Rate of complex formation for poly-n-vinyl carbazole and n-ethyl carbazole with various electron acceptors

The rates of complex formation for poly-N-vinyl carbazole and its saturated monomer analogue, N-ethyl carbazole, with various electron acceptors (chloranil, trinitrobenzene and picric acid) have been investigated. In mole ratios 1:1, the complex forming reactions in chloroform proceed rapidly, as measured by a “stopped flow” method; the rate constants are of the order of 10³ 1. mole^?1 sec^?1. The rate constants are smaller than those of the complexes with tetracyanoethylene as acceptor and decrease with decreasing electron affinity of the acceptor. The rate constants also depend on the molecular weight of the donor.     

在丙烯酰胺聚合反应中聚苯乙烯磺酸效应的研究

<正> 在聚合体系中添加具有一定结构的高分子化合物作模板,并利用此模板高分子与单体分子间存在的某种相互作用使单体分子按一定的排列进行聚合,这是所谓“模板聚合”的最初尝试,近年来,模板聚合已成为一类新的聚合方法,利用模板大分子对其周围单体分子反应过程和生成物结构、分子量的影响,有些研究者已由此成功地实现了对新生成物分子量和空间构型的控制,从而为实现高分子设计开创了新的途径。     

Kinetics of complex formation of poly-n-vinyl carbazole and n-ethyl carbazole with electron acceptors at different molar ratios

The rates of complex formation for poly-N-vinyl carbazole and its saturated low molecular analogue, N-ethyl carbazole, with tetracyanoethylene, chloranil, trinitrobenzene and picric acid in chloroform solution have been investigated at molar ratios of donor to acceptor, D/A = 1, 2, 4, 8 and 10. The reaction rate was studied by the “stopped flow” method. At mole ratio D/A > 1 the complex forming reactions follow kinetics of first order. The apparent rate constants were calculated by the least squares method. The complex formation rate constants for the monomer analogue are higher than those for the polymer. They also depend on the electron affinity of the acceptor. The reaction rate rises with increase of the electron affinity of the acceptor.     

Molecular Complexes of Crown Ethers, Part 6: Complexes of Cryptand (2,2,2) and Kryptofix 5 with Some Acceptors

The UV-Visible spectra of Cryptand (2,2,2) and Kryptofix 5 as donors, and TCNE (tetracyanoethylene), DDQ (2,3-dichloro-5,6- dicyano-1,4 benzoquinone) and PA (picric acid) as acceptors were studied. Charge transfer (CT) spectra were obtained for these systems. It was found that potassium halides have little effect on the spectra. The major process was due to an electron transfer from the donor to the acceptor. This revealed itself in very high conductivity values for the CT solutions in comparison to that of the donor or the acceptor solutions. The infrared and proton NMR spectra of the complexes indicated a strong interaction between the donor and the acceptor.     

Polymerization of methyl methacrylate induced with the peracid-type ion exchange resin

The polymerization of methyl methacrylate initiated with a peracid-type resin was studied. The peracid-type resin was prepared by the oxidation of cation-exchange resin (Amberlite IRC-50) with 60 wt-% aqueous hydrogen peroxide in the presence of p-toluenesulfonic acid. It was found that the peracid-type resin was effective as an initiator for polymerization of methyl methacrylate. The kinetic investigation indicated that this polymerization proceeded by a radical mechanism, and the overall activation energy of polymerization was 15.8 kcal/mole. No effect of macromolecular catalyst on steric structure of the resulting polymer was observed. Some graft polymer was formed in bulk polymerization. On the other hand, only a homopolymer was obtained in solution polymerization. From the results obtained, a possible mechanism of initiation with the peracid-type resin is proposed and discussed.     

Polymerization of Acrylonitrile Initiated by 1,4-Dimethyl-1,4-bis(p-nitrophenyl)-2-tetrazene

The polymerization of acrylonitrile (AN) initiated by 1,4-dimethyl-1,4-bis(p-nitrophenyl)-2-tetrazene (Ie) was studied in dimethylformamide (DMF) at high temperature. The polymerization proceeds by a radical mechanism. The rate of polymerization is proportional to [Ie]^0.64 and [AN]^1.36. The overall activation energy for the polymerization is 21.5 kcal/mole within the temperature range of 115-130°C. The chain transfer of Ie was also undertaken over the temperature range of 120-135°C. The activation parameters for the decomposition of Ie at 120°C are k_d = 2.78 × 10^?6 sec^?1, ΔH^? = 40.8 kcal/mole, and ΔS^? = 19.5 cal/mole-deg, respectively.     

Catalytic action of metallic salts in autoxidation and polymerization. IV. Polymerization of methyl methacrylate by cobalt(II) or (III) acetylacetonate–tert-butyl hydroperoxide or dioxane hydroperoxide

Polymerization of methyl methacrylate was carried out by four initiating systems, namely, cobalt(II) or (III) acetylacetonate–tert-butyl hydroperoxide (t-Bu HPO) or dioxane hydroperoxide (DOX HPO). Dioxane hydroperoxide systems were much more effective for the polymerization of methyl methacrylate than tert-butyl hydroperoxide systems, and cobaltous acetylacetonate was more effective than cobaltic acetylacetonate in both hydroperoxides. The initiating activity order and activation energy for the polymerization were as follows: Co(acac)₂–DOX HPO (E_a-9.3 kcal/mole) > Co (acac)₃–DOX HPO (E_a = 12.4 kcal/mole) > Co(acac)₂–t-Bu HPO (E_a = 15.1 kcal/mole) > Co(acac)₃–t-Bu HPO (E_a-18.5 kcal/mole). The effects of conversion and hydroperoxide concentration on the degree of polymerization were also examined. The kinetic data on the decomposition of hydroperoxides catalyzed by cobalt salts gave a little information for the interpretation of polymerization process.     

Studies of redox polymerization. I. Aqueous polymerization of acrylamide by an ascorbic acid–peroxydisulfate system

The polymerization of acrylamide initiated by an ascorbic acid–peroxydisulfate redox system was studied in aqueous solution at 35 ± 0.2°C in the presence of air. The concentrations studied were [monomer] = (2.0–15.0) × 10^?2 mole/liter; [peroxydisulfate] = (1.5–10.0) × 10^?3 mole/liter; and [ascorbic acid] = (2.84–28.4) × 10^?4 mole/liter; temperatures were between 25–50°C. Within these ranges the initial rate showed a half-order dependence on peroxydisulfate, a first-order dependence on an initial monomer concentration, and a first-order dependence on a low concentration of ascorbic acid [(2.84–8.54) × 10^?4 mole/liter]. At higher concentrations of ascorbic acid the rate remained constant in the concentration range (8.54–22.72) × 10^?4 mole/liter, then varied as an inverse halfpower at still higher concentrations of ascorbic acid [(22.72–28.4) × 10^?4 mole/liter]. The initial rate increased with an increase in polymerization temperature. The overall energy of activation was 12.203 kcal/mole in a temperature range of 25–50°C. Water-miscible organic solvents depressed the initial rate and the limiting conversion. The viscometric average molecular weight increased with an increase in temperature and initial monomer concentration but decreased with increasing concentration of peroxydisulfate and an additive, dimethyl formamide (DMF).     

Polymerization of Acrylamide with Permanganate/Mercaptosuccinic Acid Initiator System

The aqueous polymerization of acrylamide initiated by the acidified potassium permanganate/mercaptosuccinic acid redox system was studied at 35 ± 0.2°C in nitrogen. In the studied range of activator concentration (2.0 × 10^?3 to 6.25 ± 10^?3 mole/liter) the polymerization rate remains unaffected. The initial rate of polymerization varies linearly with KMnO₄ and acrylamide concentrations in the studied range. The activation energy was found to be 6.61 kcal/mole (27.63 kJ/mole) in the temperature range of 30–50°C. The molecular weight of polyacrylamide was found to be independent of [KMnO₄] but increased with increasing monomer concentration. The effect of DMF on polymerization rate and molecular weight was also investigated.     

Aromatic guest inclusion by a tripodal ligand: Fluorescence and structural studies

The newly synthesized simple tripodal ligand tris-[2-(naphthalen-2-yloxy)-ethyl]-amine (L₁) act as a fluorescence signaling system for aromatic guest. It forms inclusion complexes with several electron deficient aromatic compounds. This inclusion phenomenon has been studied by steady-state fluorescence spectroscopy and solid-state structural analysis. Electron-rich L₁ shows dramatic color change and a concomitant quenching of luminescence in solution as well as solid phase when titrated with several other electron deficient aromatic guest molecules. Rather high selectivity towards the picric acid was observed. L₁ simultaneously forms inclusion complex and organic salt co-crystal with the composition [(L₁H⁺) (Pic⁻)]  PicH (PicH = picric acid) when crystallized in the presence of picric acid. In the solid state, it forms a strong π–π, C–Hπ and C–HO type interactions.     

Structure of Charge Transfer Reaction Complexes Formed in Anionic Polymerization of Isoprene

A new mechanism is suggested for the anionic polymerization of isoprene. The key moment of this mechanism is thermal electron excitation of the complex of a living polymer with a monomer to the low lying S₁ (T₁) state involving a charge (electron) and (Li⁺) cation transfer from the terminal unit to the monomer molecule. It is stated that the probability of chemical bonding depends on the spin density on the radical centers of reactant molecules and on the geometry of the reaction complex. The semiempirical AM1 and ab initio 6-31G* quantum-chemical calculations revealed strong interaction for the ground electronic state of the complex (5-10 kcal/mole) and low energies of the excited triplet levels (<10 kcal/mole).     

Radiation-Induced Polymerization of Tetrafluoroethylene in Solution

Polymerization of tetrafluoroethylene in monochlorodifluoromethane was carried out at low temperatures with -prays from a ⁶⁰Co source. An activation energy of 4.3 kcal/mole was obtained for the in-source polymerization, and this is higher than that of bulk polymerization, 2.7 kcal/mole. It was found that a remarkable postpolymerization takes place even if the reaction system is in liquid state. A kinetic treatment for the postpolymerization is described.     

Aqueous polymerization of methacrylamide

The aqueous polymerization of methacrylamide (I) initiated by KBrO₃–thioglycolic acid (TGA) has been studied at 30 ± 0.2°C in nitrogen. The rate is given by K[M]^1.19 [thioglycolic acid]¹ [KBrO₃]^0.53 for 10–15% conversion. Activation energy was found to be 53.96 kJ/mole (12.92 kcal/mole) in the investigated range of temperature 30–45°C. The role of addition of a series of aliphatic alcohols and some salts was also determined. The kinetics of polymerization was followed iodometrically.     

Effect of amines on vinyl polymerization initiated by chromous acetate–alkyl halide systems

The radical polymerization of vinyl monomers initiated by Cr²⁺–RX in the presence of various amines was studied in DMF at 30°C. Polyamines able to form the chelate complex with Cr²⁺ accelerated the rate of polymerization of styrene in the following order: ethanolamine > triethylenetetramine > diethylenetriamine > ethylenediamine. However, aliphatic monoamine, hexamethylenediamine, and aromatic diamine did not have any effect on the polymerization. These results suggest that the effect of multidentate ligands may be associated with chelating effects which affect the electron transfer ability of the metal complex. An apparent activation energy of 8.2 kcal/mole for the polymerization of styrene was obtained in the presence of ethanolamine. With the Cr²⁺–CHCl₃ system, on addition of ethanolamine, the polymerization of methyl methacrylate was accelerated, and acrylonitrile and vinyl chloride, could be polymerized.     

Charge-transfer complexations of 1,n-di(9-ethylcarbazol-3-yl)alkanes with tetracyanoethylene and tetranitromethane

1,n-Di(9-ethylcarbazol-3-yl)alkanes, where n=1-5, as the dichromophoric model compounds of poly-3-vinylcarbazoles were synthesized to examine their complexation behaviors with the electron acceptors tetracyanoethylene (TCNE) and tetranitromethane (TNM). 9,9'-Diethyl-3,3'-dicarbazolyl, di(3-ethylcarbazol-9-yl)methane, and three monomeric analogues were also included for comparison. In dichloromethane solution, the dicarbazoles formed stable 1:1 electron donor-acceptor complexes with TCNE having formation enthalpies around -3.5kcal/mol. With TNM they formed more weakly bound complexes that showed little dependence on concentration and almost zero dependence on temperature changes having nearly 0kcal/mol enthalpies of formation. The smaller gap between the two carbazole groups in 1,n-di(9-ethylcarbazol-3-yl)alkanes with nor=3.     

Al(Cap)3 as initiator in the anionic polymerization of ε-caprolactam at high temperature

Mechanism for polymerization of ε-caprolactam in the presence of both sodium and aluminum caprolactamate was investigated at 171°C. The role of Al(Cap)₃ as an initiator was revealed. The apparent rate constant of propagation reaction decreased with the increase in the concentration of Al(Cap)₃, as the two different metal salts interact even at 171°C. The activation energy of the overall polymerization reaction with this catalyst system was estimated to be 41.18 kcal/mole.     

Anionic polymerization of a series of five-membered cyclocarbosiloxanes

A study was conducted of the anionic polymerization of a series of methyl- and/or phenyl-substituted five-membered cyclocarbosiloxanes. The polymerization was initiated by lithium n-butyldiphenylsilanolate in the presence of tetrahydrofuran. The rate of conversion of monomer to polymer was measured in an NMR spectrometer. The rate of polymerization was largely dependent upon the structure of the growing chain ends. The apparent activation energies were in the range 10–14 kcal/mole for the series.     

Vinyl polymerization. Part 268. Polymerization of acrylonitrile initiated by the system of tetramethyl tetrazene and bromoacetic acid

The polymerization of acrylonitrile (AN) initiated by the system of tetramethyl tetrazene (TMT) and bromoacetic acid (BA) in dimethylformamide (DMF) was studied. The TMT–BA system could initiate the polymerization of AN more easily than TMT alone. The polymerization was confirmed to proceed through a radical mechanism. The initial rate of polymerization R_p was expressed by the equation: R_p = [TMT]^0.62-[BA]^0.5[AN]^1.5. The overall activation energy for the polymerization was estimated as 9.4 kcal/mole. In the absence of monomer, the reaction of TMT with BA in DMF was also studied kinetically by measuring the evolution of nitrogen gas. The reaction was first-order in TMT and first-order in BA; the rate data at 49°C were k₂ = 9.1 × 10^?2l./mole-sec., ΔH? = 17.0 kcal/mole, and ΔS? = ? 6.6 eu. In addition, the treatment of TMT with BA in benzene led to the formation of tetramethylhydrazine radical cation, which was identified by its ESR spectrum. On the other hand, the relatively strong interaction between TMT and DMF was observed by absorption spectrophotometry.     

Radiation-Induced Polymerization of Tetrafluoroethylene

Polymerization of tetrafluoroethylene was carried out in bulk at low temperatures by initiation with γ-rays from a ⁶⁰ Co source. It was found that a remarkable postpolymerization takes place even in the liquid phase. Kinetical analysis has been made of the in-source and postpolymerizations. An activation energy of 2.7 kcal/mole was obtained for the in-source polymerization and 10.3 kcal/mole for the postpolymerization. The long lifetime of polymer radicals in the liquid phase at -78°C seems to be due to the slow recombination rate of the polymer radicals, based on the rodlike shape of the polymer radicals.