Reaction mechanism of the alternating copolymerization of aziridines with cyclic imides

The copolymerizations of N-substituted aziridines and cyclic imide were studied. N-Ethylsuccinimide copolymerized with ethylenimine, but N-ethylethylenimine did not copolymerize with succinimide and N-ethylsuccinimide without catalyst. The effect of additives on the copolymerization of ethylenimine with succinimide and that of N-ethylethylenimine with succinimide and N-ethylsuccinimide was also examined. The rate of copolymerization of ethylenimine with succinimide was accelerated by the addition of N-acetylethylenimine or water. The copolymerization of N-ethylethylenimine with succinimide was initiated only by water, but N-ethylethylenimine did not copolymerize with N-ethylsuccinimide in the presence of water. Gas evolved on heating the copolymer of ethylenimine and succinimide was analyzed and confirmed to be ammonia. On the basis of these results the reaction mechanisms of the copolymerization of ethylenimine with succinimide or N-ethylsuccinimide and of N-ethylethylenimine with succinimide initiated by water are discussed.     

Structural study of alternating copolymerization of aziridines with cyclic imide

The structures of copolymers of aziridines with cyclic imides were determined by means of infrared spectrometry, paper electrophoresis of the hydrolyzate, and NMR spectrometry. The structure of the repeating unit in the copolymer of ethylenimine with succinimide was \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} ({\rm CH}_2 {\rm CH}_2 {\rm NHCOCH}_2 {\rm CH}_2 {\rm CONH}\rlap{--} ) $\end{document}. The endgroups of the copolymer were N-acylethylenimine ring, N-substituted succinimide ring, and primary amide group. The copolymer of ethylenimine with N-ethylsuccinimide had the repeating unit of \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}_2 {\rm CH}_2 {\rm NHCOCH}_2 {\rm CH}_2 {\rm CON}({\rm C}_2 {\rm H}_5 )\rlap{--} ] $\end{document} and the endgroups of N-acylethylenimine and N-substituted succinimide ring. N-Ethylethylenimine did not copolymerize with succinimide, but in the presence of water, the reaction occurred to give an amorphous polymer. This copolymer had the repeating unit \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}_2 {\rm CH}_2 {\rm NHCOCH}_2 {\rm CH}_2 {\rm CON}({\rm C}_2 {\rm H}_5 )\rlap{--} ] $\end{document} and the endgroups were N-substituted succinimide ring and amine group but not N-acylethylenimine ring. On the basis of this structural information, the initiation reaction was discussed.     

Preparation, characterization and crystalline transitions of odd-even polyamides 11,12 and 11,10

The novel odd-even polyamides 11,12 (P11, 12) and 11,10 (P11, 10) were synthesized via step-heating melting-polycondensation of 1,11-diaminoundecane with dodecanedioic acid and decanedioic acid, respectively. Their chemical structures were confirmed by various spectroscopic techniques (FTIR, Raman, NMR). The thermal properties of the polyamides under consideration were measured by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The crystalline transitions of the prepared polyamides were studied by wide angle X-ray diffraction (WAXD) and Fourier transform infrared spectroscopy (FTIR). The variable temperature WXRD results indicated that P11,10 undergoes the Brill transition during the heating process before melt while P11,12 does not. From the real time FTIR spectra of P11,10, it was found that the intensity of hydrogen bond becomes weak, and the twisting of the C-CO and C-N bonds becomes enhanced. The vibration of the methylene units strengthens and the trans-zigzag conformation decreases. The ordered stacking of the methylene segments becomes gradually disordered by insertion of the gauche conformation during the crystalline transition process.     

Alternating copolymerization of carbonyl sulfide with aziridines

The copolymerization of carbonyl sulfide with aziridines such as ethylenimine, propylenimine, and N-ethylethylenimine was studied in various organic solvents. The copolymerizations occurred easily without the addition of any catalyst and gave white powdery crystalline copolymers. The copolymers produced were insoluble in many organic solvents, but soluble in p-chlorophenol and dimethyl sulfoxide. The elementary analyses and the infrared spectra showed that alternating copolymers which have a thiourethane structure were produced. In the copolymerization of carbonyl sulfide with ethylenimine, both the polymer yield and the molecular weight of the resulting polymer increased with the use of a solvent having a higher dielectric constant, and also with an increase in the ratio of carbonyl sulfide to imine in the feed. The rate of copolymerization of carbonyl sulfide with aziridines was in the order of ethylenimine > propylenimine > and N-ethylethylenimine. Irradiation of the copolymers improved their thermal properties and increased their melting point.     

Solid-phase synthesis of cyclic imides

A cyclative cleavage strategy for the synthesis of cyclic imides on a polystyrene resin is described. After optimization of the cleavage conditions, a small array of succinimides and phthalimides was synthesized. The methodology was then applied to a drug discovery project, in which it was used to synthesize a new class of delta-opioid receptor ligand by both automated and manual methods.     

Polarizability and first-order hyperpolarizability of cyclic imides

Dipole moment, polarizability, and first-order hyperpolarizability of cyclic imides (maleimide, succinimide, phthalimide and some of their derivatives) have been investigated using ab initio and density functional theory calculations. It is found that 4,5-dichloro-, and 3,4,5,6-tetrachlorophthalimide have highest mean polarizabilities and total hyperpolarizabilities among the studied molecules. Furthermore, polarized continuum model has been employed to investigate solvent effects on the nonlinear optical (NLO) properties of succinimide; results indicate that solvent polarity has considerable influence on the NLO response of the molecules.     

Intercalation of cyclic imides in kaolinite

The intercalation of two cyclic imides, succinimide and glutarimide, in the interlayer spaces of kaolinite was obtained from a "soft guest-displacement method" by displacing previously intercalated guest molecules. The dimethyl sulfoxide (DMSO)-kaolinite preintercalate was particularly efficient for that purpose. The intercalation exchange was done from a concentrated aqueous solution of the cyclic imides, at ambient temperature, in a relatively short time. Complete displacement of DMSO by the cyclic imides was confirmed by the results of several independent characterizations, including XRD, TG/DTA, FTIR, and (13)C MAS NMR analyses including dipolar dephasing experiments. The imide intercalates are two dimensionally constrained in the kaolinite interlayer spaces, and are structurally organized in a flattened configuration with their cycle roughly parallel to the ab plane of the kaolinite layers. Elemental analysis gives the following compositions: Al(2)Si(2)O(5)(OH)(4)(C(4)H(5)NO(2))(0.65) and Al(2)Si(2)O(5)(OH)(4)(C(5)H(7)NO(2))(0.49), respectively for succinimide and glutarimide. The results of the TG/DTA analyses showed enhanced thermal stabilities of the imide intercalates compared with the starting materials. The intercalation process from the aqueous solution is reversible: in prolonged contact with water, the imide molecules are released, resulting in the rebuilding of the kaolinite structure. These results demonstrate the potential use of kaolinite as a slow-releasing agent for molecules structurally related to the cyclic imides of this study.     

Radical alternating copolymerization of vinyl ethers

New alternating equimolar copolymers of electrophilic trisubstituted ethylenes, methyl 3-phenyl-2-cyanopropenoate and 2-phenyl-1,1-dicyanoethene, with ethyl, n-butyl, i-butyl, t-butyl, 2-chloroethyl, and phenyl vinyl ethers were prepared by free radical initiation. Chemical compositions of the copolymers are 1 : 1 in broad ranges of monomer ratios. The copolymerization rate of both electrophilic monomers with the vinyl ethers increase in the series 2-chloroethyl > ethyl > phenyl > n-butyl > i-butyl > t-butyl. These variations in the reactivity of the vinyl ethers are discussed in terms of their preferred conformations in donor-acceptor complexes with electrophilic trisubstituted ethylenes. © 1993 John Wiley & Sons, Inc.     

Chain transfer studies of alternating copolymerization

Dimethylaniline (DMA) induces chain transfer in the zinc bromide-complexed donor–acceptor polymerizations of styrene–acrylonitrile to form alternating copolymers. The Mayo plots are linear, but the rates decrease with increase in DMA and degradative chain transfer occurs. Although conventional free-radical transfer agents have negligible effect on the rates or molecular weights, a twentyfold reduction of molecular weight is obtained with DMA. Spectroscopic data indicate the formation of an equimolar complex of DMA and ZnBr₂, but the lowering of molecular weight is not attributable to the reduction of the effective ZnBr₂, concentration. A possible mechanism involving a competition between [ZnBr₂(DMA)₂] and [ZnBr₂,DMA,AN] is suggested.     

Heterochain polyamides Communication 6. Preparation of polyamides and amide-ester copolymers by the aminolysis of polyesters

Summary The aminolysis of polyethylene sebacate with 1,6-hexanediamine was investigated and it was found that exchange of ethylene glycol and 1,6-hexanediamine residues occurs with formation of amide-ester copolymers or polyamides, depending on the relative amounts of reactants.     

Reductive coupling of aliphatic cyclic imides with benzophenones by low-valent titanium

The reductive coupling of aliphatic cyclic imides with benzophenones by Zn–TiCl₄ in THF gave two- and four-electron reduced products selectively by controlling the reaction conditions. Although cyclic and acyclic products were formed as mixtures in most cases, cyclic dehydrated products could be selectively obtained by heating the product mixtures in the presence of cat. p-TsOH.     

Alternative copolymerization of aziridines and carbon monoxide by γ-ray irradiation

The copolymerization of carbon monoxide and aziridines such as ethylenimine and propylenimine was carried out by γ-ray irradiation. Aziridines and carbon monoxide were allowed to copolymerize under γ-ray irradiation from a Co⁶⁰ source and gave a crystalline solid copolymer. The yield of the copolymer increased with reaction temperature. The composition of copolymers obtained did not depend on the feed ratio of monomers and was found to be almost equimolar. The copolymer of ethylenimine and carbon monoxide melted at about 322–335°C. with decomposition and has an infrared spectrum identical with that of poly-β-alanine obtained by the hydrogen-migration polymerization of acrylamide. The hydrolyzed product of the ethylenimine–carbon monoxide copolymer was confirmed to be β-alanine by paper chromatography. These results lead to the conclusion that the copolymerization of aziridines and carbon monoxide took place alternatively by γ-ray irradiation, and produced crystalline poly-β-alanines.     

Preparation and evaluation of novel ferroelectric liquid crystalline cyclic siloxane tetramers

Two series of liquid crystalline cyclic siloxane tetramers, one containing the 2-methylbutyl chiral group and the other the 1-methylheptyl chiral group, were prepared to investigate, in a systematic manner, the role of molecular structure of (a) the spacer group, (b) the mesogenic side chain and (c) the chiral end group, on the liquid crystalline behaviour of these novel tetramers. The results from this systematic structure/property correlation study clearly showed the effect of the structure of both the chiral end group and the mesogenic side chain core on the thermal properties and temperature ranges of the SmC* phase (ferroelectric) exhibited by these novel materials. By the appropriate choice of spacer group, mesogenic side chain and chiral end group, a number of cyclic siloxane tetramers exhibiting wide SmC* ranges (ferroelectricity) around room temperature were synthesized.     

Preparation and evaluation of novel ferroelectric liquid crystalline cyclic siloxane tetramers

Two series of liquid crystalline cyclic siloxane tetramers, one containing the 2-methylbutyl chiral group and the other the 1-methylheptyl chiral group, were prepared to investigate, in a systematic manner, the role of molecular structure of (a) the spacer group, (b) the mesogenic side chain and (c) the chiral end group, on the liquid crystalline behaviour of these novel tetramers. The results from this systematic structure/property correlation study clearly showed the effect of the structure of both the chiral end group and the mesogenic side chain core on the thermal properties and temperature ranges of the SmC* phase (ferroelectric) exhibited by these novel materials. By the appropriate choice of spacer group, mesogenic side chain and chiral end group, a number of cyclic siloxane tetramers exhibiting wide SmC* ranges (ferroelectricity) around room temperature were synthesized.     

Comparison of microwave-assisted and conventional preparations of cyclic imides

Microwave-assisted preparation of several cyclic imides was performed with four different cyclic anhydrides. All the reactions are significantly faster and the isolated yields are significantly higher compared to conventionally heated reactions. Furthermore, many of these reactions can be performed with a minimal amount of solvent, thereby enabling the synthetic chemist to obtain high quantities of pure cyclic imides in a matter of hours.     

Synthesis of polychlorinated unsaturated cyclic dicarboxylic acid imides

A procedure has been developed for the synthesis of 3,4,5,6-tetrachlorocyclohexa-3,5-diene-1,2- and 7,8,9,10-tetrachlorobicyclo[4.4.0]deca-7,9-diene-3,4-dicarboximides from the corresponding 3,4,5,6,7,7-hexachlorobicyclo[2.2.1]hept-5-ene-2,3- and 1,8,9,10,11,11-hexachlorotricyclo[6.2.1.02,7]undec-9-ene-4,5-dicarboxylic anhydrides and pyridine in dimethylformamide. Steric structure of the products has been studied.     

Mechanistic studies of the copolymerization reaction of aziridines and carbon monoxide to produce poly-beta-peptoids

The coupling of carbon monoxide and aziridines has been shown to be selective for comonomer-alternating enchainment in the presence of PhCH2C(O)Co(CO)4 to afford poly-beta-peptoids. In this article, we have investigated the mechanistic aspects of the reaction of CO and N-butylaziridine by means of in situ infrared spectroscopy employing CH3C(O)Co(CO)3L (L = PPh3 (1) and P(o-tolyl)3 (2)) as precatalysts. Precatalyst 1 exists in solution under catalytic conditions as an equilibrium mixture of 1 and CH3C(O)Co(CO)4, and affords both poly-beta-butylalanoid and the corresponding lactam. By way of contrast, precatalyst 2 which possesses the sterically bulky and labile P(o-tolyl)3 ligand, affords only the acyl cobalt tetracarbonyl species in solution during catalysis with concomitant selective production of the copolymer. Kinetic studies conducted with precatalyst 2 showed the coupling reaction to have a first order dependence on catalyst, a first order dependence on N-butylaziridine, and only a slight dependence on the concentration of CO over the pressure range 17-69 bar. The working mechanistic model for the copolymerization reaction involves first aziridine insertion into the cobalt-acyl bond, rate determining ring opening by the cobaltate species, followed by the migratory CO insertion.     

Mechanism of alternating copolymerization of polar and hydrocarbon polymers

Radical copolymerization of butyl methacrylate with 2,3-dimethylbutadiene in the presence of Al(C₂H₅)₂Cl or ZnCl₂ results in alternating copolymers. The nature of active centers and the mechanism of polymerization in these systems have been studied by means of ESR measurements in combination with calorimetry at low temperatures. The active centers are monoradicals propagating by alternative addition of single monomer molecules; thus the reaction can be described in terms of a conventional kinetic scheme of radical additional polymerization. Participation of binary donor—acceptor complexes of the monomers in the reaction has not been confirmed. Similar conclusions have been drawn for the other alternating system studied, maleic anhydride–2,3-dimethylbutadiene. The feasibility of formation of alternating copolymers in the studied systems by the conventional mechanism of binary radical copolymerization has been confirmed by qualitative quantum-chemical treatment of the propagation reactions with due account to the donor–acceptor interactions in the transition state.