Novel Complex Catalyst of η3‐(Pentamethylcyclopentadienyl)dimethylaluminum/Titanium(IV) Butoxide (Cp*AlMe2/Ti(OBu)4) for Syndiotactic Polystyrene

A novel metallocene catalyst was prepared from the reaction of (η³‐pentamethylcyclopentadienyl)dimethylaluminum (Cp*AlMe₂) and titanium(IV) n‐butoxide Ti(OBu)₄. The resulting titanocene Cp*Ti(OBu)₃ was combined with methylaluminoxane (MAO)/tri‐iso‐butylaluminum (TIBA) to carry out the syndiotactic polymerization of styrene. The resulting syndiotactic polystyrene (sPS) possesses high syndiotacticity according to ¹³C NMR. Catalytic activity and the molecular weight of the resulting sPSs were discussed in terms of reaction temperature, concentration of MAO, amounts of scavenger TIBA added, and the hydrogen pressure applied during polymerization.     

Reduced titanium dioxide as support for Ziegler–Natta catalysts

Titanium tetrachloride heterogenized on reduced TiO₂ has been studied as a catalyst for ethylene polymerization. The catalyst has good storage stability and exhibits good activity for ethylene polymerization. The polymer chains grow linearly during ca. 1 h, giving an average molecular weight of up to 2.5 × 10⁶ which indicates that practically no β-elimination occurs. The activity of the catalyst at 50°C, based on Ti(III), is 7.6 × 10⁶ PE/mol Ti h bar and based on the quantity of polyethylene formed it is 1.25 × 10⁶ g PE/mol Ti h bar. The molecular weight of the polymer can be controlled with the addition of hydrogen, under 0.5 bar hydrogen, polyethylene with a molecular weight of 411,000 and a relatively low polydispersity index of 2.2 is obtained. The catalyst shows good thermal stability; the Arrhenius activation energy is 31.8 kJ/mol for the polymerization. The catalyst is also active for propylene polymerization, giving 3 × 10⁶ g PP/mol Ti h bar with the high isotacticity of 93%. © 1994 John Wiley & Sons, Inc.     

Novel titanium complexes bearing two chelating phenoxy‐imine ligands and their catalytic performance for ethylene polymerization

Three substituted salicylaldimine ligands ( 1a, 2a, 3a ) and their titanium complexes bis[N‐(5‐nitrosalicylidene)‐2,6‐diisopropylanilinato]titanium(IV)dichloride ( 1 ), bis[N‐(5‐chlorosalicylidene)‐2,6‐diisopropylanilinato]titanium(IV)dichloride ( 2 ) and bis[N‐(5‐bromosalicylidene)‐2,6‐diisopropylanilinato]titanium(IV)dichloride ( 3 ) were synthesized and characterized by mass spectra, ¹H NMR and elemental analyses, as well as complex 1 by X‐ray structure analysis. In the presence of methylaluminoxane (MAO), 1, 2 and 3 are efficient catalysts for ethylene polymerization in toluene. Under the conditions of T = 60 °C, p = 0.2 MPa, and n(MAO)/n(cat) = 1500, the activities of 1–3 reached 4.55–8.80 × 10⁶ g of PE (mol of Ti h bar)^?1, which is much higher than that of the unsubstituted complex bis[N‐(salicylidene)‐2,6‐diisopropylanilinato]titanium(IV)dichloride ( 4 ). The viscosity‐average molecular weight of polyethylene ranged from 24.8 × 10⁴ to 44.9 × 10⁴ g/mol for 1–3 and the molecular weight distribution M_w/M_n from 1.85 to 2.34. The effects of reaction conditions on the polymerization were examined in detail. The increase in ethylene pressure and rise in polymerization temperature are favorable for 1–3 /MAO to rise the catalytic activity and the molecular weight of polyethylene. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis of poly(4‐vinylpyridine) by reverse atom transfer radical polymerization

Controlled radical polymerization of 4‐vinylpyridine (4VP) was achieved in a 50 vol % 1‐methyl‐2‐pyrrolidone/water solvent mixture using a 2,2′‐azobis(2,4‐dimethylpentanitrile) initiator and a CuCl₂/2,2′‐bipyridine catalyst–ligand complex, for an initial monomer concentration of [M]₀ = 2.32–3.24 M and a temperature range of 70–80 °C. Radical polymerization control was achieved at catalyst to initiator molar ratios in the range of 1.3:1 to 1.6:1. First‐order kinetics of the rate of polymerization (with respect to the monomer), linear increase of the number–average degree of polymerization with monomer conversion, and a polydispersity index in the range of 1.29–1.35 were indicative of controlled radical polymerization. The highest number–average degree of polymerization of 247 (number–average molecular weight = 26,000 g/mol) was achieved at a temperature of 70 °C, [M]₀ = 3.24 M and a catalyst to initiator molar ratio of 1.6:1. Over the temperature range studied (70–80 °C), the initiator efficiency increased from 50 to 64% whereas the apparent polymerization rate constant increased by about 60%. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5748–5758, 2007     

Solvent‐free ring‐opening polymerization of cyclohexene oxide catalyzed by palladium chloride

In this study, we have for the first time demonstrated that palladium chloride (PdCl₂) is an efficient catalyst for ring‐opening polymerization of cyclohexene oxide in a solvent‐free condition. The polymerization product was in atactic structure, and reaction conditions, such as reaction temperature, time, and catalyst amount, showed effects on polymerization conversion yield, turnover number, and number‐average molecular weight of the resulting poly(cyclohexene oxide). PdCl₂ catalysis follows a cationic ring‐opening mechanism. The polymerization result is highly determined by the chemical structure of the monomers.     

Synthesis and characterization of novel renewable polyesters based on 2,5‐furandicarboxylic acid and 2,3‐butanediol

Novel polyesters from 2,5‐furandicarboxylic acid or 2,5‐dimethyl‐furandicarboxylate and 2,3‐butanediol have been synthesized via bulk polycondensation catalyzed by titanium (IV) n‐butoxide, tin (IV) ethylhexanoate, or zirconium (IV) butoxide. The polymers were analyzed by size exclusion chromatography, nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy (FTIR), matrix‐assisted laser ionization‐desorption time‐of‐flight mass spectrometry, electrospray ionization time‐of‐flight mass spectrometry, electrospray ionization quadruple time‐of‐flight mass spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. Fully bio‐based polyesters with number average molecular weights ranging from 2 to 7 kg/mol were obtained which can be suitable for coating applications. The analysis of their thermal properties proved that these polyesters are thermally stable up to 270–300 °C, whereas their glass transition temperature (T_g) values were found between 70 and 110 °C. Furthermore, a material was prepared with a molecular weight of 13 kg/mol, with a T_g of 113 °C. This high T_g would make this material possibly suitable for hot‐fill applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Ultrahigh molecular weight polyethylene produced by a bis(phenoxy‐imine) titanium complex supported on latex particles

The applicability of latex particle supports for non‐Cp type metallocene catalysts for ethylene polymerization is presented. Polystyrene latex particles were prepared by miniemulsion polymerization and functionalized with poly(ethyleneoxide)chains and pyridyl groups on the surface. These latex particles were chosen to demonstrate that a support with nucleophilic substituents on the surface can act as a carrier for a (phenoxy‐imine) titanium complex (titanium FI‐catalyst) to produce ultrahigh molecular weight polyethylene (UHMWPE). The composition of the support, the concentration of pyridyl groups on the surface, and the crosslinking of the support were optimized to provide a system where the FI‐catalyst resulted in the formation of polyethylene with a M_w of more than 6,000,000 and a relatively narrow molecular weight distribution of 3.0 ± 0.5. High activities for long polymerization times greater than 6 h resulted in a catalyst system exhibiting productivities of up to 15,000 g PE/g cat. or 7,000,000 g PE/g Ti. The resulting polymer properties showed that nucleophilic groups on the latex particle support did not negatively impact the catalyst by blocking the active site but instead created a stable environment for the titanium catalyst. In particular, pyridyl groups on the surface of the latex particle stabilized the catalyst system probably by trapping trimethylaluminium. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3103–3113, 2006     

Preparation and characterization of new sol–gel titanium(IV) butoxide–cyanopropyltriethoxysilane hybrid sorbent for extraction of polar aromatic amines

A new titanium(IV) butoxide-cyanopropyltriethoxysilane (Ti-CNPrTEOS) hybrid material was successfully synthesized for the use as sorbent for the extraction of polar aromatic amines. The sorbent was synthesized by hydrolysis and condensation of titanium(IV) butoxide and cyanopropyltriethoxysilane with the presence of hydrochloric acid as catalyst via sol–gel method. Several factors influencing the synthesized sorbent such as solvent selection, mol of water content, ratio of titanium(IV) butoxide and cyanopropyltriethoxysilane and aging temperature were investigated and optimized. The sorbents were characterized by fourier transform-infrared, field-emission scanning electron microscopy-energy, CHN elemental analysis and thermogravimetric analysis. The applicability of the sorbents for the extraction of polar aromatic amines by the batch sorption method was extensively studied and evaluated. Under the optimum synthesis conditions (tetrahydrofuran as solvent, 1.2 M of hydrochloric acid catalyst, 4 mol of water content with ratio of titanium(IV) butoxide and cyanopropylteriethoxysilane of 1:1 and aging temperature of 60 °C), the extraction showed high recovery towards the extraction of polar aromatic amines. The synthesized sorbent was successfully applied for the extraction of selected aromatic amines via batch sorption method in waste water samples prior to the gas chromatography-flame ionization detector separation. The synthesized sol–gel Ti-CNPrTEOS sorbent demonstrated the potential as an alternative extraction sorbent with higher selectivity towards polar aromatic amines.     

SET‐RAFT of MMA mediated by ascorbic acid‐activated copper oxide

In this work, cupric oxide (CuO) or cuprous oxide (Cu₂O) was used as the catalyst for the single electron transfer‐reversible addition‐fragmentation chain transfer (SET‐RAFT) polymerization of methyl methacrylate in the presence of ascorbic acid at 25 °C. 2‐Cyanoprop‐2‐yl‐1‐dithionaphthalate (CPDN) was used as the RAFT agent. The polymerization occurred smoothly after an induction period arising from the slow activation of CuO (or Cu₂O) and the “initialization” process in RAFT polymerization. The polymerizations conveyed features of “living”/controlled radical polymerizations: linear evolution of number‐average molecular weight with monomer conversion, narrow molecular weight distribution, and high retention of chain end fidelity. From the polymerization profile, it was deduced that the polymerization proceeded via a conjunct mechanism of single electron transfer‐living radical polymerization (SET‐LRP) and RAFT polymerization, wherein CPDN acting as the initiator for SET‐LRP and chain transfer agent for RAFT polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of high molecular weight and narrow molecular weight distribution poly(acrylonitrile) via RAFT polymerization

Well‐defined polyacrylonitrile (PAN) of high viscosity‐average molecular weight (M_η = 405,100 g/mol) was successfully synthesized using reversible addition‐fragmentation chain transfer polymerization. The polymerization exhibits controlled characters: molecular weights of the resultant PANs increasing approximately linearly with monomer conversion and keeping narrow molecular weight distributions. The addition of 0.01 equiv (relative to monomer acrylonitrile) of Lewis acid AlCl₃ in the polymerization system afforded the obtained PAN with an improved isotacticity (by 8%). In addition, the influence of molecular weights and molecular weight distributions of PANs on the morphology of the electrospun fibers was investigated. The results showed that, under the same conditions of electrospinning, average diameter (247–1094 nm) of fibers increased with molecular weights of PANs, and it was much easier to get “uniform” diameter fibers while using PANs with narrow molecular weight distributions as the precursor of electrospinning. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

MgCl_2负载(dbm)_2Ti(OPh)_2催化乙烯聚合

烯烃聚合的新型非茂催化剂由于合成相对简便并具有一些新特点,近年来开始受到人们的关注[1,2].ＩＶＢ族金属的β二酮络合物与烷基铝或烷氧基铝形成的催化体系对烯烃聚合也显现出一定的聚合活性.在一定压力下,β二酮锆/ＭＡＯ均相催化乙烯聚合时具有较高聚合活性[3].β二酮钛催化剂对于丙烯无规聚合和苯乙烯间规聚合均有较好结果[4～6].本文将报道用ＭｇＣｌ2负载的二苯氧基二(二苯甲酰甲烷)钛络合物((ｄｂｍ)2Ｔｉ(ＯＰｈ)2),以甲基铝氧烷(ＭＡＯ)为助催化剂,常压催化乙烯聚合的结果.1　原料ＭｇＣｌ2为抚顺301厂产品.ＭＡＯ(1.4ｍｏｌ/Ｌ甲…     

Synthesis of high-molecular-weight poly(l-lactic acid) through the direct condensation polymerization of l-lactic acid in bulk state

A strategy was attempted to produce high-molecular-weight poly(l-lactic acid) (PLLA) through the direct condensation polymerization of l-lactic acid in bulk state. Polymerizations were carried out with titanium(IV) butoxide (TNBT) as a catalyst employing different duration of decompression, esterification and polycondensation. The molecular weights were characterized by using the gel permeation chromatography (GPC). The stereosequences were analyzed from the ¹³C NMR spectra on the basis of the triad fractions.     

Synthesis,characterization, and thermal stability of poly (lactic acid)/zinc oxide pillared organic saponite nanocomposites via ring‐opening polymerization of d,l‐lactide

Poly (lactic acid) (PLA) was synthesized using d , l ‐lactide monomer and zinc oxide (ZnO) pillared organic saponite as the green catalyst, through ring‐opening polymerization. The effects of stoichiometry of catalyst and polymerization conditions on molecular weight of PLA were evaluated by orthogonal experiment. The optimum polymerization parameters were: 0.5 wt% ZnO pillared organic saponite and reaction conditions of 170°C for 20 hr. Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance spectroscopy confirmed the PLA structure. Gel permeation chromatography showed that the average molecular weight of PLA was 48,442 g/mol, and its polydispersity index was 1.875. Differential scanning calorimetry, X‐ray diffraction, and polarized optical microscopy showed that ZnO pillared organic saponite improved the crystallinity of PLA. Thermal gravimetric analysis showed improved thermal stability of PLA because of ZnO pillared organic saponite. Thermal decomposition kinetics of PLA/ZnO pillared organic saponite nanocomposites was also studied. The activation energies (E_a) for thermal degradation of PLA and PLA/ZnO pillared organic saponite nanocomposites were evaluated by the Kissinger and Ozawa methods, which demonstrated that ZnO pillared organic saponite enhanced E_a of thermal degradation of PLA and significantly improved its thermal stability. Copyright © 2015 John Wiley & Sons, Ltd.     

Polymerization of 1‐hexene with bis[N‐(3‐tert‐butylsalicylidene)phenylaminato]titanium(IV) dichloride using iBu3Al/Ph3CB(C6F5)4 as a cocatalyst

1‐Hexene polymerization was investigated with bis[N‐(3‐tert‐butylsalicylidene)phenylaminato]titanium(IV) dichloride ( 1 ) using ⁱBu₃Al/Ph₃CB(C₆F₅)₄ as a cocatalyst. This catalyst system produced poly(1‐hexene) having a high molecular weight (M_w = 445 000–884 000, 0–60°C). ¹³C NMR spectroscopy revealed that the high molecular weight poly(1‐hexene) possesses an atactic structure with about 50 mol‐% of regioirregular units.     

Branched polyethylene prepared by in situ copolymerization of ethylene with monotitanocene and modified methylaluminoxane catalyst

Branched polyethylene was synthesized in heptane used as a polymerization medium with monotitanocene catalyst composed of η⁵‐pentamethylcyclopentadienyl tribenzyloxy titanium and modified methylaluminoxane (mMAO) that contained different amounts of residual trimethylaluminum (TMA). The residual TMA more strongly reduced Ti(IV) complexes to Ti(III) and Ti(II) ones, and Ti(IV) active species were suggested to be more effective for ethylene polymerization. Influences of the polymerization temperature and Al/Ti molar ratio on the catalytic activity and the degree of branching, branch length, and molecular weight of polyethylene were investigated. The obtained polymers were confirmed by ¹³C NMR to be higher molecular weight polyethylene containing significant amounts of isolated ethyl branches, butyl branches, or both. Branched polyethylene was prepared by the in situ copolymerization of ethylene with 1‐butene and 1‐hexene, which were formed through a proposed mechanism including metallcycloheptane and metallcyclopentane intermediates of Ti(II) species that were produced by the reaction of Ti(IV) complexes with TMA coexisting in mMAO. There was a remarkable increase in the chance of 1‐butene being produced from metallcyclopentane of Ti(II) intermediates with an increase in the polymerization temperature. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4258–4263, 2000     

Rapid ring‐opening polymerization of 1,4‐dioxan‐2‐one initiated by titanium alkoxides

Ring‐opening polymerization of 1,4‐dioxan‐2‐one in bulk was initiated by three titanium alkoxides, titanium dichlorodiisopropoxide (TiCl₂(OiPr)₂), titanium chlorotriisopropoxide (TiCl(OiPr)₃), and titanium tetraisopropoxide (Ti(OiPr)₄). The results indicate that the polymerization rate increased with number of OiPr groups in the initiator. High conversion of monomer (90%) and high molecular weight (11.9 × 10⁴ g/mol) of resulting polymer can be achieved in only 5 min at 60 °C with Ti(OiPr)₄ as an initiator. Analysis on nuclear magnetic resonance (NMR) spectra suggests the initiating sites for TiCl₂(OiPr)₂, TiCl(OiPr)₃, and Ti(OiPr)₄ to be 1.9, 2.6, and 3.8, respectively. Coordination‐insertion mechanism for the polymerization via cleavage of the acyl–oxygen bonds of the monomer was proved by NMR investigation. Kinetic studies indicate that polymerization initiated by Ti(OiPr)₄ followed a first‐order kinetics, with an apparent activation energy of 33.7 kJ/mol. It is noteworthy that this value is significantly lower than earlier reported values with other catalysts, namely La(OiPr)₃ (50.5 kJ/mol) and Sn(Oct)₂ (71.8 kJ/mol), which makes it an attractive catalyst for reactive extrusion polymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Microwave‐assisted polycondensation of 4‐octylaniline with dibromoarylene

The Pd‐catalyzed polycondensation of 4‐octylaniline with various dibromoarylenes was carried out under microwave heating. Microwave heating led to a decrease in the reaction time and an increase in the molecular weight of the polymers as compared to conventional heating. Microwave heating also allowed the catalyst loading to be reduced to 1 mol %, yielding polymerization results that were comparable to those under conventional heating and 5 mol % catalyst. Investigations regarding field‐effect transistors and organic photovoltaic cells using the obtained poly(arylamine) with azobenzene units revealed that increasing the molecular weight of the polymer led to improved device performance, including hole mobility and power conversion efficiency. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 536–542     

LCP aromatic polyesters by esterolysis melt polymerization

Polyarylates have previously been synthesized from acetate esters via esterolysis (loss of methyl acetate). This polycondensation can be extended to p‐substituted aromatic monomers for liquid crystal polyesters (LCPs). For AB‐type polymers, methyl p‐acetoxybenzoate and methyl 6‐acetoxynaphthoate were copolymerized to an LCP with reasonable molecular weights. Benzoate esters, methyl 4‐benzoyloxybenzoate (MBB) and methyl 6‐benzoyloxy‐2‐naphthoate (MBN), are also investigated. Several tin and antimony oxide catalysts were effective. The rate of esterolysis polymerization of MBB and MBN is slower than that of the corresponding acidolysis melt polymerization, but fast enough to give relatively high‐molecular‐weight polymers and similar thermal stability as commercial LCP prepared by acidolysis. Using these alternative benzoyloxy groups significantly reduced the color problem, because ketene loss cannot occur. Esterolysis melt polymerizations leading to AB/AABB‐type LCPs were performed using either dimethyl 2,6‐naphthalene dicarboxylate (DMND) or dimethyl terephthalate (DMT) with methyl 4‐acetoxybenzoate and phenylhydroquinone diacetate with tin and antimony catalysts. DMT‐based monomer compositions show much faster polymerization than DMND‐based compositions using antimony oxide catalyst. All these LCPs show a T_g in the 140–170 °C range as a result of the inclusion of the naphthalene and/or phenyl hydroquinone units in the polymer chain. Compositions completely off‐balanced on either side still lead to relatively high‐molecular‐weight copolyesters because either excess monomer can be removed during polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3586–3595, 2000     

Emulsion copolymerization of D,L‐lactide and glycolide in supercritical carbon dioxide

Biodegradable polyesters were synthesized via an emulsion polymerization in supercritical carbon dioxide (SC‐CO₂). Copolymers of lactide and glycolide were synthesized in SC‐CO₂ with stannous octoate as the ring‐opening catalyst and a fluorocarbon polymer surfactant as an emulsifying agent. The conversion of lactide and glycolide was monitored with respect to the reaction time and temperature with ¹H NMR spectroscopy. The conversion of glycolide surpassed 99% within 72 h for an SC‐CO₂ phase maintained at 200 bar and 70 °C. Under the same conditions, lactide conversion reached 65% after 72 h of polymerization. Unpolymerized monomer was removed after the reaction by extraction with an SC‐CO₂ mobile phase. The molecular weights of all the copolymers were measured by gel permeation chromatography. Weight‐average molecular weights (M_w) ranged between 2500 and 30,200 g/mol and polydispersity indices ranged from 1.4 to 2.3 for polymerization times of 6 and 48 h, respectively. Although the molecular weight increased significantly during the first 48 h of reaction, there was no significant difference in the M_w for polymerization times of 48 and 72 h. Emulsion polymerization within the benign solvent SC‐CO₂ demonstrated improved conversion and molecular weight versus polymers synthesized without surfactant. The emulsion polymerization of lactide and glycolide copolymers in SC‐CO₂ is proposed as a novel production technique for high‐purity, biodegradable polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 562–570, 2001     

Synthesis of ultrahigh molecular weight poly(N‐vinylcarbazole) with a high yield using low‐temperature heterogeneous‐solution polymerization

To prepare ultrahigh molecular weight (UHMW) poly(N‐vinylcarbazole) (PVCZ) with a high conversion, I heterogeneous‐solution‐polymerized N‐vinylcarbazole (VCZ) in methanol/tertiary butyl alcohol (TBA) at 25, 35, and 45 °C with a low‐temperature initiator, 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN), and I investigated the effects of the polymerization conditions on the polymerization behavior and molecular parameters of PVCZ. A low‐polymerization temperature with ADMVN, a heterogeneous system with methanol, and a low chain transfer with TBA proved to be successful in obtaining PVCZ of UHMW [weight‐average molecular weight (M_w) > 3,000,000] and high conversion (>80%) with a smaller temperature rise during polymerization but still of free‐radical polymerization by an azoinitiator. The polymerization rate of VCZ in methanol/TBA at 25 °C was proportional to the 0.97 power of the ADMVN concentration, indicating a heterogeneous nature for the polymerization. The molecular weight was higher and the molecular weight distribution was narrower with PVCZ polymerized at lower temperatures. For PVCZ produced in methanol/TBA at 25 °C with an ADMVN concentration of 0.0001 mol/mol of VCZ, an M_w of 3,230,000 was obtained, with a polydispersity index of 2.4. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 539–545, 2001