copolymers were produced by radical copolymerization of CTFE (with HFP) and VE. Second, atom transfer radical polymerization enabled the grafting polymerization of styrene in the presence of the poly(CTFE‐alt‐VE)‐macroinitiator using the alkyl chloride group of CTFE as the initiation site. Kinetics of the styrene polymerization indicated that such a grafting had a certain controlled character. For the first time, grafting of polystyrene onto alternating fluorinated copolymers has been achieved. Differential scanning calorimetry thermograms of these graft copolymers exhibited two glass transition temperatures assigned to both amorphous domains of the polymeric fluorobackbone (ranging from ?20 to +56 °C) and the polystyrene grafts (ca. 95 °C). The thermostability of these copolymers increased on grafting. Thermal degradation temperatures at 5% weight loss were ranging from 193 to 305 °C when the polystyrene content varied from 81 to 27%. Third, chloromethylation of the polystyrene grafts followed by the cationization of the chloromethyl dangling groups led to original ammonium‐containing graft copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Stereospecific polymerization of α-methylstyrene by friedel-crafts catalysts

The relationship between stereoregularity and polymerization conditions of α-methylstyrene has been studied by means of NMR spectra. The effects of solvents and various Freidel-Crafts catalysts have been investigated. The stereoregularity of poly-α-methylstyrene increased with increased polymer solubility in the solvent used and with decreasing polymerization temperature. This behavior is completely different from the stereospecific polymerization of vinyl ethers and methyl methacrylate in homogeneous systems. This may be due to the strong steric repulsion exerted by the two substituents in the α-position of α-methylstyrene. For example, with BF₃ · O(C₂H₅)₂ as catalyst at ?78°C., atactic polymer is obtained in n-hexane, a nonsolvent for α-methylstyrene, whereas highly stereoregular polymer is produced in toluene or methylene chloride, good solvents for the polymer. However, the polarity of the solvent and the nature of the catalyst hardly affect the stereoregularity of the polymer.