2-thiophenecarbonyl Chloride Research Articles

Efficient synthesis of the cyclo-olefin copolymers at high temperature and pressure in a homogeneous mini-tubular reactor

Ethylene-norbornene copolymer (ENC) is one of the most representative cyclo-olefin copolymer (COC). Both the amorphous and semi-crystalline ENCs were efficiently synthesized by the homogeneous solution copolymerization of ethylene (E) and norbornene (NB) using rac-Et(Ind)2ZrCl2/triisobutylaluminium/(Ph3C)B(C6F5)4 ternary catalyst system in a visualized mini-tubular reactor under high temperature (90–130 °C) and given pressure (24 bar). An ultra-high activity of 7.6 × 108 g/(molZr h), as well as considerable efficiency of 14.1 kgENC/gZr was achieved in time of only 30 s at E/NB molar ratio of 3:1. Moreover, a quench-labeling method using 2-thiophenecarbonyl chloride (TPCC) was adopted to calculate the high proportion of active center [C*]/[Zr]. The novel strategy was proposed for preparation of the block semi-crystalline ENC elastomers with excellent tensile performance and high transparency via reversible chain transfer based on spatiotemporal concentration distribution in a mini-tubular reactor.

Effect of alkylaluminum structure and aggregation state on the micro-kinetics of ethylene polymerization catalyzed by α-diimine nickel complex

2-thiophenecarbonyl chloride (TPCC) quenching method was used into the study of alkylaluminum activation behavior on α-diimine nickel catalysts. The influence of alkylaluminum structure (AlEt2Cl, Al2Et3Cl3, AlEtCl2 and modified methylaluminoxane (MMAO)) and polymerization temperature on the kinetic factors (active center concentration [C*] and chain propagation rate constant kp) of ethylene polymerization catalyzed by the system was systematically studied. It was found that, compared with MMAO, alkyl aluminum chloride could better activate catalyst and produced more active centers in the polymerization system, but the value of kp was lower than MMAO. Unexpectedly, as the polymerization temperature increased, [C*] in the polymerization system with AlEtCl2 as cocatalyst gradually increased, and kp decreased. But the change of [C*] and kp of the polymerization system with MMAO as cocatalyst was opposite. It was proposed that cocatalyst is one of the factors affecting the thermal stability of catalyst.

Kinetics and mechanistic investigations of ethylene-propylene copolymerizations catalyzed with symmetrical metallocene and activated by TIBA/borate

A set of ethylene-propylene (E-P) has been copolymerized by asymmetric metallocene catalysts i.e. silylene-bridged rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (SiPh) and ethylene-bridged rac-Et(Ind)2ZrCl2 (EBI) and cocatalyzed with triisobutylaluminum(TIBA)/ borate [Ph3C][B(C6F5)4] under similar conditions for different desire time. Quenching reaction of active center ([C*]/[Zr]) with 2-thiophenecarbonyl chloride (TPCC) for determining the "Sulfur “content. The obtained E/P copolymers were characterized with GPC, FT-IR, 13C-NMR and sulfur analyzer techniques. Changes in reactivity ratios "rE and rP" (reactivity ratio of ethylene (rE) and propylene (rP)), chain propagation rate Rp (chain propagation rate for ethylene ethylene (RpE) and chain propagation rate for propylene RpP respectively) molecular weight (Mw), molecular weight distribution (MWD), and chain propagation rate constant kp (propagation rate constant for E (kpE) and propagation rate constant for propylene (kpP) respectively) also discussed. The results of the kinetic constants, changing in the polymerization time (tP) exerted evident effects on [C*]/[Zr] and kp. At initial polymerization time lower [C*]/[Zr] with higher kp was observed in both metallocenes. Initial propagation rate constant kpE and kpP were quite large and quickly declined with polymerization time (tP). The fast decline of kpE and kpP with (tP) greatly attributing to serious diffusion restriction produced by the growing polymer chains. When (SiPh) was used in E/P copolymerization presented higher steady stage [C*]/[Zr] levels as compared to EBI/borate system, and the effect of (SiPh) catalyst structure on active center [C*]/[Zr] of E/P copolymerization was considerably stronger. By taking sight into the time-dependent variations of active caters [C*]/[Zr], chain structure, molecular weight distribution, and late initiation of the centers with lesser intrinsic reactivity are suggested to be the basic reasons for the steep decline of chain propagation rate constant with time. Based on kinetic data we also discussed the structure performance relationships of C2-symmetric metallocene.

Kinetic and thermal study of ethylene-propylene copolymerization catalyzed by ansa-zirconocene activated with Alkylaluminium/borate: Effects of linear and branched alkylaluminium compounds as cocatalyst

Ethylene-propylene (EP) copolymerizations was carried out with two ansa-metallocene: rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (Mt-I) and rac-Et(Ind)2ZrCl2 (Mt-II) combined with borates activators like ([Me2NPh][B(C6F5)4] (Borate-I), [Ph3C][B(C6F5)4] (Borate-II). Different structures of alkylaluminum( triethylaluminium (TEA), triisobutylaluminium (TIBA) and TEA/TIBA mixture of 25/75, 50/50, 75/25 mol ratios were used as cocatalysts. The choice of ligand structure and, more importantly, the nature of the cocatalyst significantly impact these systems' activity and the polymeric materials' properties. Borate-II has been shown as giving higher activities than Borate-I with both ansa-metallocene, attending 5.6 × 106 g/mol Zr*h. Mt-I gives higher activities and molecular weight but produced copolymers with low ethylene content, melting points, and crystallinity than Mt-II. The activities were very close to each other with 100% TIBA. Still, Mt-I became more active than Mt-II when TEA was more than 25% in the cocatalyst system. The effects of alkylaluminiums catalysts cocatalyst on EP copolymer molecular weight (Mw) and molecular weight distribution (MWD) were much more complicated. The MWD curve changed from broad to narrow with Mt-I when TIBA was replaced by a different mole ratio of TEA/TIBA ratio. The technique used for the assessment of active centers [C*]/[Zr] fraction in the ansa-metallocene catalyst was quenched label by using 2-thiophenecarbonyl chloride (TPCC) to determine the effects of alkylaluminiums catalysts structure on the propagation rate constants (kP) of EP copolymers. The [C*]/[Zr] value of Mt-I/Borate-I/TIBA is lower than those of the Mt-I/Borate-I/TEA and Mt-I/Borate-I/TEA/TIBA system. The main differences appear between catalysts containing pure TIBA and those containing TEA, possibly due to the faster rate of chain transfer with Al—Et than with bulky Al—iBu. Adding TEA in metallocene/borate/alkylaluminiums catalysts catalysts can be applied as an effective method to regulate the molecular weight of EP copolymer with a high degree of activity

Kinetic and Thermal Study of Ethylene and Propylene Homo Polymerization Catalyzed by ansa-Zirconocene Activated with Alkylaluminum/Borate: Effects of Alkylaluminum on Polymerization Kinetics and Polymer Structure.

The kinetics of ethylene and propylene polymerization catalyzed by homogeneous metallocene were investigated using 2-thiophenecarbonyl chloride followed by quenched-flow methods. The studied metallocene catalysts are: rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (Mt-I), rac-Et(Ind)2ZrCl2 (Mt-II) activated with ([Me2NPh][B(C6F5)4] (Borate-I), [Ph3C][B(C6F5)4] (Borate-II), and were co-catalyzed with different molar ratios of alkylaluminum such as triethylaluminium (TEA) and triisobutylaluminium (TIBA). The change in molecular weight, molecular weight distribution, microstructure and thermal properties of the synthesized polymer are discussed in detail. Interestingly, both Mt-I and Mt-II showed high activity in polyethylene with productivities between 3.17 × 106 g/molMt·h to 5.06 × 106 g/molMt·h, activities were very close to each other with 100% TIBA, but Mt-II/borate-II became more active when TEA was more than 50% in cocatalyst. Similarly, Polypropylene showed the highest activity of 11.07 106 g /molMt·h with Mt-I/Borate-I/TIBA. The effects of alkylaluminum on PE molecular weight were much more complicated; MWD curve changed from mono-modal in Mt-I/borate-I/TIBA to bimodal type when TIBA was replaced by different amounts of TEA. In PE, the active center fractions [C*]/[Zr] of Mt-I/borate were higher than that of Mt-II/borate and average chain propagation rate constant (kp) value slightly decreased with the increase of TEA/TIBA ratio, but the Mt-II/borate systems showed higher kp 1007 kp (L/mol·s). In PP, the Mt-I/borate presented much higher [C*]/[Zr] and kp value than the Mt-II. This work also extend to investigate the mechanistic features of zirconocenes catalyzed olefin polymerizations that addressed the largely unknown issues in zirconocenes in the distribution of the catalyst, between species involved in polymer chain growth and dormant state. In both metallocene systems, chain transfer with alkylaluminum is the dominant way of chain termination. To understand the mechanism of cocatalyst effects on PE Mw and (MWD), the unsaturated chain ends formed via β-H transfer have been investigated by 1H NMR analysis.

Rapid kinetic evaluation of homogeneous single-site metallocene catalysts and cyclic diene: how do the catalytic activity, molecular weight, and diene incorporation rate of olefins affect each other?

The kinetics and mechanism of ethylene and cyclic diene 5-ethylidene-2-norbornene (ENB) copolymerization catalyzed by rac-Et(Ind)2ZrCl2/[Ph3C][B(C6F5)4]/triisobutylaluminium (TIBA) were investigated using a quench-labeling procedure using 2-thiophenecarbonyl chloride (TPCC). The E/ENB copolymers were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and 1H nuclear magnetic resonance (NMR) spectroscopy and sulfur analysis. To reduce the errors of the ethylene–diene copolymerization for the kinetics study, we selected E/ENB with steric and electronic features that permit us to elucidate the metallocene catalyst behavior against dienes. A quantitative approach of catalyst speciation, stereodynamics, and micro-kinetics assisted the resolution of mechanistic problems, such as the elastomeric synthesis of ethylene propylene diene monomer rubber (EPDM), the catalyst resting state nature, and how much ion-pairing occurs during polymerization. We report here the precise observation of metal–polymer species, explanation of the dynamics of their initiation, propagation, and termination, and ethylene ENB copolymer development. An approach based on acyl chloride was used to selectively quenched transition metal–polymer bonds to evaluate the polymeric catalyst in terms of its reaction rate, Rp, propagation rate content, kp, and mole fraction of active centers. It is noted that the decline in catalytic activity in the range of 1800 s, and the active center [Zr]/[*C] fraction significantly increased during the initial 1000 s and then tended towards a steady figure of 86%. It is suggested that nearly complete initiation of all olefins catalysts can be obtained after a sufficiently extended reaction. The quick increase in active sites in the first stage can be described by the immediate initiation of active sites positioned on the surfaces of catalyst particles. The initial polymerization rate, Rp, is high and the crystalline properties of the E/ENB copolymer are low due to the greater incorporation of ENB in the polymer backbone, and later the polymerization reaction rates remained stable with a lower mol% of ENB. The melting temperature (Tm) ranges from 108 to 127 °C, whereas the crystalline temperature ranges from 63 to 108 (J g−1). In the E–ENB copolymers, the value of kpE is much greater than that of kpENB; at 120 s, the kpE and kpENB values are 9115 and 431 L mol−1 s−1, respectively, implying smaller diffusion barriers in the early stages, which are close to the actual propagation rate constant.

Kinetics and mechanism of ethylene and propylene polymerizations catalyzed with ansa-zirconocene activated by borate/TIBA

Ethylene and propylene polymerizations catalyzed with two ansa-zirconocenes (rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (M-I) and rac-Et(Ind)2ZrCl2 (Mt-II)) activated by (Ph3C)B(C6F5)4/triisobutylaluminum were respectively conducted under the same conditions for different duration ranging from 0.5 to 30 min, and quenched with 2-thiophenecarbonyl chloride for determining the active center fraction ([C∗]/[Zr]). Variations of polymerization rate, molecular weight, isotacticity and thermal properties with time were also studied. The [C∗]/[Zr] fraction gradually increased with time in the first 20 min and then reached steady stage in all polymerization systems. [C∗]/[Zr] value in the steady stage of Mt-II catalyzed ethylene polymerization was significantly higher than that of propylene polymerization, similar to the phenomena previously observed in ethylene and propylene polymerizations catalyzed with Mt-II/methylaluminoxane. When M-I/borate was used as the catalyst, both ethylene and propylene polymerization showed higher steady stage [C∗]/[Zr] levels than those of the Mt-II/borate systems, and the influence of zirconocene structure on [C∗]/[Zr] of propylene polymerization was much stronger than that of ethylene polymerization. Change in zirconocene structure also significantly influenced apparent chain propagation rate constant (kp) and its time-dependent variations. By taking into consideration the time-dependent changes of [C∗]/[Zr], polymer’s molecular weight distribution and chain structure, presence of multiple active centers in the polymerization system and late activation of the centers with lower intrinsic reactivity are proposed to be the main reasons for steep decay of kp with time. Structure-performance relationships of the ansa-zirconocene catalysts have also been discussed based on the results of kinetic study.

A selective N,N-dithenoyl-rhodamine based fluorescent probe for Fe3+ detection in aqueous and living cells

A novel N,N-dithenoyl-rhodamine based fluorescent and colorimetric Fe3+ probe 1 was designed and synthesized by only one step from Rhodamine B hydrazide and 2-thiophenecarbonyl chloride. The structure of probe 1 was characterized by 1H NMR/13C NMR spectroscopy, IR spectroscopy, and HRMS spectrometry. Accompanying with significant changes in visual color and fluorescent spectrum, probe 1 displayed good sensitivity for Fe3+ with an abroad pH span. The detection limit (3.76 μmol/L, 0.2 mg/L) for Fe3+ was lower than WHO recommended value (0.3 mg/L) for drinking water. Using two thiophene carbonyl groups as coordinating functional recognition group, probe 1 showed excellent selectivity towards Fe3+ over diverse coexistent metal ions and anions. The sensing mechanism between dithenoyl-substituted probe 1 and Fe3+ was further confirmed by 1H NMR and IR titration experiments, binding constants study, and Job's plot analysis. Furthermore, probe 1 also exhibited good cell membrane permeability and could be used as an efficient Fe3+ probe in living human cells.

Deactivation Effect Caused by Catalyst-Cocatalyst Pre-contact in Propylene Polymerization with MgCl2-supported Ziegler-Natta Catalyst

Propylene slurry polymerization with a MgCl2-supported Ziegler-Natta catalyst containing internal electron donor was conducted after different durations of pre-contact of the catalyst with triethylaluminum cocatalyst. The number of active centers ([C*]/[Ti]) was determined by quenching the polymerization with 2-thiophenecarbonyl chloride and measuring sulfur content in the polymer. The pre-contact treatment caused selective deactivation of a part of active centers with low stereoselectivity and much lower activity in the initial stage of polymerization as compared with the polymerization run without the pre-contact stage. The active center concentration and polymerization activity decreased with prolonging of the pre-contact stage. The proportion of stereoselective active centers was increased by prolonging the pre-contact stage, so the isotacticity of produced polypropylene was enhanced. Release of active centers through catalyst particle fragmentation was significantly retarded, and the polymerization rate curve changed from decay type to induction type by the precontact treatment. In the induction period both non-stereoselective and stereoselective active centers were released and activated, resulting in gradual reduction of the polymer’s isotacticity in the first 5–10 min of polymerization. Selective deactivation of non-stereoselective active centers also took place in propylene polymerization using the catalyst without pre-contacting with the cocatalyst. In this case, the polymerization rate decayed with time after a short induction period of 2–5 min. Over reduction of the active center precursors with low stereoselectivity by triethylaluminum was considered as the reason for their deactivation during the pre-contact or the polymerization processes.

Theoretical and Experimental Investigations of Spectroscopic Properties of 2-Thiophenecarbonyl chloride

Molecular structure and vibrational wave numbers for 2-Thiophenecarbonyl chloride have been computed using the B3LYP method with the 6-311++G (d, p) basis set. The computation reveals that the title compound has two minimal conformers (gauche and syn). The conformational energy difference between the syn and gauche is very small, indicating that the syn conformer coexists with the gauche conformer. FT-IR and FT-Raman spectra of 2-Thiophenecarbonyl chloride were recorded and analysed in the range 3500-400 and 3500-200cm-1, respectively. The HOMO-LUMO energy gap of the two conformers have been also calculated for comparison of their chemical activities.

Influence of ligand substituents of unbridged metallocene complexes on stability of their active centers in ethylene polymerization

Four unbridged metallocene catalyst precursors, bis(2,4,7-trimethylindenyl)zirconium dichloride (Cat.1), bis(2,4,6-trimethylindenyl)zirconium dichloride (Cat.2), bis(2,4,5,6-tetramethylindenyl)zirconium dichloride (Cat.3), and bis(2-methyl-4,6-diisopropylindenyl)zirconium dichloride (Cat.4), were synthesized. Cat.4 was found thermodynamically unstable. The correlations between alkyl substituents of the indenyl ligands and olefin polymerization with the metallocene complexes Cat.1, Cat.2 and Cat.3 were investigated via kinetic study on ethylene polymerization. Change of number of active centers ([C⁎]/[Zr]) was determined by quench-labeling the propagation chains with 2-thiophenecarbonyl chloride. According to the kinetic behaviors, kinetic stability of the metallocene complexes was found to follow the order of Cat.1 > Cat.2 > Cat.3. The relationship between ligand substitution mode and kinetic stability of the metallocene complex were discussed.

1-Hexene polymerization with supported Ziegler-Natta catalyst: Correlation between catalyst particle fragmentation and active center distribution

1-Hexene was polymerized with a commercial MgCl2-supported Ziegler-Natta catalyst using triethylaluminum as cocatalyst at different monomer/catalyst mass ratio (mhexene/mcat = 5, 15, 30), and the number of active centers ([C*]/[Ti]) was determined by quench-labeling the catalyst with 2-thiophenecarbonyl chloride and monitoring sulfur content of the polymer. Changes of polymerization rate (Rp) and propagation rate constant (kp) with time were also determined. [C*]/[Ti] was found to increase with time for 3 − 5 folds in the first 10 min of polymerization, but the maximum [C*]/[Ti] value reached after the induction period markedly enhanced with increase of monomer/catalyst mass ratio. Gradual fragmentation of the catalyst particles in parallel with the [C*]/[Ti] increase was observed by SEM analysis. It means that a large proportion of active center precursors are inaccessible to cocatalyst and monomer at the beginning of reaction, and fragmentation of the particles by hydraulic force of the growing polymer chains leads to exposure and activation of these precursors. Raising the monomer concentration can provide larger hydraulic force to expose those active site precursors that are more tightly buried inside the catalyst particle. The polymer molecular weight distribution and related active center distribution was found to shift with increase of the monomer/catalyst ratio, meaning that there are different types of buried active center precursors, and their exposure requires different extent of particle fragmentation.

Study on 2-thiophenecarbonyl chloride-quenched olefin polymerization with α-diimine nickel catalysts

The number of active centers in α-diimine nickel-catalyzed olefin homogeneous polymerization system is rarely studied before. A systemic study on quenching method with 2-thiophenecarbonyl chloride (TPCC) in homogeneous catalytic system is presented. Ethylene and propylene polymerizations catalyzed with homogeneous α-diimine nickel catalysts (ArN=C(An)–C(An)=NAr)NiBr2 (cat.1, Ar=2,6-C6H3(i-Pr)2) and (ArN=C(C12H8)C=NAr)NiBr2 (cat.2, Ar=2,6-C6H3(i-Pr)2, C12H8=acenaphthene-1,8-diyl) were quenched by TPCC. The potential side reaction between TPCC and alkyl aluminum-terminated polymer chain caused by chain transfer to cocatalyst under different quenching conditions was investigated. Samples were obtained with different TPCC/AlMAO molar ratios and had similar sulfur contents; a confirmation that the excess TPCC in the system did not cause obvious side reactions which could lead to place more thiophene groups to the polymer chains. Moreover, when the quenching time was in the range of 3–20 min, the sulfur contents remained stable and the value of Npol (number of moles of polymer chains) was not obviously changed, supporting that sufficient quenching reaction had already accomplished within the first 3 min. We claimed that the side reaction could be ignored under controllable conditions. TPCC was confirmed to be an effective quenching agent in homogeneous catalytic system. The quenching method with TPCC was also established.

Influence of trimethylaluminum on kinetics of rac-Et(Ind)2ZrCl2/aluminoxane catalyzed ethylene polymerization

Ethylene polymerization with rac-Et(Ind)2ZrCl2/aluminoxane catalysts were conducted under different conditions, including varied reaction time, cocatalyst and cocatalyst concentration. Methylaluminoxane (MAO), dried MAO (dMAO) and modified MAO (MMAO) were used as cocatalyst, respectively. Changes of polymerization rate, number of active centers ([C∗]/[Zr]) and polymer molecular weight distribution (MWD) with time were traced. A method of counting active centers using 2-thiophenecarbonyl chloride as quenching agent was applied to measure [C∗]. MWD curves of polymer were deconvoluted into three Flory components, which were assigned to polymer formed by loosely associated ion pairs, contact ion pairs and ion pairs with medium cation-anion distance. The loosely associated ion pairs produce polymer of low molecular weight, and the contact ion pairs produce high molecular weight polymer. Free trimethylaluminum (TMA) in the system was found to be an important component for the formation of contact ion pairs. In ethylene polymerization activated by different cocatalysts, gradual increase of [C∗]/[Zr] with time until 30 min was observed, meaning that complete activation of all the metallocene molecules takes rather long time. Comparisons of [C∗]/[Zr] ratios at 30 min in systems activated by different cocatalysts lead to the conclusion that TMA takes part in formation of dormant active centers. The role of TMA as an efficient chain transfer agent has also been proved.

Copolymerization of Pyrrole and Thienyl end Capped Poly(dimethylsiloxane) by Iron (III) Chloride

This study presents synthesis of novel block copolymers of thienyl end capped polydimethylsiloxane and polypyrrole via chemical oxidative polymerization by iron (III) chloride. Mono hydroxy terminated poly (dimethylsiloxane) (MH.PDMS) was reacted with 2-thiophenecarbonyl chloride (ThCCl) in order to synthesize a polymer containing thienyl end-group (PDMS-ThC). Then copolymers of PDMS-ThC and pyrrole were synthesized by chemical oxidative polymerization using iron (III) chloride as an oxidant. The synthesized block copolymers (PDMS-ThC -b-PPy) were characterized by spectroscopic analysis and the electrical conductivities were investigated with 4-point probe technique. The obtained samples were also characterized morphologically by Scanning Electron Microscope (SEM).

Synthesis and Antitumor Activities of Resveratrol Derivatives on Cervical Cancer Hela Cells

Using 2-thiophenecarbonyl chloride and 2-furoyl chloride to modify the structure of the natural product resveratrol, we synthesized five novel resveratrol derivatives. The target compounds were evaluated for their antitumor activities against cervical cancer HeLa cells by the MTT method. The results indicated that the compound 3a displayed the best antitumor activities, which is higher than the value of resveratrol, and its inhibition ratio was 95.1% against HeLa cells at the concentration of 75 μmol/L.

Polypyrrole and Thienyl End Capped Polysulfone Copolymers by Iron (III) Chloride

This study presents synthesis of novel block copolymers of thienyl end capped polysulfone and polypyrrole via chemical oxidative polymerization by iron (III) chloride. Polysulfone is synthesized from bisphenol and bis (p-chlorophenyl) sulfone in presence of potassium carbonate. Polysulfone (PSU) was reacted with 2-thiophenecarbonyl chloride in order to synthesize a macromonomer containing thienyl end-group (PSU-ThC). Then copolymers of PSU-ThC and pyrrole were synthesized by chemical oxidative polymerization using iron (III) chloride as an oxidant. The synthesized block copolymers (PSU-ThC-b-PPy) were characterized by spectroscopic analysis and the electrical conductivities were investigated with 4-point probe technique. The obtained samples were also characterized morphologically by Scanning Electron Microscope (SEM).

In Situ Copolymerization of Silver Containing Nanocomposites of Pyrrole and Thienyl End-capped Ethoxylated Nonyl Phenol by Iron (III) Chloride

This study presents synthesis of novel block copolymers of thienyl end capped ethoxylated nonyl phenol and polypyrrole with silver nanoparticles via chemical oxidative polymerization by iron (III) chloride. Ethoxylated nonyl phenol (ENP) was reacted with 2-thiophenecarbonyl chloride (ThCCl) in order to synthesize a macromonomer containing thienyl end-group (ENP-ThC). Then copolymers of ENP-ThC and pyrrole were synthesized by chemical oxidative polymerization using iron (III) chloride as an oxidant. During this reaction, silver nitrate (AgNO3) solution was added in order to increase its conductivity and to give the copolymer anti-microbial property. The synthesized block copolymers (ENP-ThC-b-PPy) with silver nanoparticles were characterized by spectroscopic analysis and the electrical conductivities were investigated with 4-point probe technique. The obtained samples were also characterized morphologically by Scanning Electron Microscope (SEM).

Effects of comonomer on active center distribution of TCl4/MgCl2–AlEt3 catalyst in ethylene/1-hexene copolymerization

Ethylene/1-hexene copolymerization with MgCl2/TiCl4–AlEt3 catalyst has been conducted under different initial 1-hexene concentration (0–0.5 mol/L). Number of polymerization active centers was determined by quenching the reaction with 2-thiophenecarbonyl chloride and measuring sulfur content of the quenched polymer. Each copolymer sample was fractionated into boiling n-heptane soluble and insoluble fractions, and active centers in these fractions were also counted. The rate constants of ethylene and 1-hexene insertion in the active centers were calculated, respectively. Molecular weight distribution (MWD) curves of the polymers were deconvoluted with 4–5 Flory components, and changes of activity of the Flory components with [1-hexene] were analyzed. The polymerization activity and the number of active centers were significantly enhanced by increasing [1-hexene]. Large number of active centers were revived by small amount of 1-hexene. With the increase of [1-hexene], the number of active centers producing polymer chains with lower molecular weight and higher 1-hexene content was increased more than those producing polymer chains with higher molecular weight and lower 1-hexene content, and the MWD curve continuously inclined to the low molecular weight side. The active centers with higher 1-hexene incorporation rate have relatively smaller rate constant of ethylene insertion. When [1-hexene] was increased, the rate constant of ethylene insertion was only slightly changed, but the rate constant of 1-hexene insertion was markedly lowered, meaning that the active centers revived by 1-hexene have relatively lower ability of incorporating 1-hexene.

EFFECTS OF HYDROGEN ON ACTIVE CENTERS IN PROPYLENE POLYMERIZATION WITH SUPPORTED ZIEGLER-NATTA CATALYST

The kinetics of propylene polymerization with a TiCl4/ Di / MgCl2( Di = internal donor) supported Ziegler-Natta catalyst was studied by measuring the number of active centers using 2-thiophenecarbonyl chloride as quenching agent. Influences of hydrogen and alkoxysilane type external donors on the number of active centers and chain propagation rate constant( k p) were investigated. The number and k p value of three groups of active centers that produce atactic,medium-isotactic and isotactic polypropylene( PP) fractions were determined. The catalyst activity was found to significantly increase with the addition of hydrogen,which was a result of simultaneous increases in the number of active centers and k p value. The three groups of active centers response to hydrogen differently. Hydrogen caused lower degree of increase in the number of active centers that produce atactic PP than the other two groups of active centers,and caused the highest degree of increase in the k p value of active centers that produce medium-isotactic PP. The hydrogen response of the active centers was also influenced by external donor. Increasing the bulkiness of alkyl groups in alkoxysilane donors leads to decreased hydrogen sensitivity,meanwhile the stereo- and regio-selectivities were evidently improved,implying that there are close relations between the hydrogen effect and the stereo-and regio-selectivities of the catalyst.A mechanistic model was proposed to explain the hydrogen effect.