以丙烯为主体的二元及三元共聚研究──丙烯与乙烯和丁烯－1的共聚合

研究了ＭｇＣｌ２载体高效催化剂用于丙烯为主体的与乙烯和丁烯－１的二元及三元共聚合反应：选择了最佳的共聚合条件；实验测定了共聚单体配比对共聚合活性、共聚物分子量和物理性能的影响；并用１３Ｃ—ＮＭＲ分析了共聚物组成、序列分布和支链结构等微观结构信息．     

新一代高活性后过渡金属烯烃聚合催化剂

介绍了近几年发展起来的新一代后期过渡金属(Fe,Co,Ni,Pd)烯烃聚合催化剂,对催化剂的结构、性能及催化烯烃聚合进行了阐述。     

Structural analysis of linear/branched ethylene block copolymers

Chain shuttling polymerization has provided new pathway for introduction of different architectures in a single chain. Unlike the commercially available ethylene/1‐octene block copolymers, synthesis and microstructure of linear/branched polyethylene with blocky nature is not extensively studied. In this work, such block copolymers are synthesized based on reversible transfer of growing chains between an ansa metallocene and α‐diimine catalysts, forming linear and branched structures from ethylene, respectively. Investigation of thermal properties reveals that application of 550 equivalent of chain shuttling agent makes blocky structures that show the most deviation from the longstanding relationship between melting temperature and crystallinity or density, alongside with turning broad molecular distribution into unimodal. Thermal fractionation by successive self‐annealing demonstrates formation of broad distribution of linear blocks, as comprehended through appearance of uniform melting peaks at lower temperatures. Corresponding dynamic mechanical properties and crystalline structures reveal soft elastomeric properties, specifically at temperatures around −50°C, opposed to the purely linear chains or linear/branched blends. Correspondingly, blend samples demonstrate significant morphological change upon treatment with a suitable solvent for the branched fraction, contrary to the blocky microstructures.     

Polymerization with TMA-protected polar vinyl comonomers. I. Catalyzed by group 4 metal complexes with η5-type ligands

This paper describes the use of several kinds of group IV Cp based catalyst systems, in the synthesis of co- and terpolymers of ethylene, propylene and α-olefins endowed with OH and COOH functional groups. The hydroxy monomers used were 5-hexen-1-ol (4) and 10-undecen-1-ol (5) and the carboxy monomer was 10-undecen-1-oic acid (6). The three catalyst systems used were the C₂ symmetric ansa-zirconocene (1) the “in-site” titanium complex (2) and the non-rigid zirconocene (3), all activated by methylaluminoxane. Trimethylaluminium was used to protect the functional group of polar monomers. The first two catalyst systems suffer similar activity loss in the presence of polar monomer whereas the third one exhibited better tolerance toward the hydroxyolefins. NMR and FTIR spectroscopies were used to characterize the polymerization products. All three catalyst systems afforded functionalized co- and terpolymers by direct polymerization of ethylene/propylene/hydroxy-α-olefins but only the catalyst system (1)/MAO displays appreciable activities for direct polymerization of ethylene, propylene and carboxy-α-olefins. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2457–2469, 1999     

Poly(ethylene terephthalate) terpolyesters containing isophthalic and 5‐tert‐butylisophthalic units

Poly(ethylene terephthalate‐co‐isophthalate‐co‐5‐tert‐butylisophthalate) (PETI^tBI) terpolymers were investigated with reference to poly(ethylene terephthalate) (PET) homopolymer and poly(ethylene terephthalate‐co‐isophthalate) (PETI) copolymers. Three series of PETI^tBI terpolyesters, characterized by terephthalate contents of 90, 80, and 60 mol %, respectively, with different isophthalate/5‐tert‐butylisophthalate molar ratios, were prepared from ethylene glycol and mixtures of dimethyl terephthalate, dimethyl isophthalate, and 5‐tert‐butylisophthalic acid. The composition of the terpolymers and the composition of the feed agreed. All terpolymers had a random microstructure and number‐average molecular weights ranging from 10,000 to 20,000. The PETI^tBI terpolyesters displayed a higher glass‐transition temperature and a lower melting temperature than the PETI copolymers having the same content of terephthalic units. Thermal stability appeared essentially unchanged upon the incorporation of the 5‐tert‐butylisophthalic units. The PETI^tBIs were crystalline for terephthalate contents higher than 80 mol %, and they crystallized at lower rates than PETI. The crystal structure of the crystalline terpolymers was the same as that of PET with the 1,3‐phenylene units being excluded from the crystalline phase. Incorporation of isophthalate comonomers barely affected the tensile modulus and strength of PET, but the brittleness of the terpolymers decreased for higher contents in 5‐tert‐butylisophthalic units. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 124–134, 2003     

Et(Ind)_2ZrCl_2/MAO催化乙烯和ω-对甲苯基-α-烯烃共聚合的研究

使用Et(Ind)2ZrCl2/MAO催化剂催化乙烯和3种ω-对甲苯基-α-烯烃(对甲苯基-1-丙烯,4-对甲苯基-1-丁烯,6-对甲苯基-1-己烯)共聚,主要研究了共单体加入量对催化剂活性和所得共聚物性能的影响.4-对甲苯基-1-丁烯表现出最好的共聚性能.使用1H-NMR、13C-NMR、GPC和DSC对共聚物进行了表征.     

Characterization of Ethylene Copolymers with Liquid Chromatography and Melt Rheology Methods

Summary: Melt rheology and polymer chromatography methods were applied to characterize molecular heterogeneities in products of free radical copolymerization of ethylene with methyl acrylate and vinyl acetate comonomers performed in continuously stirred tank and tubular reactors. We found that the ethylene–vinyl acetate copolymers made in both reactors had similar linear viscoelastic properties typical to branched products of the high pressure process. But the ethylene–methyl acrylate copolymers obtained in the tubular reactor had unusually high melt viscosity at low shear rate and much lower onset of shear thinning despite the narrower molecular weight distribution and the lower overall amount of long-chain branches compare to their autoclave counterparts with similar average molecular weight and chemical composition. Using interaction polymer chromatography method called gradient elution at critical point of adsorption we found that ethylene-acrylate copolymers from the tubular reactor had very broad chemical composition distribution, which was consistent with a significant difference in reactivity ratios between ethylene and acrylate comonomers. Such chemical composition heterogeneity can be a reason for the observed unusual rheological properties of these copolymers.     

Nuclear magnetic resonance studies on microstructure of ethylene copolymers. VII. Proton resonance spectra of hydrolyzed ethylene–vinyl acetate copolymers1

Complete and partial alcoholyses of ethylene–vinyl acetate (E–VA) copolymers yield ethylene–vinyl alcohol (E–VOH) copolymers and ethylene–vinyl acetate–vinyl alcohol (E–VA–VOH) terpolymers, respectively. From the 220-MHz proton NMR spectra of E–VOH copolymers the stereoregular and chemical sequence distributions of the comonomers can be readily determined. Partially hydrolyzed E–VA polymers were acetylated with perdeuterated acetic anhydride. The monomer distributions in the terpolymers were then quantitatively determined by examining the proton spectra of the derived products. It was found that alcoholysis of E–VA polymers occurs preferentially at VA units which have neighboring VA groups.     

The influence of comonomer on ethylene/α-olefin copolymers prepared using [bis(N-(3-tert butylsalicylidene)anilinato)] titanium (IV) dichloride complex

We describe the synthesis of [bis(N-(3-tert-butylsalicylidene)anilinato)] titanium (IV) dichloride (Ti-FI complex) and examine the effects of comonomer (feed concentration and type) on its catalytic performance and properties of the resulting polymers. Ethylene/1-hexene and ethylene/1-octene copolymers were prepared through copolymerization using Ti-FI catalyst, activated by MAO cocatalyst at 323 K and 50 psi ethylene pressure at various initial comonomer concentrations. The obtained copolymers were characterized by DSC, GPC and 13C-NMR. The results indicate that Ti-FI complex performs as a high potential catalyst, as evidenced by high activity and high molecular weight and uniform molecular weight distribution of its products. Nevertheless, the bulky structure of FI catalyst seems to hinder the insertion of α-olefin comonomer, contributing to the pretty low comonomer incorporation into the polymer chain. The catalytic activity was enhanced with the comonomer feed concentration, but the molecular weight and melting temperature decreased. By comparison both sets of catalytic systems, namely ethylene/1-hexene and ethylene/1-octene copolymerization, the first one afforded better activity by reason of easier insertion of short chain comonomer. Although 1-hexene copolymers also exhibited higher molecular weight than 1-octene, no significant difference in both melting temperature and crystallinity can be noticed between these comonomers.     

N‐Isopropylacrylamide/monoalkyl itaconate copolymers and N‐isopropylacrylamide/itaconic acid/dimethyl itaconate terpolymers

Temperature‐ and pH‐sensitive copolymers and terpolymers of N‐isopropylacrylamide (NIPAAm) with itaconic acid (IA), monomethyl itaconate (MMeI), monobutyl itaconate (MBuI), monooctyl itaconate (MOcI), monocetyl itaconate (MCeI), and dimethyl itaconate (DMI) were prepared by free radical solution polymerization method. The dependence of coil‐to‐globule transition on pH and composition, molecular structures, and reactivities of monoalkyl itaconates, molecular weight distributions, and glass transition temperatures of copolymers and terpolymers were investigated using FT‐IR and UV–visible spectroscopic techniques, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and acid–base titration methods. The temperature‐/pH‐dependent coil‐to‐globule transition measurements showed that, upon increasing the content and length of alkyl chains, the lower critical solution temperatures (LCSTs) were shifted to higher temperatures. This meant that with increase in the length of hydrophobic alkyl chain in the monoitaconates intramolecular intreactions between the carboxyl groups were suppressed and LCSTs increased. The aqueous solution behaviors of NIPAAm/IA/DMI terpolymers also revealed that, even if the terpolymer hydrophobicity is increased by adding DMI units, the presence of IA units overcame the decrease in hydrophilicity of the terpolymers. The presence of DMI units in the terpolymers balanced the hydrophilic character of IA. DSC results supported the ones obtained from the pH‐dependent coil‐to‐globule transition measurements. An increase in both the chain length of alkyl groups attached to the monoitaconates and the contents of the mono‐ and dialkyl itaconates in the copolymers and terpolymers decreased the T_gs. In the case of NIPAAm/IA and NIPAAm/MMeI copolymers, the presence of the carboxyl groups forming hydrogen bonds increased the T_g, while the monoalkyl and dialkyl itaconates such as MBuI, MOcI, MCeI and DMI lead to a decrease in T_g of copolymers and terpolymers because of the suppression of intramolecular interactions (resulting from the ? COOH and ? COO^? groups) through the longer alkyl spacers. The dependence of the thermosensitivity of these NIPAAm copolymers and terpolymers on different conditions of pH, and the nature and content of comonomers suggests that they can be useful in biotechnology and drug delivery applications which involve small changes in pH and temperature. Copyright © 2009 John Wiley & Sons, Ltd.     

Observation of different catalytic activity of various 1-olefins during ethylene/1-olefin copolymerization with homogeneous metallocene catalysts

This research aimed to investigate the copolymerization of ethylene and various 1-olefins. The comonomer lengths were varied from 1-hexene (1-C?) up to 1-octadecene (1-C??) in order to study the effect of comonomer chain length on the activity and properties of the polymer in the metallocene/MAO catalyst system. The results indicated that two distinct cases can be described for the effect of 1-olefin chain length on the activity. Considering the short chain length comonomers, such as 1-hexene, 1-octene and 1-decene, it is obvious that the polymerization activity decreased when the length of comonomer was higher, which is probably due to increased steric hindrance at the catalytic center hindering the insertion of ethylene monomer to the active sites, hence, the polymerization rate decreased. On the contrary, for the longer chain 1-olefins, namely 1-dodecene, 1-tetradecene and 1-octadecene, an increase in the comonomer chain length resulted in better activity due to the opening of the gap aperture between C(p)(centroid)-M-C(p)-(centroid), which forced the coordination site to open more. This effect facilitated the polymerization of the ethylene monomer at the catalytic sites, and thus, the activity increased. The copolymers obtained were further characterized using thermal analysis, X-ray diffraction spectroscopy and 13C-NMR techniques. It could be seen that the melting temperature and comonomer distribution were not affected by the 1-olefin chain length. The polymer crystallinity decreased slightly with increasing comonomer chain length. Moreover, all the synthesized polymers were typical LLDPE having random comonomer distribution.     

Thermal properties of ethylene/long chain α-olefin copolymers produced by metallocenes

Metallocene type copolymers of ethylene with the α-olefins 1-octene, 1-tetradecene and 1-octadecene were characterized by dynamic scanning calorimeter (DSC) and by dynamic mechanical analysis (DMA). At a similar comonomer content above 3 mol%, the higher α-olefins gave lower melting points, crystallinities and densities than 1-octene. In DSC a separation technique sorting the crystalline sequence lengths of the polymer into groups was applied, and DSC index, DI, which gave a semiquantitative idea of the chemical homogeneity of the comonomer compositional distributions. By DMA the storage modulus as an indicator of stiffness and loss modulus and loss tangent as a measure of the effect of branching on the β relaxations were studied. The DMA measurements showed the loss modulus maximum to be a more sensitive value than the loss tangent maximum for the characterization of the comonomer distribution. The intensity of the β transition of 1-octadecene did not increase with increasing branching in contrast to the situation for 1-octene and 1-tetradecene copolymers.     

Pressure–Volume–Temperature properties of polyolefin liquids and their melt miscibility

The pressure–volume–temperature (P–V–T) properties of a number of metallocene-produced polyolefins were measured experimentally at 10 MPa ≤ P ≤ 200 MPa and 30°C ≤ T ≤ 220°C in a dilatometer-type P–V–T apparatus. These included ethylene copolymers typical of linear low density polyethylene, with several α-olefins as comonomers and a wide range of comonomer content. The experimental P–V–T data were correlated with the equations of state from the Sanchez–Lacombe and Flory–Orwoll–Vrij theories. The solubility parameter map of the polyolefins, at atmospheric pressure, was established on the basis of the thermodynamic data. As the temperature increases, the solubility parameter of the polyolefin decreases. The solubility parameters of copolymers of ethylene with propylene, butene, hexene, and octene under constant temperature are all more or less the same at equal weight percent of comonomer. As the incorporation of branches increases, the solubility parameter decreases. The melt miscibility of the polyolefin blends can be predicted to design various blend products for specific applications from this solubility parameter map. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2835–2844, 1999     

Olefin oligomerization,homopolymerization and copolymerization by late transition metals supported by (imino)pyridine ligands

In this review, the key advances achieved over more than 10 years on the design and development of (imino)pyridyl transition metal complexes as catalyst precursors for the transformation of ethylene, higher α-olefins and cyclic olefins into either linear/branched homopolymers or oligomers are highlighted. Particular attention has been paid to the relationships between the catalytic activity exhibited by the catalysts and their electronic and geometrical structure.     

Synthesis and biodegradability of amylose block copolymers

The synthesis of amylose block co-and terpolymers is described. Fully acetylated amylose triacetate was hydrolyzed by hydronium ions to give a hydroxy-terminated amylose triacetate oligomer (HATA), which was reacted with diisocyanates to produce block copolymers. Prepolymers of HATA and MDI or TDI were reacted with both hydroxy-terminated polybutadiene and polypropylene glycol to form block terpolymers. Block co- and terpolymer formation was demonstrated by intrinsic viscosity increases, gel permeation chromatographic results, and NMR and IR spectroscopy. The products were easily deacetylated by NaOMe in methanol to yield amylose block co- and terpolymers. These polymers were readily degraded by α-amylase. The enzymatic hydrolysis was monitored by intrinsic viscosity measurements. The rate of biodegradation was influenced by the DS of the amylose block and the composition of the block terpolymers.     

Amphiphilic comb-shaped polymers from poly(ethylene glycol) macromonomers

Comb-shaped amphiphilic graft copolymers composed of hydrophobic backbones and hydrophilic side chains were prepared by radical copolymerization of poly(ethylene glycol) monomethacrylate macromonomers, and methacrylate and acrylate comonomers in toluene. The copolymerizations were very sensitive to the reaction conditions, and insoluble cross-linked gels were easily formed. The yields of soluble copolymers were affected by the initiator concentration, the macromonomer concentration, and the choice of chain transfer agents and comonomers. Solubilities of the copolymers in water or methanol were found to depend on the sizes and the numbers of the PEG side chains. The copolymers showed surface activity with CMC:s in the order of 0.1–1.5 g/L and surface tensions of 36–56 dyn/cm. When tested as emulsifiers most of the copolymers gave oil-in-water type emulsions at room temperature. Polymers carrying MPEG 2000 side chains were crystalline with melting points of 38–44°C, while those based on PEG 400 and 1000 were mostly amorphous with glass transition temperatures between -55 and -60°C. © 1992 John Wiley & Sons, Inc.     

Thermotropic liquid-crystalline copolyesters containing substituted phenylene terephthalate and ethylene terephthalate units

Three series of aromatic, thermotropic copolyesters, based on terephthalic acid (TA), ethylene glycol (EG), and another diol were prepared. The third monomer was selected from three different hydroquinones including, ethoxyhydroquinone (EHQ), phenylhydroquinone (PHQ), and hydroquinone itself (HQ). The amounts of the different hydroquinone terephthalate units were varied while the amounts of ethylene terephthalate units remained constant. The copolymers and terpolymers were characterized for solubility, for morphology by polarized light microscopy (PLM), for molecular weight by solution viscometry, and by NMR, DSC, and TGA. At elevated temperatures all samples, when observed by PLM, displayed the characteristic texture of a nematic phase. The melting transition temperatures, T_m, were found to vary from 255 to 325°C, while the 5 wt % loss temperatures, T_d, were found to vary from 330 to 440°C. The inherent viscosities varied from 0.6 to 1.9 dL/g. Increases in the HQ monomer content caused a decreased solubility and an increase in melting point. Copolymer compositions determined by NMR showed that only about one-half of the EG added was incorporated into the copolymers. © 1997 John Wiley & Sons, Inc.     

Co-oligomerization of ethylene and higher linear alpha olefins. I. Co-oligomerization with the sulfonated nickel ylide-based catalytic system

Co-oligomers of ethylene and a series of linear α-olefins (propylene, 1-butene, 1-hexene, 1-heptene, 1-octene, and 1-decene) were synthesized with a homogeneous catalyst consisting of sulfonated nickel ylide and diethylaluminum ethoxide at 90°C. GC analysis of the co-oligomerization products allowed complete structural identification of all reaction products, α-olefins with linear and branched chains, vinylidene olefins, and linear olefins with internal double bonds. The article describes the reaction scheme of ethylene–olefin co-oligomerization. The scheme includes chain initiation reactions (insertion of ethylene or an olefin into the Ni? H bond), chain propagation reactions, and chain termination reactions via β-hydride elimination. Primary and secondary inertions of α-olefins into the Ni? H bond in the initiation stage proceed with nearly equal probabilities. Higher olefins participate in the chain growth reactions (insertion into the Ni? C bond) also both in primary and secondary insertion modes. The primary insertion of an α-olefin molecule into the Ni? C bond produces the β-branched Ni? CH₂? CR₁R₂ group. This group is susceptible to β-hydride elimination with the formation of vinylidene olefins. However, the Ni? CH₂? CR₁R₂ groups can participate in further ethylene insertion reactions and thus form vinyl oligomerization products with branched alkyl groups. On the other hand, the secondary insertion of an α-olefin molecule into the Ni? C bond produces the α-branched Ni? CR₁R₂ bond which does not participate in further chain growth reactions and undergoes the β-hydride elimination reaction with the formation of linear reaction products with internal double bonds. Most co-oligomer molecules contain only one α-olefin fragment. However, the analysis of ethylene-propylene and ethylene-1-heptene co-oligomers allowed identification of products with two olefinic fragments which are also formed in the copolymerization reactions with small yields.     

Effect of branching on the thermal properties of novel branched poly(4‐ethyleneoxy benzoate)

Poly(4‐ethyleneoxy benzoate) (PEOB) was synthesized by the self‐condensation of ethyl 4‐(2‐hydroxyethoxy) benzoate (E4HEB) under transesterification conditions. Branched PEOB was prepared by the condensation of E4HEB with an AB₂ monomer, ethyl 3,5‐bis(2‐hydroxyethoxy) benzoate (EBHEB), under similar conditions. Varying amounts of branching (0–50%) were introduced into the linear polymer by changes in the composition of the comonomers in the feed. The solution viscosity of the polymers indicated that they had reasonable molecular weights; the extent of branching in these copolymers was established from their ¹H NMR spectra. Differential scanning calorimetry studies indicated that, as expected, the introduction of branching drastically affected the percent crystallinity of the copolymers (as seen from their ΔH_m, the enthalpy of melting), and when the extent of the incorporation of the AB₂ monomer exceeded 10 mol %, the copolymers were completely amorphous. The melting temperatures of the copolymers decreased with an increase in the branching content, whereas the peak crystallization temperature in quenched (amorphous) samples followed the exactly opposite trend. The glass‐transition temperatures (T_g) of the branched copolymers first decreased at low extents of branching, passed through a minimum, and then increased to attain the T_g of the pure hyperbranched polymer of EBHEB. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 261–268, 2000     

Radiation-induced terpolymerization of methyl α,β,β-trifluoroacrylate with tetrafluoroethylene and α-olefin

Radiation-induced terpolymerizations of methyl α,β,β-trifluoroacrylate (MTFA) with tetrafluoroethylene (TFE) and α-olefins, such as ethylene, propylene, and isobutylene, were carried out in bulk at 25°C for the purpose of controlling the content of ester group in the MTFA-α-olefin alternating copolymers. These monomers polymerized to form alternating terpolymers which contained 50 mole % α-olefin in a wide range of monomer composition. The content of MTFA, namely, the ester group in polymer, can be varied without destruction of the alternating structures between fluoroolefins (MTFA, TFE) and α-olefin by changing the MTFA/TFE ratio in the monomer mixture. The relative reactivities of MTFA and TFE in the terpolymerization were discussed according to kinetic treatments by free propagating and complex mechanisms. The relation between the MTFA/TFE ratio in the monomer mixture and that in terpolymer was explained favourbly by the complex mechanism. It was also concluded that the relative reactivity of MTFA is larger than that of TFE in the terpolymerizations.