Polymerization Of Α-methylstyrene Research Articles

Living Cationic Polymerization of α-Methylstyrene. 2. Synthesis of Block and Random Copolymers with 2-Chloroethyl Vinyl Ether and End-Functionalized Polymers

Living Cationic Polymerization of α-Methylstyrene. 2. Synthesis of Block and Random Copolymers with 2-Chloroethyl Vinyl Ether and End-Functionalized Polymers

Living cationic polymerization of .alpha.-methylstyrene initiated with a vinyl ether-hydrogen chloride adduct in conjunction with tin tetrabromide

The first example of living cationic polymerization of α-methylstyrene was achieved with an initiating system that consist of the HCl-adduct of 2-chloroethyl vinyl ether [1a: CH 3 CH(OCH 2 CH 2 Cl)Cl] and SnBr 4 in CH 2 Cl 2 at -78°C. The number-average molecular weight of the polymers increased in direct proportion to monomer conversion up to 110 000 (DP n =1000) and agreed with the calculated values assuming that one polymer chain forms per 1a molecule. Throughout the reaction, the molecular weight distribution of the polymers stayed very narrow (M w /M n ∼1.1)

Synthesis and reactions of polymers with photoactive terminal groups—4. the use of oxocarbenium polymerization for the synthesis of poly(α-methylstyrene) with N-acyl dibenz[b,f]azepine terminal units

N-chlorocarbonyl dibenz[b,f]azepine in conjunction with AgSbF 6 initiated the cationic polymerization of α-methylstyrene in methylene chloride. Polymer samples obtained this way contained terminal dibenzazepine units. Chain extension occurred upon irradiating these polymers with u.v. in benzene solution containing benzophenone or benzil, via cyclobutane formation.

Interaction of stilbene with disodium α-methylstyrene tetramer

Electron absorption spectra of anionic centres in disodium α-methylstyrene tetramer (DSTMS), of benzylsodium and of their complexes with stilbene (STB) have been calculated. Downwards-shifted (< 0.5 eV) excited charge-transfer levels have been found for benzyl anion pairs separated by STB; thermal occupation of these levels leads to electron transfer resulting in the formation of the STB − Na + anion radical. A comparison of the calculated and experimentally determined spectra provides evidence on the formation of the STB − Na + anion radical also in the reaction of STB with DSTMS. The calculated spectra of benzyl, phenylisopropyl and stilbenyl radicals shows that the detection of these species is complicated because of the low intensity of transition in the visible part of the spectrum. Polymerization of α-methylstyrene in the system DSTMS-CTB was investigated.

Study of the interaction of small particles of alkaline metals with α-methylstyrene in non-polar media

The reaction of α-methylstyrene particles with lithium, sodium and their mixtures in a hydrocarbon medium at a monomer concentration below equilibrium has been studied. It is shown that at least two processes occur simultaneously: dispersion of the metals and polymerization of α-methylstyrene on the surface of the metallic particles formed. The kinetics of polymerization and the molecular mass distribution of the polymers obtained have been studied. It is shown that the molecular mass of the polymer is determined by the nature and number of the bimetallic active centres.

High conversion polymerization of α-methylstyrene with maleimide at different monomer-to-monomer ratios in the feed

High conversion polymerization of α-methylstyrene (α-MeSt) with maleimide (Ml) was performed in Calvet differential microcalorimeter under different monomer-to-monomer ratios in the feed using AIBN as initiator. From the calorimetric curve it was observed that in the presence of an excess of Ml, alternating copolymer is quantitatively formed prior to the formation of poly (Ml).

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, Mw/Mn - 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

Polymer-Supported Lewis Acid Catalysts. II. Cationic Polymerization of α-Methylstyrene with Polystyrene-Gallium Trichloride Complex as Initiator

Abstract The polymerization of α-methylstyrene catalyzed by a polymer-supported Lewis acid catalyst, polystyrene-gallium trichloride complex, is described. The kinetic equation of the cationic polymerization is Rp = k˙Cms˙Ccat , and the apparent activation energy is 20.9 kJ/mol. The effect of different solvents on the polymerization rate is quite pronounced; for example, the polymerization rate decreased in the following order in the three solvents: CH2 ClCH2 Cl < CH2 Cl2 < CCl4. High molecular weight poly(α-methylstyrene) (Tg = 185°C) could be obtained at room temperature. The mechanism of the polymerization is also discussed.

Solvent effect on the equilibrium polymerization of α-methylstyrene

The Flory-Huggins interaction parameter χ has been determined from static vapour-pressure measurements for four binary mixtures: α-methylstyrene in p-dioxane or cyclohexane, and poly(α-methylstyrene) in p-dioxane or cyclohexane. For the first system, measurements were carried out at 25 and 40°C, yielding values between 0.12 and 0.18 for χ. The second one was investigated at 30, 35 and 40°C leading to χ values between 0.50 and 0.58. The values at 40°C for the third system lie between 0.40 and 0.46 when the polymer volume fraction varies from 0.10 to 0.35. The last system, also at 40°C, has χ values of 0.49 and 0.60 for polymer volume fraction of 0.10 and 0.27, respectively. These parameters were used to compute the equilibrium compositions of monomer and polymer, at any solvent concentration, for the polymerization of α-methylstyrene in different solvents.

Interaction parameters and the equilibrium anionic polymerization of α-methylstyrene in tetrahydrofuran

Flory–Huggins interaction parameters, χ12, have been determined for α-methylstyrene + tetrahydrofuran and tetrahydrofuran + poly(α-methylstyrene) mixtures from static vapour-pressure measurements. For the first system, experiments were performed at five temperatures varying from 20.0 to 40.0 °C and yield values of χ between –0.30 and –0.40. Experimental data for the second system were obtained at 25.0 and 35.0 °C, leading to χ values slightly greater than 0.40. These results are applied to the data obtained for the equilibrium anionic polymerization of α-methylstyrene in tetrahydrofuran and used for the computation of the free energy of polymerization, ΔG1c. Values of ΔG1c obtained in this fashion are found to be in good agreement with previously obtained results.

Electro-initiated cationic polymerization of α-methylstyrene by direct electron transfer

Electro-initiated cationic polymerization of α-methylstyrene in a tetrabutylammonium fluoroborate-dichloromethane system has been investigated at various temperatures by constant potential electrolysis. It is established that polymerization occurs at low temperatures with higher yields. Apparent activation energy of the electro-initiated polymerization is −64.3 kJ mol −1.

Primary processes of the radiation-induced cationic polymerization of α-methylstyrene enhanced by triphenylsulfonium hexafluorophosphate

Primary processes of the radiation-induced cationic polymerization of α-methylstyrene in dichloromethane solution containing (C 6H 5) 3SPF 6, which enhances the polymerization, were studied by pulse radiolysis. The yield and lifetime of α-methylstyrene dimer radical cations are increased by the addition of the salt. This has been attributed to the stabilization of the monomer and dimer radical cations toward neutralization through ion-pair formation with PF 6-. The effect of ( n-C 4H 9) 4NPF 6 observed by the pulse radiolysis is similar to that of (C 6H 5) 3SPF 6, but the former salt does not enhance the polymerization probably because of a radiolysis product, tributylamine, inhibiting the polymerization. Comparison is made with the previous results for (C 6H 5) 2IPF 6 which also enhances the polymerization.

Radiation-induced cationic polymerization of α-methylstyrene enhanced by diphenyliodonium hexafluorophosphate

Radiation-induced cationic polymerization of α-methylstyrene enhanced by diphenyliodonium hexafluorophosphate

The anionic bulk polymerization of α-methylstyrene-II. Kinetic study of the propagation

A kinetic study of the anionic bulk polymerization of α-methylstyrene initiated with tert-butyllithium ( t-BuLi) in presence of N, N, N′, N′-tetramethylethylenediamine (TMEDA) has been performed. Kinetic measurements have been carried out using dilatometry at 25° and 40° up to 37% conversion. The reactivity of the system is found to be a function of the ratio r = [TMEDA]/[ t-BuLi]. The apparent rate constant decreases with increasing values of r for r < 1 and increases for r > 1. The results are explained by the presence of three different active species, viz. contact ion-pairs contact ion-pairs stretched solvated with a TMEDA molecule, ion-pairs stretched by nTMEDA molecules. When the temperature is raised to 62°, the active centres become unstable and cyclic oligomers are formed.

Quasiliving Carbocationic Polymerization. VII. Block Polymerization of α-Methylstyrene from Quasiliving Poly(isobutyl Vinyl Ether) Dication

Abstract Poly(α-methylstyrene-b-isobutyl vinyl ether-b-α-methylstyrene) triblock polymers have been prepared by blocking α-methyl-styrene (αMeSt) from biheaded quasiliving poly(isobuty1 vinyl ether) (PIBVE) cations generated with the bifunctional p-dicumyl chloride/AgSbF6 initiating system in methylene chloride solvent at -90°C. The products were fractionated with 2-propanol, a good solvent for PIBVE and a nonsolvent for PaMeSt. The 2-propanol-insoluble fractions had much higher molecular weights (M n = 30,500–69,100) than the starting PIBVE (M n =6,600–10,600) and contained 13–29 wt% IBVE together with 87–71 wt% αMeSt units. The 2-propanol-soluble fractions (M n = 7,300–11,600) contained ∼90 wt% IBVE and ∼10 wt% αMeSt units.

Carbocationic Polymerization in the Presence of Sterically Hindered Bases. V. The Polymerization of α-Methylstyrene by the “H2O”7BCI3Initiating System

Abstract The influence of 2,6-di-tert-butylpyridine (DtBP) on the polymerization of α-methylstyrene (αMeSt) induced by the “H2O”/BC13 initiating system in the -20 to −60°C range has been studied in detail. Adventitious H2O (“H2O”) is the initiating cationogen and initiation most likely proceeds by a concerted route in the absence of free protons or the acid H⊕BC13 OH⊕ Polymerizations are extremely rapid and kinetic termination is absent (conversions are 100%) in the absence of DtBP. In the presence of DtBP, polymerizations are still very fast; however, conversions are reduced. Significantly, conversions increase with decreasing temperatures, which suggests the operational presence of terminative proton entrapment. Molecular weights increase with decreasing temperatures in the presence and absence of DtBP and the slopes of the linear Arrhenius plots (In [Mbar]w versus 1/T) are parallel; the molecular weights obtained in the presence of DtBP are close to a factor of 10 higher than those produced in the absence of this hindered pyridine. The virtual identity of the slopes of Arrhenius plots indicates close similarity between the nature and rate of molecular-weight-determining events in the absence and presence of DtBP, i.e., kp/ktr,m and kp/ktr,G⊕ DtBP profoundly affects molecular weight dispersity: [Mbar]w/[Mbar]n = 3.0–4.0 in the absence of DtBP whereas [Mbar]w/[Mbar]n = 1.5 -1.8 in the presence of DtBP. The number w of polymer molecules formed (yield/[Mbar]n) in the absence of DtBP whereas [Mbar]w/[Mbar]n = 1.5–1.8 in presence of DtBP. The number of polymer molecules formed (yield/[Mbar]n) = 1.5–1.8 in the presence of DtBp. The number of polymer molecules formed (yield/[Mbar]n) in the absence of DtBP decreases with decreasing temperature while those formed in the presence of DtBP remain constant. According to Mayo, (1/[Mbar]n versus 1/ [M] plots chain transfer to monomer in the peresence of DtBP is vey low (ktr,m /kp = 6.4 × 10−4 and 2.8 × 10−4 at −30 and −50°C) but not zero. Conceivably two kinds of chain transfer to monomer reactions may exist (direct and indirect) and only one (i.e., the indirect one) may be trappable by DtBP. The effect of [DtBP] on the percent converstion and [Mbar]n was investigated: Above a fairly well defined [DtBP], neither conversions nor [Mbar]n's were affected by [DtBP]. With increasing [DtBP] molecular weight dispersions rapidly decrease and [Mbar]w [Mbar]n's seem to level off at ∼ 1.5 at relatively high [DtBP]. Changing the polarity of the solvent characteristically affects the mechanism of α MeSt polmerzation in the presence and absence of DtBP results in a strong increase in [Mbar]w/[Mbar]n (from ∼ 1.5 to ∼ 4.0), in the presence of DtBP [Mbar]w/[Mbar]n remains virtually unchanged at ∼1.5.

Carbocationic Polymerization in the Presence of Sterically Hindered Bases. I. α-Methylstyrene Polymerization in the Presence of Sterically Hindered Bases

Abstract The effect of the sterically hindered base 2,6-di-tert-butyl-pyridine (DtBP) on the polymerization of α-methylstyrene (αMeSt initiated by “H2O”/BCl3 in a wide temperature range) has been investigated. αMeSt polymerizations carried out under identical conditions except in the presence of DtBP give much lower yield, much higher molecular weight, and noticeably narrower distributions than those obtained in the absence of this hindered base. The possibility of DtBP acting as an inhibitor is ruled out. Yields, molecular weights, and molecular weight distributions virtually do not change by changing DtBP concentration from 1.0 × 10−1 to 1.0 × 10−3 M. Differences in conversion levels do not explain the observed phenomena. PaMeSt samples obtained in the presence of trace amount of DtBP were of much higher molecular weight than those prepared in the absence of hindered pyridine, even at the same conversion level. These findings are explained by proposing that DtBP is a specific proton scavenger able to trap protons emerging during chain transfer to monomer, and that other elementary events remain unaffected by the presence of this hindered base.

Carbocationic Polymerization in the Presence of Sterically Hindered Bases. VII. The Polymerization of α-Methylstyrene with the Pentamethyl Benzyl Chloride/SnCl4Initiating System

Abstract The polymerization of α-methylstyrene by the Me5C6 CH2C1/ SnCl4 nonprotic initiating system has been studied in the presence and absence of 2,6-di-tert-butylpyridine (DtBP) in CH2C12 in the −30 to −80°C temperature range. Model experiments demonstrate that initiation involves direct carbocationation of the olefin by Me5C6C⊕H2. According to kinetic studies, polymerizations in the absence of DtBP are very rapid (no induction) and terminationless, and molecular weights are determined by chain transfer to monomer. In the presence of DtBP, polymerizations do not go to completion due to terminative proton entrapment. Reducing the temperature increases the yields and molecular weights. Evidently a decrease in temperature reduces the rate of proton expulsion and thus the rate of terminative proton entrapment is also reduced. That chain transfer to monomer is absent in the presence of DtBP is demonstrated by the constancy of the number of polymer molecules formed and initiator efficiencies obtained under ...

Carbocationic Polymerization in the Presence of sterically Hindered Bases. VI. The Polymerization of Methylstyrene with the “H2O”/SnCl4Initiating System

Abstract The polymerization of α-methylstyrene has been investigated using the “H2O”/SnCl4 initiating system in the presence of 2,6-di-tert-butylpyridine (DtBP) in CH2Cl2 solvent at −60°C. In the absence of DtBP and at low DtBP concentrations conversions are about 100%, but with increasing amounts of DtBP conversions drop to 3–5%. Polydispersity decreases with increasing [DtBP], The [Mbar]n versus [DtBP] plot shows a maximum; thus [Mbar]n increases from ∼70,000 to ∼120,000 by increasing [DtBP] from 6 × 10−7 to 4.8 × 10−4 M and decreases to ∼ 10,000 on further increasing DtBP. The effect of DtBP on this polymerization system can be explained by assuming nonprotic initiation, termination only by DtBP, depressed chain transfer to monomer, and complex formation between the propagating carbocation and DtBP.

Carbocationic Polymerization in the Presence of Sterically Hindered Bases. VIII. High Efficiency Grafting of Poly(α-methylstyrene) Branches from Chlorobutyl and Polychloroprene Rubbers in the Presence of Proton Traps

Abstract The syntheses of chlorobutyl rubber-g-poly(α-methylstyrene) and poly(chloroprene-g-α-methylstyrene) have been accomplished with 90–97% grafting efficiencies. The synthesis principle involves the initiation of α-methylstyrene polymerization by chlorobutyl rubber or polychloroprene rubber in conjunction with BCI3 or SnCU coinitiators in the presence of 2,6-di-t-butylpyridine proton trap. Selective solvent extraction coupled with molecular weight determination and molecular size distribution indicate satisfactory separation procedures and reliable grafting efficiency data. The close agreement between theoretical and experimental graft copolymer molecular weights suggests that backbone scission or gelation does not occur during grafting. According to graft composition and molecular weight data, 6 to 11 poly(α-methylstyrene) branches have been attached per chlorobutyl or polychloroprene rubber backbones.