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     

Self-organized Multilayer Films and Porous Nanocomposites of Gold Nanoparticles with Octa(3-aminopropyl)octasilsesquioxane

Successive deposition of octa(3-aminopropyl)octasilsesquioxane octahydrochloride and gold nanoparticles coated with carboxylate groups (Au–COO⁻) on glass substrates alternately under mild basic conditions led to systematic buildup of a gold colloidal multilayer. The driving force of the self-assembly was electrostatic interaction between ammonium cations of octa(3-aminopropyl)octasilsesquioxane octahydrochloride and carboxylate anions on Au–COO⁻. A linear increase of surface plasmon resonance of Au–COO⁻ with the deposited bilayers indicated the multilayer manipulation was reproducible. Porous nanocomposites were accomplished by precipitation of octa(3-aminopropyl)octasilsesquioxane octahydrochloride modified polystyrene (PS) latex particles and Au–COO⁻ followed by removal of the PS particles via tetrahydrofuran (THF) extraction. Porous nanocomposite films were obtained by layer-by-layer (LBL) self-assembly of the octa(3-aminopropyl)octasilsesquioxane octahydrochloride modified PS latex particles and Au–COO⁻ followed by removal of the PS particles via THF extraction. Dedicated to Professor Christopher W. Allen for his advances in inorganic ring and polymer chemistry.     

Scale-up precision synthesis of octa-arm polyisobutylene stars

Summary This paper concerns the scale-up precision synthesis of octa-arm polyisobutylene (PIB) stars. Specifically, we have optimized to the 100–200 g scale the preparation of star polymers consisting of eight PIB arms radiating from a calix[8]arene core. The synthesis strategy involved the use of a calix[8]arene fitted with eight p-C(CH₃)₂OCH₃ groups as the initiator in conjunction with mixed BCl₃/TiCl₄ coinitiators in hexanes/methyl chloride solvent systems at − 80 °C. Various possible side-reactions have been identified and means for their suppression/elimination were developed. Received: 29 December 1999/Revised version: 22 May 2000/Accepted: 22 May 2000     

Synthesis of Halogen-Free Polyisobutylene by in situ Hydride Transfer to Living Polyisobutylene from Tributylsilane

Summary Hydride transfer reaction between living polyisobutylene cation (PIB⁺) and tributylsilane in hexanes/methyl chloride 60/40 (v/v) solvent mixtures at -80, -70 and -60 °C was studied to synthesize halogen-free polyisobutylene (PIB). The hydride transfer reaction between tributylsilane and living PIB capped with 1,1-ditolylethylene (PIB-DTE⁺) have also been carried out under similar conditions at -80 °C. The rate of hydride transfer reaction increases with the increase of tributylsilane concentration for the reaction of both PIB⁺ and PIB-DTE⁺ with tributylsilane. Gel Permeation Chromatography and NMR Spectroscopy suggested practically complete capping of the polymeric cation and the absence of side reactions.     

Coupling and linking reactions of living polyisobutylene by allylsilanes

The reactions of living polyisobutylene (PIB⁺) with different allylsilanes, as potential linking and coupling agents, have been studied. Quantitative monoaddition of 2-Phenylallyltrimethylsilane to living PIB⁺ yielded macromonomer (I), however coupling was absent. Rapid and quantitative coupling has been observed with 1,3-bis[2-(3-trimethylsilyl)-propenyl]benzene (bTPB). Using 1-(2-propenyl)-3-[2-(3-trimethylsilyl)-propenyl]benzene (PTPB) star polymers with an average of four arms have been prepared with high efficiency. The study of this linking reaction revealed that star formation takes place in two well separated steps. In the first step a macromonomer is formed in situ by the rapid reaction of PIB⁺ with the allyltrimethylsilyl functionality. Subsequent reaction of this macromonomer with the remaining electrophilic PIB⁺ ends followed by interchain reactions results in the formation of star polymers. Received: 16 May 1999/Revised version: 1 September 1999/Accepted: 1 September 1999     

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.     

Polyamide-silica gel hybrids containing metal salts: Preparation via the sol-gel reaction

The hydrolysis and condensation of tetramethoxysilane in a DMF solution of polyamides containing LiCl, CaCl₂ or ZnCl₂, both in presence and absence of polyoxazoline, resulted in the facile formation of polyamide-silica gel hybrids. Films were cast from the resulting mixtures and evaporation of the solvent resulted in the formation of clear, transparent hybrids with the salts dispersed at the molecular level. Pyrolysis of hybrids at 600 °C gave porous silica. Pore size and surface characteristics of these silica gel samples indicated a porous nature with a pore radius of 1.1 nm for silica gels obtained from hybrids HPA-6 (containing no salt) and HPA-9 (containing ZnCl₂) and a surface area of 213 m² g⁻¹ and 310 m² g⁻¹, respectively. Silica gel from hybrid HPA-7 (containing LiCl) had a pore radius of 1.9 nm and a surface area of 15 m² g⁻¹. The silica gel samples obtained from hybrids HPA-6, HPA-7 and HPA-9 exhibited narrow slit-like pores with a pore volume of 0.68 cm³ g⁻¹. Received: 7 January 1997/Accepted: 6 March 1997     

Synthesis of sterically hindered ethyl vinyl ethers containing electron acceptors and their polymerization behaviors

3,5-Dimethoxy-4-(2′-vinyloxyethoxy)benzylidenemalononitrile (2) and methyl 3,5-dimethoxy-4-(2′-vinyloxyethoxy)benzylidenecyanoacetate (3) were prepared and polymerized by radical and cationic initiators. Bifunctional monomers 2 and 3 did not polymerize by radical initiators, but copolymerized readily with ethyl vinyl ether in γ-butyrolactone solution at 65 °C. The trisubstituted terminal double bond participated in the vinyl polymerization and radical polymerization of 2 and 3 with ethyl vinyl ether led to swelling polymers 8 and 9 that were not soluble in common solvents due to cross-linking. Under the same polymerization conditions ethyl vinyl ether polymerized well with model compounds of 3,4,5-trimethoxybenzylidenemalononitrile (10) and methyl 3,4,5-trimethoxybenzylidenecyanoacetate (11), respectively, to give 1 : 1 alternating copolymers 12 and 13 in high yields. Polymers 8 and 9 showed a thermal stability up to 300 °C without any characteristic T_g peaks in DSC thermograms. Alternating copolymers 12 and 13 were soluble in common solvents such as acetone and DMSO, and the inherent viscosities of the polymers were in the range of 0.33 – 0.55 dL/g. Films of polymers 12 and 13 cast from acetone solution were cloudy and tough and T_g values obtained from DSC thermograms were in the range of 163 – 168 °C. Received: 2 August 1996/Revised version: 17 September 1996/Accepted: 20 September 1996     

Oxyethylation and carbonation of telechelic polyisobutylene anions

Summary The synthesis of (CH₃)₃C≈PIB≈CH₂ C(=CH₂) CH₂CH₂CH₂OH and (CH₃)₃C≈PIB≈CH₂ (=CH₂) CH₂COOH have been achieved by oxyethylation and carbonation of telechelic polyisobutylene anions: (CH₃)₃C≈PIB≈CH₂C(=CH₂)CH₂⊝. The latter macroanions were prepared from (CH₃)₃C≈PIB≈CH₂C(CH₃)₂Cl by one-pot dehydrochlorination-metalation with n-BuLi/t-BuOK in hexanes. The structure of the products was established by detailed ¹H and ¹³C NMR analyses which also involved the characterization of 4-neopentyl-4-penten-1-ol and 3-neopentyl-3-butenoic acid model compounds.     

Synthesis and chain flexibility of poly(cyclohexylethyl methacrylate)

The synthesis and characterization of fractions of poly(cyclohexylethyl methacrylate) (PCHEM) are reported. A combination of low-angle laser light scattering and intrinsic viscosity experiments was employed to estimate the characteristic ratio (C_∞) of this polymer. The value of 10.7 obtained for PCHEM is similar to the value of 11.3 found previously for poly(phenylethyl methacrylate) but is smaller than values measured for poly(cyclohexyl methacrylate) and poly(cyclohexylmethyl methacrylate) (C_∞ = 11.6 and 11.9, respectively). Received: 28 October 1996/Revised: 16 December 1996/Accepted: 19 December 1996     

Polymerization of vinyl acetate in ternary microemulsions stabilized with hexadecyltrimethylammonium bromide

The polymerization of vinyl acetate (VA) in three component o/w microemulsions stabilized with the cationic surfactant, CTAB, is presented. Initiation is achieved thermally with a water soluble initiator (V-50). Stable latex containing small particles (ca. 35 nm) with molecular weights (M_w) of around 4 × 10⁵ are obtained. Analysis of the molecular weight distribution suggests that chain transfer to monomer (and not to polymer, which is the typical termination mechanism in emulsion polymerization, specially at high conversions) is the dominant mechanism of termination. Received: 11. October 1996/Revised: 16 January 1997/Accepted: 21 January 1997     

Amphiphilic networks. XIV

Summary The synthesis and characterization of novel amphiphilic networks based on dimethylacrylamide and crosslinked by methacrylate telechelic three-arm star polyisobutylene (?(PIB-MA)₃) are reported. The networks are characterized by two M _c's and possess “homogeneous” and “heterogeneous” crosslinks. The networks swell both in water and n-heptane which indicates a cocontinuous hydrophobic-hydrophilic microarchitecture. Water-swollen networks exhibit higher tensile strengths and elongations, than those made previously with linear MA-PIB-MA's of similar overall compositions (i.e., ∼1.0 versus ∼0.5 Mpa, and ∼300% versus ∼200%, respectively). The enhanced mechanical properties of the new networks are being exploited in biomedical applications. Received: 28 July 1999/Revised version: 25 October 1999/Accepted: 27 October 1999     

Polyisobutylene-containing block polymers by sequential monomer addition

Novel poly(acenaphtylene-b-isobutylene-b-acenaphtylene) (PAc-PIB-PAc) triblock copolymers exhibiting thermoplastic elastomer (TPE) properties have been prepared. The synthesis involved the addition of acenaphtylene (Ac) to living polyisobutylene dications (PIB) obtained by living isobutylene (IB) polymerization induced by the dicumyl methyl ether (DiCumOMe)/TiCl₄ initiating system at-80°C. The triblocks contain very short polyacenaphtylene (PAc) blocks (M_n9,000) and consequently yield very soft, low modulus TPEs. Efforts to develop conditions for the living carbocationic polymerization (LCPzn) of Ac have failed.For Part VIII of this subseries see J. P. Kennedy, S. Midha, B. Keszler: Macromolecules (in press)     

Diffusion and phase relaxations within the interphase domain of polymer blendlike particles

A single-photon counting technique in conjunction with a direct energy transfer (DET) method was used to study the diffusion of small dye molecules within the interphase domain of anthracene (An)- and/or phenanthrane (Phe)-labeled poly(methyl methacrylate) (PMMA) particles sterically stabilized by polyisobutylene (PIB). Mean lifetimes of fluorescing donor molecules were measured during diffusion. A Fickian model for diffusion was employed to fit the experimental data and diffusion coefficients were found to be around 10⁻¹⁹ and 10⁻¹⁶ cm^2/s at room and above glass transition temperatures (T_g) for the corresponding samples, respectively. A reversed Gaussian distribution was detected for the PMMA phase density at the interphase domain. An increased amount of self-quenching of naphthalene (N) dyes labeled to the PMMA phase was investigated against annealing temperature above T_g and the results were attributed to phase relaxations at the interphase domain. © 1996 John Wiley & Sons, Inc.     

Temperature dependent electrical conductivity of p-doped poly(3,4-ethylenedioxythiophene) and poly(3-alkylthiophene)s

Summary Temperature dependent electrical conductivity of substituted polythiophenes (poly(3,4-ethylenedioxythiophene) PEDOTh and head-to-tail type poly(3-alkylthiophene) HT-P3RTh) has been measured. The electrical conductivity (σ) of p-doped PEDOTh and HT-P3RTh obeys equations of a type, ln σ= ln σ_o− (T_o/T)^0.25, with the T_o value of about 10⁵–10⁷ K. Received: 21 December 1998/Revised version: 8 February 1999/Accepted: 15 February 1999     

Synthesis of polyarylene homopolymers and copolymers via nickel(0)-catalyzed homocoupling of arylenebismesylates derived from bisphenols

A general and inexpensive procedure for the synthesis of poly(arylene)-type homopolymers and copolymers containing alternating oligophenylene and a functional group (X) (e.g. X = −O−, −CO−, −SO₂−, −C(CH₃)₂−, −CH₂−CH(Et)−, etc) is described. The synthetic method is based on the Ni(0)-catalyzed homocoupling of aryl bismesylates (MsOAr−X−ArOMs) derived from bisphenols. Symmetric X groups lead to regioregular crystalline and insoluble polymers whereas bulky, asymmetric X groups or the incorporation of comonomers yield regioirregular polymers and, respectively, copolymers with decreased crystallinity and increased solubility. This new synthetic method can be applied to the preparation of polymers with controlled rigidity which are amorphous, crystalline or liquid crystalline. Received: 22 January 1997/Accepted: 24 February 1997     

Electrical conductivity in iodine-doped nonconjugated polyanilinefurfural

Polyanilinefurfural (PAF) has been prepared. Its chain contains aromatic and furan rings, but the backbone is nonconjugated. However, when treatment with iodine, the color of PAF turns metallic black, and PAF becomes electrically conductive. The electrical conductivity of I₂-doped PAF can reach 10⁻³ S ⋅ cm⁻¹ which is more than 10 orders of magnitude higher than what was observed at the pristine state. The effects of iodine content on the conductivity of PAF and the conductivity stability were investigated. FTIR spectra, U.v./vis absorption spectra, E.s.r. measurement and X.p.s. measurement of the undoped and doped PAF were studied. This paper will demonstrate that: if given appropriate substituents and dopants, significant charge transfer may be expected even for nonconjugated polymers and it may display electronic conductivity to a certain level. Received: 20 November 1996/Revised: 7 February 1997/Accepted: 10 February 1997     

Nonlinear biodegradable polyanhydrides synthesized from natural fatty acids through a new way

Ricinoleic acid was esterified by fatty diacid chlorides to yield intermediate diacids, which were next converted to corresponding polyanhydrides by vacuum-melt polycondensation. The intermediates and polymers were characterized by means of ¹H NMR, IR spectroscopy, differential scanning calorimetry (DSC), X-Ray diffraction and light scattering. The optimized reaction conditions of melt polycondensation were investigated and copolyanhydride with molecular weight (weight average) up to 1.38 × 10⁵ and intrinsic viscosity of 126 cm³/g was obtained. DSC and X-ray diffraction analysis showed that the synthesized copolyanhydrides exhibited much lower crystallinity and improved thermal properties in comparison with aliphatic linear homopolyanhydrides. Received: 8 October 1996/Revised: 14 April 1997/Accepted: 22 April 1997     

Properties of thin films of isotactic polypropylene blended with polyisobutylene and ethylene-propylene-diene terpolymer rubbers

An experimental study was carried out to investigate the kinetic, morphological and thermodynamic properties of thin films of isotactic polypropylene (iPP) blended with several elastomers such as ethylene-propylene-diene terpolymer (EPDM) and three samples of polyisobutylene (PIB) with different molecular masses. The addition of the rubber to iPP causes drastic modifications in the morphology, nucleation density, spherulite growth rate and thermal behaviour of iPP. Such modifications depend strongly on the chemical and molecular mass of the added elastomer and on the composition of the blend. All the elastomers studied seem to act as nucleating agents for the iPP spherulites. The addition of PIB to iPP results in a reduction of the spherulite growth rate G, whereas the addition of EPDM does not seem to have a great influence. For the iPP/PIB_HM iPP/PIB_MM and iPP/EPDM blends a depression of the equilibrium melting temperature T_m, with respect to that of pure iPP, is observed. This depression is increased for the blend containing 20% rubber. This effect is probably related to phenomena of partial miscibility in the melt and to the coexistence of processes such as molecular fractionation and preferential dissolution of the more defective molecules.     

Syntheses and radical ring-opening polymerizations of 1,1-bis(hydroxymethyl)-2-vinylcyclopropane and 1,1-bis(methoxymethyl)-2-vinylcyclopropane

Homo- and copolymerizations of 1,5-hexadiene with ethene and styrene using halfsandwich metallocene catalyst Me₂Si(Me₄Cp)(N-tert.-butyl)TiCl₂/MAO (Cp = cyclopentadienyl, Me = methyl, MAO = methylalumoxane) were investigated. According to ¹³C-NMR spectroscopic microstructure analysis, cyclopolymerization of 1,5-hexadiene afforded randomly distributed cis- and trans-cyclopentane rings in the homo- and copolymer backbone. 1,5-hexadiene incorporation reached 52 mol-%. The ratio of vinyl side chains to cyclopentane rings was controlled by 1,5-hexadiene concentration, where low 1,5-hexadiene concentration promoted cyclopolymerization. Copolymer glass transition temperatures increased with increasing content of cyclic units in the backbone. Styrene was used successfully as termonomer in ethene/1,5-hexadiene polymerization, resulting in a semicrystalline terpolymer with cyclic and styrenic units in the polymer backbone. Received: 5 September 1996/Accepted: 11 November 1996