Ethylene Copolymerization with Linear and End-Cyclized Olefins via a Metallocene Catalyst:Polymerization Behavior and Thermal Properties of Copolymers

Olefin solution polymerization can be used to obtain high-performance polyolefin materials that cannot be obtained via other polymerization processes.Polyolefin elastomers(POE)are a typical example.Due to cost,only a few linear a-olefins(e.g.,1-butene,1-hexene,and 1-octene)are used as comonomers in solution polymerization in industry.However,a-olefin comonomers with other structures may have different effects on polymerization in comparison with common linear ones.Moreover,the properties of the corresponding materials may differ significantly.In this work,copolymers of ethylene with linear and endcyclized a-olefins are synthesized using a metallocene catalyst.The copolymerization of ethylene with linear a-olefins results in a higher turn-over frequency(TOF)and lower incorporation than copolymerization with end-cyclized a-olefins,which may indicate that end-cyclized a-olefins have a higher coordination probability and lower insertion rate.In this reaction,the comonomer is distributed randomly in the polymer chain and efficiently destroys crystallization.End-cyclized a-olefins exhibit a much stronger crystallization destructive capacity(CDC)in the copolymer than linear a-olefins,possibly because linear a-olefins act mainly in the radial direction of the main chain of the polymer,while end-cyclized a-olefins act mainly in the axial direction of the main chain.

i-PP/EPR REACTOR ALLOY PREPARED THROUGH ETHYLENE/PROPYLENE SLURRY COPOLYMERIZATION CATALYZED BY METALLOCENE SUPPORTED iPP PARTICLES

i-PP/m-EPR reactor alloy were prepared through ethylene/propylene slurry copolymerization catalyzed by metallocene(rac-Et(Ind)_2ZrCl_2)supported on porous iPP particles.Polar monomer(dihydromyrcene alcohol)treated with triethyaluminum was added in the preparation of porous iPP particles to introduce hydroxyl groups and thus enhance the ability for chemically supporting the metallocene catalyst.The effects of MAO/Zr ratio and monomer composition in feed on the reaction activity and property of polymer were i...

COPOLYMERIZATION OF ETHYLENE AND PROPYLENE WITH (CpCH_2CH_2CH=CH_2)_2MCl_2(M=Zr,Hf)AND Cp_2ZrCl_2 CATALYSTS

(CpCH_2CH_2CH = CH_2)_2MCl_2(M=Zr, Hf)/MAO and Cp_2ZrCl_2/MAO (Cp=cyclopentadienyl; MAO=methylaluminoxane) catalyst systems have been compared for ethylene copolymerization to investigate the influence of theligand and transition metal on the polymerization activity and copolymer properties. For both CH_2CH_2CH=CH_2 substitutedcatalysts the catalytic activity decreased with increasing propene concentration in the feed. The activity of the hafnocenecatalyst was 6～8 times lower than that of the analogous zirconocene catalyst, ^(13)C NMR analysis showed that the copolymerobtained using the unsubstituted catalyst Cp_2ZrCl_2 has greater incorporatien of propene than those produced byCH_2CH_2CH=CH_2 substituted Zr and Hf catalysts. The melting point, crystallinity and the viscosity-average molecularweight of the copolymer decreased with an increase of propenc concentration in the feed. Both CH_2CH_2CH= CH_2 substitutedZr and Hf catalysts exhibit little or no difference in the melting point and crystallinity of the produced copolymers. However,there are significant differences between the two zirconocene catalysts. The copolymer produced by Cp_2ZrCl_2 catalyst havemuch lower T_m and X_c than those obtained with the (CpCH_2CH_2CH=CH_2)_2ZrCl_2 catalyst. The density and molecular weightof the copolymer decreased in the order: (CpCH_2CH_2CH=CH_2)_2HfCl_2>(CpCH_2CH_2CH=CH_2)_2ZrCl_2>Cp_2ZrCl_2. The kineticbehavior of copolymerizaton with Hf catalyst was found to be different from that with Zr catalyst.

DFT Studies on Isoprene/Ethylene Copolymerization Catalyzed by Cationic Scandium Complexes Bearing Different Ancillary Ligands

The isoprene/ethylene copolymerization catalyzed by cationic rare earth metal complexes [（η5-C5Me5）Sc（CH2SiMe3）]＋ （A） had afforded alternating isoprene-ethylene copolymer with rich 3,4-polyisoprene microstructures,whereas no isoprene-ethylene copolymer was observed by using analogous [（PNpPh）Nc（CH2SiMe3）]＋ （B） under the same conditions.Theoretical calculations in this work have revealed that,in the case of A,successive 3,4-insertion of isoprene resulted in a noncovalent interaction between the C =C double bond of penultimate unit and the metal center,suppressing the further insertion of monomers due to higher energy barrier and endergonic character.On the other hand,the ethylene pre-inserted species with alkyl active site is more suitable for the subsequent kinetically and thermodynamically favorable isoprene insertion and copolymerization is therefore realized.In the case of B,the experimentally observed cis-l,4-specific homopolymerization of isoprene was the outcome of both kinetic and thermodynamic control.And,the unfavorable ethylene insertion into the isoprene pre-inserted species with allyl active site could account for the experimental finding that no isoprene-ethylene copolymer was obtained.These computational results are expected to provide some hints for the design of rare earth copolymerization catalysts.

SYNTHESIS OF POLY(ETHYLENE TEREPHTHALATE)-POLYCAPROLACTONE BLOCK COPOLYMER BY DIRECT COPOLYMERIZATION

Po ly(ethylene terephthalate)-polycaprolactone block copolymer (PCL-b-PET) is a polyester with improved biodegradability. In the present paper, a new direct copolymerization method of epsilon-caprolactone (epsilon-CL) and bishydroxyethylene terephthalate (BHET) in the presence of Ti(OBu)(4) was proposed for the synthesis of PCL-b-PET. The PCL-b-PET copolymer was characterized by IR, GPC and H-1-NMR techniques, and the effects of synthesis conditions, such as temperature, reaction time and concentration of catalyst on the copolymerization were discussed.

Vanadium(V) Complexes Containing Unsymmetrical N-Heterocyclic Carbene Ligands: Highly Efficient Synthesis and Catalytic Behavior towards Ethylene/Propylene Copolymerization

The highly efficient method has been developed for the synthesis of NHC·VOCl_(3) containing symmetrical or unsymmetrical Nheterocyclic carbene(NHC) ligands by the transmetallation reaction of NHC·AgCl with VOCl_(3).The total isolated yield of VOCl_(3)[1,3-(2,4,6-Me_(3)C_(6)H_(2))_(2)(NCH=)_(2)C:](V4') reached 86% by transmetallation reaction,which is much higher than that(48%) by direct coordination method.This methodology has also been used to synthesize the novel vanadium complexes containing unsymmetrical NHC ligands of VOCl_(3)[PhCH_(2)NCH=CHNR)C:](V5',R=2,4,6-Me_(3)C_(6)H_(2);V6',R=2,4-Me_(2)-6-Ph-C_(6)H_(2);V7',R=2,6-^(i)Pr_(2)-C_(6)H_(3)) with high yield,which could not be obtained by direct coordination method.The catalytic activity and copolymerization ability would be improved by introducing unsymmetrical NHC ligands due to their less steric bulky effect.The vanadium complex V5' containing unsymmetrical NHC ligand exhibits higher catalytic activity(3.7×10^(5)g_(copolymer)·mol^(-1) of V·h^(-1)) than that of V4' containing symmetrical NHC ligand.Moreover,the higher propylene incorporation ratio(45.6 mol%) in the copolymers of ethylene with propylene could be obtained by using V5' than that(39.9%) by using V4'.The results would provide a highly efficient strategy for the synthesis of early transition metal complexes containing versitile NHC ligands,affording the catalyst with both high catalytic activity and copolymerization ability for the synthesis of high performance polyolefin elastomers.

PREPARATION OF HIGH DENSITY POLYETHYLENE/POLYETHYLENE-BLOCK-POLY(ETHYLENE GLYCOL)COPOLYMER BLEND POROUS MEMBRANES VIA THERMALLY INDUCED PHASE SEPARATION PROCESS AND THEIR PROPERTIES

High density polyethylene （HDPE）/polyethylene-block-poly（ethylene glycol） （PE-b-PEG） blend porous membranes were prepared via thermally induced phase separation （TIPS） process using diphenyl ether （DPE） as diluent. The phase diagrams of HDPE/PE-b-PEG/DPE systems were determined by optical microscopy and differential scanning calorimetry （DSC）. By varying the content of PE-b-PEG, the effects of PE-b-PEG copolymer on morphology and crystalline structure of membranes were studied by scanning electron microscopy （SEM） and wide angle X-ray diffraction （WAXD）. The chemical compositions of whole membranes and surface layers were characterized by elementary analysis, Fourier transform infrared spectroscopy-attenuated total reflection （FTIR-ATR） and X-ray photoelectron spectroscopy （XPS）. Water contact angle, static protein adsorption and water flux experiments were used to evaluate the hydrophilicity, antifouling and water permeation properties of the membranes. It was found that the addition of PE-b-PEG increased the pore size of the obtained blend membranes. In the investigated range of PE-b-PEG content, the PEG blocks could not aggregate into obviously separated domains in membrane matrix. More importantly, PE-b-PEG could not only be retained stably in the membrane matrix during membrane formation, but also enrich at the membrane surface layer. Such stability and surface enrichment of PE-b-PEG endowed the blend membranes with improved hydrophilicity, protein absorption resistance and water permeation properties, which would be substantially beneficial to HDPE membranes for water treatment application.

Sound Absorption Properties of Discarded Feathers/Ethylene Vinyl Acetate Copolymer Thermoplastic Composite Materials

The discarded feathers / ethylene vinyl acetate copolymer( EVA) thermoplastic composite materials was obtained with discarded feathers as reinforced material and EVA powders as matrix material by hot pressing method. Sound absorption properties were studied by changing mass ratio of discarded feathers and EVA,thickness of composite materials,hot pressing pressure and hot pressing temperature. It was found that the sound absorption properties of composite materials were good when the mass ratio of discarded feathers and EVA was 1: 1,thickness of composite materials was 30 mm,hot pressing pressure was 8 MPa,and hot pressing temperature was 80 ℃. Under the optimum conditions,the effect of composite density on sound absorption property was analyzed. In a certain range,the sound absorption property was enhanced with the decrease of the composite density.When the composite density was 0. 1g /cm^3, the maximum absorption coefficient was 0.96. Finally,the capillary theory was used to calculate the maximum sound absorption coefficient of discarded feathers / EVA thermoplastic composite materials. The good agreements of experimental results and calculated results proved the validity of the theoretical models.

NMR SPECTROSCOPIC STUDY ON COPOLYMER OF ETHYLENE-NORBORNENE

A series of ethylene-norbornene copolymers were synthesized using VO (Oft) Cl-2/Al2Et3Cl3 catalytic system and their structure was characterized by H-1-NMR, H-1-H-1 COSY NMR and C-13-NMR. Assignments of NMR spectra were given and discussed in detail.

SYNTHESIS OF BRANCHED POLYETHYLENE USING (α-DIIMINE)NICKEL(Ⅱ)TiCl_4 COMBINED AND SUPPORTED CATALYST

Diimine)nickel {[C 6 H 5 -N = C(CH 3 ) - C(CH 3 ) = N - QH 5 ]NiBr 2 }-TiCl 4 , abbreviated as NiL-TiCl 4 combined catalyst which is supported on MgCl 2 -SiO 2 carrier has been prepared, by using alkyl aluminum (AlR 3 ) as the cocatalyst in place of methylaluminoxane (MAO) to catalyze ethylene oligomerization and copolymerization in situ. The influences of procedure for supporting NiL-TiCl 4 , the molar ratio of NiL to TiCl 4 , cocatalyst type and polymerization temperature on the catalytic performance were studied. The degree of branching and the composition of the branched chain of polymers produced have been investigated by IR and 13C-NMR spectra. The results show that the combined catalyst can synthesize the branched polyethylene with various banched chains .The polymerization reaction was monitored by gas chromatography and mass spectrometry (GC-MS). The results show that this catalyst promotes the oligomerization and copolymerization in situ for ethylene.

Embolization of brain arteriovenous malformations with squid co-polymer embolic material:Initial experience

Objective:To analyze the safety and effectiveness of the ethylene-vinyl alcohol copolymer(EVOH)liquid embolic agent Squid(Emboflu,Switzerland)for the treatment of brain arteriovenous malformations.Materials and procedures:Between April 2015 and July 2017,46 embolization treatments for brain arteriovenous malformations(BAVM)were performed in 25 patients using two Squid formulations(18 and 12).Six female and 19 male patients with a mean age of 34 years(range,9–62 years)were included.A total of 46 procedures were performed.The BAVMs were classified as Spetzler-Martin gradeⅡin 4 procedures,Ⅲin 27 procedures,and 1V in 15 procedures.Among the 25 patients,15 presented with hemorrhage,5 with seizures,and 5 with headache and neurology.The BAVMs were located in the temporal lobe in 5 patients,parietal lobe in 7 patients,frontal lobe in 3 patients,posterior fossa in 6 patients,basal ganglia in 3 patients,and parasagittal lobe in 1 patient.Results:The obliteration rate of the BAVMs ranged from 10%to 100%,with a mean of 33%.Most patients underwent their first or second embolization procedure.Four patients(8%)developed intracranial bleeding post procedure,with one death(2%).One patient(2%)experienced a seizure during the procedure;however,no intracranial bleeding was observed.Seven patients(15%)experienced perforations during catheter manipulation.One case(2%)of fractured catheter was recorded,but no significant complications were observed.The average volume of copolymer injected was 0.6 ml per nidus.Thirteen procedures used the Squid-12 formulation,29 procedures used the Squid-18 formulation,and 3 procedures used a combination of Squid-12 and-18 formulations.Conclusion:Squid is a safe and effective embolic agent for treating BAVMs.

COPOLYMERIZATION OF ETHYLENE AND 1-HEXENE WITH TiCl_4/MgCl_2 CATALYSTS MODIFIED BY 2,6-DIISOPROPYLPHENOL

A supported TiCl4/MgCl2 catalyst without internal electron donor （O-cat） was prepared firstly. Then it was modified by 2,6-diisopropylphenol to make a novel modified catalyst （M-cat）. These two catalysts were used to catalyze ethylene/l-hexene copolymerization and l-hexene homopolymerization. The influence of cocatalyst and hydrogen on the catalytic behavior of these two catalysts was investigated. In ethylene/l-hexene copolymerization, the introduction of 2,6- iPr2C6H3O- groups did not deactivate the supported TiCl4/MgCl2 catalyst. Although the 1-hexene incorporation in ethylene/1- hexene copolymer prepared by M-cat was lower than that prepared by O-cat, the composition distribution of the former was narrower than that of the latter. Methylaluminoxane （MAO） was a more effective activator for M-cat than triisobutyl- aluminium （TIBA）. MAO led to higher yield and more uniform chain structure. In 1-hexene homopolymerization, the presence of 2,6-ipr2C6H3O- groups lowered the propagation rate constants. Two types of active centers with a chemically bonded 2,6-iprzCaH3O- group were proposed to explain the observed phenomena in M-cat.

Synergistic Effects of the ZnCl_2-SiCl_4 Modified TiCl_4/MgCl_2/THF Catalytic System on Ethylene/1-Hexene and Ethylene/1-Octene Copolymerizations

The copolymerizations of ethylene with 1-hexene or 1-0ctene by using TiC14/MgCI2/THF catalysts modified with different metal halide additives （ZnCI2, SIC14, and the combined ZnC12-SiCl4） were investigated based on catalytic activity and copolymer properties. It was found that the catalyst modified with mixed ZnC12-SiC14 revealed the highest activities for both ethylene/1-hexene and ethylene/1-0ctene copolymerization. The increase in activities was due to the formation of acidic sites by modifying the catalysts with Lewis acids. Based on the FTIR measurements, the characteristic C--O--C peaks of the catalysts modified with metal halide additives were slightly shifted to lower wavenumber when compared to the unmodified catalyst. This showed that the modified catalysts could generate more acid sites in the TiC14/MgC12/THF catalytic system leading to an increase in activities as well as comonomer insertion （as proven by IaC-NMR）. However, Lewis acid- modifications did not affect the microstructure of the copolymers obtained. By comparison on the properties of copolymers prepared with the unmodified catalyst, it was found that polymers with ZnC12 and/or SIC14 modification exhibited a slight decrease in melting temperature, crystallinity and density. It is suggested that these results were obtained based on the different amount of ct-olefins insertion, regardless of the types of Lewis acids and comonomer.

The Use of Zinc Oxide Nanoparticles in Eva to Obtain Food Packing Films

The increasing demand for new packages with increased shelf life properties has stimulated the increase of research in the active packaging sector. The use of antimicrobial agents requires an in-depth study of their properties to avoid loss of efficiency of the polymer processing. In this context, the objective of this work was to evaluate the preparation of an 18% ethylene vinyl acetate copolymer (EVA) nanocomposite and zinc oxide (ZnO) as microbicidal nanoparticle, prepared in a monosulfon extruder. The nanoparticle was modified with octadecylamine and EVA 18 nanocomposite films were prepared and compared to the systems containing modified nanoparticle. These new materials were characterized by thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), Dynamic Mechanical Analysis (DMA), Time Domain Nuclear Magnetic Resonance (NMR) to investigate the effect of zinc oxide nanoparticles on thermal properties, EVA crystallinity and antimicrobial effect. The TGA showed a tendency of increase of the thermal stability in different proportions of ZnO. DSC results did not show significant changes in thermal parameters. The XRD analysis showed an increase in the degree of crystallinity of the nanocomposites in relation to the EVA matrix and change in the crystallinity with the increase of ZnO percentages. DMA analysis indicates change in structural organization through the variation of storage modulus, loss, and tan delta. Time domain NMR data corroborate with XRD data through the change in molecular mobility.

MOLECULAR AND SUPRAMOLECULAR ORDERING IN CONFINED ENVIRONMENTS

Crystal and phase morphologies and structures determined by self-organization of crystalline-amorphous diblockcopolymers, crystallization of the crystallizable blocks, and vitrification of the amorphous blocks are reviewed through asystematic study on a series of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymers. On the base ofcompetitions among these three processes, molecular and supramolecular ordering in confined environments can beinvestigated. In a concentration-fluctuation-induced disordered (D_(CF)) diblock copolymer, the competition between crystalli-zation of the PEO blocks and vitrification of the PS blocks is momtored by time-resolved simultaneous small angle X-rayscattering (SAXS) and wide angle X-ray diffraction (WAXD) techniques. In the case of T_c<T_g^(PS-rich), the crystallization of thePEO blocks is observed to be confined within the bicontinuous D_(CF) phase due to the rapid vitrification of the PS-rich phase.Overall crystallization rate, crystal melting behavior, and crystallinity results further confirm the competition betweencrystallization and vitrification at different temperatures. In an ordered lamellar PEO-b-PS diblock copolymer, the crystalli-zation of the PEO blocks is completely confined within the ordered lamellae due to rapid vitrification of the PS layers asobserved by time-resolved SAXS and WAXD experiments. From the combined two-dimensional SAXS and WAXDmeasurements, the crystal orientation within the confined lamellar geometry is found parallel to the lamellar surface normalwhen it is isothermally crystallized at 35℃. In an ordered cylindrical PEO-b-PS sample, the crystallization of the PEO blocksis also observed to be confined within the ordered cylinders because of rapid vitrification of the PS matrix. The crystalorientation within the confined cylinders is found perpendicular to the cylinder axis as it is crystallized at 35℃.

Flammability Characterization and Effects of Magnesium Oxide in Halogen-free Flame-retardant EVA Blends

The effects of magnesium oxide （MgO） on the flame retardant performance of intumescent systems based on ammonium polyphosphate （APP） and pentaerythritol （PER） in ethylene vinyl acetate copolymer （EVA） were studied. The results showed that MgO affects both the quality and quantity of residual char. There is an optimal value for the loading amount of MgO. More or less MgO loading may cause the formation of defective char layers and worsen the flame retardancy of EVA. According to the results of limiting oxygen index （LOI）, vertical flammability test （UL94 rating） and cone calorimetry （CONE）, the best flame retardancy with a strong and well intumescent char is obtained from the sample with 1 wt% of MgO, which has the highest LOI value of 27.9, UL94 rating of V-0 and the lowest peak heat release rate of 242 kW·m-2.