Progress in the catalyst for ethylene/α-olefin copolymerization at high temperature

Ethylene/α-olefin copolymers are one of the most widely-used polyolefin materials. With the continuous improvement of polyolefin catalysts, high-performance polyolefin materials were synthesized by adjusting the chain microstructure, changing the comonomer type and comonomer insertion amount, among which the ethylene/α-olefin random copolymer elastomer (POE) and olefin block copolymer elastomer (OBC) are the most famous and well accepted by the market. The excellent properties of POE and OBC first depend on their polymer chain microstructure. The chain microstructure of polyolefins is fundamentally determined by the catalysts, polymerization conditions, comonomer feed policies, and reaction engineering. High-performance ethylene/α-olefin copolymer elastomers are currently prepared by high-temperature solution polymerization process, which needs to be carried out at a temperature above the melting point of the polymer and is beneficial to speed up the polymerization reaction rate and control the polyolefin chain microstructure. However, the high-temperature solution polymerization process launched more stringent requirements for the olefin coordination polymerization catalyst. Systematic reports on catalysts for high-temperature solution copolymerization of ethylene and α-olefins are lacking. In this review, we screened some catalysts suitable for the controllable copolymerization and high-temperature solution copolymerization of ethylene/α-olefin based on the catalyst's heat resistance, copolymerization activity, comonomer insertion ability, molecular weight, and distribution of the copolymer, including traditional Z–N catalysts, metallocene catalysts, and post-metallocene catalysts. And the future development of catalysts for high-temperature solution copolymerization of olefins, catalysts for precise control of polyolefin chain microstructures, and catalysts for olefin copolymerization with polar monomers at high temperature are envisaged.     

Controlled synthesis of azobenzene functionalized homo and copolymers via direct acyclic diene metathesis polymerization

A powerful and efficient strategy for obtaining a series of azobenzene functionalized linear unsaturated polyolefins is described, which involves the first design and synthesis of three different α,ω-diene monomers with different reactivity of acrylates and terminal double bonds and their subsequent acyclic diene metathesis (ADMET) polymerization under mild reaction conditions. Different ruthenium based metathesis catalysts and conditions were tested to optimize the ADMET polymerization of these monomers. Besides, this polycondensation method is also reported allowing for the synthesis of alternating and diblock azobenzene-containing copolymers with molecular weight control by using the selectivity of olefin cross-metathesis between acrylates and terminal olefins. The resulting polymers showed well-defined molecular weights, reasonable polydispersity index, and reversible photoresponsive behavior. This special combination of the benefits of metathesis polymerization and azobenzene is a highly versatile system for materials in many applications.     

Combining Ziegler-Natta and mettalocene catalysis: New heterophasic propylene copolymers from the novel multicatalyst reactor granule technology

A new process that combines the excellent morphology control of Ti-based catalysts with the unique features of polyolefins from mettalocenes has been devised. First, propylene is polymerized with the Ti-based catalysts, having spherical form; then, activated mettalocene catalysts are introduced into the porous PP spheres, through an in situ impregnation and drying process, once the Ti has been deactivated. Then, the olefins polymerization, catalyzed by the mettalocene, is carried out in gas phase. This step, as well as the morphology of the as-polymerized polymer particles, has been investigated in detail. New heterophasic copolymers (PP/EPR) having free-flowing spherical form have been achieved, and the morphology of the copolymer spheres pointed out that the rubber is well dispersed inside the polymer granule. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1831–1837, 1997     

Synthesis and properties of styrene copolymers. Preparation of film‐modified electrodes to detect Pb2+ ions

Organic solvent‐soluble polymers containing different functional groups able to coordinate metal ions from low concentration were synthesized to build complexing polymer film modified electrodes. Poly(acetamide acrylic acid‐co‐styrene) and poly(itaconic acid‐co‐styrene) were synthesized by radical polymerization. The copolymers were characterized by Fourier transform infrared and ¹H NMR spectroscopy, electron scanning microscopy, and thermal analysis. The molecular weight and molecular weight distribution were determined by size exclusion chromatography. These complexing polymers have been used in the preparation of complexing modified electrodes (CME) by spin coating. The CME have been tested for the detection of metal ions using the chemical preconcentration‐anodic stripping technique. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2380–2385, 2006     

Borylated Polyolefins and their Applications

Different preparative routes for the attachment of organoboron moieties to polyolefins and applications of such materials are reviewed. Preparation from boron-functionalized monomers represents one possible synthetic strategy with free radical polymerization, Ziegler–Natta polymerization, and ring-opening metathesis polymerization methods as the most thoroughly studied procedures. Recent advances in the preparation of boron-containing polymers through polymer modification reactions provide an interesting alternative that allows for the facile preparation of well-defined organoboron polymers of various architectures including homo polymers, random copolymers, block copolymers, and telechelic polymers. New opportunities for organoboron polymers as supported catalysts, sensors, luminescent materials, device components, and precursors to ceramics are briefly discussed.     

Synthesis and properties of polymer film modified electrodes to detect metal ions

In order to obtain modified polymeric electrodes, polymers were synthesized that are insoluble in water but soluble in common organic solvents and contain different functional groups that are able to coordinate metal ions from low concentrations. Poly(acrylic acid‐co‐styrene), poly(acrylamide‐co‐4‐vinyl pyridine), and poly(styrene‐co‐4‐vinyl pyridine) were synthesized by radical polymerization. The copolymers were characterized by FTIR, ¹H‐NMR, ¹³C‐NMR, scanning electron microscopy, and thermal analysis. The molecular weight and molecular weight distribution were determined by size exclusion chromatography. These complexing polymers were used in the preparation by spin coating of complexing chemically modified electrodes. The polymer film modified electrodes were then tested for the detection of metal ions using the chemical preconcentration and anodic stripping technique. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1192–1197, 2005     

Functionalization of polyethylene using borane reagents and metallocene catalysts

A new method to prepare functionalized polyethylene involving borane intermediates and transition metal catalysts is described. Two processes, direct and post polymerizations, were employed to prepare borane-containing polyethylene (PE-B), which can be transformed to functionalized polyethylene (LLDPE-f) with various functional groups, such as ? BR₂, ? OH, ? NH₂, ? OSi(CH₃)₃. In the direct process, the PE-B copolymers were prepared in one step by copolymerization of ethylene with a borane monomer (ω-borane-α-olefin). The post polymerization process requires two steps: copolymerization of ethylene and 1,4-hexadiene, and subsequential hydroboration reaction of unsaturated PE. Three transition metal catalysts, including two homogeneous metallocene (Cp₂ZrCl₂ [bis(cyclopentadienyl) zirconium dichloride] and Et(Ind)₂ZrCl₂ [1,1′-ethylenedi-η⁵-indenyl-zirconium dichloride] with MAO (methylaluminoxane)) and one heterogeneous (TiCl₃·AA/Et₂AlCl) ones, were studied in the copolymerization reactions. The single site Et(Ind)₂ZrCl₂/MAO homogeneous catalyst, with a strained ligand geometry and opened active site, is by far the most effective system in the incorporation of high olefins into polyethylene structures.     

Copolymerization of ethene and dimethanooctahydronaphthalene with aluminoxane containing catalysts

With homogeneous catalysts on the basis of chiral metallocenes and methylaluminoxane it has become possible to polymerize cyclic olefins like cyclobutene, cyclopentene, norbornene, or dimethanonaphthalene (DMON). No ring opening reaction occurs. The crystalline polycycloalkenes show extremely high melting points between 400 and 600°C. Copolymers of DMON with ethene are amorphous. They have molecular weights between 50000 and 150000 and high glass transition points up to 160°C. These copolymers could be used as materials for optical discs and fibers.     

Cationic Polymerization of β-Pinene Using B(C6F5)3 as a Lewis Acid for the Synthesis of Tackifiers in Pressure Sensitive Adhesives

β-pinene is a well-known bio-based monomer that can be polymerized via cationic polymerization to give low molecular weight resins that find use commercially as tackifiers. However, the controlled synthesis of these polymers by cationic polymerization is challenging due to the reactivity of commonly used Lewis acid catalysts and the propagating carbocationic species with water. Here, the cationic polymerization of β-pinene under mild conditions using the water stable Lewis acid tris(pentafluorophenyl)borane is demonstrated. It is shown that when combined with a suitable alcohol initiator the molecular weight of the polymer can be tuned while the kinetics are largely controlled by the concentration of tris(pentafluorophenyl)borane. The final poly(β-pinene) is shown to perform well as a tackifier in the formation of pressure sensitive adhesives based on polystyrene-b-polyisoprene-b-polystyrene triblock copolymers.     

Synthesis and characterization of propylene‐α‐olefin random copolymers with isotactic propylene sequence. II. Propylene–hexene‐1 random copolymers

A series of novel hexene‐1–propylene random copolymers with isotactic sequence of propylene was synthesized with a MgCl₂‐supported Cr(acac)₃ catalyst. The molecular weight distribution of copolymers and homopolymers was considerably narrower than that of typical polyolefins produced by heterogeneous Ziegler–Natta catalysts. The crystallizability of the copolymers having a propylene‐unit content of more than 50 mol % drastically decreased with decreasing propylene‐unit content, and the copolymers with a propylene content of less than 50 mol % were completely amorphous. In the present novel type of random copolymers with crystallizable and noncrystallizable units, a single glass transition was observed between pure polypropylene and polyhexene‐1, and a major component was found to govern the final morphology and the mechanical characteristics. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2949–2954, 2004     

Polymeric corrosion inhibitors for copper and brass pigments

Copper and brass pigments corrode in aqueous alkaline media with the absorption of oxygen that can be measured gasvolumetrically. These corrosion reactions can be inhibited by certain polymers; the metallic sparkle and the color of the pigments is preserved. The brass pigment is inhibited more effectively than the copper pigment. Some low‐molecular mass styrene–maleic acid (SMA) copolymers are efficient corrosion inhibitors; a low acid number is necessary but not sufficient for corrosion inhibition. At pH 8.5 there is a potential correlation between the acid number of the low‐molecular mass SMA and the oxygen volumes absorbed from brass pigment dispersions; oxygen volumes decrease with decreasing acid number. Furthermore, increasing copolymer addition effects an increase of corrosion inhibition. Polyacrylic acids, polyvinyl alcohols and high‐molecular mass SMA copolymers are ineffective. The most efficient group of polymers examined in this study are the styrene–acrylate copolymers because by addition of these the overall lowest volumes of oxygen were absorbed by the metal pigments. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 475–483, 2001     

乙烯与极性单体共聚的研究进展

聚烯烃属于非极性聚合物,通过在其分子链上引入极性基团可以将其功能化,从而可以有效地改善聚烯烃的性质,拓宽聚烯烃的商业用途。本文主要从极性单体的种类、乙烯与极性单体共聚的催化剂体系两个方面介绍了乙烯与极性单体共聚合研究的最新进展。Ziegler-Natta催化剂、茂金属催化剂以及后过渡金属催化剂都可用于乙烯与极性单体的共聚合反应。文中重点介绍了后过渡金属催化剂,其催化活性高,聚合能力强,可以催化乙烯与大多数极性单体的共聚反应。     

α-二亚胺后过渡金属配合物在烯烃聚合中的应用研究进展

介绍了α-二亚胺配体后过渡金属烯烃聚合催化剂的研究进展,对此类催化剂因改变配体空间位阻、改变配体取代基电子效应而对催化活性、相对分子质量、分子结构的影响进行了综述。三联苯基配体催化剂兼具高活性和高稳定性,刚性环和轴向给电子基团有机结合的α-二亚胺配体后过渡金属催化剂具有高活性、产物高相对分子质量、高线型、低支化度的特点,为新型催化剂的制备以及新型材料的合成提供了新思路。     

Amine-activated color in anhydride functional styrene/acrylic copolymers

Anhydride functional copolymers, usually prepared from maleic anhydride, styrene and acrylic monomers, are an increasingly important group of co-reactants for polyol and epoxide crosslinked coatings. Aliphatic tertiary amines, the preferred catalysts for crosslinking, generate strong colors when they are added to many of the polymers. Color formation was investigated using tristimulus colorimetry to determine the influence of composition of the anhydride copolymer and the process for copolymer preparation. A structural feature of the copolymers, tentatively identified as unsaturated anhydride end groups from termination by disproportionation, and residual maleic anhydride were found to be major contributors to amine-activated color. Partial hydrolysis of the polymer moderates color development, but increases solution viscosity. Acid level increases and anhydride content decreases as more n-butyl methacrylate is included in the copolymers, possibly because water is formed during the initiation process with this monomer.     

Well-defined phosphonated homo- and copolymers via direct ring opening metathesis polymerization

Phosphonated polymers with a well-defined molecular weight, composition and architecture have been prepared via ring opening metathesis polymerization (ROMP) of phosphonated and non-phosphonated norbornene imides at room temperature for the first time. ROMP was proven to be living and versatile. This enabled preparation of a broad range of phosphonated homopolymers, statistical copolymers, AB diblock as well as ABA and BAB triblock copolymers based on poly(norbornene imide)s with low polydispersity (1.09–1.32). Complete hydrolysis of phosphonated poly(norbornene imide)s under mild conditions yielded the phosphonic acid derivatives. Thermogravimetric analysis indicated high thermal and thermo-oxidative stability of the polymers. Free standing and transparent films with good mechanical stability were obtained from the phosphonic acid functional homopolymers, diblock and triblock copolymers. Combining these basic properties with the advantages mentioned above makes ROMP a promising pathway for accessing a wide diversity of phosphonated macromolecular structures. These new phosphonated polymers will open new perspectives in advanced application areas, which require a high level of control over polymer structure.     

Polymerization of olefins through heterogeneous catalysis. VI. Effect of particle heat and mass transfer on polymerization behavior and polymer properties

The multigrain model for polymerization of olefins over solid catalysts is used to predict kinetic behavior, molecular weights, and polydispersities. The effects of intraparticle and external boundary layer transport resistance on the kinetic behavior and polymer properties are explored. Means for the experimental detection of intraparticle diffusion resistance are suggested. The importance of catalyst physical properties, such as the porosity, and the catalyst loading is illustrated through simulation. Finally, the hypotheses of diffusion resistance and site heterogeneity as explanations for the broad molecular weight distributions of olefin polymers are critically evaluated, and molecular weight distribution control in industrial catalysts is discussed.     

Correlations of single-point parameters of linear rheology and molecular weight distribution of polypropylene homo- and copolymers

For various purposes, it is required to compress the shape of the molecular weight distribution (MWD) of polymers into a limited set of parameters. With increasing molecular weight and polydispersity, the MWD data obtained from chromatography become increasingly unreliable due to deficiencies in the high molecular weight region, making estimation via melt rheology more preferable. A number of empirical parameters obtained from melt rheology can be related back to MWD parameters. The target of this study is to establish the reliability of such relations for polypropylene homo- and copolymers. It is found that correlations between polydispersity from rheological crossover modulus and polydispersity via chromatography are not always valid. Therefore, the range of applicability must be kept in mind when attempting predictions based on these correlations because rheological measurements are sensitive to molecular characteristics in ways different from chromatography. The use of a modified polydispersity index is shown to be more reliable.     

Oxydation mehrfach ungesättigter polymerer mit organischen hydroperoxiden

A series of results is known about oxidation of low molecular weight olefins with alkyl hydroperoxides in the presence of derivates of transition metals. Depending on the catalyst the reaction products mainly have epoxide or alkenyl alkyl peroxide groups. The reactions of polymers with a high degree of unsaturation - mainly performed with tertiary butyl hydroperoxide - gave on catalysis with molybdenum compounds almost exclusively polymers containing epoxide groups. With vanadium derivates polymers having mainly epoxide groups were obtained. Application of derivates of manganese, cobalt, and copper resulted in a selective formation of polyfunctional peroxides. The reaction is inhibited by water. No cross-linking was observed when the reaction was performed in solution. Explanations are given for the formation of epoxides or peroxides in the presence of transition metal compounds as catalysts. Reaction mechanisms for the epoxidation or peroxidation are proposed. On epoxidation of liquid polybutadienes with tertiary butyl hydroperoxide the presence of molybdenyl bisacetylacetonate curable liquid epoxidized poly-butadienes are obtained. In the presence of acetylacetonates of copper, manganese, and cobalt polyfunctional polybutadienyl tertiary butyl peroxides with a “critical temperature” of about 120°C are obtained which are useful for the initiation the polymerization of styrene.     

High molecular weight 1-olefin/carbon monoxide copolymers: a new class of versatile polymers

The moderate electrophilicity of palladium(II)-phosphine catalysts compared to those of zirconocene dichlorides makes them more tolerant toward a variety of polar functionalities of olefinic monomers. This allows use of Pd(II) complexes as catalysts for the copolymerization of olefins with readily available polar monomers, like acrylic acid derivatives or carbon monoxide. In particular, developments during the recent years have opened the way to a new and broad family of high molecular weight 1-olefin/CO co- and terpolymers. These 1,4-polyketone materials show interesting and easily variable properties which can be tuned from insoluble, highly crystalline to thermoplastic elastic. The latter polymers resemble in some cases flexible PVC and even vulcanized natural rubbers. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis and reactive blending of amine and anhydride end-functional polyolefins

Polyolefins having low polydispersity and containing terminal functional groups are difficult to synthesize, due to limitations in catalysis technology. We have developed methods for preparing model polyolefins with terminal amine or anhydride functionality and of controlled molecular weight and narrow polydispersity. Both 1,4- or 1,2-polybutadienes are prepared by living anionic polymerization, with introduction of a functional group precursor during chain termination. The functional groups are protected as tert-butyl carbamate and tert-butyl ester for the amine and anhydride, respectively. The polymers are hydrogenated heterogeneously, with subsequent deprotection yielding saturated polymers with functionalities of up to 90%. These materials, due to their low polydispersity, comprise a useful model system for measuring melt reaction kinetics by gel permeation chromatography. Melt blending of amine- and anhydride-functional PEE90 (polyethylethylene) with complementary functional polystyrenes quickly yields extensive amounts of block copolymer with complex, sub-micron scale morphologies. Similar fine morphologies are observed for blends of amine- and anhydride-functional PE (polyethylene) with functional polystyrene. These functional PE and PEE90 polymers can also be used as reactive compatibilizers for polyethylene and polypropylene blends, respectively. The concentration of compatibilizer required to obtain sub-micron particles, however, is as high as 20% by weight.