COORDINATION COPOLYMERIZATION OF STYRENE WITH MALEIC ANHYDRIDE BY RARE-EARTH COORDINATION CATALYSTS

The study on coordination copolymerization of styrene (S) with maleic anhydride (MA) by rare-earth coordination catalysts, NdL_3-Al(i-Bu)_3, has been successfully carried out for the first time. Some features, kinetic behavior, and mechanism of the SMA copolymerization by Nd(naph)_3-Al(i-Bu)_3 system are described and discussed. The copolymex of styrenemaleic anhydride prepared by the NdL_3-Al(i-Bu)_3 systems in benzene at 50℃ is an alternating-rich white powder having high number-average molecular weight of 6—8.5×10~5. The overall activation energy for the polymerization was found to be 10.5KJ/mol. The polymerization was not suppressed by addition of hydroquinone. The catalytic activity of various ligands in NdL_3 for the copolymerization decreases in the following order: Nd (naph)_3>Nd-(P_(507))_3～NdCl_3-6H_2O>Nd(P_(204))_3>Nd(acac)_3. 3H_2O. The experimental results are explained based on a mechanism to be the coordination-type copolymerization in terms of the participation of a monomer-monomer c     

HETEROCYCLIC SCHIFF BASE NEODYMIUM COMPLEX AS CATALYST FOR RING-OPENING POLYMERIZATION OF ε-CAPROLACTONE

An aromatic heterocyclic Schiff base neodymium complex bearing thiazole was synthesized and its activity in the ring-opening polymerization ofε-caprolactone(CL)was examined.The conditions of the CL/Nd molar ratio,monomer concentration,polymerization time and temperature were investigated.Activities of ca.171 kg/Nd·h were obtained under the optimum condition(CL/Nd=1600(molar ratio),[CL]=2.26 mol L~(-1),1 h at 50℃),giving a poly(ε-caprolactone)(PCL)of number-average molecular weight M_n=5.4×10~4 and molecular weight distribution MWD=1.96.The conversion of CL monomer as high as 94% was observed after polymerized for one hour.The mechanism of coordination polymerization has also been illustrated.     

STUDIES ON TiCI4/Mg (OEt)_2/EB SUPPORTED CATALYSTS FOR PROPYLENE POLYMERIZATION

The supported catalysts for propylene polymerization were prepared by milling Mg (OEt)_2 with EB (ethylbenzoate) and treating with TiCl_4 solution. When TiCl_4/(Mg(OEt)_2/EB) (mol.) ratio was increased, decrease in contents of-OEt and Ti of the catalysts was observed, while the content of EB increased. It is proved by analyses of IR, X-ray and XPS that during co-milling Mg(OEt)_2 with EB no reactions have taken place. But after treatment with TiCl_4 solution, Mg(OEt)_2 converts into MgCl_2 and EB coordinates on the resulting MgCl_2 carrier, a surface complex forms.The activity of catalysts,isotacticity and vicosimetric molecular weight of polypropylene increase with the decrease of the content of ethoxyl group. The kinetic curves of propene polymerization obtained with present catalysts system display decay curves. It is found from the triad tacticity calculated from the expanded spectra of methyl carbon region that, ethoxyl group in catalyst has an effect on the configuration of polymer chain.     

A highly active neodymium chloride isopropanol complex/modified methylaluminoxane catalyst for preparing polyisoprene with high cis-1,4 stereospecificity and narrow molecular weight distribution

<正>Neodymium chloride isopropanol complex(NdCl_3·3~iPrOH) activated by modified methylaluminoxane(MMAO) was examined in isoprene polymerization in hexane,with regards to Nd compounds,aluminum(Al) compounds,[Al]/[Nd] ratio,polymerization temperature and time.NdCl_3-3~iPrOH exhibited high activity producing polymers featuring high cis-1,4 stereospecificity(96%),very high molecular weight(M_n1.0×10~6) and fairly narrow molecular weight distribution (MWD,M_w/M_n2.0) simultaneously.In comparison,neodymium isopropoxide also showed high activity providing polymers with narrow MWD(M_w/M_n = 2.07),but somewhat low cis-1,4 content(ca.92%),while neodymium chloride had no activity under present polymerization conditions.The Al compounds affected the polymer yield in the order of Al(i-Bu)_3MMAOAl(i-Bu)_2H.MMAO as cocatalyst afforded polyisoprene with high M_n over 1.0×10~6,whereas as stronger chain transfer agent than MMAO,Al(i-Bu)_3 and Al(i-Bu)_2H yielded polymers with low M_n(1.0×10~5-8.0×10~5). NdCl_3·3~iPrOH/MMAO catalyst showed a fairly good catalytic activity even at relatively low[Al]/[Nd]ratio of 30,and the produced polymer remained high cis-1,4 content of 95.8%along with high M_n over 1.0×10~6 even at elevated temperatures up to 70℃.The polymerization rate is of the first order with respect to the concentration of isoprene.The mechanism of active species formation was discussed preliminarily.     

PREPARATION AND CHARACTERIZATION OF cis-,4-POLYBUTADIENE CONTAINING A FRACTION OF trans-1,4-POLYBUTADIENE

Polymerization of butadiene catalysed first with V(acac)_3-Al(i-Bu)_2Cl, then with Co(acac)_3-H_2O-Al(i-Bu)_2Cl has been studied. The polymer obtained was identified to be a new variety of cis-1,4-polybutadiene which contained a fraction of trans-1,4-polybutadiene chemically bonded to the cis-1,4-polybutadiene chains. Its molecular weight and trans-1,4 content can be regulated by varying the catalyst composition and concentration as well as other polymerization conditions. The trans-1,4 fraction, although it presents only in 9—16%, forms a crystalline phase in the matrix at room temperature and facilitates the crystallization of the polymer.     

RING OPENING COPOLYMERIZATION OF SUCCINIC ANHYDRIDE-ETHYLENE OXIDE BY Al(Ⅲ) ORGANOMETALLIC CATALYSTS

Ring opening copolymerization of succinic anhydride (SA) with ethylene oxide (EO)was successfully carried out by using a series of aluminum-based catalyst in 1,4-dioxane at62±2℃. The results showed that in-situ AlR_3-H_2O (R=ethyl, iso-butyl) catalysts gavehigher molecular weight (M_w～10~4), while Al(OR)_3 catalysts gave the higher alternatingcopolymer structure with slightly lower molecular weight. The in-situ AlR_3-H_2O systemshave been evaluated in more detail for the reaction which showed the optimum H_2O/Almolar ratio to be 0.5. The copolymers with different composition (F_(SA)/F_(EO)= 36/64to 45/55 mol/mol) were synthesized by using different monomer feed ratio. The melt-ing point (T_m), glass transition temperature (T_g) and enthalpy of fusion (ΔH_f) of thesecopolymers are depended on the copolymer composition and in the range of 87～102℃,-12～-18℃, and 37～66J/g, respectively. The second heating scan of DSC also in-dicated that the higher alternating copolymer was more easily recrystallized. The onsetdecomposition temperature was more than 300℃ under nitrogen and influenced by thecopolymer composition.     

Studies on the Self-condensing Vinyl Polymerization of a Novel Maleimide Inimer

The self-condensing vinyl polymerization(SCVP) of a novel maleimide inimer(initiator-monomer) 1, N-(4-α-bromobutyryloxy phenyl) maleimide with the complex of CuBr/Bipy (2, 2‘-bipyridine) as the catalyst was studied. GPC was used to determine the molecular weight and the results show that the molecular weight increases exponentially with polymerization time during the first hour, and then the rate of increase molecular weight slows down. The molecular weight also increases with increasing dosage of the catalyst. The coincidence of the molecular weights determined by ^1H NMR and GPC proves that the polymer obtained from the SCVP of inimer 1 has a linear structure, whichis further verified by ^13C NMR spectrum. A hyperbranched polymer was obtained by the copolymerization of inimer 1 and styrene.     

Molecular chain properties of poly (N-isopropyl acrylamide)

A series of poly( N-isopropyl acrylamide) (PNIPAM) samples with molecular weight ranging from 2.23×10~4 to 130×10~4 and molecular weight distribution M_w/M_n≤1.28 were obtained by free radical polymerization and repeat precipitation fractionation. The molecular weight M_w, second virial coefficient A_2 as well as the mean-square-root radius of gyration 〈S~2〉 for PNIPAM samples in tetrahydrofuran (THF) were determined by light scattering, and the relations were estimated at A_2 ∞ M_w~0.25) and 〈S~2〉~(1/2)=1.56×10~(-9) M_w~(0.56). The intrinsic viscosity for THF solution and methanol solution of PNIPAM samples was measured and the Mark-Houwink equations were obtained as [η]=6.90×10~(-5) M~(0/73) (THF solution) and [η]=1.07×10~(-4) M~(0.71) (methanol solution). The above results indicate that both THF and methanol are good solvents for PNIPAM. The limit characteristic ratio C_∞ for PNIPAM in the two solutions was determined to be 10.6 by using Kurata-Stockmayer equation, indicating that the f     

SYNTHESIS AND CHARACTERIZATION OF FOUR-ARMED BLOCK POLY(STYRENE-b-p-NITROPHENYL METHACRYLATE)PREPARED BY THE ATRP METHOD*

A novel tetrafunctional initiator, C [CH_2O (CH_2)_3 OOCCH(Br)CH_3]_4 (1), was synthesized through the reaction oftetraol with α-bromopropionyl chloride, and then was used as initiator of atom transfer radical polymerization (ATRP) in thepreparation of 4-armed polystyrene (PSt) with narrow polydispersity. The structure, molecular weight and molecular weightdistribution (MWD) of each arm were studied by ~1H-NMR and GPC data of hydrolyzed products of the 4-armed PSt. TheATRP of St using 1/CuBr/bpy as initiator system is of "living" character based on the following evidence: narrow MWD,constant concentration of chain radical during the polymerization, control of molecular weight by the molar ratio of monomerconsumed to 1. The 4-armed poly(St-b-p-nitrophenyl methacrylate) [poly(St-b-NPMA)] was prepared by the ATRP ofNPMA using 4-armed PSt with terminal bromine as the initiator, and characterized by FT-IR, ~1H-NMR spectra and GPCcurves. The micelles with PSt as core, and PNPMA as shell were formed by dropping DMSO into a solution of 4-armedpoly(St-b-NPMA) in DMF, as proved by laser light scatter (LLS) method.     

Neodymium-catalyzed Polymerization of C5 Fraction: Efficient Synthesis of 1,3-Pentadiene-isoprene Copolymer Rubbers

The polymerization of C5 fraction without separation and concentration by using a commercial available Nd(P204)3/ AliBu3/AlEt2Cl has afforded for the first time a new kind of 1,3-pentadiene-isoprene random copolymers as rubber materials. Isoprene (IP) and E-1,3-pentadiene (EPD) acted as polymerization monomers, cyclopentadiene acted as poison, and other substances like alkanes, monoolefins, Z-1,3-pentadiene acted as solvents in this multicomponent C5 fraction polymerization system. The data of kinetic experiments, NMR, and DSC indicated that the polymerization of C5 fraction by Nd(P204)3/AliBu3/AlEt2Cl afforded the IP-EPD random copolymers. By controlling polymerization conditions such as [Al]/[Nd]/[Cl] molar ratio and polymerization temperature, the random EPD-IP copolymers containing high cis-1,4-poly(IP)(with selectivity 96%) and moderate cis-1,4-poly(EPD)(with selectivity 60%) units with a low glass transition temperature (about 60 ℃), controllable molecular weight (Mn = 3.8 × 10^4-14.3 × 104), and moderate molecular weight distribution (Mw/Mn = 2.17-2.78) were obtained in a high yield.     

THE POLYMERIZATION OF ACETYLENE BY COORDINATION CATALYSTS COMPOSED OF NEODYMIUM COMPOUND, ALUMINUM TRIALKYL AND A THIRD COMPONENT

This paper describes the polymerization of acetylene by coordination catalysts composed ofvarious neodymium compounds, (Nd (P_(204))_3; Nd (P_(507))_3; Nd (NO_3)_3 3P_(350); Nd (BA)_3.2H_2O; andNd (acac)_3.2H_2O), aluminum trialkyl and an electron donor. The catalysts show fairly high catalyticactivity and high cis stereospecificity on acetylene polymerization at 30℃.     

Living polymerization of 1,3-butadiene catalyzed by half-titanocene complex bearing dibenzhydryl-substituted aryloxide ligand

Half-titanocene complexes bearing dibenzhydryl-substituted aryloxide ligands(2a-2d) were prepared. Among them, 2c adopted a three-legged distorted tetrahedral geometry evidenced by X-ray crystallography. The poly-1,3-butadiene with high molecular weight and narrow molecular weight distribution was obtained by using these complexes as the catalysts activated with methylaluminoxane(MAO). The catalytic activities of the complexes depended on their structures. The Ti―O―C bond in the complexes with large angle afforded them with higher activity, while Cp*-based complexes exhibited lower activities than the Cp-based analogues. The activity of complex increased with increasing the polymerization temperature while the selectivity remained no change, indicating the high thermal stability. Furthermore, the polymerization of 1,3-butadiene catalyzed by 2a/MAO at 0 °C has been found in a living fashion.     

RING-OPENING POLYMERIZATION OF ε-CAPROLACTONE BY LANTHANOCENE CATALYSIS*

Ring-opening polymerization of ε-caprolactone (CL) catalyzed bylanthanocenes, O(C_2H_4C_5H_3CH_3)_2YCl (Cat-YCl) and Me_2Si[(CH_3)_3SiC_5H_3]_2NdCl(Cat-NdCl) has been carried out for the first time. It has been found that both yttroceneand neodymocene are very efficient to catalyze the polymerization of CL, giving high molec-ular weight poly (ε-caprolactone) (PCL ). The effects of [cat] / [ε- CL] molar ratio, polymeriza-tion temperature and time, as well as solvents were investigated and polymerization tem-perature is found to be the most important factor affecting the polymerization. The bulkpolymerization gives higher molecular weight PCL and higher conversion than that in solu-tion polymerization. NaBPh_4 was found to promote the polymerization of ε-caprolactone,and thus to increase both the polymerization conversion and MW of poly (ε- caprolactone ).     

Promoting effect of nitrogen doping on carbon nanotube-supported RuO_2 applied in the electrocatalytic oxygen evolution reaction

RuO_2 nanoparticles supported on multi-walled carbon nanotubes(CNTs) functionalized with oxygen(OCNTs) and nitrogen(NCNTs) were employed for the oxygen evolution reaction(OER) in 0.1 M KOH.The catalysts were synthesized by metal-organic chemical vapor deposition using ruthenium carbonyl(Ru_3(CO)_(12)) as Ru precursor. The obtained RuO_2/OCNT and RuO_2/NCNT composites were characterized using TEM, H_2-TPR, XRD and XPS in order probe structure–activity correlations, particularly, the effect of the different surface functional groups on the electrochemical OER performance. The electrocatalytic activity and stability of the catalysts with mean RuO_2 particle sizes of 13–14 nm was evaluated by linear sweep voltammetry, cyclic voltammetry, and chronopotentiometry, showing that the generation of nitrogen-containing functional groups on CNTs was beneficial for both OER activity and stability. In the presence of RuO_2, carbon corrosion was found to be significantly less severe.     

稀土硫化物：e–己内酯开环聚合新催化剂

The ring-opening polymerization （ROP） of ε-caprolactone （ε-CL） using lanthanide thiolate complexes [（CH3CsH4）2Sm（μ-SPh）（THF）]2 （1） and Sm（SPh）3（HMPA）3 （2） as initiators has been investigated for the first time. Both of 1 and 2 were found to be highly efficient initiators for the ROP of ε-CL. The poly（ε-caprolactone） （PCL） with molecular weight Mn up to 1.97 ×10^5 and relatively narrow molecular weight distributions （1.20〈MW/Mn〈 2.00） have been obtained in high yield in the temperature range of 35-65℃. According to the polymer yield, 2 showed much higher activity than 1. However, the number-average molecular weight of PCL obtained with 2 was much lower than with 1. The possible polymerization mechanism of the ε-CL polymerization has been proposed based on the results of the end group analysis of the ε-CL oligomer.     

SINGLE LANTHANUM TRIS(N-PHENYLETHYL-3,5-DI-t-BUTYLSALICYLALDIMINATO)S INITIATOR FOR RING-OPENING POLYMERIZATION OF 1,4-DIOXAN-2-ONE IN BULK

A rare earth Schiff base complex:lanthanum tris(N-phenylethyl-3,5-di-t-butylsalicylaldiminato)s [La(OPEBS)_3] was successfully applied as single component initiator for the ring-opening polymerization of 1,4-dioxan-2-one (PDO) in bulk.The influence of reaction conditions,such as polymerization temperature,the molar ratio of the monomer to initiator (M/I) on the monomer conversion and molecular weight of the polymer has been investigated.Poly(1,4-dioxan-2-one) with a viscosity-average molecular weight (My...     

Rh/ZnO-Al2O3催化剂用于巴豆醛选择性加氢（英文）

Gas phase hydrogenation of crotonaldehyde was performed over 1 wt% Rh/ZnO-Al2O3 catalysts with various Zn/Rh atomic ratios. Monometallic Rh/Al2O3 was also prepared for comparison. The samples were prepared by the successive impregnation of Al2O3 with chlo-ride precursors of zinc and rhodium. The solids have been characterized by H2 chemisorption,temperature-programmed reduction,scanning electron microscopy,and cyclohexane dehydrogenation. Their catalytic behaviour in the gas phase crotonaldehyde hydrogenation reaction after reduction treatment in flowing hydrogen at 723 K was investigated. The relationship between catalytic activity,selectivity for crotyl alcohol,and physicochemical properties of the catalysts was examined. Results obtained showed that the presence of Zn clearly promotes the hydrogenation of the carbonyl bond. The catalyst with Zn/Rh atomic ratio of 5 displayed good catalytic stability and the highest selectivity for crotyl alcohol(70%) along with alloy formation.     

SYNTHESIS AND PROPERTIES OF HOMOPOLYMER AND COPOLYMERS OBTAINED FROM 1-OCTADECENE WITH ZIRCONOCENE CATALYSTS

Studies related to the behavior of different metallocene catalysts for the homopolymerization of 1-octadecene andits copolymerization with ethylene will be presented. The metallocenes: rac-Et(Ind)_2ZrCl_2, rac-Me_2Si(Ind)_2ZrCl_2 andPh_2C(Flu)(Cp)ZrCl_2 were chosen for the homopolymerization study. They show important differences in catalytic activity athigh temperatures (≥70℃), with rac-Et(Ind)_2ZrCl_2 showing the highest activity. At lower temperatures (≤30℃) thedifferences are negligible. For the copolymerization of ethylene with 1-octadecene only the catalysts rac-Et(Ind)_2ZrCl_2 andrac-Me_2Si(Ind)_2ZrCl_2 were studied. The results show that their catalytic activity is just like that for the homopolymerizationof 1-octadecene, with higher activity for the metallocene with the Et-bridged catalyst. ~(13)C-NMR analysis shows that thecomposition of the copolymerization products depends on the catalytic systems. Copolymers obtained with rac-Me_2Si(Ind)_2ZrCl_2 have greater comonomer incorporation. Thermal analysis shows that poly-1-octadecene synthesized withthe catalyst rac-Et(Ind)_2ZrCl_2 is very dependent on the polymerization temperature. The homopolymer obtained at 70℃presents two endothermal peaks at 41℃ and 53℃, as compared with the one obtained at 30℃ which presents one wider peakwith a maximum at 67℃. For the catalyst rac-Me_2Si(Ind)_2ZrCl_2 this trend is not observed. The type of metallocene and thereaction time do not significantly change the intrinsic viscosity, but the polymerization temperature changes it drastically,giving higher values at lower temperature. Viscosity measurements on the copolymers show that an increase of comonomerconcentration in the feed reduces the molecular weight of the copolymer, and it was also found that for homopolymer, themolecular weight is independent of the catalytic systems.     

SYNTHESIS AND APPLICATION AS POLYMER ELECTROLYTE OF HOMO- AND COPOLYMERS OF 3-(2-CYANO ETHOXY)METHYL- AND 3-(METHOXY(TRIETHYLENOXY))METHYL-3''''-METHYLOXETANE

Two oxetane-derived monomers, 3-(2-cyano-ethoxy)methyl- and 3-(methoxy-(triethylenoxy))methyl-3'-methyloxetane (COX and MTOX), were prepared from 3-hydroxymethyl-3'-methyloxetane. Their homo- and co-polymerization in solution were carried out by the cationic ring-opening polymerization with BF3·Et2O and 1,4-butanediol as co-initiator. The molecular weight and molecular weight distribution were determined using GPC so as to reveal the competition and interchange between active chain end (ACE) and activated monomer (AM) mechanism in the process. The reactivity ratios of the two monomers were calculated according to Kelen-Tudos using 1H-NMR analysis. The influence of functional side chains in the monomers on the copolymerization behaviors was discussed in virtue of the reactivity ratio data. When doped with lithium salt LiTFSI, the ion conductivity of the homopolymer of MTOX reached 10-3.58 S/cm at 30℃and 10-2.73 S/sm at 80℃, respectively, showing its potential to be used as polymer electrolyte for lithium ion battery.     

PREPARATION OF POLY （LACTIC ACID） THROUGH THIONYL CHLORIDE ACTIVATED POLYCONDENSATION

A two-step process was used to synthesize the high molecular weight poly (lactic acid) using thionyl chloride as an activator for the polycondensation of prepolymer of lactic acid.The products were characterized by GPC,DSC and 1H-NMR.Poly(L-lactic acid)(PLLA) with molecular weight Mw:32875 was obtained when thionyl chloride was used.while low molecular weight PLLA MW:7350 was yielded without thionyl chloride.Effects of the concentration of thionyl chloride,polymerization time and bases on the molecular weight of poly(lactic acid) were investigated.In DSC scans the glass transition temperatures(Tg)of the resulting polymers varied from 25.3 to 57.6℃.and the Tg of poly(L-lactic acid)was higher than that of poly (D,L0lactic acid)(PDLLA).The melting points of poly(L-lactic acid)and poly (D,L-lactic acid) could not be found unless the polymers were obtained by thionyl chloride activator.