BF_3,络合的丙烯酸乙酯与丙烯的共聚机理

BF_3络合的丙烯酸乙酯(EA)与丙烯(P)在25℃进行自由基共聚。聚合速率和引发剂浓度的平方根成直线关系。链转移剂CCl_4可显著影响共聚物的[η];溶剂的介电常数越小,共聚反应速率越大;两种单体浓度相等时共聚反应速率最大。~1H-NMR和 _13C-NMR表明,当[EA·BF_3]/[EA·BF_3]+[P]>O.5时所得共聚物为富于EA的无规共聚物。实验数据表明,共聚反应按三元络合物与二元络合物的无规共聚机理进行,当[EA·BF_3]/[EA·BF_3]+[P]<0.5时,得到交替共聚物,共聚反应按三元络合物均聚机理进行。UV光谱测得了戊烯-1(丙烯的同系物)与EA·BF_3三元络合物的存在,这对三元络合物的均聚机理是有力的证据。     

Kinetics and mechanism of metallocene‐catalyzed olefin polymerization: Comparison of ethylene,propylene homopolymerizations,and their copolymerization

A series of ethylene, propylene homopolymerizations, and ethylene/propylene copolymerization catalyzed with rac‐Et(Ind)₂ZrCl₂/modified methylaluminoxane (MMAO) were conducted under the same conditions for different duration ranging from 2.5 to 30 min, and quenched with 2‐thiophenecarbonyl chloride to label a 2‐thiophenecarbonyl on each propagation chain end. The change of active center ratio ([C^*]/[Zr]) with polymerization time in each polymerization system was determined. Changes of polymerization rate, molecular weight, isotacticity (for propylene homopolymerization) and copolymer composition with time were also studied. [C^*]/[Zr] strongly depended on type of monomer, with the propylene homopolymerization system presented much lower [C^*]/[Zr] (ca. 25%) than the ethylene homopolymerization and ethylene–propylene copolymerization systems. In the copolymerization system, [C^*]/[Zr] increased continuously in the reaction process until a maximum value of 98.7% was reached, which was much higher than the maximum [C^*]/[Zr] of ethylene homopolymerization (ca. 70%). The chain propagation rate constant (k_p) of propylene polymerization is very close to that of ethylene polymerization, but the propylene insertion rate constant is much smaller than the ethylene insertion rate constant in the copolymerization system, meaning that the active centers in the homopolymerization system are different from those in the copolymerization system. Ethylene insertion rate constant in the copolymerization system was much higher than that in the ethylene homopolymerization in the first 10 min of reaction. A mechanistic model was proposed to explain the observed activation of ethylene polymerization by propylene addition. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 867–875     

STUDIES ON THE OXIDATION AND GRAFT COPOLYMERIZATION OF POLYETHERS

Polyethers could form hydroperoxide under air-oxidation or photo-oxidation in the presence of H_2O_2. The scission of ether linkage induced by moderate oxidation was prevented by controlling the reaction time and hydroperoxide concentration. The oxidation rate was affected by the end groups of polyethers. The decreasing order of oxidation rate for various poly(tetramethylene ether) glycol derivatives having different end groups are as follows: poly(tetramethylene ether) glycol (PTMG)>poly(tetramethylene ether)acetate (PTMGAC) >poly(tetramethylene ether) phenyl carbamate (PTMGPC). The urethane end groups in PTMGPC increase the resistance toward oxidation. Polyether hydroperoxide reacts with ferrous ion or N,N-dimethyl toluidine (DMT) to form polymericoxy radical which then initiates the graft copolymerization of vinyl monomers at low temperature, and was devoid of homopolymerization. The copolymer after separation and purification was proved to be a graft one by IR analysis and elemental analysis.     

Ternary Molecular Complex in the Alternating Copolymerization of Methyl Methacrylate with Styrene Using Stannic Chloride

The equimolar alternating copolymerization of methyl methacrylate (MMA) with styrene (St) in the presence of stannic chloride in toluene (Tl) is investigated kinetically. The concentrations of the ternary molecular complexes, [SnCl₄-MMA … St] and [SnCl₄-MMA … T1], are calculated by use of the formation constants of the ternary molecular complexes. The rates of copolymerization under photo-irradiation and with tri-n-butyl boron-benzoyl peroxide as an initiator are proportional to the 1.5th order and 1. Oth order, respectively, of the concentration of the ternary molecular complex [SnCl₄ · MMA … St]. The alternating copolymerization precedes the homopolymerization of the methyl methacrylate charged in excess. The alternating regulation of the copolymerization is ascribed to the homopolymerization of the ternary molecular complex from the kinetic results. The magnitudes of the shifts for     

Alternating ethylene–alkyl acrylate copolymers. I. polymer preparation

High molecular weight alternating ethylene–ethyl acrylate copolymers were prepared by using boron trifluoride to complex the acrylate ester. The polymerizations were run under mild conditions (25–50°C, 6–20 atm ethylene) in dichloromethane or dichloroethane solution with free-radical initiation. At lower ethylene pressures or at less than stoichiometric levels of BF₃, the polymers are acrylate-rich. This is due to ethyl acrylate homopolymerization competing with the copolymerization reaction. The effect of other polymerization variables is also discussed.     

Copolymerization of vinyl cyclohexane and α-methyl vinyl cyclohexane with acrylonitrile

Copolymerization of vinyl cyclohexane and α-methyl vinyl cyclohexane with acrylonitrile in the presence of a complexing agent AlEtCl₂ results in the formation of alternate copolymers. In the copolymerization of vinyl cyclohexane with acrylonitrile the copolymer composition depends on the ratio of acrylonitrile to AlEtCl₂. If this ratio is unity, alternating copolymers of the composition 1:1 are formed; with a ratio greater than unity statistical copolymers that contain more than 50% acrylonitrile units are produced. The ¹H-NMR spectroscopy measurements indicate that the interaction between the comonomers and the complexing agent leads to the formation of ternary donor–acceptor complexes of equimolar composition. The equilibrium constants of these complexes at ?60°C have been determined. The effects of temperature, nature of solvent and dilution on the yield, and composition of the copolymers of vinyl cyclohexane with acrylonitrile formed have been studied. By lowering the temperature the yield of copolymers increases but their composition remains equimolar. An increase in the polarity of the medium results in an increase in copolymer yield, whereas the yield decreases if the reaction is conducted in a donor-solvent medium. Dilution of the reaction mixture disrupts the alternation of units in the macrochain of copolymers. The kinetic pecularities of copolymerization have been investigated. The linear dependence of the copolymerization rate on the product of comonomer concentration is observed. The rate of copolymerization is proportional to the square root of the incident light intensity. Various additions of radical type and irradiation accelerate the process of copolymerization. The mechanism of alternating copolymerization of vinyl cyclohexane monomers with acrylonitrile in the presence of AlEtCl₂ is discussed in terms of homopolymerization of the comonomer complex.     

ON THE KINETICS AND MECHANISM OF THE COPOLYMERIZATION OF ACRYLONITRILE WITH STYRENE IN THE PRESENCE OF COPPER CHLORIDE

The copolymerization of styrene (St) and acrylonitrile (AN) complexed with CuCl_2 monomer by a free radicalmechanism was performed using benzoyl peroxide as an initiator at 65℃ under N_2 atmosphere for 150 min. The rate ofpolymerization (R_p) was found to increase linearly with the concentration (in mol/L) of CuCl_2, AN and St through scalingrelations. The activation energy of the copolymerization process in the presence and absence of CuCl_2 was found to be46.5 kJ/mol and 102 kJ/mol, respectively. The viscosity average molecular weigh of the copolymer and the k_p~2/k_t ratio weredctermired to further assess the accelerating effect of CuCl_2 on the copolymerization process. The copolymerization processin the presence of CuCl_2 has a radical complex mechanism.     

Analysis of microstructure of ethylene–1-hexene copolymer prepared over thermally pretreated MgCl2/THF/TiCl4bimetallic catalyst

Thermally pretreated catalysts were prepared by heating MgCl₂/THF/TiCl₄ (TT-0) at 80°C for 5 min (TT-1) and 60 min (TT-2), and at 108°C for 5 min (TT-3) and 60 min (TT-4). Ethylene–1-hexene copolymers were prepared with these catalysts. The TT-1 catalyst produced more blocky and higher 1-hexene content polymer than TT-0, 2, 3, and 4. Temperature rising elution fractionation (TREF) analysis was used to investigate the chemical composition distribution of the ethylene–1-hexene copolymer, exhibiting bimodal distribution for TT-0 and trimodal for TT-1, 2, 3, and 4. A portion of higher hexene content of the copolymer markedly increased when the copolymerization was performed with TT-1, indicating that copolymerization active sites were newly generated. Portion of homopolyethylene increased drastically when the copolymerization was performed with TT-4, indicating that ethylene homopolymerization active sites were increased. Gel permeation chromatography (GPC) also revealed that three kinds of active sites existed on the catalyst. ¹³C-NMR spectrum of each fraction after TREF analysis suggested that the isospecific active site could polymerize 1-hexene well, resulting in random and alternating copolymers. A scheme for generation of the active site and change of its nature during thermal treatment of bimetallic complex catalyst is proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 291–300, 1998     

Mechanism of Donor-Acceptor Alternating Copolymerization

The alternating copolymerization of butadiene and an acrylic compound in the presence of ethyl aluminum dichloride and vanadium oxychloride as complexing agents was studied kinetically for the comparison of two mechanisms, i. e., one involving an intermediate of a ternary complex of butadieneacrylic monomer-EtAIClz and the other without the complex formation. The rate of propagation was found to attain a maximum at a definite monomer composition, and this composition is not varied by changing the amount of EtAICl₂ but decreased with increasing the concentration of total monomer. This fact is explained only by the mechanism of the ternary complex intermediate. In relation to the mechanism, NMR study of the ternary complex, ESR study of the growing radical NMR study of the regularity of the copolymer, and the elementary reaction of the propagation are reviewed with discuss ion.     

Radical copolymerization of alkyl 2‐norbornene‐2‐carboxylate with alkyl acrylates: Facile incorporation of norbornane framework into poly(alkyl acrylate)s

Radical copolymerization of alkyl 2‐norbornene‐2‐carboxylates (alkyl = Me 1a , nBu 1b ) with alkyl acrylates (alkyl = ethyl, methyl, and n‐butyl) was investigated. Copolymerization of 1a,b with the alkyl acrylates initiated by 1,1′‐azobis (cyclohexane‐1‐carbonitrile) at 85 °C proceeded to give random copolymers, although the homopolymerization of 1a,b did not proceed efficiently under the same conditions. Typically, bulk copolymerization of 1a with ethyl acrylate in a feed ratio of 1:3 ([ 1a ]:[EA]) afforded a copolymer with M_n = 33,300 containing 19.4 mol % of 1a unit in the composition. An increase of T_g derived from the incorporation of the rigid norbornane framework was observed, although the extent of the temperature rise was rather moderate. The ternary radical copolymerization of 1a,b /alkyl acrylate/N‐phenylmaleimide proceeded to give copolymers with the three repeating units in the main chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4597–4605, 2007     

Preparation and Solution Characteristics of a Novel Hydrophobically Associating Terpolymer for Enhanced Oil Recovery

Hydrophobically associating terpolymers were prepared by the micellar copolymerization technique using acrylamide (AM), 2-trimethylammonium ethyl methacrylate chloride (TMAEMC) as a cationic monomer, and small amounts of 5,5,5-triphenyl-1-pentene (TP<0.5 mol-%) as the hydrophobe. The structure of the copolymer was characterized by FT-IR and ¹H-NMR. The aqueous solution properties of the terpolymers were also investigated as functions of polymer concentration, salinity, temperature and shear rate. The results showed that the thickening behavior of these terpolymers are remarkably dependent on both the number and length of hydrophobic segments in the copolymer chains. As expected, the terpolymers exhibited improved viscosity enhancement properties as the concentration exceeded 0.25 g⋅dL⁻¹, due to intermolecular hydrophobic association. Additional evidence for hydrophobic microdomains was obtained utilizing pyrene-probe fluorescence. Additionally, the ternary copolymers showed favorable salt tolerance, temperature resistance, and recoverable viscosity after shearing.     

Copolymerization of Carbon Dioxide and Propylene Oxide by Binary Cobalt Salen Complexes with Various Anion Groups

A series of salen–Co (III )(X) complexes tethering quaternary ammonium salts are designed to investigate the influence of the axial group X in the complex and the anion Y of quaternary ammonium salt on the copolymerization of CO₂ and PO . By copolymerization, the complex 9 , where X and Y are both 2,4‐dinitrophenolate, has the highest catalytic efficiency. When X is OAc and Y is BF₄ ⁻/NO₃ ⁻, the complexes 11/12 have lower catalytic efficiency. For the complex 10 , where X and Y are both OAc , the catalytic efficiency is the lowest. At the same time, complex 9 can produce the copolymer with the highest carbonate fraction and M _n. And the best copolymerization conditions were as follows: reaction temperature 30°C, copolymerization time 24 h, and CO₂ pressure 2 MPa with complex 9 . The thermal properties of the copolymers are also studied by differential scanning calorimetry (DSC) and thermogravimetry (TG) .     

1H和19F NMR研究镍系催化丁二烯聚合中醇类对BF3·Oet2的增溶作用

The solubility of BF₃OEt₂ in hydrogenated gasoline was improved greatly by means of premixing BF₃OEt₂ with C₃H₁₇OH in nickel catalyst system, so that the effeciency of fluorine in the system was increased markedly. It is confirmed that there was a intermolecular hydrogen bond between alcohol and BF₃OEt₂ molecules by using ¹H NMR, which was a vital factor to lead the solubilization of BF₃OEt₂ in hydrogenated gasoline. Otherwise, the caculation formula of the chemical shift ofproton in hydroxy, ¹H = xipi,was suggested in hydrogen bond system.     

The features of syndiotactic polypropylene

The mechanism of stereoselectivity of propylene insertion in propylene-ethylene copolymerization on a C_S symmetrical zirconium complex i-Pr(Cp) (Flu) ZrCl₂ catalyst is discussed. Calculation results indicate that not only the β-carbon in the growing chain end of the polymer but also the substituent of the β-carbon play an important role in the selectivity of the prochiral face of the next-coming propylene monomer. The stereoregularity of propylene units connected to an ethylene unit (PPE) in propylene-ethylene copolymer was observed to be lower than that in propylene sequences (PPP) in the ¹³C NMR spectrum, which supports the calculation results. Furthermore, the structure and properties of propylene-olefin (ethylene, 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene) copolymers prepared with the i-Pr(Cp) (Flu) ZrCl₂ catalyst system were studied. Propylene-1-butene copolymer exhibits peculiarly lower melting point depression because 1-butene units enter into the unit cell of the crystal structure of syndiotactic polypropylene.     

P(VAc-MMA)为基体的聚合物电解质研究

以醋酸乙烯酯(VAc)和甲基丙烯酸甲酯(MMA)为单体, 采用半连续种子乳液聚合法制备了无规共聚物聚(醋酸乙烯酯-甲基丙烯酸甲酯)[P(VAc-MMA)], 并以此聚合物为基体制备了聚合物电解质. 用红外光谱(FTIR)、核磁共振氢谱(¹H NMR)、扫描电镜(SEM)、差热/热重分析(DSC/TG)、X射线衍射(XRD)、机械性能测试和电化学交流阻抗等方法对聚合物和聚合物电解质的性质进行了研究. 测试结果表明: VAc和MMA聚合生成P(VAc-MMA); 聚合物膜含有大量微孔结构, 利于离子传输; 聚合物电解质膜具有优良的热稳定性和机械强度; 25 ℃下, 最高的离子电导率达到了1.27× 10^－3 S•cm^－1; 离子电导率随着温度的升高而迅速增加, 电导率-温度曲线符合Arrhenius方程.     

Application of Et3NHCl-AlCl3 ionic liquid as an initiator in cationic copolymerization of 1,3-pentadiene with styrene

Cationic copolymerization of 1,3-pentadiene (PD) with styrene (St) using the triethylamine hydrochloride-aluminium chloride (Et₃NHCl-AlCl₃) room temperature ionic liquid as an initiator in toluene has been investigated. The polymerization proceeds to high conversions, indicating high initiating reactivity of Et₃NHCl-AlCl₃ in these copolymerization systems, although molecular weights of the polymers are limited which are similar to polymerization initiated by Lewis acids such as TiCl₄, BF₃, BF₃·OEt₂. The polymers were analyzed using IR spectra in conjunction with gel permeation chromatography (GPC).     

l-Lactide homopolymerization and l-lactide-ε-caprolactone block copolymerization by lanthanide tris(2,4,6-trimethylphenolate)s

The l-lactide (LLA) homopolymerization and copolymerization with ε-caprolactone (CL) in solution initiated by lanthanide tris(2,4,6-trimethylphenolate)s (Ln(OTMP)₃) are systematically investigated. The results indicate that La(OTMP)₃ is quite effective for the LLA polymerization. The ¹H NMR spectrum suggests the homopolymerization proceeds through an acyl-oxygen bond cleavage. Thermal analysis of homopolymers by DSC shows typical features of optically pure PLLA. The copolymerization of LLA with CL can only be achieved when CL is first polymerized followed by LLA. Feeding the two monomers simultaneously, however, only results in the formation of LLA homopolymers. The structure of the copolymers has been characterized by ¹H NMR and ¹³C NMR and the thermal behavior has also been evaluated. All these measurements demonstrate the pure diblock copolymer has been synthesized successfully.     

In-situ High Resolution NMR Investigation on Polymerization Mechanism. II. Comparison between BF3·Bu2O and CI-N2PF6 as Catalysts in Homopolymerization of Trioxane and Copolymerization with Ethylene Oxide

A comparison of BF₃ ·Bu₂O and Cl-N₂PF₆ as catalysts for cationic homopolymerization and copolymerization of trioxane has been made by employing high resolution nuclear magnetic resonance techniques. While no substantial difference was detected for the homopolymerization, two important differences were observed for the copolymerization with ethylene oxide; viz., 1) with Cl-NPF₆ there is a lower build-up of formaldehyde concentration; 2) with Cl[sbnd]N₂PF₆, a lesser amount of cyclic compounds containing ethylene oxide units is formed (e.g., 1,3-dioxolane). Both observations suggest that depolymerization occurs to a lesser extent with the cl-N₂PF₆ catalyst.     

Cationic copolymerization of ε‐caprolactone and L,L‐lactide by an activated monomer mechanism

The cationic homopolymerization and copolymerization of L,L ‐lactide and ε‐caprolactone in the presence of alcohol have been studied. The rate of homopolymerization of ε‐caprolactone is slightly higher than that of L,L ‐lactide. In the copolymerization, the reverse order of reactivities has been observed, and L,L ‐lactide is preferentially incorporated into the copolymer. Both the homopolymerization and copolymerization proceed by an activated monomer mechanism, and the molecular weights and dispersities are controlled {number‐average degree of polymerization = ([M]₀ ? [M]_t)/[I]₀, where [M]₀ is the initial monomer concentration, [M]_t is the monomer concentration at time t, and [I]₀ is the initial initiator concentration; weight‐average molecular weight/number‐average molecular weight ～1.1–1.3}. An analysis of ¹³C NMR spectra of the copolymers indicates that transesterification is slow in comparison with propagation, and the microstructure of the copolymers is governed by the relative reactivity of the comonomers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 7071–7081, 2006     

Polymerization of coordinated monomers. XII. Alternating copolymerization of γ-crotonolactone with styrene with the use of stannic chloride

γ-Crotonolactone and styrene copolymerize alternately in the presence of stannic chloride at -10°C under photoirradiation. The intrinsic viscosity of the resulting copolymer is in the range of 0.6–0.8 dl/g at 30°C in chloroform. The equilibrium constants for the complex formation between stannic chloride and γ-crotonolactone were determined in 1,2-dichloroethane-toluene solution at 0 and ?20°C by use of absorption band at 350 nm. Continuous variation plots based on the ¹H-chemical shift show a 1:1 interaction between styrene and the γ-crotonolactone coordinated to stannic chloride. The equilibrium constants for the ternary molecular complex formation between the coordinated γ-crotonolactone and styrene were determined in 1,2-dichloroethane in the temperature range from ?20 to 0°C. The equilibrium constants, derived independently from the measurements of the nonequivalent protons in γ-crotonolactone, are equal to each other within the experimental error. The mechanism of the alternating copolymerization of γ-crotonolactone and styrene in the presence of stannic chloride is discussed in terms of the homopolymerization of the ternary molecular complex.