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1.
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  相似文献   

2.
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.  相似文献   

3.
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  相似文献   

4.
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.  相似文献   

5.
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  相似文献   

6.
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 Mn versus amount of polyisobutylene (PIB) formed (WPIB) plots starting at the origin and corresponding horizontal number of PIB moles formed (N) versus WPIB 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.  相似文献   

7.
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  相似文献   

8.
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 Tg 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 Tg 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  相似文献   

9.
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.  相似文献   

10.
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  相似文献   

11.
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 (Mw) 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  相似文献   

12.
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  相似文献   

13.
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 cm2/s at room and above glass transition temperatures (Tg) 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 Tg and the results were attributed to phase relaxations at the interphase domain. © 1996 John Wiley & Sons, Inc.  相似文献   

14.
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 (Mn9,000) 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)  相似文献   

15.
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 σo− (To/T)0.25, with the To value of about 105–107 K. Received: 21 December 1998/Revised version: 8 February 1999/Accepted: 15 February 1999  相似文献   

16.
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  相似文献   

17.
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  相似文献   

18.
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  相似文献   

19.
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/PIBHM iPP/PIBMM and iPP/EPDM blends a depression of the equilibrium melting temperature Tm, 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.  相似文献   

20.
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  相似文献   

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