Investigation of 1,3,5-tris(2-metoxypropane)benzene/BCl3 initiated living isobutylene polymerization by C13 and B11 NMR spectroscopy

Summary The living carbocationic polymerization of isobutylene initiated by 1,3,5-tris(2-methoxypropane) benzene (TriCumOMe)/BCl₃ system was investigated by C¹³ and B¹¹ NMR spectroscopy. The reaction between the TriCumOMe and BCl₃ at-30°C in CH₂Cl₂ after 15 mins reaction time resulted in 1,3,5-tris(2-chloropropane) benzene (TriCumCl) and methyl-dichloroboronite (BCl₂OMe). The same system in the presence of isobutylene yielded three-arm star, chlorine terminated telechelic polyisobutylene and BCl₂OMe. No counterions, i.e., BCl₃OMe, BCl ₄ , or neutral boron complexes, e.g., TriCumOMe, 3BCl₃ could be detected. The simultaneous measurement of static permittivity (direct monitoring method) showed different reaction rate patterns in the case of AMI method, and when the TriCumOMe+BCl₃ mixture was aged and the polymerization was started by isobutylene.     

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers)

Summary The possibility of undesirable intramolecular cycloalkylation exists in the polymerization of iso-butylene induced by the p-dicumyl chloride/BCl₃ inifer system. A scheme has been proposed which shows the sequence of reactions leading to indane skeletons. The structure of the indane derivatives has been characterized by ¹H NMR spectroscopy. Systematic experiments have been carried out using low isobutylene and high p-dicumyl chloride concentrations leading to polyisobutylene oligomers needed for accurate endgroup analysis. The effect of temperature, solvent composition (polar/nonpolar) , isobutylene and BCl₃ concentration on the extent of indane skeleton formation has been investigated. Indane skeleton formation can be completely suppressed by the use of relatively non-polar media, e.g., 11 mixture of CH₂Cl₂ :n-C₆H₁₄, at or below –40°C, and conditions under which symmetrical telechelic polyisobutylenes can be obtained have been defined.     

Living polymerization of isobutylene initiated byp-dicumyl chloride/BCl3/n-Bu4NX systems

Summary The 1,4-di-(2-chloro-2-propyl)-benzene (pDCC)/BCl₃/IB system was investigated in the presence and absence ofn-Bu₄NX. The presence ofn-Bu₄NX (X=Cl or I) changes the mechanism increasing the living character of the polymerization of isobutylene in both cases. Whenn-Bu₄NCl is added, BCl₄ ^– is formed and as a common ion in excess it shifts the dissociation equilibrium toward the non-dissociated species. In the case of the addition ofn-Bu₄NI, an exchange reaction between the gegenions, i.e., BCl₄ ^– and BCl₃I^– has been recognised and a possible reaction mechanism is given.     

Carbocationic polymerization in supercritical carbon dioxide

Polymerization of isobutylene (IB) in supercritical carbon dioxide (SC·CO₂) at 32.5°C and 140 bar by the use of 2-chloro-2,4,4-trimethyl-pentane (TMPCl) initiator in conjunction with a mixture of TiCl₄/BCl₃ leads to well-defined polyisobutylenes (PIB) capped by a t-Bu head group and a t-Cl tail group (tBu-PIB-Cl^t) of M_n1800 g/mole and M_w/M_n=1.3. The TiCl₄/BCl₃ mixture may be viewed a new Friedel-Crafts Acid that effects rapid initiation, essentially chaintransferless propagation and reversible termination. The mechanism of IB polymerization of TiCl₄/BCl₃ mixtures is discussed.     

Free radical copolymerization behavior of vinyl acetate with butyl acrylate in the presence of GeCl4 and BCl3

No alternating copolymers of vinyl acetate (VAc) and butyl acrylate (BA) were obtained by free radical copolymerization in the presence of GeCl₄ and BCl₃ (compared with the acrylic acid–vinyl acetate copolymerization system). By ultraviolet spectral analysis, it was concluded that both BCl₃ and GeCl₄ can form complexes with butyl acrylate. The BA–BCl₃ complex constants were determined by ¹H NMR; K_B=33·2 (25°C). The reason for the gel formation in the BA–Vac–BCl₃ copolymerization system was discussed. When vinyl acetate reacted with BCl₃, cationic polymerization probably occurred. A white gel product probably resulted from the polymerization of the BA–BCl₃ complex. © 1998 SCI.     

A new asymmetric-telechelic polyisobutylene prepared by thecis-2-pinanol/BCl3, initiating system

Summary A new asymmetric-telechelic polyisobutylene (PIB): has been prepared by the polymerization of isobutylene (IB) using the novelcis-2-pinanol/BCl₃ initiating system in CH₃Cl diluent in the –30 to –50°C range. The molecular weight range explored was ¯M_n = 1000–35,000. The polymerization most likely involves thein situ formed 2-pinanyl chloride.     

Complexation of the propagating chain-end in living cationic polymerization

Summary Kinetics of polymerization has been studied in the system isobutylene/dicumylmethylether/BCl₃ (CH₂Cl₂, –80°C) in the presence of dimethyl sulphoxide added as electron donor in a broad concentration range. The apparent propagation rate constant showed a DMSO concentration dependence typical for complex equilibria.At a given DMSO concentration, the apparent rate constant decreases with increasing initial monomer concentration showing a seemingly zero-order propagation. A possible explanation of this phenomenon is the formation of a chain-end/monomer complex. Equilibrium and propagation rate constants have been determined.     

Direct monitoring of cationic polymerization by temperature,conductivity and permittivity measurements

Summary Direct monitoring of cationic polymerization was accomplished by simultaneous measurement of the average dielectric constant, representing the dipoles, of the conductivity, produced by unpaired ions, and of the temperature, characteristic for reaction rate. The ionogenic equilibria during the living polymerization of isobutylene by 1, 3, 5-tris(2-methoxy-2-propyl)benzen/BCl₃ in CH₂Cl₂ at-25°C were demonstrated. Temperature, resistance and capacitance were measured directly in the reaction mixture by a specially designed instrument.Both the conductivity and the average dielectric constant change characteristically during the living polymerization, indicating the presence and simultaneous change of unpaired ions and strongly polarized species.The differences between the AMI, and the aging technique were demonstrated and explained. In the latter case slow initiation was observed due to the methoxy-chlorine exchange caused by a reaction with BCl₃.The applied direct monitoring method helps to understand the role of polarized and ionic species in polymerizations and related processes.     

New polyisobutylene stars XI. Synthesis and characterization of allyl-telechelic octa-arm polyisobutylene stars

The synthesis and characterization of a novel star comprising eight allyl-terminated polyisobutylene (PIB) arms radiating from a calix[8]arene core is described. The synthesis was accomplished by a core-first method, by inducing the living polymerization of isobutylene (IB) by a suitably functionalized calix[8]arene initiator (1) in conjunction with BCl₃-TiCl₄ coinitiators, and terminating the growth of the living PIB^⊕ arms by allyltrimethylsilane. The relative concentrations of BCl₃ and TiCl₄ are critical for the synthesis of well-defined 8-arm stars. Characterization of the products (which included triple detector GPC studies and ¹H NMR spectroscopy) indicated quantitative allylation. A mechanism which summarizes the experimental observations is proposed. Received: 17 July 1997/Revised version: 11 September 1997/Accepted: 19 September 1997     

Synthesis and characterization of a novel octa-arm polyisobutylene star

Summary The synthesis and characterization of a novel telechelic star consisting of a well defined C-pentyl-calix[4]1,3-dicumyl alcoholarene (3) core out of which radiate eight well-defined polyisobutylene arms, each fitted with an allyl terminus is described. The synthesis was accomplished by a core-first method, by inducing the living polymerization of isobutylene by 3 in conjunction with BCl₃-TiCl₄ coinitiators. The product was characterized by GPC coupled with laser light scattering (LLS) and referactive index (RI) detectors, and by ¹H NMR spectroscopy. Quantitative functionality analysis indicated the presence of exactly eight PIB arms per molecule. Received: 3 April 2001 / Revised version: 22 June 2001 / Accepted: 22 June 2001     

Initiation of cationic polymerization with alcohol/Lewis acid systems

Alcohols in conjunction with BCl₃ have been found to be efficient initiating systems for the polymerization of isobutylene in CH₂Cl₂ solvent. The following alcohols exhibited high initiating activity: tert.-butanol, 1,1-diphenyl ethanol, 2-phenyl-2-propanol, benzhydrol. The organic moiety of the alcohol becomes the head-group of the polyisobutylene formed. The tailgroup of the polymer is a tertiary chlorine most likely because termination is by chlorination by the BCl₃OH^Θ counter anion.     

Electron donors in carbocationic polymerization

Summary Low molecular weight (¯M_n 900–5000) narrow molecular weight distribution (MWD; ¯M_w/M_n = 1.1–1.2)tert.-chlorine telechelic polyisobutylenes (PIBs) have been synthesized by the use of thetrans-2,5-dimethyl-2,5-diacetoxy-3-hexene (DiOAcDMeH₆)/BCl₃ initiating system in the presence of the electron donor (ED) dimethyl sulfoxide (DMSO) in methyl chloride diluent at –30°C. The living character of the polymerization was demonstrated by linear M_n versus W_p (weight of polymer) plots starting at the origin with the slope of 1/[I_o] (where [I_o] = initiator concentration). DMSO reduces the overall rate of polymerization, however, it increases the initiator efficiency (I_eff) to 100%. The number averagetert.-chlorine end functionality is -F_n=1.97±0.04, by¹H NMR spectroscopy. Polymerization mechanistic details are discussed. This is the first time narrow MWDtert.-chlorine telechelic PIB has been prepared close to the reflux temperature of methyl chloride.Paper XXVII in the series on Living Carbocationic Polymerization. For paper XXVI see Kaszas et al., J. Macromol. Sci. Chem. to appear (1989)     

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers)

Summary The unsaturated aliphatic dichlorides cis and trans Cl(CH₃)₂C-CH=CH-C(CH₃)₂Cl in conjunction with BCl₃ have been found to be excellent binifers and yield tert.-Cl capped polyisobutylenes PIB in CH₃Cl at –30°C. Intramolecular cyclization is absent and terminal chlorine functionality is F_n = 2.0±0.1. The normalized inifer constants have been determined: ^CItrans = 1.05, and ^CIcis = 3.8 and 1.05, respectively, for the first and second allylic chlorines in the cis isomer. The inequality of the chlorines have been analyzed. The cis and trans isomers have identical relative termination constants (k_t/k_p = 6×10^–3). The structure of the PIBs obtained has been analyzed by a variety of techniques. Model experiments with isobutylene/Cl-(CH₃)₂C-CH=CH-C(CH₃)₂Cl = 2/1 in the presence of BCl₃ gave the expected trans Cl(CH₃)₂CCH₂-(CH₃)₂C-CH=CH-C(CH₃)₂-CH₂C(CH₃)₂ -Cl. The end groups of polymers have been quantitated. The central position of the -CH=CH- residue in polymers has been demonstrated by molecular weight determinations i.e., the M_n of PIB has decreased by a factor of two after oxidative cleavage. The uniform distribution of -CH=CH-group across all polymeric species has also been established.     

Living carbocationic polymerization

Mono- and bifunctionaltert-alcohols, i.e., cumyl alcohol (CumOH), 2,4,4-trimethyl-2-pentanol (TMPOH), 2,6-dihydroxy-2,4, 4, 6-tetramethylheptane (TMHDiOH), in conjunction with BCl₃ have been shown to be efficient initiating systems for the living polymerization of isobutylene (IB) in CH₃Cl or CH₂Cl₂ solvents in the –10° to –80°C range. The living nature of the polymerizations was demonstrated by linear M_n versus amount of polyisobutylene (PIB) formed (W_PIB) plots starting at the origin and corresponding horizontal number of PIB moles formed (N) versus W_PIB plots. Quenching with methanol producestert-chlorine terminated PIBs. Quantitative dehydrochlorination of the latter products yields exo-olefin (isopropylidene) end groups. These experiments demonstrate that living carbocationic polymerizations have in fact been conducted in these laboratories long ago (1) without having been recognized as such.     

Living carbocationic polymerization

Summary The effect of polymer precipitation that occurs during polymerization on the number average molecular weight ¯M_n has been investigated in conjunction with the recently described trans-2,5-diacetoxy-2,5-dimethyl-3-hexene (DiAcODMH₆)/BCl₃/isobutylene(IB)/CH₃Cl/- 35° system using both the IMA and AMI techniques. All the experimental data could be described by a common rectilinear l/¯M_n versus l/W_p (W_p = weight of polymer) plot exhibiting an intercept l/¯M_n,max. A simple equation has been derived that explains quantitatively the results and suggests that product molecular weights obtained in heterogeneous polymerizations are determined by polymer precipitation which in turn leads to chain transfer. An Arrhenius analysis of ¯M_n,max values obtained at various temperatures corroborates this proposition and suggests polymer precipitation to control ¯M_n. That precipitation conditions determine ¯M_n seem also to hold true for conventional AlCl₃-induced IB polymerizations.Papers XXI of this series will appear in Polymer Preprints, R. Faust and J.P. Kennedy, 29(2), 1988     

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers)

Summary Three new symmetrical alkylaromatic sturctures p-bis(3-chloro-1,1,3-trimethylbutyl)benzene (I), p-bis(1,1,3-trimethyl-3-butenyl)benzene (II), and 1,1, 3,3,5,5,7,7-octamethyl-s-hydrindacene (III) have been synthesized. These new model compounds were needed to study the mechanism of intramolecular cycloalkylation (indane-skeleton formation) during the preparation of telechelic polyisobutylenes by the inifer technique. The ¹³C NMR spectrum of polyisobutylene obtained by the p-dicumyl chloride/BCl₃ inifer system has been analyzed and the resonances identified.     

Living carbocationic polymerization

Electron donors (EDs) effectively mediate living carbocationic polymerizations (LC^⊕Pzn), for example, that of isobutylene (IB). The purpose of this research was to investigate the effect of various new EDs, specifically esters and ketones on the LC^⊕Pzn of IB, and to determine the effect of these EDs on the molecular weight distribution, (MWD) of polyisobutylene (PIB) under various experimental conditions. Thus the LC^⊕Pzn of IB was effected by the dicumyl chloride (DCC)/BCl₃ initiating system in the presence of various EDs, such as dimethyl phthalate, di-t-octyl phthalate, methyl benzoate, ethyl isobutyrate, dimethyl 3,3-dimethylglutarate, dimethyl terephthalate, dimethyl 5-t-butyl-isophthalate, trimethyl 1,3,5-benzenetricarboxylate; and acetophenone and benzophenone, in CH₃Cl at-80°C, and the of the PIB was determined. It was found that the nature and the concentration of the ED strongly influence MWD. Under well-defined conditions in the presence of dimethyl phthalate or di-t-octyl phthalate, polymers with close to Poisson distribution could be obtained. For paper LX in this series see I. Majoros, J.P. Kennedy, et al. Polym. Bull. 31, 255 (1994)     

13C NMR characterization of unsaturated terminal structures in oligoisobutylenes

Summary ¹³C NMR analysis revealed the existence of additional unsaturated terminal structures in oligoisobutylene samples, in addition to the well-known-CH₂C(CH₃)=CH₂ and-CH=C(CH₃)₂. Structure with a double bond between two quaternary carbons was detected both in commercial Oppanol B3 and in a oligoisobutylene (PIB) sample prepared by polymerization in CH₂Cl₂ with a high concentration of monomer in the presence of BCl₃ at-20°C. In the latter sample, another type of the structure with a double bond between quaternary carbon and methine carbon (-CH=C(CH₃)-CH₂CH₃) was found in a large amount.     

Synthesis,characterization and diels-alder extension of cyclopentadiene telechelic polyisobutylene

The use of 1-chlorodicyclopentadiene (DCp-Cl) as a minifer for the polymerization of isobutylene leading to asymmetric telechelic polymers having dicyclopentadienyl head groups and t-chloro tail groups, has been investigated. BCl₃ is ineffective, however, diethylaluminum chloride was found to be a suitable coinitiator for the polymerization. According to kinetic investigations chain transfer to monomer is absent and DCp-Cl is an efficient minifer. Polymer characterization indicated a DCp functionality close to 1.0. The t-chloro functionality was 0.27, probably due to side reactions of the t-chloro group with the strong Lewis acids formed during the polymerization.Part XXXII of the series New Telechelic Polymers and Sequential Copolymers by Polyfunctional Initiator-Transfer Agents (Inifers).The first part of this series was presented at the Kansas City Am. Chem. Soc. Meeting, September 12–17, 1982, Polym. Prepr., 23, 103 (1982) which is considered Part XXXI of the series New Telechelic Polymers and Sequential Copolymers by Polyfunctional Initiator-Transfer Agents (Inifers).     

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer-agents (inifers)

Summary Linear and three-arm star telechelic polyisobutylenes PIB's with perfect end-functionalities (¯F_n = 2.0±0.1 or 3.0±0.1) have been synthesized by the use of 1,3-di(2-bromo-2-propyl)5-tert-butylbenzene (m-tBuDCB) binifer or 1,3,5-tri(2-bromo-2-propyl)benzene (TCB) trinifer/BCl₃ systems. The counter anion is most likely BCl₃Br in these polymerizations. The inifer efficiencies of these brominated inifers are lower than those of the chlorinated analogues, probably because of side reactions during the polymerization. The rate of chain transfer to inifer is similar for both the chlorinated or brominated inifer/ BCl₃ systems but that of termination is faster in the former system. Elementary analysis shows that the PIB's obtained with m-tBuDCB carry 90% bromine and 10% chlorine end groups.