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1.
Mg(n‐Bu){η2‐HC[C(Me)NMes]2} ( 2 ) (Mes = mesityl, 2,4,6‐Me3C6H2), a new β‐diketiminate‐supported magnesium alkyl, has been synthesized and structurally characterized. The X‐ray analysis of the lanthanum half‐sandwich complex Cp*La(BH4)2(THF)2 ( 1 ) (Cp* = pentamethylcyclopentadienyl; THF = tetrahydrofuran) is also reported. Complex 2 has been assessed as both alkylating agent and chain transfer agent for the lanthanum‐catalysed polymerization and coordinative chain transfer polymerization of isoprene and styrene using 1 as the pre‐catalyst. The results are compared with those for n‐butylethylmagnesium (BEM) which is traditionally used for this purpose. The 1,4‐trans stereospecific polymerization of isoprene shows a more controlled character using 2 versus BEM, and higher activities are observed for the chain transfer polymerization of styrene when 2 is used as chain transfer agent. The activity is in turn lower than that observed using BEM when 1 equiv. of magnesium compound is used for the polymerization of styrene. The combination of 1 , 2 and Al(i‐Bu)3 leads finally to a 1,4‐trans stereoselective coordinative chain transfer polymerization of isoprene, in a similar way to BEM. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

2.
The lanthanide nitrate complexes with 13-crown-4(13-C-4) have been prepared in AcOEt. These new complexes with the general formula Ln(NO3)3.(13-c-4) (Ln = La–Nd, Sm–Lu) have been characterized by means of elemental analysis, IR and 1H-NMR spectra, conductivity measurements, and TG-DTA techniques. The crystal and molecular structure of Nd(No3)3. (13-c-4) has been determined by single crystal X-ray diffraction. It crystallizes in the monoclinic space group P21/a with Z = 8. Lattice parameters are a = 15.393(1), b = 12.578(1), c = 19.279(2) Å, β = 113.05(1)°, V = 3435 Å3, Dc = 2.01 g cm?3, μ = 31.0 cm?1 (Mok2), F(000) = 2056. The structure was solved by Patterson and Fourier techniques and refined by least-squares to a final conventional R value of 0.032 for 5218 independent reflections with I ? 3σ(I). There are two independent Nd(No3)3 · (13-C-4) monomers in one asymmetrical unit. The coordination numbers are ten in these two independent monomers.  相似文献   

3.
Two derivatives, 3 L and 9 L , of a ditopic, multiply hydrogen‐bonding molecule, known for more than a decade, have been found, in the solid state as well as in solvents of low polarity at room temperature, to exist not as monomers, but to undergo a remarkable self‐assembly into a complex supramolecular species. The solid‐state molecular structure of 3 L , determined by single‐crystal X‐ray crystallography, revealed that it forms a highly organized hexameric entity 3 L 6 with a capsular shape, resulting from the interlocking of two sets of three monomolecular components, linked through hydrogen‐bonding interactions. The complicated 1H NMR spectra observed in o‐dichlorobenzene (o‐DCB) for 3 L and 9 L are consistent with the presence of a hexamer of D3 symmetry in both cases. DOSY measurements confirm the hexameric constitution in solution. In contrast, in a hydrogen‐bond‐disrupting solvent, such as DMSO, the 1H NMR spectra are very simple and consistent with the presence of isolated monomers only. Extensive temperature‐dependent 1H NMR studies in o‐DCB showed that the L 6 species dissociated progressively into the monomeric unit on increasing th temperature, up to complete dissociation at about 90 °C. The coexistence of the hexamer and the monomer indicated that exchange was slow on the NMR timescale. Remarkably, no species other than hexamer and monomer were detected in the equilibrating mixtures. The relative amounts of each entity showed a reversible sigmoidal variation with temperature, indicating that the assembly proceeded with positive cooperativity. A full thermodynamic analysis has been applied to the data.  相似文献   

4.
The water-soluble monomers, 1-methyl-4-vinylimidazole, 1-methyl-5-vinylimidazole, 1-ethyl-5-vinylimidazole, and 1-propyl-5-vinylimidazole have been synthesized, polymerized, and copolymerized with 4(5)-vinylimidazole. The copolymers were characterized by 14C-labeling, NMR, pKa determination and viscosity measurements. The monomer reactivity ratios determined by 14C counting are r1 = 1.04; r2 = 0.94 [M1 = 4(5)-vinylimidazole, M2 = 1-methyl-4-vinylimidazole] and r1 = 1.01; r2 = 0.86 [M1 = 4(5)-vinylimidazole, M2 = 1-methyl-5-vinylimidazole]. The esterolytic activity of the copolymers for the hydrolysis of p-nitrophenyl acetate (PNPA) at pH 7–8 in 28.5% ethanol–water was higher than that of the mixtures of homopolymers. At pH 5–6 the esterolytic activities of the copolymers and the mixtures were similar. The most efficient esterolytic activity for PNPA hydrolysis at pH 7.11 in 28.5% ethanol–water occurred for copolymers containing 75 mole % 4(5)-vinylimidazole and for copolymers containing 1-methyl-4-vinylimidazole rather than 1-methyl-5-vinylimidazole.  相似文献   

5.
Methylated β-cyclodextrin (me-β-CD) was used to complex the hydrophobic monomers isobornyl acrylate ( 1 ) and butyl acrylate (2) yielding the water-soluble host/guest complexes isobornyl acrylate/me-β-CD ( 1a ) and butyl acrylate/me-β-CD ( 2a ). The included monomers were copolymerized in water by free-radical mechanism and the kinetics were studied. In order to evaluate these results, the corresponding uncomplexed monomers 1 and 2 were also copolymerized in organic solution. The reactivity ratios of 1a and 2a (r 1a = 0.3, r 2a = 1.7) differ significantly from the reactivity ratios of the corresponding uncomplexed acrylates 1 and 2 in organic solution (r 1 = 1.3, r 2 = 1.0). In addition, we found that the weight averages of the copolymers prepared by using me-β-CD are significantly higher than those of the corresponding polymers prepared from uncomplexed monomers in organic solution.  相似文献   

6.
Chain transfer constants to monomer have been measured by an emulsion copolymerization technique at 44°C. The monomer transfer constant (ratio of transfer to propagation rate constants) is 1.9 × 10?5 for styrene polymerization and 0.4 × 10?5 for the methyl methacrylate reaction. Cross-transfer reactions are important in this system; the sum of the cross-transfer constants is 5.8 × 10?5. Reactivity ratios measured in emulsion were r1 (styrene) = 0.44, r2 = 0.46. Those in bulk polymerizations were r1 = 0.45, r2 = 0.48. These sets of values are not significantly different. Monomer feed compcsition in the polymerizing particles is the same as in the monomer droplets in emulsion copolymerization, despite the higher water solubility of methyl methacrylate. The equilibrium monomer concentration in the particles in interval-2 emulsion polymerization was constant and independent of monomer feed composition for feeds containing 0.25–1.0 mole fraction styrene. Radical concentration is estimated to go through a minimum with increasing methyl methacrylate content in the feed. Rates of copolymerization can be calculated a priori when the concentrations of monomers in the polymer particles are known.  相似文献   

7.
Three new monomers of p-phenylacrylamide derivatives were prepared by either the reaction of p-methyl-, p-nitro-, and p-chloroaniline with acryloyl chloride or with acrylic acid in the presence of dicyclohexyl carbodiimide (DCCI). The prepared monomers were copolymerized with each of tri-n-butyltinacrylate and tri-n-butyltinmethacrylate. Copolymerization reactions were carried out in dioxane at 70°C using 1 mol % azobisisobutyronitrile as a free radical initiator. The structure of the new monomers and the prepared copolymers were investigated by IR and 1H-NMR spectroscopy. The monomer reactivity ratios for the copolymerization of p-chlorophenylacrylamide (M1) with each of tri-n-butyltinacrylate (TBTA) and tri-n-butyltinmethacrylate (TBTMA) (M2) were found to be r1 = 2.6; r2 = 0.83 and r1 = 1.3; r2 = 1.71, respectively. In case of p-tolyacrylamide (M1) with TBTA and TBTMA (M2) r1 = 0.35, r2 = 1.03 and r1 = 1.38, r2 = 0.366 respectively. The Q and e values for the prepared p-tolyl- and p-chlorophenylacrylamide were calculated © 1993 John Wiley & Sons, Inc.  相似文献   

8.
The copolymers prepared in this study by free radical copolymerization of N-vinylpyrrolidone (M 2) with 4-vinylbenzylchloride (M 1) using 2,2′-azobisisobutyronotrile (AIBN) initiator in 1,4-dioxane solvent at 70°C were characterized by FTIR, 1H-NMR and 13C-NMR techniques. Polymer solubility was tested in both polar and nonpolar solvents. The thermal properties were studied by thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). Copolymer compositions were established by H1-NMR spectra, while reactivity ratios of the monomers were computed using the linearization methods viz., Fineman-Ross (FR) (r 1 = 1.67 and r 2 = 0.67), Kelen-Tudos (KT) (r 1 = 1.77 and r 2 = 0.65) and extended Kelen-Tudos (EK-T) (r 1 = 1.72 and r 2 = 0.63) methods at lower conversion. Furthermore, reactivity ratios in nonlinear error-in-variables method (RREVM) also compute the reactivity ratios (r 1 = 1.76 and r 2 = 0.66); these are found to be in good agreement with each other. The distribution of monomer sequence along the copolymer chain was calculated using a statistical method based on the calculated reactivity ratios.  相似文献   

9.
Copolymers of the cyclic ketene acetals, 2-methylene-5,5-dimethyl-1,3-dioxane, 3 , (M1) with 2-methylene-1,3-dioxolane, 4 , (M2) or 2-methylene-1,3-dioxane, 5 , (M2), were synthesized by cationic copolymerization. An experimental method was designed to study the reactivity of these very reactive and extremely acid sensitive cyclic ketene acetal monomers. The reactivity ratios, calculated using a computer program based on a nonlinear minimization algorithm, were r1 = 6.36 and r2 = 1.25 for the copolymerization of 3 with 4 , and r1 = 1.56 and r2 = 1.42 for the copolymerization of 3 with 5. FTIR and 1H-NMR spectra when combined with the values of r1 and r2 showed that these copolymers were formed by a cationic 1,2-polymerization (ring-retained) route. Furthermore the tendency existed to form very short blocks of M1 or M2 within the copolymers. Cationic copolymerization of cyclic ketene acetals have the potential to be used for synthesis of novel polymers. © 1996 John Wiley & Sons, Inc.  相似文献   

10.
The influence of three aromatic tertiary diamines, bis(4-dimethylamino phenyl) methane (DMAPM), N,N,N′,N′-tetramethyl-p-phenylenediamine (p-TMPDA), and N,N,N′,N′-tetramethyl-o-phenylenediamine (o-TMPDA), on the kinetics of polymerization of isoprene in hexane solution, with n-BuLi as initiator, was studied for different values of ratio r = [amine]/[n-BuLi]. It is shown that added amine increases initiation rate according to its complexing ability (DMAPM < p-TMPDA « o-TMPDA); this result is explained by the formation of complexes between amine A and n-BuLi, (n-BuLi, A)x, where x = 6, 4, and 1 for the three amines, respectively. The propagation rate and the structure of polyisoprene are modified with o-TMPDA only; the decrease in propagation rate and the increase in 3,4 units in the polymer obtained when r increases are assigned to the formation of solvated ion pairs PI?Li+, o-TMPDA.  相似文献   

11.
The stereoregularity of polydienes is almost the same in regard to the individual elements of the lanthanide series, whereas the activity of the Ln catalysts in diene polymerization varies from one to the other within the series. The latter may be attributed to the difference in the number of electrons that occupy the 4f orbitals. It has been proved that the polymerization of dienes with Ln catalysts under certain conditions proceeds by a “living polymer” mechanism. With regard to the polymerization of butadiene, the most active catalyst is a Nd3+species a new binary system of NdCl3-3ROH + AlR3 has been discovered. The cis- 1,4 content in polybutadiene is about 97% and the 1,2 content, less than 1%. For the polymerization of isoprene with a Nd3+ catalyst system, the effects of ligand and alkyl groups in AIR3 on cis-1,4 content (ca. 95%) in polyisoprene can be neglected. For the copolymerization of butadiene and isoprene, the cis-1,4 contents of these two monomeric units in the copolymer are greater than 95% the reactivity ratios r1 and r2 are determined. and the Tg's of the copolymers of various compositions deviate slightly from the calculated values for random copolymers. A linear relationship exists between the yield strength from the stress-strain curve of Ln-polvbutadiene and its [n] This relationship is verified by Ln-polyisoprene and natural rubber but different slopes are obtained  相似文献   

12.
The crystal structure of the macrocyclic complex [Ni(PCHA)](ClO4)2 (II) (PCHA = 4-methyl-1,3,5,8,11,14-hexaazatricyclooctadecane) is described. In the presence of succinate acid, [Ni(PCHA)](ClO4)2 (II) is obtained by recrystallization of orange crystals of [Ni(PCHA)](ClO4)2 (I), whose structure has previously been identified. The [Ni(PCHA)](ClO4)2 (II)crystal belongs to the monoclinic P2(1)/c space group with a = 15.8561(3) ?, b = 9.4409(2) ?, c = 13.9297(2) ?, α = 90°, β = 94.8840(10)°, γ = 90°, M r = 526.02, Z = 4, V = 2077.65(7) ?3. The structure is ionic with [Ni(L)]2+ and two perchlorate anions with a supermolecular interaction.  相似文献   

13.
A polymer-supported Ziegler–Natta catalyst, polystyrene-TiCl4AlEt2Cl (PS–TiCl4AlEt2Cl), was synthesized by reaction of polystyrene–TiCl4 complex (PS–TiCl4) with AlEt2Cl. This catalyst showed the same, or lightly greater catalytic activity to the unsupported Ziegler–Natta catalyst for polymerization of isoprene. It also has much greater storability, and can be reused and regenerated. Its overall catalytic yield for isoprene polymerization is ca. 20 kg polyisoprene/gTi. The polymerization rate depends on catalyst titanium concentration, mole ratio of Al/Ti, monomer concentration, and temperature. The kinetic equation of this polymerization is: Rp = k[M]0.30[Ti]0.41[Al]1.28, and the apparent activation energy ΔEact = 14.5 kJ/Mol, and the frequency factor Ap = 33 L/(mol s). The mechanism of the isoprene polymerization catalyzed by the polymer-supported catalyst is also described. © 1993 John Wiley & Sons, Inc.  相似文献   

14.
Introduction Molecular recognition and molecular self-assemblycarried out by cooperation of the weak interactions(electrostatic reaction, hydrogen bonds, van der Waalsforce, short-range repulsive force, etc) are the commonphenomena in nature. In recent years, the research onsupramolecular complex has been a crossing focus ofseveral subjects such as chemistry, physics, biology,material and information.1 Supramolecular complex hasa wide application foreground in material, catalysis,conductor,…  相似文献   

15.
The polymerization ability of two new pyrazolone-containing monomers—3-methyl-1-phenyl-4-crotonoyl-pyrazolone-5 ( Cr ) and 3-methyl-1-phenyl-4-(3′-phenyl-acryloyl) pyrazolone-5 ( Cy )—was investigated. The monomers were obtained by acylation of 3-methyl-1-phenyl-pyrazolone-5 with crotonyl chloride or cinnamoyl chloride, respectively. It was established that the two monomers do not homopolymerize either under the action of ionic and radical initiators nor with γ-rays (doses between 2 and 10 MRad). In contrast to this, the two monomers copolymerize with other vinyl comonomers. Copolymers of Cr and Cy with methacrylic acid (MAA), methyl methacrylate (MMA), and Styrene (St) were synthesized by radical copolymerization. The molecular weights of the polymer products obtained were in the 10,000–65,000 range. It was established that the molecular weight characteristics of the copolymers were affected by the concentration of the pyrazolone-containing monomer and by the chemical nature of the solvent used. The copolymerization of Cr and Cy with MAA was investigated in detail in order to evaluate the relative activity of the new monomers during copolymerization. The reactivity ratios (r) were calculated by three different methods with good agreement. The values obtained for the monomer pairs are: rMAA = 0.61 ± 0.01, rCr = 0.04 ± 0.01; rMAA = 0.64 ± 0.05, rCy = 0.02 ± 0.02. The Q/e values for Cr and Cy were determined using the reactivity ratios of both monomers.  相似文献   

16.
4‐Methacryloyl‐2,2,6,6‐tetramethyl‐piperidine (MTMP) was applied as reactive hindered amine piperidine. Photo‐induced copolymerization of methyl methacrylate (MMA, M1) with MTMP (M2) was carried out in benzene solution at ambient temperature. The reactivity ratios for these monomers were measured by running a series of reactions at various feed ratios of initial monomers, and the monomer incorporation into copolymer was determined using 1H NMR. Reactivity ratios of the MMA/MTMP system were measured to be r1 = 0.37 and r2 = 1.14 from extended Kelen‐Tüdos method. The results show that monomer MTMP prefers homopolymerization to copolymerization in the system, whereas monomer MMA prefers copolymerization to homopolymerization. Sequence structures of the MMA/MTMP copolymers were characterized using 1H NMR. The results show that the sequence structure for the main chain of the MMA/MTMP copolymers is mainly composed of a syndiotactic configuration, only with a little heterotactic configuration. Three kinds of the sequences of rr, rr′, and lr′ in the syndiotactic configuration are found. The sequence‐length distribution in the MMA/MTMP copolymers is also obtained. For f1 = 0.2, the monomer unit of MMA is mostly separated by MTMP units, and for f1 = 0.6, the alternating tendency prevails and a large number of mono‐sequences are formed; further up to f1 = 0.8, the monomer unit of MTMP with the sequence of one unit is interspersed among the chain of MMA. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

17.
Rate coefficients for the gas‐phase reaction of isoprene with nitrate radicals and with nitrogen dioxide were determined. A Teflon collapsible chamber with solid phase micro extraction (SPME) for sampling and gas chromatography with flame ionization detection (GC/FID) and a glass reactor with long‐path FTIR spectroscopy were used to study the NO3 radical reaction using the relative rate technique with trans‐2‐butene and 2‐buten‐1‐ol (crotyl alcohol) as reference compounds. The rate coefficients obtained are k(isoprene + NO3) = (5.3 ± 0.2) × 10?13 and k(isoprene + NO3) = (7.3 ± 0.9) × 10?13 for the reference compounds trans‐2‐butene and 2‐buten‐1‐ol, respectively. The NO2 reaction was studied using the glass reactor and FTIR spectroscopy under pseudo‐first‐order reaction conditions with both isoprene and NO2 in excess over the other reactant. The obtained rate coefficient was k(isoprene + NO2) = (1.15 ± 0.08) × 10?19. The apparent rate coefficient for the isoprene and NO2 reaction in air when NO2 decay was followed was (1.5 ± 0.2) × 10?19. The discrepancy is explained by the fast formation of peroxy nitrates. Nitro‐ and nitrito‐substituted isoprene and isoprene‐peroxynitrate were tentatively identified products from this reaction. All experiments were conducted at room temperature and at atmospheric pressure in nitrogen or synthetic air. All rate coefficients are in units of cm3 molecule?1 s?1, and the errors are three standard deviations from a linear least square analyses of the experimental data. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 37: 57–65, 2005  相似文献   

18.
The effects of SnCl4 on the radical polymerization of N-allyl-N-phenylmethacrylamide (APM) and N-allyl-N-phenylacrylamide (APA) were investigated. The polymerizations of APM and APA with dimethyl 2,2-azobisisobutyrate (MAIB) were carried out at 50°C in benzene at various concentrations (0-1.0 mol/L) of SnCl4. The polymerization rates showed a maximum on varying the SnCl4 concentration, while the molecular weights of the resulting poly(APM) and poly(APA) were decreased with increasing SnCl4 concentration. In both systems, the degree of cyclization of polymers were decreased with the SnCl4 concentration. From the IR results, the cyclic structure of the resulting poly(APM)s was confirmed to be five-membered, whereas poly(APA)s contained not only five-membered but also six-membered rings. The 1H-NMR examination on the interactions of APM and APA with SnCl4 revealed that these monomers form 1:1 and 2:1 complexes with SnCl4 with fairly large stability constants. Copolymerizations of APM (M1) with methyl methacrylate (MMA) and styrene (St) (M2) were investigated at 60°C in benzene in the absence of SnCl4. APM units were found to be incorporated exclusively as five-membered rings in the resulting copolymer. Monomer reactivity ratios were estimated to be r1 = 0.29, r2 = 4.88 for APM/MMA and r1 = 0.66, r2 = 5.39 for APM/St. The presence of equimolar (to APM) SnCl4 was found to enhance the reactivity of APM toward poly(MMA) radical; r1 = 0.24, r2 = 2.56. © 1996 John Wiley & Sons, Inc.  相似文献   

19.
Forced ideal carbocationic copolymerization of isobutylene and isoprene has been achieved by continuous addition of monomer mixtures of different compositions to cumyl chloride/TiCl4 charges at -50°C. The overall rate of copolymerization could be kept equal to that of addition rate with up to 10 mol% isoprene in the mixed monomer feed. In this monomer concentration range the composition of the copolymer was identical to that of the feeds. At higher diene concentrations in the feed, chain transfer to monomer and other side reactions (intramolecular cyclization, gel formation) could not be completely avoided. The number-average molecular weight of the copolymers increased almost linearly with the amount of consumed monomers at 10 mol% isoprene concentrations in the feed (i.e., in the quasiliving range). According to 1H-NMR and 13C-NMR spectroscopy, the products are random copolymers.  相似文献   

20.
Abstract

Free radical copolymerization of styrene (St) and N(4-bro-mophenyl)maleimide (4BPMI) in dioxane solution gave an alternating copolymer in all proportions of feed comonomer compositions. The monomer reactivity ratios were found to be r 1, = 0.0218 ± 0.0064 (St) and r 2, = 0.0232 ± 0.0112 (4BPMI), and the activation energy of the copolymerization reaction for the equimolar ratios of comonomer was E a, = 51.1 kJ/mol. The molecular weights of the copolymers obtained are relatively high, the T g's showed similar values (490 K), and the thermal stability is higher than that of polystyrene. The initial rate of copolymerization depends on the total concentration of the comonomers and the maximum occurred at higher 4BPMI mol fractions; however, the overall conversion is highest at equimolar comonomer composition. It has been shown that a charge-transfer complex participates in the process of copolymerization. The initial reaction rate was measured as a function of the monomer molar ratios, and the participation of the charge-transfer complex monomer and the free monomers was quantitatively estimated.  相似文献   

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