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Dimethoxysilanes as external donors have been used in propylene polymerization for many years. To explore the effect of adding a carbon atom between silicon and oxygen on the performance of external donors, new bis(methoxymethyl)silane compounds including bis(methoxymethyl)diphenylsilane (Donor-PhS), diisopropylbis(methoxymethyl)silane (Donor-PS), and dicyclopentylbis(methoxymethyl)silane (Donor-DS) were first synthesized and then employed as external donors for propylene polymerization with a MgCl2-supported Ziegler–Natta catalyst. It was found that these new bis(methoxymethyl)silane external donors were conducive to improving the isotacticity of polypropylene and the catalytic activity, especially in the case of low addition. In addition, the bis(methoxymethyl)silane donors have good hydrogen regulation sensitivity. The density functional theory (DFT) calculation shows that the new bis(methoxymethyl)silanes have a wider O1–O2distance and lower electron cloud density than those of dimethoxysilanes, which indicate that the external donor has better control ability on the catalyst performance at low addition.

Reversible addition-fragmentation chain transfer radical polymerization of styrene and maleic anhydride was successfully performed in continuous-flow microreactor. Results of the structural characterization showed that the obtained styrene-maleic anhydride (SMA) copolymers possessed controlled molecular weight, low dispersity and alternating structures. Subsequently, effects of the polymerization conditions, including reaction pressure, temperature, feed flowrate and tube length, on the polymerization kinetics and molecular structure of the SMA copolymers were investigated in detail. It was found that the reaction rate was increased as the reaction temperature increased within certain limits, as well as the feed flowrate due to the increased mass and heat transfer efficiency. Besides, first-order kinetics of the polymerization was observed when the reaction times were adjusted by only changing the tube length. Good stability was exhibited when the reaction conducted continuously for 10 h. This approach can reduce the reaction time significantly from several hours to about half an hour.

A series of polypropylene (PP) alloys containing different ethylene contents have been prepared by the in situ sequential polymerization technique, using Ziegler–Natta catalyst (MgCl2/TiCl4/BMF; BMF is 9,9‐bis(methoxymethyl)fluorine, as an internal donor) without any external donor. The structure and properties of PP alloys obtained have been investigated by nuclear magnetic resonance, Fourier transform infrared spectroscopy, dynamic mechanical analysis, differential scanning calorimetry, and scanning electron microscopy (SEM). The results have suggested that PP alloys are the complex mixtures containing PP, the copolymer with long sequence ethylene chain, ethylene‐propylene rubber (EPR), and block copolymer etc. In the alloys, PP, EPR, and the copolymer with long sequence ethylene chain are partially compatible. The investigation of the mechanical properties indicates that notched Izod impact strength of PP alloy greatly increases at 16°C/−20°C in comparison with that of pure PP. The noticeable plastic deformation is observed in SEM photograph. The increase in the toughness, the mechanical strength of PP alloy decreases to a certain extent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4804–4810, 2006

Isotactic polypropylene graft copolymers, isotactic[polypropylene‐graft‐poly(methyl methacrylate)] (i‐PP‐g‐PMMA) and isotactic[polypropylene‐graft‐polystyrene] (i‐PP‐g‐PS), were prepared by atom‐transfer radical polymerization (ATRP) using a 2‐bromopropionic ester macro‐initiator from functional polypropylene‐containing hydroxyl groups. This kind of functionalized propylene can be obtained by copolymerization of propylene and borane monomer using isospecific MgCl2‐supported TiCl4 as catalyst. Both the graft density and the molecular weights of i‐PP‐based graft copolymers were controlled by changing the hydroxyl group contents of functionalized polypropylene and the amount of monomer used in the grafting reaction. The effect of i‐PP‐g‐PS graft copolymer on PP‐PS blends and that of i‐PP‐g‐PMMA graft copolymer on PP‐PMMA blends were studied by scanning electron microscopy. Copyright © 2006 Society of Chemical Industry

Isotactic polypropylene graft copolymers, isotactic[polypropylene‐graft‐poly(methyl methacrylate)] (i‐PP‐g‐PMMA) and isotactic[polypropylene‐graft‐polystyrene] (i‐PP‐g‐PS), were prepared by atom‐transfer radical polymerization (ATRP) using a 2‐bromopropionic ester macro‐initiator from functional polypropylene‐containing hydroxyl groups. This kind of functionalized propylene can be obtained by copolymerization of propylene and borane monomer using isospecific MgCl2‐supported TiCl4 as catalyst. Both the graft density and the molecular weights of i‐PP‐based graft copolymers were controlled by changing the hydroxyl group contents of functionalized polypropylene and the amount of monomer used in the grafting reaction. The effect of i‐PP‐g‐PS graft copolymer on PP‐PS blends and that of i‐PP‐g‐PMMA graft copolymer on PP‐PMMA blends were studied by scanning electron microscopy. Copyright © 2006 Society of Chemical Industry

A difunctional organolithium compound was prepared by the addition of butyllithium (BuLi) to 1,4‐bis(4‐methyl‐1‐phenylethenyl)benzene (MPEB). The effects of the solvent, polar modifier (THF), butyl lithium structure, and reaction time on the formation of the difunctional organolithium compound were studied. Results showed that toluene as solvent was in favor of the addition reaction over cycohexane, in the absence of the polar modifier. However, cycohexane was a better option as solvent for the addition reaction, when polar modifier was employed. A small amount of polar modifier could efficiently accelerate the reaction rate and have no significant effect on the structure of the polydiene, which was initiated by the polar modifier containing organolithium compound. Results also showed that isobutyl lithium was more active in the addition reaction than n‐butyl lithium, because of inductive effect. The optimum molar ratio of THF/Li+ was determined as 4. The THF containing difunctional organolithium cyclohexane solution was sequentially used in the step‐wise polymerization of triblock thermoplastic copolymer SIBS. The so‐prepared SIBS shared the similar phase separation structure with SBS and exhibited excellent mechanic properties. As the content of the central polyisoprene block increases, the tensile strength of the copolymer is decreased, and the elongation at break is increased. The glass transition temperature Tg of the central block was correlated with its content as Tg = 0.33 × −62.81, where × is the wt % of the central block, based on the triblock copolymer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1395–1402, 2006

2,6‐Bis(imino)pyridyl iron catalyst and traditional Ziegler–Natta catalyst were combined together as tandem catalytic system, activated with the mixture of TEA and MAO, and used for synthesis of branched polyethylene by in situ polymerization of ethylene. The branched polyethylene with branches from 8/1000C to 29/1000C was produced by adjusting reaction conditions: the amount of TEA, MAO, iron catalyst used, and reaction temperatures. Not only the short branches such as ethyl and butyl but also the longer branches (hexyl and longer than hexyl) were detected in the products. The products exhibited higher molecular weight and broader molecular weight distribution than those obtained from metallocene catalysts, which would provide the materials excellent mechanical properties and processability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

Combining the template method with the extrusion technology, polymer nanofibers have been prepared when molten polymer is forced through the pores of anodic aluminum membrane and cooled to complete the nanofiber formation process. The microstructures of nanofibers are determined by SEM, TEM, XRD, and DSC. The results suggest that the PE nanofibers consist of extended‐chain crystals and the transition from an orthorhombic to a hexagonal phase and the latter phase melting occurs at 159.8°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1018–1023, 2006

This article demonstrates the influence of the molar ratio between diether as internal donor and Magnesium dichloride in processing of the catalyst preparation on the catalytic performance for propylene polymerization with MgCl2‐supported Ziegler–Natta catalyst. The effect of electron donor on catalyst is investigated. The experimental data find that diether content on catalyst increases and Ti content on catalyst decreases with the increase of diether/Mg molar ratio. This result indicates that diether as internal donor is not coordinated to Ti species but to Mg species on catalyst. The introduction of diether remarkably improves the catalytic activity. The extents of improvement closely connect with diether/Mg molar ratio. The stereospecificity of catalyst intensively depends on the structure of diether as internal donor. The possible model of multi‐active sites on heterogeneous Ziegler–Natta catalyst is proposed to explain these phenomena. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1399–1404, 2006

Activated with methylaluminoxane (MAO), phenoxy‐based zirconium complexes bis[(3‐tBu‐C6H3‐2‐O)‐CH&dbond;NC6H5]ZrCl2, bis[(3,5‐di‐tBu‐C6H2‐2‐O)‐PhC&dbond;NC6H5] ZrCl2, and bis[(3,5‐di‐tBu‐C6H2‐2‐O)‐PhC&dbond;N(2‐F‐C6H4)]ZrCl2 for the first time have been used for the copolymerization of ethylene with 10‐undecen‐1‐ol. In comparison with the conventional metallocene, the phenoxy‐based zirconium complexes exhibit much higher catalytic activities [>107 g of polymer (mol of catalyst)−1 h−1]. The incorporation of 10‐undecen‐1‐ol into the copolymers and the properties of the copolymers are strongly affected by the catalyst structure. Among the three catalysts, complex c is the most favorable for preparing higher molecular weight functionalized polyethylene containing a higher content of hydroxyl groups. Studies on the polymerization conditions indicate that the incorporated commoner content in the copolymers mainly depends on the comonomer concentration in the feed. The catalytic activity is slightly affected by the Al(MAO)/Zr molar ratio but decreases greatly with an increase in the polymerization temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5944–5952, 2005

The synergistic thermal stabilization effect of polyamide (PA) and melamine (MA) on polyoxymethylene (POM) was studied by isothermal weight loss analysis and nonisothermal thermogravimetric analysis, which showed that the complex stabilizer PA/MA was more efficient than the single‐use formaldehyde absorbents MA or PA in improving the thermal stability of POM. The nonisothermal degradation kinetics study further demonstrated the synergistic thermal stabilization effect of PA/MA on POM. The mechanical property investigation showed that the addition of a proper amount of PA or the proper reduction of MA content improved the impact strength of POM. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2387–2391, 2005

An iron oligomerization catalyst, [(2‐ArN&dbond;C(Me))2C5H3N]FeCl2 [Ar = 2,6‐C6H3(F)2], was combined with rac‐ethylene bis(indenyl)zirconium (IV) dichloride [rac‐Et(Ind)2ZrCl2] to prepare linear low‐density polyethylene (LLDPE) by the in situ copolymerization of ethylene. A series of LLDPEs with different properties were prepared by the alteration of the reaction temperature, Fe/Zr molar ratio, Al/(Fe + Zr) molar ratio, and reaction time. The structures of the polymers were characterized with differential scanning calorimetry, 13C NMR, gel permeation chromatography (GPC), and so forth. The melting points, crystallizations, and densities of the resulting products increased, and the average branching degree decreased, as the reaction temperature, Al/(Fe + Zr) ratio, and reaction time increased. The melting points, crystallizations, and densities of the polymers decreased, and the average branching degree increased, when the Fe/Zr ratio increased. The 13C NMR and GPC results showed that there were no unreacted α‐olefins remaining in the resulting polymers because the percentage of low‐molar‐mass sections (C4–C10) of the oligomers obtained with this catalyst was very high (>70%). In addition, the formation of polymers with two melting points under different reaction conditions was examined in detail, and the results indicated that the two melting points of the polymers could be attributed to polyethylene with different branches. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 984–993, 2005

A mesoporous molecular sieve MCM‐41 supported iron‐based diimine catalyst (MC) was prepared for the first time. The kinetic behavior of ethylene polymerization with MC was studied. The effects of Al/Fe molar ratio and various cocatalysts on the catalytic activity and properties of the polyethylene obtained were investigated. The results showed that good catalytic activities can be reached with cocatalyst methylaluminoxane (MAO) and triethylaluminium (TEA). Ethylene polymerization with MC gave polymers with higher molecular weight, melting temperature and onset temperatures of decomposition (Tonset) and better morphology than those obtained with the corresponding homogeneous catalyst. Copyright © 2004 Society of Chemical Industry

A series of cycloalkylidene‐bridged cyclopentadienyl metallocene complexes, [(CH2)nC(C5H4)2MCl2] (M = Ti, n= 4 (4), 5 (5), 6 (6); M = Zr, n= 4 (7), 5 (8), 6 (9); M = Hf, n= 4 (10), 5 (11), 6 (12)), have been synthesized and applied to ethylene polymerization after activation with methyl aluminoxane (MAO). The cycloalkylidene‐bridged titanocene catalysts exhibit much higher activities than the corresponding zirconocene and hafnocene analogues, and have the highest activities at higher temperatures. In comparison, the silacyclopentylidene‐bridged metallocene complexes [(CH2)4Si(C5H4)2MCl2] (M = Ti (13), Zr (14)) and isopropylene‐bridged metallocene complexes [Me2C(C5H4)2MCl2] (M = Ti (15), Zr (16)) have also been synthesized and applied to ethylene polymerization. In both cases, the titanocene complexes show much higher activities than the corresponding zirconocene analogues, especially at a lower temperature. The molecular structures of complexes 4–9have been determined by X‐ray diffraction. The structure–activity relationships, especially the effects of the bridges of ansa‐metallocene complexes, are discussed.

This article discusses a facile and inexpensive reaction process for preparing polypropylene‐based graft copolymers containing an isotactic polypropylene (i‐PP) main chain and several functional polymer side chains. The chemistry involves an i‐PP polymer precursor containing several pendant vinylbenzene groups, which is prepared through the Ziegler–Natta copolymerization of propylene and 1,4‐divinylbenzene mediated by an isospecific MgCl2‐supported TiCl4 catalyst. The selective monoenchainment of 1,4‐divinylbenzene comonomers results in pendant vinylbenzene groups quantitatively transformed into benzyl halides by hydrochlorination. In the presence of CuCl/pentamethyldiethylenetriamine, the in situ formed, multifunctional, polymeric atom transfer radical polymerization initiators carry out graft‐from polymerization through controlled radical polymerization. Some i‐PP‐based graft copolymers, including poly(propylene‐g‐methyl methacrylate) and poly(propylene‐g‐styrene), have been prepared with controlled compositions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 429–437, 2005

A series of amphiphilic graft copolymers, PE‐graft‐PEO, containing hydrophobic polyethylene (PE) as the backbone and hydrophilic poly(ethylene oxide) (PEO) as the side‐chain, have been synthesized by a novel route. The graft structure and the molecular weight, as well as the molecular weight distribution of the graft copolymer can easily be controlled. The molecular weight of the side‐chain PEO is proportional to the reaction time and the monomer concentration, which indicates the ‘living’ character of the anionic polymerization of ethylene oxide. The produced copolymers PE‐graft‐PEO were characterized by 1H NMR and DSC measurements. Copyright © 2004 Society of Chemical Industry

Linear low‐density polyethylene (LLDPE) was prepared by in situ copolymerization of ethylene with dual‐functional catalysts that were composed of rac‐Et(Ind)2ZrCl2 supported on montmorillonite (MMT) and {[(2‐ArN&dbond;C(Me))2C5H3N]FeCl2} [Ar = 2,4‐C6H4(Me)2] oligomerization catalyst. A series of polyethylenes with different degrees of branching were obtained by adjusting the ratio of Fe and Zr (Fe/Zr). DSC, NMR, GPC, SEM, and density‐gradient method were used to characterize the polymers. With increasing Fe/Zr ratio, the densities and melting points of polymers decreased, whereas the branching degrees and molecular weights increased. When the Fe/Zr ratio was increased, the activities of the catalysts decreased at atmospheric pressure and increased at 0.7 MPa ethylene pressure. SEM micrographs revealed that the morphology of branched polyethylene, produced with the catalyst supported on MMT, is better than that produced by the catalyst in a homogeneous system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1690–1696, 2004

Summary:Copolymerization of propylene and 1,4‐divinylbenzene was successfully performed by a MgCl2‐supported TiCl4catalyst, yielding isotactic poly(propylene) (i‐PP) polymers containing a few pendant styrene groups. With a metalation reaction with butyllithium and a hydrochlorination reaction with dry hydrogen chloride, the pendant styrene groups were quantitatively transformed into benzyllithium and 1‐chloroethylbenzene groups, respectively, which allowed the synthesis of i‐PP‐based graft copolymers by living anionic and atom transfer radical (ATRP) polymerization mechanisms.

A novel synthetic route for preparing polypropylene-graft-polystyrene (PP-g-PSt) was set up. With this synthetic route, a series of PP-g-PSt copolymers containing different percentages of polystyrene chain were synthesized, based on the different reactivities of two kinds of C&bond;C double bonds on 4-(3-butenyl) styrene. Characterization data, including ¹H-NMR, ¹³C-NMR, GPC, and DSC, demonstrated that the graft copolymers were all very pure. Furthermore, it was also attempted to use this new kind of propylene–styrene graft copolymer as a compatibilizer. DMA and SEM results illustrated that the PP-g-PSt obtained is an efficient compatibilizer for the polypropylene–polystyrene blend. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 314–322, 2004

Blends of polyethylene (PE) were produced in a single reactor using a combination of {[(2-ArN&dbond;C(Me))2C5H3N]FeCl2} [Ar&dbond;2,6-2CH3(C6H4)] and rac-Et(Ind)2ZrCl2. The experimental results showed that the PEs obtained have a broad molecular weight distribution (MWD) and both the molecular weight and the MWD can be regulated through changing the mole ratio of the two active sites. In addition, the polymerization activities decreased with the increase of the Fe/Zr mole ratio whereas the crystallinity of the PE obtained exhibited a contrary trend, decreasing as the Fe/Zr mole ratio went up. The morphology of the blends also directly relates to the Fe/Zr mole ratio, and more iron content in the bimetallic catalysts system gives rise to compact PEs of high crystallinity. This reflects that the reactor blends are morphology controllable as well and can be easily applied to present processing techniques because of adjustable molecular weights and their distribution. Differential scanning calorimetry, thermogravimetric analysis, gel permeation chromatography, and scanning electron microscopy were employed to characterize the properties of the reactor blends of PEs. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1515–1518, 2003

New cobalt catalysts {[2,6-(CH₃C=NAr)₂C₅H₃N]CoCl₂} (Ar=2-methyl-4-methoxyphenyl, 1) and (Ar=2,4-dimethylphenyl,2) were synthesized and found to exhibit good selectivity for α-olefins with methylaluminoxane (MAO) as co-catalyst. With only ethylene as the feed monomer cobalt catalysts 1 or 2 can be coupled with zirconium catalyst Dichloro [rac-ethylenebis(indenyl)]Zirconium (IV) rac-EtInd₂ZrCl₂ (3) to produce linear low density polyethylene by in situ polymerization. Spectra of resulting materials exhibit ethyl, butyl and long-chain branches in the backbone of polyethylene. The ratio of Co/Zr and Δt, which is defined as the interval between introductions of two catalysts into the reactor, influenced catalytic activity and the resulting materials greatly. Compatibility and complementary behaviour of different catalysts proved to be two most important factors for in situ copolymerization. Copyright © 2003 Society of Chemical Industry

The copolymerization of butadiene (Bd) and isoprene (Ip) with a supported titanium-triisobutyl aluminum catalyst system was studied. An analysis using differential scanning calorimetry, X-ray diffraction, and ¹³C-NMR spectra indicated that products with 25–60 mol % Bd units were random copolymers and that the melting temperatures and glass-transition temperatures (Tg) were 30–40 and −74°C (or thereabout), respectively, which were very similar to those of natural rubber. The chemical structure of these copolymers was characterized by a high-trans 1,4-configuration: the trans 1,4-content of Ip units was greater than 98%, and the trans 1,4-content of Bd units was greater than 90%. The reactivity ratio of Bd was greater than that of Ip (rBd = 5.7 and rIp = 0.17). The sequence distribution of the monomer units of the copolymers followed a first-order Markov statistical model. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1800–1807, 2003

Vinyl-addition polymerization of norbornene was accomplished by two novel dinuclear diimine nickel dichloride complexes in combination with methylaluminoxane (MAO). The activities were moderate. The catalyst structure, Al/Ni molar ratio, solvents, and polymerization temperature all affected the catalytic activities. The obtained polynorbornenes were characterized by ¹H-NMR, ¹³C-NMR, FTIR, DSC, WAXD, and intrinsic viscosity measurements. The vinyl-addition polymers were amorphous but with a short-range order and high packing density. The polynorbornenes showed glass transition temperatures (Tg) above 240°C and decomposed above 400°C. The catalyst structure and polymerization conditions have effects on the molecular weight and the microstructure of the polymers. The nickel complex with bulkier substituents in the ligand produced polynorbornene with a higher packing density and higher regularity and, therefore, with higher Tg. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3273–3278, 2003

A supported iron-based diimine catalyst (SC) was prepared by immobilization of 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine iron chloride (I) on silica and employed in ethylene polymerization. The kinetic behavior of ethylene polymerization with SC was studied. The effects of the Al/Fe molar ratio, reaction temperature, and cocatalyst on the catalytic activity as well as the melting temperature, molecular weight, and morphology of the polymers obtained were also investigated. The results showed that good catalytic activities can be obtained even with a small amount of the cocatalyst methylaluminoxane (MAO) or triethylaluminum (AlEt3). The polyethylenes obtained with a supported catalyst had higher molecular weight, higher melting temperature, and better morphology than those obtained with a homogeneous catalyst. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 466–469, 2003

Novel bridged dinuclear diimine nickel and palladium complexes catalyzed the vinyl addition polymerization of norbornene at a single active site with high activity. The latter exhibited higher activity than the former. Smaller substituents around the imido group in the ligand were more favorable for increasing the activity than bulkier ones. The polynorbornenes were all noncrystalline but had short-range order and their glass transition temperature, Tg, ranged from 270 to 400 °C. Furthermore, the random copolymerization of norbornene and styrene was catalyzed by the bridged dinuclear diimine nickel complex with MAO (methylaluminoxane). Gel permeation chromatography (GPC), FTIR and ¹H NMR spectroscopies, wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC) indicated that the copolymers are “true” copolymers. The reactivity ratios were rstyrene = 0.281, rnorbornene = 18.7. The packing density, thermostability and the glass transition temperatures of copolymers are increased relative to polystyrene. The solubility and processability of the copolymers are improved relative to polynorbornene. The structures of bridged dinuclear diimine nickel and palladium complexes.

This article discusses an effective route to prepare amphiphilic diblock copolymers containing a poly(ethylene oxide) block and a polyolefin block that includes semicrystalline thermoplastics, such as polyethylene and syndiotactic polystyrene (s-PS), and elastomers, such as poly(ethylene-co-1-octene) and poly(ethylene-co-styrene) random copolymers. The broad choice of polyolefin blocks provides the amphiphilic copolymers with a wide range of thermal properties from high melting temperature ~270 °C to low glass-transition temperature ~−60 °C. The chemistry involves two reaction steps, including the preparation of a borane group-terminated polyolefin by the combination of a metallocene catalyst and a borane chain-transfer agent as well as the interconversion of a borane terminal group to an anionic (&bond;O⁻K⁺) terminal group for the subsequent ring-opening polymerization of ethylene oxide. The overall reaction process resembles a transformation from the metallocene polymerization of α-olefins to the ring-opening polymerization of ethylene oxide. The well-defined reaction mechanisms in both steps provide the diblock copolymer with controlled molecular structure in terms of composition, molecular weight, moderate molecular weight distribution (Mw/Mn < 2.5), and absence of homopolymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3416–3425, 2002

In this work, the preparation and characterization of metallocene-catalyzed polyethylene (PE)/kaolin composites were presented. The composites was prepared by the so-called polymerization-filling method in which the PE matrix was formed directly on the kaolin surface by ethylene polymerization with the prefixed Cp2ZrCl2/methylaluminoxane (MAO) catalyst system on the kaolin surface. SEM, FTIR, and DMA were carried out to characterize the composites. The experimental results showed the new composites had homogeneous distribution of kaolin particles in the PE matrix and strong interfacial interaction between the PE matrix and kaolin particles. At the molecular level, the interfacial interaction caused the decrease of the mobility of PE molecular chains. In addition rheological testing showed that the introduction of kaolin by polymerization filling could improve the rheological behavior of prepared composites. The relationship between the rheological behaviors and the interfacial conditions were discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2913–2921, 2002

A Correction has been published for this article in Polymer International 51(6) 2002, 561The late transition metal catalyst 2,6‐bis[1‐(2,6‐diisopropylphenylimino)ethyl]pyridine iron(II) chloride was supported on silica. Fourier transform infrared spectroscopy, scanning electronic micrograph and X‐ray photoelectron spectroscopy measurements were utilized to examine the process of supporting catalyst on silica and investigate the possible mechanism of support. Furthermore, ethylene polymerizations with the supported catalysts were carried out in various conditions such as different reaction temperatures and Al/Fe molar ratios. The results showed that MAO first reacted with the hydroxyl of silica forming Si&bond;O&bond;Al bonds and then the catalyst was bridged through MAO on the surface of silica. Compared with homogeneous catalysts, the supported catalysts show some decrease in catalyst activity. However, they can show good activity at a lower Al/Fe molar ratio with MAO as co‐catalyst and give rise to higher molecular weight and melting temperature of the polymer. Better morphology of polyethylene was obtained by a supported catalyst than by its corresponding homogeneous catalyst.The late transition metal catalyst 2,6‐bis[1‐(2,6‐diisopropylphenylimino)ethyl]pyridine iron(II) chloride was supported on silica. Fourier transform infrared spectroscopy, scanning electronic micrograph and X‐ray photoelectron spectroscopy measurements were utilized to examine the process of supporting catalyst on silica and investigate the possible mechanism of support. Furthermore, ethylene polymerizations with the supported catalysts were carried out in various conditions such as different reaction temperatures and Al/Fe molar ratios. The results showed that MAO first reacted with the hydroxyl of silica forming Si&bond;O&bond;Al bonds and then the catalyst was bridged through MAO on the surface of silica. Compared with homogeneous catalysts, the supported catalysts show some decrease in catalyst activity. However, they can show good activity at a lower Al/Fe molar ratio with MAO as co‐catalyst and give rise to higher molecular weight and melting temperature of the polymer. Better morphology of polyethylene was obtained by a supported catalyst than by its corresponding homogeneous catalyst.© 2002 Society of Chemical Industry

The isothermal crystallization kinetics of polypropylene/montmorillonite (PP/MMT) nanocomposites synthesized via intercalation polymerization were investigated by using differential scanning calorimeter and polarizing optical microscope (POM). The crystallinity of the nanocomposites decreased with the increase of the montmorillonite content, indicating that the MMT layers dispersed in the PP matrices confined the PP chains and hindered the crystallization of the PP chains. The POM photographs showed that the spherulites of the PP/MMT nanocomposites were greatly decreased in size as MMT was introduced. On the other hand, the crystallization rate increased dramatically with the increasing of MMT content. The interfacial free-energy per unit area perpendicular to PP chains in PP/MMT nanocomposites decreased with increasing MMT content, suggesting that the MMT layers acted as heterogeneous nuclei in the nucleation of crystallization. The nucleus density increased with the increasing of MMT content, leading to a positive effect on the crystallization. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 83: 1978–1985, 2002

Polynorbornene was synthesized by β-diketonate titanium / MAO (methylaluminoxane) catalysts. The polymerization activity was up to 8 × 103g polymer/(mol Ti h). FT-IR, 1H NMR, 13C NMR and WAXD analyses showed that the polynorbornenes contained both ring-opening metathesis (trans and cis) and addition polymer chain structures and they are amorphous. The portions of trans- and cis- double bonds decreased when the polymerization temperature and Al/Ti molar ratio decreased. In addition, using 1,2-dichlorobenzene, instead of toluene, as the polymerization solvent increased the activity and produced the polymer containing more cis-double bonds. The glass transition temperature of the elastic polymers ranged from 330°C ∼ 400°C.

Polypropylene/clay (PP/clay) nanocomposites were synthesized via intercalative polymerization. The nanostructure of the composites was investigated by wide-angle X-ray diffractometry (WAXD) and transmission electron microscopy (TEM). The WAXD patterns of the PP/clay nanocomposites indicated that the characteristic diffraction peak of the clay disappeared. The TEM image showed the clay was exfoliated into nanometer size and dispersed uniformly in the PP matrix. The composites exhibited much higher storage modulus compared to that of pure PP. At temperatures higher than Tg, the storage modulus of the PP/clay nanocomposites with 8.1 wt % clay content increased three times that of the pure PP. Additionally, the thermal stability of the nanocomposites significantly increased. The maximum decomposition temperature was increased by 44°C with the introduction of about 10 wt % clay. The heat-distortion temperatures (HDTs) of the nanocomposites also increased. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3611–3617, 2001

Polyethylene has been modified and synthesized in situ by a combination of Cp2ZrCl2 and 8‐aminoquinoline nickel dichloride catalysts with methylaluminoxane co‐catalyst. The results indicate that the crystallinity and Tm of polyethylene both decrease with increasing Ni/Zr mol ratio when the Ni catalyst is added first. Oligomers formed by 8‐aminoquinoline nickel dichloride within a certain Ni/Zr mol ratio could be completely converted into polymer. Three methods used to introduce catalysts to the reaction system resulted in different products. Polyethylene with the lowest melting point, crystallinity and the highest degree of branching resulted when the Zr catalyst was added after that of the Ni compound.© 2001 Society of Chemical Industry

A novel highly active catalyst 2,6‐bis[1‐(2‐methylnaphthylimino)ethyl]pyridineiron(II) chloride (1) is reported for ethylene polymerization. Compared with 2,6‐bis[(1‐naphthylimino)ethyl]pyridineiron(II) chloride (2) reported recently, catalytic activities of this new complex are high with maximum activity 6.51×106g PE·mol–1·Fe·h–1·bar–1at 40°C. The activity of the catalyst, and the molecular weight and melting temperature of the polymers depend on the methylaluminoxane/1molar ratio and polymerization temperature.

The unusual flow behaviors of linear PE melts are caused by high molecular weight, tight entanglements of molecular chains, and strong adsorption of the melt at the capillary wall. Especially, the extreme change of interface adsorption is followed by an unusual flow, and at the molecular level, the dynamic variety of entanglement and disentanglement between the adsorption chain near the wall and the nonadsorption chain is the cause of the extrusion pressure vibration. Ultrahigh molecular weight polyethylene (UHMWPE)/kaolin composites prepared by polymerization filling could be smoothly extruded through the capillary. Also, with increase of the kaolin content, the apparent viscosity of the composite decreased and the processability was improved. Under slip boundary conditions, the real shear rate and shear stress of the melt near the capillary wall were reduced. The viscosity descent (desorption) and the deformation energy decrease of the melt near the wall were the important preconditions to gain a steady flow in a second glossy zone. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2154–2161, 2001

The activities of a several titanium-based constrained geometry metallocenes (CGM) have been examined with respect to their central-metal net charges. A simple method consisting of a combination of the molecular mechanics and the charge equilibration method was adopted here to determine the structure and the net charge. The results obtained indicate that the net charge on the central-metal of the CGM does dominate the activity. A new CGM, (2,6-dipropylphenylamide) dimethyl (tetramethylcyclopentadienyl) silane titanium dichloride, was synthesized and analyzed.

The activities of a several titanium‐based constrained geometry metallocenes (CGM) have been examined with respect to their central‐metal net charges. A simple method consisting of a combination of the molecular mechanics and the charge equilibration method was adopted here to determine the structure and the net charge. The results obtained indicate that the net charge on the central‐metal of the CGM does dominate the activity. A new CGM, (2,6‐dipropylphenylamide) dimethyl (tetramethylcyclopentadienyl) silane titanium dichloride, was synthesized and analyzed.

A new generation of MgCl2‐supported catalysts for the polymerization of propene without any external donors was prepared. Two diethers, 9,9‐bis(methoxymethyl)fluorene (for Cat‐A) and 2,2‐dipropyl‐1,3‐dimethoxypropane (for Cat‐B) differing in the bulkiness of alkyl substituents in position 2, have been used as internal donors in MgCl2/TiCl4/diether‐AlR3catalysts. The weight‐average molecular weights produced with both catalysts were over 3.5×105at low temperature in slurry polymerization (< 40°C). Cat‐A showed higher activity and produced higher isotactic polypropene than Cat‐B. The activity of both catalysts proved to be dependent on the temperature.

Two new silolene-bridged metallocenes for isotactic polypropylene, racemic (1,4-butanediyl) silylene-bis (1-η⁵-2-methyl-indenyl) dichlorozironium and racemic diphenyl silylene-bis (1-η⁵-2-methyl-indenyl) dichlorozironium, were designed in terms of the mechanism and concept of the activity and selectivity of metallocenes. The predictions on which the designs were based were carried out for four metallocene catalysts through molecular modeling methods such as molecular mechanics and charge equilibrium. In a comparison of the data from three of the catalysts that were successfully synthesized, the predicted orders of the activity and selectivity were consistent. This shows that classical methods such as charge equilibrium are useful in predicting the activity of catalysts. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2232–2238, 2000

A new iron‐based catalyst, 2,6‐bis[(1‐naphthanylimino)ethyl]pyridine iron(II) chloride I, has been successfully synthesized and characterized. Ethylene was polymerized by I/methylaluminoxane to give branched, low‐density polymers with good activity. The result shows that the new diimino ligand has improved the characteristics of the resulting polyethylene.© 2000 Society of Chemical Industry

Ethylene was polymerized with cycloalkylidene‐bridged cyclopentadienyl metallocene catalysts 1–9in the presence of methyl aluminoxane (MAO) as the cocatalyst. Unlike the normal titanocene catalysts, the cycloalkylidene‐bridged cyclopentadienyl titanocene catalysts show much higher activities than the corresponding zirconocene and hafnocene catalysts and show the highest activities at higher temperature. This indicates that the cycloalkylidene‐bridged cyclopentadienyl titanocene system is very thermally stable and maybe a very promising catalyst system for industrial application.