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1.
The polymers consisting of polydiacetylene (PDA) backbones were obtained from the novel monomer derivatives, R CC CC R′ CC CC R [where R =  (CH2)4OCONHCH2COOC4H9, R′ =  (CH2)n ; n = 2, 4, 8] [4BCMU4A(n)], in which linear methylene chain is sandwiched between two diacetylene moieties by solid-state 1,4-addition reaction. The polymerization process was investigated in detail by using spectroscopic techniques such as solid-state 13C-NMR, visible absorption, and IR absorption spectra. It was estimated that the polymerization of 4BCMU4A(8) and 4BCMU4A(4) takes place by two consecutive 1,4-addition reactions to form two PDA backbones, which constitute the two poles of the respective ladders. The bridging methylene chain length in the monomer was found to play a vital role as far as the polymerization process is concerned. Thus, the monomers with eight or four methylene units could form the ladder–PDAs by a two-step process, whereas the monomer containing two methylene units could only undergo one-step of 1,4-addition reaction. Further, it was found that the crystallinity of the polymers depends on the methylene chain length in the monomers, 4BCMU4A(8) being the most crystalline of all. These structural features strongly affect their absorption spectra. The third-order nonlinear optical susceptibilities (χ(3)) for these polymers were measured using third-harmonic generation method. The largest χ(3) value obtained was 3.4 × 10−11 esu for the poly[4BCMU4A(8)] thin film in resonant region. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3537–3548, 1999  相似文献   

2.
An AB2 monomer PhBr2  C  C  Ph  C  CH containing one acetylene group and two bromide groups was efficiently synthesized by a strategy based on the different reactivity between aromatic iodide and bromide in Sonogashira reaction. The Sonogashira polymerization of PhBr2  C  C  Ph  C  CH was investigated to get hyperbranched poly(p‐phenyleneethynylene‐altm‐phenyleneethynylene) (hb‐PMPE) in terms of the effects of monomer addition method, core molecule with different functionality, and ratio of [monomer]/[core molecule]. The results showed that narrow dispersities (D) (D: 1.23∼1.50) were obtained by slow monomer addition and with core molecule. Bifunctional core molecule induced narrower dispersity than monofunctional core molecule. The molecular weight of hb‐PMPE increased with increasing ratio of [monomer]/[core molecule], however, a negative deviation from calculated value was observed. The dispersity slightly increased with increasing [monomer]/[core molecule]. When the ratio of [monomer]/[core molecule] was below 50/1, monomodal distribution was observed; whereas when the ratio increased to 70/1, bimodal distribution was obtained. All the polymers showed degrees of branching (DBs) around 0.6. The hb‐PMPEs showed one major absorption band with λmax around 330 nm, and emission band with λmax around 390 nm. All the polymers showed relative quantum yields (Φr) above 0.5 in dilute THF solution. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 96–104  相似文献   

3.
Dendritic carbosilanes based on phenylethynylmethylsilanes (PhCC)4−nMenSi (n = 0–2) as cores were synthesized. The building blocks of the dendrimers consist of double bonds ( PhCCHMeSi ) in the inner shell and triple bonds [(PhCC)2MeSi ] on the outmost periphery. The synthetic methods used the iterative alkynylation and hydrosilation cycle, which was composed of lithium phenylacethylide and dichloromethylsilane. The limiting generation of the dendrimer for the four branching type (PhCC)4Si at a core molecule has 32 phenylethynyl groups on the third generation, 48 for the three branching type (PhCC)3MeSi on the fourth generation, and 64 for the two branching type (PhCC)2Me2Si on the fifth generation. The dendrimers were characterized by the use of NMR, Maldi mass, SEC, DSC, UV as well as elemental analysis. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2749–2759, 2000  相似文献   

4.
An on‐line electron spin resonance (ESR) technique was applied to investigate the oxidation states of the metallocene catalysts CpTiCl3, CpZrCl3, Cp2TiCl2, and Cp2ZrCl2. These metallocene catalysts were activated by modified methylaluminoxane (MMAO). It was found that the titanocene catalysts (CpTiCl3 and Cp2TiCl2) were readily reduced to the trivalent state while the zirconocene catalysts (CpZrCl3 and Cp2ZrCl2) were quite stable with respect to reduction. The concentrations of the trivalent species Ti(III) and Zr(III) showed linear relationships with the concentrations of metallocene catalyst precursors. However, their slopes were always smaller than unity indicating the existence of bimetallic interactions of the active sites. The ESR detectable Ti(III) and Zr(III) concentrations initially increased with the MAO/catalyst ratio and then leveled off after an 800–1000 Al/catalyst molar ratio. The deactivation processes were followed as a function of aging time over a range of temperature (25–100°C). The decay curves strongly depended on aging temperature with higher temperature giving faster decay rates. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1465–1472, 1999  相似文献   

5.
The initial active site concentrations, [C*]0, have been determined with CH3OT radiolabeling for the Cp2ZrCl2/MAO and CpZrCl3/MAO catalysts (Cp = η5 : cyclopentadienyl, MAO = methyl aluminoxane). Almost all the Zr are found to be catalytically active in 70°C ethylene polymerizations; [C*]0 = [Zr] and [C*]0 = 0.8[Zr] at Al/Zr ratios of 104 and 103, respectively. Lowering the temperature to 50°C and Al/Zr to 5.5 × 102 reduces [C*]0 to 0.2[Zr]. The rate constant of propagation at 70°C was calculated to be 1.6 × 103(M s)?1 for both catalysts at Al/Zr = 1.1 × 104; the values are decreased fivefold and tenfold, respectively, for the CpZrCl3 and Cp2ZrCl2 systems. The usage of 14CO to determine the propagating Zr–P species was investigated. With regard to the time of reaction of 14CO with the polymerization mixture, the initial phase is attributed to reversible CO complexation and reversible migratory insertion. The second slower phase may be due to the formation of enediolate. During the course of a batch polymerization the 14C radioactivity incorporated is small compared to the number of active sites found by CH3OT determination; it is only ca. 10% of [C*]0 at maximum rate of polymerization. Therefore, 14CO radiolabeling cannot be used to count C*.  相似文献   

6.
Addition of [Li2(THF)4][C(NPh)3] (2) to a THF solution of Cp*ZrCl3 (Cp*=C5Me5) yields, after recrystallization in Et2O, the zwitterionic species Cp*[C(NPh)3]ZrCl2Li(Et2O)(THF) (3). Treating 3 with excess methylaluminoxane (MAO) affords a homogeneous Ziegler–Natta catalyst for ethylene polymerization. Addition of LiNPh2 to 3 allows for Cl substitution to give the new product Cp*[C(NPh)3]Zr(NPh2)ClLi(THF)2 (4). A single crystal diffraction study of 4 reveals that the [C(NPh)3] ligand is η2-bound. The group 5 complex Cp*[C(NPh)3]TaMe2 (5) was prepared by addition of 2 to Cp*TaMe2Cl(OSO3CF3). The X-ray diffraction structure of 5 shows that the [C(NPh)3] ligand is η2-bound to tantalum and that, when compared to 4, there is less electron delocalization across the inner core of [C(NPh)3].  相似文献   

7.
Two kinds of SiO2-supported Cp*TiCl3 (Cp* = η5-1,2,3,4,5-pentamethylcyclopentadienyl) catalysts were prepared, using SiO2 modified with 3-aminopropyltrimethoxysilane (N SiO2) and the ordinary SiO2 as the carrier. The copolymerization of ethylene and 1-octene was conducted over them combined with methylaluminoxane (MAO) as cocatalyst. From a detailed analysis of the produced copolymers, it was found that the N SiO2 supported Cp*TiCl3 catalyst gives poly(ethylene-co-1-octene) with a higher content of 1-octene and a narrower molar mass distribution as well as a narrower chemical composition.  相似文献   

8.
The subject of this work is ethylene polymerisation using Kaminsky type catalysts: Cp2MR2=methylaluminoxane [M=Zr, W, Nb; R=Cl, CH3]. Active center determination and kinetic studies of the (Cp2WCl2+methylaluminoxane) and Cp2ZrCl2+methylaluminoxane) systems are described, using a quenching method with tritiated methanol. The activity of the polymer was determined by liquid scintillation counting. We have found 0.5% and 87% of active centers, respectively for W and Zr system. The catalytic activity of complexes Cp2WCl2 and Cp2NbCl2 was compared with that of Cp2ZrCl2. The W and Nb complexes are found to be less active than the Zr complex.  相似文献   

9.
Thermal degradation of two series of polyacrylates containing long fluorocarbon chains [abbr.: PFnA {HCF2(CF2)n−1  CH2 O C(O) , n = 4, 6, 8, 10} and abbr.: PFFnEA {CF3(CF2)n−1  CH2CH2 O C(O) , n = 6, 8, 10}] was investigated by TG /FTIR. Thermal degradation behavior of polymers changed depending on the type of tie groups, which link the fluorocarbon chains to the main chain, and also on the length of fluorocarbon chains. It was clarified that the apparent activation energies (ΔEa ) of PFnA series obtained by Ozawa's method varied in the order of PF4A > PF6A > PF8A > PF10A, while those of PFFnEA series having tie group of  CH2 CH2 O C(O) were almost constant. The results for PFnA series (tie group:  CH2 O C(O) ) are attributable to the shield effect of long fluorocarbon chains on the back‐biting reaction in the thermal degradation of comb polymers rather than the change of C C bond dissociation energy in the main chain. It was found that TG curves of PFFnEA series were shifted to the lower temperature region than those of PFnA. This result can be attributable to the scission of side groups followed by the evaporation of fluorocarbon compounds and carbon dioxide. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2794–2803, 2000  相似文献   

10.
Four new mixed‐ring zirconium completes, [CH2 = CH(CH2)n ‐C5H4](RC5H4)ZrCl2 [n = l, R = CH3OCH2CH2(3); n = 2, R = CH3OCH2CH2 (4); n = 2, R=Me3Si (5); n = 2, R = allyl (6)], have been prepared by the reaction of CH2 = CH(CH2)n C5H4ZrCl3, DME[n = l (1); n = 2 (2)] with RC5H4Li. When activated with methylaluminoxane (MAO), the catalytic activities of the above complexes in ethylene polymerization were tested. Complexes 5 and 6 show high activities similar to Cp2ZrCl2. Introduction of methoxyethyl group into Cp‐ligand dramatically decreases the catalytic activities of complexes 3 and 4, which can be overcome by increasing the amount of MAO. For complex 5, the dependence of activity and molecular weight (Mη) on the Al/Zr ratio, the polymerization time (tP), polymerization temperature (TP) and the polymerization solvent volume (V) was investigated.  相似文献   

11.
The polymerization behavior of 2-(2′-pyridyl) quinoxaline nickel dibromide/Cp2ZrCl2/MAO system was investigated in three ways: the Ni catalyst was added first, followed by addition of Zr catalyst (method I); the Ni and Zr catalysts were added simultaneously (method II); and the Zr catalyst was added first, followed by addition of Ni catalyst (method III). Results of GC-MS, GPC,13C NMR and DSC investigations indicated that the properties of resulting polyethylene were greatly varied by changing feeding orders of the two catalysts. Decreasing Ni/Zr molar ratio or increasing polymerization temperature gave corresponding polyethylenes with less branches and higher melting point. Compared to the procedure using Cp2ZrCl2 catalyst only, the activity of Zr catalyst in those combined system decreased because of the competition of ethylene between the [Ni−C] and [Zr−C] active centers. In addition, other zirconocenes were also employed as copolymerization catalysts in the combined system with nickel complex. compared to Cp2ZrCl2 case, the ethyl-bridged Zr catalyst performed better for polymerization of ethylene while the Si-bridged Zr catalyst showed better copolymerization ability.  相似文献   

12.
Metallocene complex Cp2^ttZrCl2(Cp^tt=η^5-1,3-^tBu2C5H3)(1)has been prepared from the reaction of LiCp^tt with ZrCl4 in good yield.Reactions of 1 with dilithium dichalcogenolate o-carboranes afforded new type of half-sandwich compounds with dichalcogenolate o-carboranyl ligands,[Li(THF)4][Cp^ttZr(E2C2B10H10)2](E=S,2a;E=Se,2b)in which only one cyclopentadienyl ring ligand existed.Complexes 1 and 2a were structurally characterized by X-ray analyses.In complex 2a,the Zr(IV)ion is η^5-bound to one 1,3-ditert-cyclopentadienyl ring and σ-bound to four μ2-sulfur atoms of two dithio-carboranes.the zirconium atom and four sulfur atoms form a distorted pyramid.The coordination sphere around the zirconium atom resembles in a piano stool structure with four legs of sulfur stoms and the fulcrum at the zirconium stom.  相似文献   

13.
Ethylene polymerization was carried out with zirconocene catalysts supported on montmorillonite (or functionalized montmorillonite). The functionalized montmorillonite was from simple ion exchange of [CH3O2CCH2NH3]+ (MeGlyH+) ions with interlamellar cations of layered montmorillonites. The functionalized montmorillonites [high‐purity montmorillonite (MMT)‐MeGlyH+] had larger interlayer spacing (12.69 Å) than montmorillonites without treatment (9.65 Å). The zirconocene catalyst system [Cp2ZrCl2/methylaluminoxane (MAO)/MMT‐MeGlyH+] had much higher Zr loading and higher activities than those of other zirconocene catalyst systems (Cp2ZrCl2/MMT, Cp2ZrCl2/MMT‐MeGlyH+, Cp2ZrCl2/MAO/MMT, [Cp2ZrCl]+[BF4]/MMT, [Cp2ZrCl]+[BF4]?/MMT‐MeGlyH+, [Cp2ZrCl]+[BF4]?/MAO/MMT‐MeGlyH+, and [Cp2ZrCl]+[BF4]?/MAO/MMT). The polyethylenes with good bulk density were obtained from the catalyst systems, particularly (Cp2ZrCl2/MAO/MMT‐MeGlyH+). MeGlyH+ and MAO seemed to play important roles for preparation of the supported zirconocenes and polymerization of ethylene. The difference in Zr loading and catalytic activity among the supported zirconocene catalysts is discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1892–1898, 2002  相似文献   

14.
Tailoring of the molecular weight distribution (MWD) in ethylene polymerization was attempted by selectively combining different types of metallocene catalysts onto a single support. The catalyst produced by supporting Et[Ind]2ZrCl2 and Cp2HfCl2 onto a single MAO pretreated silica support was able to produce polymers with unimodal or bimodal MWD's. This approach permits the synthesis of polyethylene with different MWD's using the same catalyst as a function of the polymerization conditions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 331–339, 1999  相似文献   

15.
Two supported metallocene catalysts (CS 1: PQ 3030/MAO/Cp2ZrCl2 and CS 2: PQ 3030‐BuGeCl3/MAO/Cp2 ZrCl2) were prepared by sequentially loading MAO and Cp2ZrCl2 on partially dehydroxylated silica PQ 3030. In catalyst CS 2, nBuGeCl3 was used to functionalize the silica. These catalysts were characterized by DR‐FTIR spectroscopy, CPMAS NMR spectroscopy, and XPS. Their catalytic performance was evaluated by polymerizing ethylene using the MAO cocatalyst and characterizing the resulting polymers by GPC. Both catalysts produced two metallocenium cations (Cation 1: [Cp2ZrCl]+ and Cation 2: [Cp2ZrMe]+) with comparable equilibrium concentrations and showed varying solid‐state electronic environments. The modified supports (PQ 3030/MAO and PQ 3030‐BuGeCl3/MAO) acted as weakly coordinating polyanions and stabilized the above cations. BuGeCl3 did not affect the solid‐state electronic environment. However, it increased the surface cocatalyst to catalyst molar ratio (Al:Zr), acted as a spacer, increased catalyst activity, and enhanced chain‐transfer reactions. The separately fed MAO cocatalyst shifted the equilibrium between Cation 1 and Cation 2 toward the right. Consequently, more Cation 2 was generated, which acted as the effective and active single‐site catalytic species producing monomodal PDI. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

16.
Methoxydimethylsilane and chlorodimethylsilane‐terminated telechelic polyoctenomer oligomers (POCT) have been prepared by acyclic diene metathesis (ADMET) chemistry using Grubbs' ruthenium Ru(Cl2)(CHPh)(PCy3)2 [Ru] or Schrock's molybdenum Mo(CH CMe2Ph)(N 2,6 C6H3i Pr2)(OCMe(CF3)2)2 [Mo] catalysts. These macromolecules have been characterized by FTIR, 1H‐, 13C‐, and 29Si‐NMR spectroscopy. The molecular weight distributions of these polymers have been determined by GPC and vapor pressure osmometry (VPO). The number‐average molecular weight (Mn) values of the telechelomers are dictated by the initial ratio of the monomer to the chain limiter. The termini of these oligomers (Mn = 2000) can undergo a condensation reaction with hydroxy‐terminated poly(dimethylsiloxane) (PDMS) macromonomer (Mn = 3300) [HO Si(CH3)2 O { Si(CH3)2O }x  Si(CH3)3], producing an ABA‐type block copolymer, as follows: (CH3)3SiO [ Si(CH3)2O ]x [ CHCH (CH2)6 ]y [ OSi(CH3)2 ]x OSi(CH3)3. The block copolymers were characterized by 1H‐ and 13C‐NMR spectroscopy, VPO, and GPC, as well as elemental analysis, and were determined by VPO to have a Mn of 8600. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 849–856, 1999  相似文献   

17.
Comparative analysis of catalytic activity of substituted bis(cyclopentadienyl)zirconium dichlorides with the general formula (R n Cp)2ZrCl2 (Cp2ZrCl2, (MeCp)2ZrCl2, (PriCp)2ZrCl2, (Pri 2Cp)2ZrCl2, (BunCp)2ZrCl2, (BuiCp)2ZrCl2, (ButCp)2ZrCl2, Cp* 2ZrCl2 (Cp*=Me5C5), (Me3SiCp)2ZrCl2, (cyclo-C6H11Cp)2ZrCl2, and [(cyclo-C6H11)2Cp]2ZrCl2) in ethene polymerization using polymethylalumoxane as the cocatalyst was performed. The molecular mass characteristics of the polyethylene samples obtained were determined. A linear correlation of the specific activity of the catalysts and the turnover number with the electronic and steric characteristics of substituents at the Cp ring of the complexes was established for the first time. Analysis of the polymerization kinetics and the obtained correlation between the specific activity of the complexes and molecular mass characteristics of the polyethylene samples suggest that alkyl substituents participate in reactions responsible for the restriction of the polymer chain growth and regeneration of the active center. These interactions most likely involve associates of AlMe3 with polymethylalumoxane molecules.  相似文献   

18.
The PM3(tm) semiempirical method was used to show the effect of a second ethylene molecule in the backside position on the frontside ethylene insertion in the Cp2Zr nPr+ γ‐agostic resting state. The same calculations without a companion second ethylene molecule were performed to compare geometrical parameters, energies, and electrostatic charges. The results obtained show that the geometrical parameters for both cases were identical, but differences in the electrostatic charges were observed. The energy profile presented two barriers, the first corresponding to the alkyl‐chain rotation along the Zr Cα bond and the second relating to the insertion process itself. The presence of a companion second ethylene molecule affected the energetic profile by lowering the energy barrier of the first stage with respect to the process without the companion second ethylene molecule. These results provide some theoretical support to the well‐known trigger effect. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 571–582, 2000  相似文献   

19.
An early transition metal metallocene compound, Cp2ZrCl2, with an anionic surfactant, sodium n‐dodecyl sulfate (SDS) as emulsifier and NaBPh4 as cocatalyst has been found to be an effective catalytic system for polymerization and copolymerization of monomers like styrene and methyl methacrylate in aqueous medium. The diameters of the latex particles were found to be in between 20 and 40 nm. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011  相似文献   

20.
A critical look at the possibility of controlling the molecular weight distribution (MWD) of polyolefins by combining metallocene/methylalumoxane (MAO) catalysts is offered. Catalysts investigated were bis(cyclopentadienyl)zirconium dichloride (Cp2ZrCl2), its titanium and hafnium analogues (Cp2TiCl2 and Cp2HfCl2), as well as rac-ethylenebis(indenyl)zirconium dichloride (Et(Ind)2ZrCl2). As observed by other researchers, the MWD of polyethylene can be manipulated by combining soluble catalysts, which on their own produce polymer with narrow MWD but with different average molecular weights. Combined in slurry polymerization reactors, the catalysts in consideration produce ethylene homopolymer just as they would independently. Unimodal or bimodal MWDs can be obtained. This effect can be mimicked by blending polymers produced by the individual catalysts. We demonstrate how a variability in catalyst activity translates into a variability in MWD when mixing soluble catalysts in polymerization. Such a variability in MWD must be considered when setting goals for MWD control. We introduce a more quantitative approach to controlling the MWD using this method. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 831–840, 1998  相似文献   

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