Heat-resistant foamed organoplastics based on a combination of polyimide felt, polyimide binders, and montmorillonite nanoparticles

A series of foamed organoplastics based on a combination of foamed fully aromatic polyimide binders and Arimid T polyimide felt were prepared. New composite foamed organoplastics reinforced with montmorillonite nanoparticles were prepared using commercially available aromatic monomers.     

Synthesis of multicentered polyimide initiators for the preparation of regular graft copolymers via controlled radical polymerization

Multicentered initiators for the controlled (pseudoliving) radical polymerization are synthesized via polymer analog transformation of hydroxyl-containing polyimides based on o-aminophenols. Conditions providing variations in the degree of functionalization of polyimides by initiating 2-bromoisobutyrate groups are determined, and optimum conditions for the preparation of macroinitators containing the above groups in each repeat polyimide unit are found. Via the method of controlled radical polymerization with the atom transfer on multicentered macroinitiators in the presence of complexes of univalent copper halides, graft copolymers of poly(methylmethacrylate) on polyimide backbone are obtained. Molecular-mass characteristics of graft copolymers are studied via multiple-detection size-exclusion liquid chromatography. Preparation of graft copolymers (polymer brushes) with a homogeneous grafting density and a homogeneous length of side chains necessitates grafting of the side chain on the polyimide initiator, which contains initiating groups in each repeat unit.     

Preparation and Structure of Polyimides Derived from H Complexes of Benzophenonetetracarboxylic Acid with Diaminodiphenyl Ether

The possibility of using H complexes of dialkyl dihydrogen 3,3',4,4'-benzophenonetetracarboxylates and 4,4'-diaminodiphenyl ether and of polyimides prepared therefrom as polyimide foam materials, carbon-reinforced plastics, and foam composites was examined.     

Viscosity of Melts of H Complexes Based on Acidic Diesters of Benzophenonetetracarboxylic Acid and Diaminodiphenylmethane or m-Phenylenediamine

The time dependences of the viscosity of melts of H complexes formed by dimethyl or diethyl dihydrogen 3,3',4,4'-benzophenonetetracarboxylate and 4,4'-diaminodiphenylmethane, m-phenylenediamine, or equimolar mixture of these diamines at 95 and 105°C were studied.     

Viscosity and Structure of Melts of H Complexes of Acid Diesters of Aromatic Tetracarboxylic Acids with Aromatic Diamines

The viscosity, lifetime, and structure of melts of supramolecular H-bonded complexes of acid diethyl and dimethyl esters of 3,3',4,4'-(diphenyl oxide)tetracarboxylic or 3,3',4,4'-diphenyltetracarboxylic acids with aromatic diamines (diaminodiphenylmethane or m-phenylenediamine) are studied.     

Molecular polyimide brushes as a novel membrane material for pervaporation processes

Samples of molecular polyimide brushes with poly(methyl methacrylate) side chains with substantially different grafting densities and lengths of side chains are obtained by the atom-transfer radical polymerization of methyl methacrylate using samples of polyimide multicenter macroinitiators with different contents of initiation groups. Strong homogeneous films suitable for use as diffusion membranes for pervaporation separations of liquid mixtures are cast from solutions of polyimide brushes in dimethylformamide. Investigations are performed for films of polyimide brushes with loosely grafted short side chains or densely grafted long side chains as well as for films of a polyimide identical in its chemical structure to the backbone of polyimide brushes. It is shown that all film membranes sorb water moderately and do not sorb isopropanol. For membranes made of the polyimide and the loosely grafted brush, which is close to the polyimide in its properties, the active sorption of acetonitrile is demonstrated. It is found that all membranes exhibit high selectivities for water upon pervaporation of water–isopropanol mixtures. In addition, membranes made of the brush with densely grafted side chains show high productivity.     

Synthesis of graft copolyimides via controlled radical polymerization of methacrylates with a polyimide macroinitiator

The atom-transfer radical polymerization of methyl methacrylate and tert-butyl methacrylate with a polyimide multicenter macroinitiator in the presence of a CuCl-2,2′-bipyridine catalytic system is investigated. The kinetic features of the process, the molecular-weight characteristics of the formed side chains, and the post-polymerization of methyl methacrylate with graft polyimides containing polymethacrylate side chains are studied. The conditions of controlled polymerization yielding graft copolyimides with narrowly dispersed living poly(methyl methacrylate) or poly(tert-butyl methacrylate) side chains of variable lengths are determined.     

Influence of the Molecular Structure of H Complexes of Dialkyl Dihydrogen Benzophenonetetracarboxylates with Aromatic Diamines on the Viscosity of Their Melts

The possibility of preparing from dialkyl dihydrogen 3,3',4,4'-benzophenonetetracarboxylates and 4,4'-diaminodiphenylmethane or 4,4'-diaminodiphenyl ether H complexes of both amorphous and crystalline structures was elucidated. Methods were proposed for disordering the supramolecular structure of the H complexes, which is technologically essential for reducing the melt viscosity when preparing polyimide carbon-filled plastics and foamed composites.     

Methods of acrolein polymerization and investigation of structures of the polymers obtained

Two methods for the polymerization of acrolein are proposed: suspension polymerization in water with the redox system K₂S₂O₈:AgNO₃ = 1:0.1 with respect to the monomer and a static method with the system K₂S₂O₈:PA–SO₂ adduct. The dependencies of yield, molecular weight, and structure of polyacrolein under investigation on the following factors: the amount and the ratio of the initiator components, the pH of the medium, and the monomer:solvent ratio were investigated. The structure of polyacrolein was studied by infrared spectroscopy, thermogravimetric analysis, and chemical functional analysis. The molecular weight distribution of samples of static and suspension polyacroleins modified under identical conditions was determined by gel permeation chromatography.     

Study of the mechanism of the thermochemical reaction of polyimides with hydroxyl groups via vibrational-spectroscopy and quantum-chemistry methods

The thermochemical transformation of polyimides with one hydroxyl group in a diamine fragment that leads to changes in the polymer structure is studied. It is found that in an inert atmosphere in the temperature range 400–450°C, an intramolecular thermochemical reaction accompanied by evolution of carbon dioxide occurs. The FTIR spectra of all studied polyimide films prepared from different solvents and annealed in an inert atmosphere in the range 25–450°C show similar changes that do not agree with the structures of the reaction products (polybenzoxazole and polydehydrocyclobutabenzene) described in the literature. Possible reaction paths are calculated via quantum-chemistry methods. A mechanism of the intramolecular thermochemical transformation and the related structure of the formed polymer (aromatic lactam) are proposed.