苯甲醛及其衍生物对铈离子存在下丙烯酰胺聚合的影响

<正> 虽然Santappa等早已报道Ce~(4+)(高氯酸铈)/甲醛体系能引发丙烯腈(AN)、甲基丙烯酸甲酯(MMA)的聚合,但对醛的活性以及参与引发单体聚合的自由基都未有详细报道,近来孙燕慧等发现脂肪醛能显著促进Ce~(4+)(硝酸铈铵CAN)引发丙烯酰胺(AAM)的聚合,而且醛的活性远大于相应的醇。至于芳香醛对于Ce~(4+)引发烯类单体的聚合的影响也未见详细报道。本文扼要报道苯甲醛(BA)及其衍生物对-硝基苯甲醛(PNBA)、间-硝基苯甲醛(MNBA)、间-溴苯甲醛(MBBA)、对-氯苯甲醛(PCBA)对Ce~(4+)(CAN)存在下丙烯酰胺聚合的影响,测定了其聚合速率,以UV吸收光谱、ESR波谱测定     

Studies on the kinetics of ceric-thiourea initiated aqueous polymerization of methyl methacrylate—II. Mechanistic features in strongly acid solutions

The kinetics of ceric-thiourea initiated aqueous polymerization of methyl methacrylate in 1 M H₂SO₄ have been studied. Ceric ion and thiourea initially form an 1:1 complex which then reacts with uncomplexed ceric ion to form the initiating thiocarbamido radicals. The termination is predominantly biomolecular below an initial ceric concentration of 0.66 × 10^?2 M (depending upon the rate of initiation). At higher initial ceric concentrations, polymer radicals are terminated overwhelmingly by ceric ions. Substituted thioureas reduce the rate of polymerization according to the order of increasing electron density on the sulphur atom. The overall activation energy of polymerization is 12.1 kcal/mol in the region of bimolecular termination and 10.2 kcal/mol in the region of metal ion termination.     

STUDIES ON THE INITIATION MECHANISM OF CERIC ION AND ACETYLACETONE REDOX SYSTEM IN VINYL POLYMERIZATION

The initiation mechanism of acrylamide (AAM)polymerization using ceric ion/acetylacetone system as an initiator has been studied. The redox polymerization was revealed by the low value of overall activation energy of AAm polymerization. The structure of free radicals formed from above-mentioned initiation sytem were detected by radical trapping and ESR spectra techniques and the end groups of polymers obtained were determined by FT-IR spectra analysis method. Based on these results the initiation mechanism is proposed.     

Polymerization of Methacrylamide Initiated by Ceric Ion-Citric Acid Redox System

Homogeneous polymerization of methacrylamide initiated by the ceric ammonium sulfate-citric acid (CA) redox pair has been investigated and reported at 35 ± 0.2°C under nitrogen atmosphere. The initiation was caused by the free radical generated by the decomposition of the complex formed between ceric ion and citric acid. The rate of monomer disappearance was found to be proportional to [CA]^0.4, [Ce^0.4+]^0.65, and [Monomer]¹ The rate of ceric ion disappearance was directly proportional to the ceric ion concentration but independent of the monomer concentration. The initial rate was independent of [H₂SO₄]. The activation energy of the system was found to be 21.4 kJ/mol.     

Determination of concentration of propagating species in cationic polymerization of tetrahydrofuran

A spectroscopic method is described for the determination of the concentration of propagating species, [P^*], in the polymerization of tetrahydrofuran catalyzed by a mixture of AlEt₃?H₂O (1:0.5) and epichlorohydrin. A phenyl ether group was introduced at the polymer chain end by the quantitative reaction of the propagating species with excess sodium phenoxide. From the amount of phenyl ether groups in the polymer and of the remaining sodium phenoxide, [P^*] was determined by means of ultraviolet spectroscopy. The [P^*] value so determined was found to be in good agreement with that calculated from the amount and molecular weight of polymer based on a stepwise addition mechanism without chain transfer or termination. The present method of [P^*] determination was employed to examine the course of polymerization. It has now been found that [P^*] increases progressively during an induction period and remains unchanged in the subsequent period of polymerization.     

Polymerization of acrylonitrile initiated by ceric ion–citric acid redox system

Heterogeneous polymerization of acrylonitrile initiated by ceric ammonium sulfate–citric acid (C.A.) redox system is reported at 35 ± 0.2°C under nitrogen atmosphere. The rate of monomer disappearance is found to be proportional to [C.A.]⁰, [Ce⁴⁺]^0.63, and [Monomer]^1.59. The rate of ceric ion disappearance is directly proportional to ceric ion concentration but independent of monomer concentration. The initial rate was independent of [H₂SO₄]. The molecular weight of polyacrylonitrile increases with increasing monomer concentration and decreasing ceric ion concentration. Activation energy was found to be 27.9 kJ/mol.     

A ytterbium polymer incorporating ethyl-4,5-imidazole-dicarboxylate and formate coligand: Structure, luminescent, and magnetic properties

A new lanthanide-organic coordination polymer incorporating both substituted imdazole dicarboxylate and formate auxiliary ligand, namely {[Yb₃(HEimda)₄(μ₂-HCOO) · 4H₂O] · 2H₂O} _n (I) (H₃Eimda = 1H-2-ethyl-4,5-imidazole-dicarboxylic acid), has been prepared and was structurally characterized by elemental analysis, IR and X-ray diffraction. It crystallizes in the monoclinic system, space group of C2/c. The polymer I is built from two dimensional (2D) double decker networks based on the Ln₄HEimda₄ tetranuclear basic carboxylate as secondary building unit. The extensive hydrogen bonds extend the 2D lamellar network into a 3D supramolecular aggregate. The emission spectrum of polymer I exhibits ligand-to-metal charge-transfer luminescence. Variable-temperature magnetic susceptibility measurement reveals that the end to end bridging fashion of formate group results in the depopulation of the stark levels for a single Yb³⁺ ion and/or possible antiferromagntic interactions between Yb³⁺ ions within the carboxylato bridged dinuclear unit.     

Atom Transfer Radical Polymerization of Butadiene Initiated by Benzyl Chloride/MoCl5 Substituted by 1-octanol/PPh3

A novel initiator system, benzyl chloride/MoCl₅ substituted by 1-octanol/triphenyl phosphine (PPh₃), was applied to the atom transfer radical polymerization (ATRP) of butadiene. The characterization revealed the linear increase of the number average molecular weight with the monomer conversion and the rather wide molecular weight distributions of the polymerization products. The microstructure of the butadiene was detected by IR and ¹H-NMR. The chlorine atom at ω –end group of the polymer and the change of valence states of molybdenum detected by UV–Vis spectra revealed that the polymerization accorded primarily with the mechanism of ATRP.     

Redox-Initiated Polymerization of Methyl Methacrylate

The redox-initiated polymerization of methyl methacrylate (MMA) by the Ce(IV)-malic acid system has been carried out in aqueous medium under an inert atmosphere. The rate of polymerization was found to be proportional to [MMA]^3/2 [MA]^1/2 [Ce(IV)]^1/2 and the rate of ceric ion disappearance was proportional to [Ce(IV)] but independent of [MMA]. The rate increased linearly up to a certain range of [MA], above which it remained constant. Increasing [H₂SO₄] decreased the rate. The activation energy was found to be 57.44 kJ/mol.     

Amino and Acetamide Functional Group Effects on the Ionization and Fragmentation of Sugar Chains in Positive-Ion Mass Spectrometry

To elucidate the influence of amino (-NH₂) and acetamide (-NHCOCH₃, -NAc) groups in sugar chains on their ionization and fragmentation, cycloamyloses (cyclodextrins, CyDs) and lacto-oligosaccharide are analyzed by MALDI TOF/TOF and ESI Q-TOF mass spectrometry. CyD derivatives substituted by amino or acetamide groups are ideal analytes to extract the function group effects, which are amino-CyD with one hexosamine (HexNH₂) and acetamide-CyD with one N-acetyl hexosamine (HexNAc). Interestingly, the relative ion intensities and isotope-like patterns in their product ion spectra depend on the functional groups and ion forms of sugar chains. Consequently, the results indicate that a proton (H⁺) localizes on the amino group of the amino sugar, and that the proton (H⁺) induces their fragmentation. Sodium cation (Na⁺) attachment is independent from amino group and exerts no influence on their fragmentation patterns in amino group except for mono- and disaccharide fragment ions because there is the possibility of the reducing end effect. In contrast, a sodium cation localizes much more frequently on the acetamide group in acetamide-CyDs because the chemical species with HexNAc are stable. Thus, their ions with HexNAc are abundant. These results are consistent with the fragmentation of lacto-neo-N-tetraose and maltotetraose, suggesting that a sodium cation generally localizes much more frequently on the acetamide group in sugar chains.

Dinuclear peroxo complexes of molybdenum(VI) containing Mannich base ligands

Dinuclear molybdenum(VI) peroxo complexes containing Mannich base ligands having formulae [Mo₂O₄(O₂)₂L-L(H₂O)₂] · H₂O [where L-L = N-[1-morpholinobenzyl] acetamide (MBA), N-[1-piperidinobenzyl] acetamide (PBA), N-[1-morpholino(-4-nitrobenzyl)] benzamide (MPNBB), N-[1-piperidino(-3-nitrobenzyl)] benzamide (PMNBB), N-[1-morpholino(-2-nitrobenzyl)] acetamide (MONBA), and N-[1-morpholino(-3-nitrobenzyl)] acetamide (MMNBA)] have been synthesized by stirring ammonium heptamolybdate with excess 30% aqueous hydrogen peroxide followed by treatment with ethanolic solution of corresponding ligands. The complexes have been characterized by elemental analysis, molar conductance, magnetic measurements, infrared (IR), electronic, TGA/DTA, mass spectral, and ¹H NMR studies. The complexes are non-electrolytes and diamagnetic. The IR spectral studies suggest that the ligands are bidentate to metal through carbonyl oxygen and ring nitrogen. Thermal analyses provide conclusive evidence for the presence of coordinated, as well as lattice water in the complexes. Dinuclear complexes preserve the individuality of the molybdenum oxo peroxo core. The complexes exhibit higher antibacterial activity against bacterium Ralastonia solanacearum (Pseudomonas solanacearum) than the free ligands.     

Vinyl polymerization of acrylonitrile by the Ce(IV)-glucose redox system

Aqueous polymerization of acrylonitrile (M) initiated by the Ce(IV)-glucose (R) redox system has been studied under nitrogen in the temperature range of 30–40 °C. The rate of polymerization (Rp) is proportional to [M]², [R] and inversely proportional to [Ce(IV)]. The rate of ceric ion disappearance is proportional to [R] and [Ce(IV)]. The end group in the polymer is characterised by IR spectra. A suitable kinetic scheme has been proposed and explained in the light of these experimental findings.     

4,5‐Di­hydro‐3‐methyl‐5‐(4‐methyl­phenyl)‐1H‐pyrazole‐1‐carboxamidinium acetate acetone hemisolvate

The X‐ray structure analysis of the unexpected product of the reaction between 4‐(4‐methyl­phenyl)­but‐3‐en‐2‐one and amino­guanidine revealed the title compound, C₁₂H₁₇N₄⁺·C₂H₃O₂^?·0.5C₃H₆O, consisting of a protonated amidine moiety joined to a substituted pyrazoline ring at the N1 atom. The amidine group is protonated and the positive charge is delocalized over the three C—N bonds in a similar manner to that found in guanidinium salts. The amidinium moiety of the cation is linked to the acetate anions through four N—H?O hydrogen bonds, with N?O distances of 2.749 (4), 2.848 (4), 2.904 (4) and 2.911 (4) Å. The pyrazoline ring adopts a flattened envelope conformation and the substituted phenyl ring is oriented perpendicular to the attached heterocycle. The acetone solvate molecule lies across a twofold rotation axis.     

含联吡啶，Eu(III)或Gd(III)的手性高分子配合物的合成及荧光性质研究

手性高分子P–1由(R)-5,5′-二溴-6,6′-二(4-三氟甲基苯基)-2,2′-二正辛氧基-1,1′-联萘(R–M–1)和5,5′-二乙烯基-2,2′-联吡啶(M–2)通过Pd催化的Heck偶合反应合成得到,高分子配合物P-2和P-3由高分子P-1与Eu(TTA)3·2H2O和Gd(TTA)3·2H2O (TTA– = 2-噻吩甲酰三氟丙酮)反应生成。手性高分子P-1能发射强的蓝色荧光,这是由于手性重复单元(R)-6,6′-二(4-三氟甲基苯基)-2,2′-二正辛氧基-1,1′-联萘和单元2,2′-联吡啶通过亚乙烯基桥连形成共轭高分子结构造成的。在不同的激发波长激发下,含Eu(III)的高分子配合物P–2不仅显示高分子荧光,还可显示Eu(III) (5D0→7F2)特征荧光。含Gd(III)的高分子配合物P–3仅发射高分子荧光。基于高分子及含RE(III)的高分子配合物的荧光性质研究发现,共轭高分子并没有把能量转移到Eu(III)或Gd(III) 配合物部分,只发射它自身的荧光,含Eu(III)的高分子配合物P–2发射Eu(III) (5D0→7F2)特征荧光能量主要来源于配阴离子TTA–。     

VINYL RADICAL POLYMERIZATION INITIATED WITH CERIC ION AND ETHYL N, N-DIETHYLDITHIOCARBAMYL ACETATE SYSTEM

Acrylamide polymerization initiated with a redox initiation system consisting of cericion and ethyl N, N-diethyldithiocarbamyl acetate (EDCA) has been studied. It was foundthat the polymerization rate equation is in good agrement with that of a redox initiatedpolymerization, and the overall activation energy of the polymerization was determinedto be 25.2kJ·mol~(-1). Accordingly, the system belongs to a redox initiator. The initiationmechanism was proposed based on the end group analysis using FT-IR, UV spectroscopies.Analysis results revealed that the N, N-diethyldithiocarbamyl radical produced from theredox reaction of EDCA with ceric ion can initiate acrylonitrile (AN) polymerization andform the end group on PAN. The resulting PAN was photopolymerized with butyl acrylate(BA) to form PAN-b-PBA block copolymer.     

Specific F binding to phenyl ring of aromatic polymers

Most of the hydrogels deswell more remarkably in F⁻ containing solutions than in other monovalent anion containing solutions. However, significant deswelling followed by abnormal reswelling of polymer gel in KF solutions with increasing F⁻ concentration was observed in a series of polymer gels consisted of phenyl rings, for instance, poly(styrene sulfonic acid) (PSSA), hydroxypropyl methylcellulose phthalate (HPMCP) and poly(4-vinyl phenol) (P4VPh) gel. Driving force of this phenomenon was studied to reveal the specific interactions involved in the aqueous systems of aromatic polymers. Elemental analysis and XPS results suggest that F⁻ is embedded to the gel by the physical adsorption of KF, as well as the interactions between phenyl ring and F⁻. Further theoretical calculations revealed that the interaction may be (phenyl)CH?F⁻(H₂O)_n interaction, which is stronger than (phenyl)CH?(H₂O)_n hydrogen bond. This kind of interaction decreases with the increasing water number and it is invalid when the surrounding water number is more than 5 for the phenol-F⁻(H₂O)_n system. Therefore, we conclude that F⁻ could bind to phenyl ring via such (phenyl)CH?F⁻(H₂O)_n interaction in solutions with low hydrophilicity. The strong polarization effect of F⁻ and (phenyl)CH?F⁻(H₂O)_n interaction are two important driving forces for the reswelling of gels.     

Ceric Ion Initiated Graft Polymerization onto Poly(vinyl Alcohol)

This paper describes the kinetics of the ceric ion-initiated graft co-polymerization of vinyl acetate-acrylonitrile to poly(vinyl alcohol). The graft copolymerization rate R_p was found to be first order with respect to the total concentration of the comonomer mixture [M], the concentration of vinyl alcohol repeating units [PVA], and the mole fraction of vinyl acetate in the comonomer feed mixture. R_p was independent of cerous ion. The grafting rate was independent of ceric ion above a ceric concentration of 0.0020 M but first order in ceric ion below that concentration. Rp initially increased rapidly with [H⁺] to a maximum and then decreased and levelled off at hgher [H⁺]. The rate of ceric ion disappearance was first order in [PVA], independent of [MI, and increased with increasing [H⁺] with a leveling off at high [H⁺]. A reaction mechanism.     

Initiation Mechanism of Polymerization of Acryl－amide by Ceric Ion／2－Benzoyl Acetanilide System

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Different molecular conformations co‐exist in each of three 2‐aryl‐N‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)acetamides: hydrogen bonding in zero,one and two dimensions

4‐Antipyrine [4‐amino‐1,5‐dimethyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐one] and its derivatives exhibit a range of biological activities, including analgesic, antibacterial and anti‐inflammatory, and new examples are always of potential interest and value. 2‐(4‐Chlorophenyl)‐N‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)acetamide, C₁₉H₁₈ClN₃O₂, (I), crystallizes with Z′ = 2 in the space group P, whereas its positional isomer 2‐(2‐chlorophenyl)‐N‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)acetamide, (II), crystallizes with Z′ = 1 in the space group C2/c; the molecules of (II) are disordered over two sets of atomic sites having occupancies of 0.6020 (18) and 0.3980 (18). The two independent molecules of (I) adopt different molecular conformations, as do the two disorder components in (II), where the 2‐chlorophenyl substituents adopt different orientations. The molecules of (I) are linked by a combination of N—H…O and C—H…O hydrogen bonds to form centrosymmetric four‐molecule aggregates, while those of (II) are linked by the same types of hydrogen bonds forming sheets. The related compound N‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)‐2‐(3‐methoxyphenyl)acetamide, C₂₀H₂₁N₃O₃, (III), is isomorphous with (I) but not strictly isostructural; again the two independent molecules adopt different molecular conformations, and the molecules are linked by N—H…O and C—H…O hydrogen bonds to form ribbons. Comparisons are made with some related structures, indicating that a hydrogen‐bonded R₂²(10) ring is the common structural motif.     

Synthesis of highly branched polyethylene using para‐phenyl‐substituted α‐diimine nickel catalysts

A series of para‐phenyl‐substituted α‐diimine nickel complexes, [(2,6‐R₂‐4‐PhC₆H₂N═C(Me))₂]NiBr₂ (R = ⁱPr ( 1 ); R = Et ( 2 ); R = Me ( 3 ); R = H ( 4 )), were synthesized and characterized. These complexes with systematically varied ligand sterics were used as precatalysts for ethylene polymerization in combination with methylaluminoxane. The results indicated the possibility of catalytic activity, molecular weight and polymer microstructure control through catalyst structures and polymerization temperature. Interestingly, it is possible to tune the catalytic activities ((0.30–2.56) × 10⁶ g (mol Ni·h)^?1), polymer molecular weights (M_n = (2.1–28.6) × 10⁴ g mol^?1) and branching densities (71–143/1000 C) over a very wide range. The polyethylene branching densities decreased with increasing bulkiness of ligand and decreasing polymerization temperature. Specifically, methyl‐substituted complex 3 showed high activities and produced highly branched amorphous polyethylene (up to 143 branches per 1000 C).