Novel Epoxide Initiators for the Carbocationic Polymerization of Isobutylene

Summary: We recently reported the synthesis of polyisobutylene (PIB) via direct initiation by epoxycyclohexyl isobutyl polyhedral oligomeric silsesquioxane (POSS®) (Figure 1 ) in conjunction with titanium tetrachloride (TiCl₄). This system successfully initiated the living carbocationic polymerization of isobutylene (IB) in hexane/methyl chloride (Hx/MeCl -60/40, v/v) at T = −80 °C, yielding an asymmetric telechelic PIB with one POSS® cage head group and one tert-Cl end group. 1 This paper will discuss IB polymerizations initiated by 1,2-epoxycyclohexane and bis[3,4-(epoxycyclohexyl)ethyl]-tetramethyl-disiloxane, in conjunction with TiCl₄.     

Living carbocationic copolymerization of isobutylene with styrene

The carbocationic copolymerization of isobutylene (IB) and styrene (St), initiated by 2‐chloro‐2,4,4‐trimethylpentane/TiCl₄ in 60/40 (v/v) methyl chloride/hexane at ?90 °C, was investigated. At a low total concentration (0.5 mol/L), slow initiation and rapid monomer conversion were observed. At a high total comonomer concentration (3 mol/L), living conditions (a linear semilogarithmic rate and M_n–conversion plots) were found, provided that the St concentration was above a critical value ([St]₀ ～ 0.6 mol/L). The breadth of the molecular weight distribution decreased with increasing IB concentration in the feed, reaching M_w/M_n ～ 1.1. St homopolymerization was also living at a high total concentration, yielding polystyrene with M_n = 82,000 g/mol, the highest molecular weight ever achieved in carbocationic St polymerization. An analysis of this system by both the traditional gravimetric–NMR copolymer composition method and FTIR demonstrated penultimate effects. IB enrichment was found in the copolymers at all feed compositions, with very little drift at a high total concentration and above the critical St concentration. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1778–1787, 2007     

Polyisobutylene-containing block polymers by sequential monomer addition. I. The living carbocationic polymerization of styrene

The living carbocationic polymerisation of styrene (St) has been investigated by the 2-chloro-2,4,4-trimethylpentane (TMPCI)/TiCl₄ initiating system in the presence of various additives such as electron pair donors (ED_s) and the proton trap 2,6-di-tert-butylpyridine (DtBP) by the use of the mixed solvent CH₃Cl/methyl-cyclohexane (MCHx) (40/60 v/v) at ?80°C under conventional laboratory conditions. The TMPCl/TiCl₄ system in the absence of additives produces ill-defined bimodal molecular weight distribution (MWD) polymers. Much better defined polystyrenes (PSt) can be obtained in the presence of EDs, such as N,N-dimethylacetamide (DMA) and hexamethylphosphoramide (HMPA). Monomer depletion should be avoided to prevent intra- or intermolecular alkylation yielding indanyl end groups or branched polymers, respectively. In the combined presence of an ED and the proton trap, i.e., DMA + DtBP, the living polymerization of St has been achieved and thus the foundations for the carbocationic synthesis of PSt block polymers by sequential monomer addition have been laid.     

Poly(styrene‐b‐isobutylene) multiarm star‐block copolymers

Multiarm star‐branched polymers based on poly(styrene‐b‐isobutylene) (PS‐PIB) block copolymer arms were synthesized under controlled/living cationic polymerization conditions using the 2‐chloro‐2‐propylbenzene (CCl)/TiCl₄/pyridine (Py) initiating system and divinylbenzene (DVB) as gel‐core‐forming comonomer. To optimize the timing of isobutylene (IB) addition to living PS⊕, the kinetics of styrene (St) polymerization at −80°C were measured in both 60 : 40 (v : v) methyl cyclohexane (MCHx) : MeCl and 60 : 40 hexane : MeCl cosolvents. For either cosolvent system, it was found that the polymerizations followed first‐order kinetics with respect to the monomer and the number of actively growing chains remained invariant. The rate of polymerization was slower in MCHx : MeCl (k_app = 2.5 × 10⁻³ s⁻¹) compared with hexane : MeCl (k_app = 5.6 × 10⁻³ s⁻¹) ([CCl]_o = [TiCl₄]/15 = 3.64 × 10⁻³M; [Py] = 4 × 10⁻³M; [St]_o = 0.35M). Intermolecular alkylation reactions were observed at [St]_o = 0.93M but could be suppressed by avoiding very high St conversion and by setting [St]_o ≤ 0.35M. For St polymerization, k_app = 1.1 × 10⁻³ s⁻¹ ([CCl]_o = [TiCl₄]/15 = 1.82 × 10⁻³M; [Py] = 4 × 10⁻³M; [St]_o = 0.35M); this was significantly higher than that observed for IB polymerization (k_app = 3.0 × 10⁻⁴ s⁻¹; [CCl]_o = [Py] = [TiCl₄]/15 = 1.86 × 10⁻³M; [IB]_o = 1.0M). Blocking efficiencies were higher in hexane : MeCl compared with MCHx : MeCl cosolvent system. Star formation was faster with PS‐PIB arms compared with PIB homopolymer arms under similar conditions. Using [DVB] = 5.6 × 10⁻²M = 10 times chain end concentration, 92% of PS‐PIB arms (M_n,PS = 2600 and M_n,PIB = 13,400 g/mol) were linked within 1 h at −80°C with negligible star–star coupling. It was difficult to achieve complete linking of all the arms prior to the onset of star–star coupling. Apparently, the presence of the St block allows the PS‐PIB block copolymer arms to be incorporated into growing star polymers by an additional mechanism, namely, electrophilic aromatic substitution (EAS), which leads to increased rates of star formation and greater tendency toward star–star coupling. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1629–1641, 1999     

Kinetics and mechanisms in carbocationic polymerization: The quest for true rate constants

This article is a critical analysis of kinetic dataavailable on carbocationic polymerizations. A survey of published propagation rate constant (k_p) data revealed several orders of magnitude differences. In this article, an explanation of this apparent discrepancy is offered with a case study involving the carbocationic polymerization of 2,4,6‐trimethylstyrene (TMS). With the polymerization mechanism originally proposed for this system, k_p = 1.35 × 10⁴ L mol^?1 s^?1 was extracted from experimental data with the Predici polyreaction package. The alternative mechanism yielded k_p = 1.01 × 10⁷ L mol^?1 s^?1, close to that predicted by Mayr's Linear Free Energy Relationship (LFER). We propose that true rate constants can only be obtained from direct competition experiments or from kinetic interpretation based on independently proven mechanisms. The second part of this review discusses critical analysis of the temperature and concentration dependence of various living IB systems. Comparison of the temperature dependence in systems initiated with 2‐ chloro‐2,4, 4‐ trimethylpentane (TMPCl)/TiCl₄ from various laboratories yielded of ΔH ～?25 and ?34.5 kJ/mol for high and low TMPCl/TiCl₄ ratios, respectively. Aromatic (cumyl‐type) initiators show ΔH ～ ?40 kJ/mol, whereas H₂O/TiCl₄ in the presence of the strong electron‐ pair donor dimethylacetamide gave ΔH = ?12 kJ/mol. The significant differences indicate different underlying mechanisms with complex elementary reactions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5394–5413, 2005     

Living carbocationic polymerization. LXII. Living polymerization of styrene,p-methylstyrene and p-chlorostyrene induced by the common ion effect

The effect of common anion producing salt, tetrabutylammonium chloride (n-Bu₄NCl), on the livingness and kinetics of styrene (St), p-chlorostyrene (pClSt), and p-methylstyrene (pMeSt) polymerization initiated by the 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl₄ system has been investigated. Uncontrolled (conventional) carbocationic polymerization of St and p MeSt can be converted to living polymerization by the use of n-Bu₄NCl. Under similar conditions the polymerization of p ClSt is living even in the absence of n-Bu₄NCl, although the molecular weight distribution (MWD) of the polymer becomes narrower in the presence of this salt. The apparent rates of polymerizations decrease in the presence of n-Bu₄NCl in proportion with the concentration of the salt. The rate of living polymerization of p ClSt is noticeably lower than that of St, while that of p MeSt is higher. The apparent rate constants, k_p^A, of these polymerizations have been determined, and the effects of the electron donating p Me- and electron withdrawing p Cl-substituents relative to the rate of St polymerization have been analyzed. [For part LXI, see J. Si and J. P. Kennedy, Polym. Bull., 33 , 651 (1994)]. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3341–3347, 1997     

Quasiliving Carbocationic Polymerization. XVII. Synthesis Of Poly (Styrene-β-Isobutylene-β-Styrene)

Poly(styrene-b-isobutylene-b-styrene) has been synthesized by sequential carbocationic polymerization under quasiliving conditions at -90°C. The quasiliving synthesis was effected by first continuously and slowly condensing gaseous isobutylene (IB) to a bifunctional initiating system (p-dicumyl chloride/TiCl₄) dissolved in a hexane-methylene chloride (60:40 v/v) mixture. After the quasiliving polyisobutylene (PIB) sequence had reached a desired molecular weight, styrene (St) was continuously and slowly added to produce the polystyrene (PSt) sequence. The products consisted of the target triblock. However, due to initiation by impurities and possibly to chain transfer to both IB and St, it also contained diblocks and small amounts of homopolymers. While the latter could be removed by selective fractionation, the triblocks and diblocks could not be separated. The mechanism of quasiliving polymerization leading to PIB/PSt blocks is discussed.     

Similarities and differences of epoxide, aldehyde and peroxide initiators for Cp2TiCl-catalyzed styrene living radical polymerizations

Cp₂TiCl is the first example of a single electron transfer (SET) agent that both provides initiating radicals from three different types of functionalities (i.e. radical ring opening of epoxides and reduction of aldehydes and peroxides) and doubles as mediator for the living radical polymerization of styrene (St) by reversibly endcapping the growing polymer chains. An initiator (I) comparison was performed using 1,4-butanediol diglycidyl ether (BDE), benzaldehyde (BA) and benzoyl peroxide (BPO) as models. The investigation of the effect of reaction variables was carried out over a wide range of experimental conditions ([Cp₂TiCl₂]/[I] = 0.5/1-4/1; [Zn]/[Cp₂TiCl₂] = 0.5/1-3/1, [St]/[I] = 50/1-400/1 and T = 60-130 °C) to reveal living polymerization features such as a linear dependence of molecular weight on conversion and narrow molecular weight distribution (M_w/M_n) for each initiator class. However, progressively lower polydispersities and larger initiator efficiencies are obtained with increasing the [Cp₂TiCl₂]/[I] and [Zn]/[Cp₂TiCl₂] ratios and with decreasing temperature. Accordingly, optimum conditions correspond to [St]/[I]/[Cp₂TiCl₂]/[Zn] = [50-200]/[1]/[2-3]/[4-6] at 70-90 °C. By contrast to peroxides, aldehydes and the more reactive epoxides provide alcohol end groups useful in block or graft copolymers synthesis.     

Living Carbocationic Polymerization. Li. Living Carbocationic Copolymerization of Indene and p-Methylstyrene. 1. Demonstration of the Living and Random Copolymerization of Indene and p-Methylstyrene

Abstract

The living carbocationic polymerization and copolymerization of indene (Ind) and p-methylstyrene (pMeSt) have been investigated by the use of the 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl₄ and the 2-chloro-2-propylbenzene (cumyl chloride, CumCl)/BCl₃ initiating systems in the presence of triethylamine (Et₃N) as electron donor and CH₃Cl or CH₃Cl/QH14 mixed solvents at ?80°C. The TMPCl/TiCl₄ initiating system gives essentially living copolymerization with slow initiation up to M _n ≈ 20,000. The CumCl/BCl₃ initiating system also induces living Ind homopolymerization up to at least M _n ≈ 13,000. The homopolymerization of pMeSt with the latter initiating system, however, is not living as it shows evidence for a large amount of chain transfer. Thus, with the CumCl/BCl₃ combination a small amount of chain transfer has apparently been observed in the presence of 50% of pMeSt in the charge. Reactivity ratio studies, fractionation, ¹H- and ¹³C-NMR spectroscopy, and glass transition temperature (T_g ) investigations indicate that virtually random Ind-co-pMeSt copolymers of M _n ≈ 20,000 can be obtained under suitable conditions. The T_g of the copolymers can be controlled between ≈115°C (the T_g of PpMeSt) and ≈194°C (the T_g of PInd) by the relative composition of the two monomers in the charge.     

Living carbocationic polymerization of isobutyl vinyl ether and the synthesis of poly[isobutylene-b-(isobutyl vinyl ether)]

The MeCH(O-i-Bu)Cl/TiCl₄/MeCONMe₂ initiating system was found to induce the rapid living carbocationic polymerization (LC^⊕Pzn) of isobutyl vinyl ether (IBuVE) at ?100°C. Degradation by dealcoholation which usually accompanies the polymerization of alkyl vinyl ethers by strong Lewis acids is “frozen out” at this low temperature and poly(isobutyl vinyl ether)s (PIBuVEs) with theoretical molecular weights up to ca. 40,000 g/mol (calculated from the initiator/monomer input) and narrow molecular weight distributions (M?_w/M?_n ≤ 1.2) are readily obtained. According to ¹³C-NMR spectroscopy, PIBuVEs prepared by living polymerization at ?100°C are not stereoregular. The MeCH(O-i-Bu)Cl/TiCl₄ combination induces the rapid LC^⊕Pzn of IBuVE even in the absence of N,N-dimethylacetamide (DMA). The addition of the common ion salt, n-Bu₄NCl to the latter system retards the polymerization and meaningful kinetic information can be obtained. The kinetic findings have been explained in terms of TiCl₄. IBuVE and TiCl₄ · IBuVE and TiCl₄ · PIBuVE complexes. The HCl (formal initiator)/TiCl₄/DMA combination is the first initiating system that can be regarded to induce the LC^⊕Pzn of both isobutylene (IB) and IBuVE. Polyisobutylene (PIB)–PIBuVE diblocks were prepared by sequential monomer addition in “one pot” by the 2-chloro-2,4,4-trimethylpentane (TMP-Cl)/TiCl₄/DMA initiating system. Crossover efficiencies are, however, below 35% because the PIB^⊕ + IBuVE → PIB-b-PIBuVE^⊕ crossover is slow. © 1993 John Wiley & Sons, Inc.     

Investigation of the effect of epoxide structure on the initiation efficiency in isobutylene polymerizations initiated by epoxide/TiCl4 systems

The effect of the chemical structure of styrene-based epoxides, namely, styrene epoxide (SE), α-methylstyrene epoxide (MSE), p-methylstyrene epoxide (pM-SE) and α-methyl-p-methylstyrene epoxide (pM-MSE), in conjunction with TiCl₄, on the initiation efficiency (I_eff) in the carbocationic polymerization of isobutylene (IB) was investigated. SE yielded living polymerization, but the initiation efficiency was low when compared to MSE (I_eff=8% and 35%, respectively). pM-SE led to non-living IB polymerization, while pM-MSE revealed linear M_n-conversion plot and narrow MWD with a non-linear first order rate plot. Among the epoxides investigated, MSE was the best initiator to scale up the one-step synthesis of polyisobutylenes (PIBs) carrying one primary hydroxyl head group and one tertiary chloride end group. The hydroxyl functionality of these PIBs determined by ¹H-NMR was F_n=1.09±0.16 from 24 experiments.     

Synthesis and Characterization of PS-PIB-PS Triblock Copolymers

Abstract

Poly(styrene-isobutylene-styrene) (PS-PIB-PS) block copolymers synthesized via living carbocationic polymerization using a di- or tricumyl chloride/TiCl₄/pyridine initiating system in 60/40 (v/v) hexane/methyl chloride cosolvents. The kinetics of formation of the PIB block at ? 80°C were found to be first order in isobutylene (IB) concentration, first order in the concentration of initiating sites, second order in TaiCl₄ concentration, and a negative fractional order with respect to the pyridine concentration. The rate of polymerization was found to decrease with increasing temperature, indicating an equilibrium between dormant, covalent and active, ionized chain ends, and chain-end concentration studies suggested that there was no contribution by free ions to the rate of propagation. Diagnosis of the livingness of the IB polymerization indicated that at high (≥90%) monomer conversion, β-proton elimination becomes important, causing the timing of addition of styrene to be critical. Addition of styrene at an IB reaction time significantly exceeding the time necessary for complete IB consumption resulted in contamination of the product with a substantial amount of homo-PS; conversely, addition at intermediate IB conversion resulted in slow copolymerization between IB and styrene and the formation of a tapered block copolymer. Addition of styrene at an IB conversion of about 90% resulted in well-defined block copolymers which displayed ordered, phase-separated morphologies consisting of cylinders of PS in a continuous phase of PIB. The block copolymers possessed properties consistent with those of physically crosslinked rubbers. Dynamic mechanical spectroscopy revealed two glass transitions with a broad rubbery plateau extending from about 0 to 100°C, and tensile strengths of up to 25 MPa and elongations to 1000% were observed for some samples.     

Cp2TiCl-catalyzed radical chemistry: living styrene polymerizations from epoxides, aldehydes, halides, and peroxides

Four different Cp₂TiCl-activated radical sources (1,4-butanediol diglycidyl ether, benzaldehyde, (1-bromoethyl)benzene, and benzoyl peroxide) were investigated as initiators in the Cp₂TiCl-catalyzed living radical polymerization of styrene (St). The effect of reaction variables was investigated over a wide range of values ([St]/[I]=50/1-400/1, [I]/[Cp₂TiCl₂]=1/0.5-1/4, [Cp₂TiCl₂]/[Zn]=1/0.5-1/3 and T=40-130 °C). A linear dependence of molecular weight on conversion was observed for each initiator, but larger initiator efficiencies and lower polydispersities were obtained upon increasing [Cp₂TiCl₂] and [Zn] and decreasing temperature. The optimum conditions are initiator dependent but broadly correspond to [St]/[I]/[Cp₂TiCl₂]/[Zn]=[50-200]/[1]/[2-3]/[4-6] at 70-90 °C. The most robust initiators are aldehydes followed by peroxides, epoxides, and finally halides.     

Synthesis,characterization, and crosslinking of novel stars comprising eight poly(isobutylene‐azeotropic‐styrene) copolymer arms with allyl or hydroxyl termini. II. Stars of eight isobutylene/styrene azeotropic copolymer arms emanating from a calix[8]arene core

Our objective was the precision synthesis of novel stars consisting of a well‐defined calix[8]arene core out of which radiate eight poly(isobutylene‐aze‐styrene) [P(IB‐aze‐St)] arms fitted with crosslinkable end groups. We reached our objective by preparing the octafunctional calixarene derivative C[8]OCH₃, inducing the living azeotropic copolymerization of IB/St charges with the C[8]OCH₃/BCl₃·TiCl₄ initiating system, and end‐quenching living IB/St copolymerizations with allyltrimethylsilane. With this strategy, we obtained stars C[8]? [P(IB‐aze‐St)? CH₂CH?CH₂]₈ of various molecular weights. The number of ? CH₂CH?CH₂ termini of the arms was 8.0 ± 0.2 by quantitative ¹H NMR analysis. The eight allyl termini were quantitatively converted to ? CH₂CH₂CH₂OH termini by hydroboration/oxidation. To confirm that the latter second‐generation stars possessed eight primary alcohol end groups, we quantitatively converted the ? CH₂OH termini to ? OSi(CH₃)₃ termini, the concentration of which was quantitated by ¹H NMR spectroscopy. According to this analysis, the stars contained 8.0 ± 0.3 hydroxyl termini. The glass‐transition temperatures of the P(IB‐aze‐St) arms increased from 59 to 65 °C as the weight‐average molecular weights of the arms increased from about 2500 to about 4300 g/mol, respectively. The α and K constants of the Mark–Houwink–Sakurada relationship and the intrinsic viscosity of a representative allyl‐telechelic star were determined and compared with a linear azeotropic IB/St copolymer of similar molecular weight. The crosslinking of C[8]? [P(IB‐aze‐St)CH₂CH₂CH₂OH]₈ stars with 4,4′‐methylene bis(phenyl) diisocyanate and 2,4‐tolylene diisocyanate in various solvents afforded tightly crosslinked films of potential interest for scratch‐resistant coatings, mar‐resistant coatings, or both. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1525–1532, 2001     

Tailored macromolecules by living carbocationic techniques

This presentation concerns our latest results for the controlled synthesis of various homopolymers, blocks, random copolymers, networks, by living carbocationic polymerization (LC^⊕ Pzn). We start with an analysis of the Winstein ionicity spectrum, a roadsign toward LC^⊕ Pzn systems. Living isobutylene (IB) homopolymerization can be effected by the addition of common anion salts to conventional polymerization charges, e.g., by adding nBu₄NCl to a 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl₄/IB system. Various AB diblocks have been prepared by sequential monomer addition. The first clean svnthesis of an AB poly(olefin-b-alkyl vinyl ether) diblock, ie., poly(isobutylene-b-methyl vinyl ether), by sequential monomer addition was accomplished. These novel amphiphilic diblocks promise to be excellent nonionic detergents. The field of linear A-B-A triblocks and three-arm star blocks where A = glassy and B = rubbery (polyisobutylene) segment, is vigorously expanding. Several new thermoplastic elastomers (TPEs) have been prepared, characterized and tested, e.g., poly-(indene-b-isobutylene-b-indene). The synthesis of random copolymers, e.g., isobutylene/2,4,4-dimethyl-1,3-pentadiene, by living reactivity leveling has been demonstrated. Transformation of the polyisobutylene cations PIB^⊕ and ^⊕PIB^⊕ yielded the corresponding anions PIB^⊖ and ^⊖PIB^⊖, which upon block polymerization of butadiene (Bd) and methyl methacrylate (MMA), respectively, gave rise to the new diblock PIB-PBd and triblock PMMA-PIB-PMMA. In the latter, the largely syndiotactic sPMMA endblocks were stereocomplexed with isotactic iPMMA and thus the upper use-temperature of these novel TPEs was enhanced. Novel amphiphilic networks comprising hydrophilic polymethacrylates (e.g., dimethylaminoethyl methacrylate (DMAEMA) or hydroxyethyl methacrylate (HEMA)) crosslinked by methacrylate-telechelic PIBs were prepared and their potential usefulness for biomedical applications has been studied.     

Living Carbocationic Polymerization. LVII. Kinetic Treatment of Living Carbocationic Polymerization Mediated by the Common Ion Effect

Abstract

The effect of anion concentration on the apparent rate constant of polymerization k^A _p of isobutylene (IB) induced by the 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl₄ initiating system using the CH₂Cl₂/nC₆H₁₄ (60/40 v/v) solvent system at ?40 and ?80°C was studied by the use of nBu₄NCl. Computer simulation has shown that k^A _p decreases several orders of magnitude upon the addition of even a very small amount of common anion TiCl^?- ₅ to the charge. The rate of change is reduced in the concentration range of experimental interest. It was concluded that the decrease of k^A _p with increasing TiCl ^?- ₅ concentration is mainly due to the decreasing contribution of propagation by free ions. The contribution (%) of propagation by free ions to the apparent rate of propagation was calculated.     

A chemical approach to the problem of slow initiation in living cationic polymerizations

The effect of slow initiation on initiation efficiency and MWD has been investigated, with regard to the living carbocationic polymerization of isobutylene. The initiating system trans−2,5-diacetoxy-2,5-dimethyl−3–hexene(DiOAcDiMeH₆)BCl₃ has been investigated at −35°C in CH₃Cl. Based on considerations valid also for anionic polymerizations, the following methods have been applied to increase the initiation efficiency: 1. Increasing [M_o]/[I_o] (batch, AMI) or [ΔM].j/[I_o] (IMA). The applicability of this method is limited by the solubility of the polymer. 2. Increasing k_i/k_p, by (i) increasing k_i, e.g., by introducing an electron withdrawing substituent into the initiator, (ii) decreasing k_p, e.g., by the addition of a strong electron donor (DMSO) to the system, (iii) using Cl-CH₂-CH₂-Cl.     

Living cationic polymerization of isobutylene coinitiated by FeCl3 in the presence of isopropanol

A simple but effective FeCl₃‐based initiating system has been developed to achieve living cationic polymerization of isobutylene (IB) using di(2‐chloro‐2‐propyl) benzene (DCC) or 1‐chlorine‐2,4,4‐trimethylpentane (TMPCl) as initiators in the presence of isopropanol (iPrOH) at ?80 °C for the first time. The polymerization with near 100% of initiation efficiency proceeded rapidly and completed quantitatively within 10 min. Polyisobutylenes (PIBs) with designed number‐average molecular weights (M_n) from 3500 to 21,000 g mol^?1, narrow molecular weight distributions (MWD, M_w/M_n ≤ 1.2) and near 100% of tert‐Cl terminal groups could be obtained at appropriate concentrations of iPrOH. Livingness of cationic polymerization of IB was further confirmed by all monomer in technique and incremental monomer addition technique. The kinetic investigation on living cationic polymerization was conducted by real‐time attenuated total reflectance Fourier transform infrared spectroscopy. The apparent constant of rate for propagation (k_p^A) increased with increasing polymerization temperature and the apparent activation energy (ΔE_a) for propagation was determined to be 14.4 kJ mol^?1. Furthermore, the triblock copolymers of PS‐b‐PIB‐b‐PS with different chain length of polystyrene (PS) segments could be successfully synthesized via living cationic polymerization with DCC/FeCl₃/iPrOH initiating system by sequential monomer addition of IB and styrene at ?80 °C. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Catalytic Action of Metallic Salts in Autoxidation and Polymerization. VII. Polymerization of Methyl Methacrylate by Cobalt(ll) or (III) Acetylacetonate-Dioxane Hydroperoxide

Abstract

Polymerization of methyl methacrylate by Co(II or III) acetylacetonate-dioxane hydroperoxide [abbreviated as Co(acac)2, Co(acac)₃, and DOX HPO, respectively] was carried out in dioxane solvent, and the differences in polymerization rate and the degree of polymerization between two initiating systems were compared. Co(acac)₂-DOX HPO for the initiation of the polymerization system was more effective than Co(acac)₃-DOX HPO. The polymerization rate equations for both initiating systems obtained from kinetic data were as follows. For Co(acac)₂-DOX HPO initiating system: R_p=k [M]^3/2[Co(acac)₂]^1/7[DOX HPO]^?