Effect of the backbone-chain structure of acrylimide-forming copolymers on the maximum degree of their thermal imidization

The effect of the backbone-chain structure of acrylonitrile and methacrylic acid copolymers of various compositions on the maximum degree of intramolecular imidization has been studied. An estimating method for calculating this value on the basis of ¹³C NMR spectroscopy data on the sequences of comonomers units in the initial copolymers is proposed. Poly-2-cyanoacrylic acid, in which the carboxylic acid and nitrile groups are located at the same carbon atom, has been used as a reference “ideally regular” polymer. The actual maximum degree of the intramolecular imidization of copolymers after thermolysis was ascertained by means of IR Fourier spectroscopy with the use of Lorentz approximations for deconvolution of absorption peaks in the spectra.     

Estimating the molecular mass between epoxy-amine network junctions from glass-transition-temperature data

The average molecular mass between network junctions is estimated for several epoxy-amine systems of various compositions with comparable molecular masses of the epoxy oligomer and the curing agent. This estimation is based on the experimental data on glass-transition temperatures of curing epoxy-amine mixtures. The constant that relates these physicochemical characteristics is dependent on the nature of the epoxy-amine system and the rigidity of polymer chains located between network junctions. Correlations are found between the constant and the glass-transition temperature of the crosslinked epoxy-amine system and between the constant and the difference in the glass-transition temperatures of uncured and ultimately cured epoxy-amine systems.     

含硝基偶氮苯侧基的丙烯酸酯类液晶聚合物的合成、结构与性质研究——Ⅱ.分子结构对T_g的影响

利用DSC研究了分子结构对含硝基偶氮苯侧基的丙烯酸酯液晶聚合物玻璃化温度的影响。结果表明,随柔性间隔基长度增加,T_g降低;当引入丙烯酸甲酯(MA)作为非晶共聚组分时,T_g降低;T_g真随MA摩尔百分含量增加而降低;当引入丙烯酸作为非晶共聚组分时,T_g升高。     

Binary and ternary copolymers of norbornene and its derivatives with acrylates as novel materials for optoelectronics

The free-radical copolymerization of norbornene with methacrylate, tert-butyl acrylate, acrylic acid, and decyl acrylate and the benzoyl peroxide-initiated copolymerization of tert-butyl norbornenecar-boxylate and tert-butyl acrylate are studied for the first time. Novel binary and ternary copolymers are obtained, and experimental conditions (the temperature and time of reaction, initiator concentration, and comonomer ratio) affecting the compositions, molecular masses, glass-transition temperatures, and yields of the copolymers are determined. It is ascertained that the copolymers of norbornene with methyl acrylate and tert-butyl acrylate have high transparency (93?C94%) in the range 300?C800 nm. Because of this fact, the copolymers show promise as matrices for creation of nanocomposite materials suitable for optoelectronic applications.     

Controlled synthesis of styrene-n-butyl acrylate copolymers with various chain microstructures mediated by dibenzyl trithiocarbonate

Copolymers of styrene and n-butyl acrylate are synthesized via pseudoliving radical copolymerization mediated by dibenzyl trithiocarbonate as a reversible addition fragmentation chain transfer agent. In a wide range of monomer feed compositions, narrowly dispersed compositionally uniform copolymers of desired molecular masses are formed, and their gradient structures are controlled by the compositions of the initial monomer feeds. The effects of the compositions, the chain microstructures, and the compositional homogeneity of the copolymers on their glass-transition temperatures are studied.     

Effect of thermal curing on the properties of thin films based on benzophenonetetracarboxylic dianhydride and 4,4′-diamino-3,3′-dimethyldiphenylmethane

The processing of polyimide films from polyamidic acid solutions involves the simultaeous loss of solvent and chemical conversion, and may imply structural reorganization such as orientation or crystallization. The effect of thermal treatment on the thermal, mechanical and dielectric properties of polymer films based on benzophenonetetracarboxylic dianhydride and 4,4’-diamino-3,3’-dimethyl diphenylmethane have been investigated. The thermal treatment of polyamidic acid at different temperatures led to compounds with different degree of imidization; it turned out that the imidization process took place with high speed until 240 °C and then remained constant. The dynamic mechanical analysis (DMA), contact angles, and dielectric measurements revealed that the storage modulus and contact angles increased with increasing of curing temperature while the dielectric constant decreased.     

Synthesis and characterization of some copolycarbonates of 2,2-bis (4-hydroxyphenyl)propane (bisphenol-A) and 1,4-bis(hydroxymethyl) cyclohexane

Copolycarbonates of Bisphenol-A (BPA) and 1,4-bis(hydroxymethyl)cyclohexane have been prepared. The resulting copolymers have slightly lower glass-transition temperatures than BPA polycarbonate homopolymers. Crystallisation and annealing effects are also reduced. The results are generally similar to those obtained with copolymers of BPA and 1,4-bis(hydroxymethyl)decafluorobicyclo(2,2,1)-heptane [1] but the differences are less marked.     

Phase equilibrium and glass-transition temperatures in plasticized amorphous bisphenol-A polycarbonate

Glass-transition temperatures and phase separation have been studied in amorphous bisphenol-A polycarbonate plasticized with pentaerythritol tetranonanoate (PETN), trimellitic acid, tridecyloctyl ester (TMDO), and tritolyl phosphate. (TTP). Phase separations occur with partially compatible plasticizers like PETN or TMDO. With PETN, for compositions situated in the miscibility gap, the system is composed of a pure plasticizer phase and of a plasticized polymeric phase characterized by a transition temperature of 110°C. In the case of TMDO and additional phase separation occurs below 55°C and two plasticized polycarbonate phases are observed. In compositions falling in the region where the could point curve crosses the glass-transition diagram the phase separation may be delayed by quick cooling. TTP is completely compatible with polycarbonate and the variation of the glass-transition temperature follows a Gordon and Taylor equation.     

Effect of curing accelerators on thermal imidization of polyamic acids at low temperature

The effect of new additives on the thermal conversion of a range of polyamic acids to polyimides at temperatures lower than 100°C was investigated using infrared spectroscopy. Additives such as m-hydroxybenzoic acid, p-hydroxyphenylacetic acid, and p-hydroxybenzenesulfonic acid were found to be highly effective as curing catalysts or accelerators. The degree of imidization of polyamic acids in the presence of additives increased with an increase in the reaction temperature, and complete imidization was achieved at 140–200°C. The reaction was characterized by a rapid rate that slowed with time. © 1996 John Wiley & Sons, Inc.     

Properties of Methacrylic Acid–Methyl Acrylate Copolymers of Varied Structure

Physicomechanical and surface properties of films of copolymers of methacrylic acid with methyl acrylate, which have close compositions and molecular masses (M_n ≈ 5.7 × 10⁴) and various chain structures (gradient copolymer and statistical copolymer), were studied. The thermodynamic characteristics of the copolymers were determined; two glass-transition points (29.6 and 141.0°C) were found for the gradient copolymer, and one glass-transition point of 40.1°C, for the copolymer with a statistical distribution of units along the chain. It was found that more mechanically strong films with tensile stress of 2.8 MPa are characteristic of the gradient copolymer. The wetting method was used to determine by using the Hood–Kaelble–Dann–Fowkes approach the surface Gibbs energies of the films and their polar and dispersion components. Atomic-force microscopy was used to find heterogeneities (0.1–0.3 μm) on the surface of a film of a statistical copolymer, whereas the film of a gradient polymer has a homogeneous structure.     

Synthesis and properties of hyperbranched copolymers based on perfluorinated germanium hydrides

Hyperbranched copolymers of various structures and molecular masses in the range 2.0 × 10⁴?4.4 × 10⁵ are prepared via the activated copolycondensation of tris- and bis(pentafluorophenyl)germane in tetrahydrofuran performed in the presence of triethylamine as an activator. The kinetics of copolycondensation is studied via the method of heat-conduction reaction calorimetry. It is found that tris(pentafluorophenyl)germane shows a higher activity in copolycondensation than bis(pentafluorophenyl)germane. Shear moduli, loss factors, and glass-transition temperatures of the copolymers are determined by dynamic mechanical analysis and differential-scanning calorimetry. The copolymers feature glass-transition temperatures up to 250°C. These values are considerably higher than those of perfluorinated polyphenylenegermane (162°C).     

Electron spin resonance investigation of molecular motions in oil-extended styrene–butadiene–styrene block copolymers. I. The temperature dependence of resonance spectra: Glass,narrowing, and inflection temperatures

Spin-probe research into nanometer-scale molecular motions occurring in oil-extended styrene–butadiene–styrene diblock copolymers within the glass-transition range is reported. Complex resonance spectra are deconvoluted, and their intricate temperature dependence, resulting from the convolution of individual spectra due to nitroxide molecules located in different phases of the block copolymers, is analyzed. It is proved that a Boltzmann sigmoid accurately describes the temperature dependence of outer line separation. The characteristic inflection point of each sigmoid is used to assign an inflection temperature to each phase of the block copolymers. The inflection temperature coincides with the narrowing temperatures, within the experimental error. It is concluded that the inflection temperature is estimated with a higher accuracy than the narrowing temperature and that it allows a more profound analysis of molecular motions. The anomalous dependence of the glass, narrowing, and inflection temperatures for spin probes immobilized within the hard phase on the oil content has been assigned to morphological modifications, on the nanometer scale, induced by oil molecules added to the block copolymers. The experimental data demonstrate the sensitivity of spin-probe data to modifications of the nanometer-size architecture of block copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1960–1971, 2004     

A plasticizer-resistant bonding composition based on oligodieneurethane epoxy rubber

A study on creation of plasticizer-resistant bonding composition for bonding of a highly filled polymer composition, which is based on butadiene nitrile rubber plasticized by a polar plasticizer, with a rigid multilayer substrate has been performed. Rheokinetic regularities of curing of the bonding composition based on oligodieneurethane epoxy rubber in relation to the content of quinolic ether used as a curing agent have been studied. The constants of the processes of viscous flow, curing, and gelation of the bonding composition have been calculated. Physical and mechanical characteristics of the bonding composition, its glass-transition temperature, and swelling in a polar plasticizer, as well as the strength of bonding with a highly filled polymeric composition, have been determined.     

Synthesis and physicochemical properties of copolymers of aniline and 3,4-ethylenedioxythiophene

Copolymers of various compositions have been synthesized via copolymerization of aniline with 3,4-ethylenedioxythiophene in the presence of a poly(4-styrenesulfonic acid) matrix, and a mechanism of copolymerization has been suggested. It has been shown that the synthesized copolymers are included in non-stoichiometric interpolyelectrolyte complexes with matrices stabilized by salt bonds and nonionic interactions. The copolymers of aniline and ethylenedioxythiophene possess electrical conductivity and can enter into redox and acid-base reactions.     

Effects of structure and composition on the titration curves of some synthetic copolymers in nonaqueous media

p-Aminobenzoic acid, p-hydroxybenzoic acid, and formaldehyde were condensed in various molar proportions in the presence of acid catalyst to obtain copolymers of various compositions. Conductometric and potentiometric titrations were carried out on seven copolymers having different feed compositions in nonaqueous solvents with acid as well as base. The titration curves indicated a large number of additional breaks inflections before the complete neutralization of COOH, OH, or NH₂ groups. These observations have been interpreted in terms of degree of polymerization, composition, and structure of the copolymers.     

Features of the foaming of acrylamide-acrylic acid copolymers

The processes that occur during the processing and foaming of thermosetting composites based on a random copolymer of acrylamide and acrylic acid—softening, foaming, and curing of the copolymer—are studied with the use of methods of chemical kinetics, Fourier transform infrared spectroscopy, and thermomechanical analysis. The above processes are coordinated with respect to time and temperature; prognostic methods for calculating the dynamics of these processes and the properties of foam materials as functions of the composition of the original foam-forming composite and the foaming conditions are proposed.     

Study of the chemical copolymerization of 2-aminoterephthalic acid and aniline.: Synthesis and copolymer properties

Aniline (ANI) and 2-aminoterephthalic acid (2ATA) copolymers, with different compositions, were prepared by chemical oxidative polymerization varying the feed ratio. The new materials have been characterized by techniques such as XPS, FTIR, Raman spectroscopies and thermal analysis. It has been checked that 2ATA units are included in the polymer backbone. Different properties have been studied as solubility, conductivity, optical absorption, fluorescence and electroactivity. The copolymers are soluble in aqueous alkaline medium and show clear electroactivity in aqueous acid medium.     

Investigation of process of polyimide formation from complexes of diester of benzophenonetetracarboxylic acid with diamines. 1. Investigation of thermal imidization by means of IR spectroscopy

The thermal imidization of complexes of benzophenonetetracarboxylic acid diester with diamines is greatly different from the thermal imidization of the corresponding mechanical mixtures. Preliminary complexation gives a considerably greater degree of completion of the imidization. It is concluded that diffusion processes play a decisive role in the solid-phase thermal imidization of the complexes. On the basis of similar values of the free energy of activation at identical temperatures for complexes with different diamines, it is concluded that the reactivity of the functional groups has little influence on the kinetics of solid-phase imidization of the complex. Alternative schemes are proposed for the formation of polyimides from the complexes, leading to an intermediate mixed-unit prepolymer with amido acid, amido ester, and imide units in the chain.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2462–2468, November, 1989.The authors wish to thank V. V. Shamanin for discussion of the results.     

Imide-aryl ether ketone block copolymers

Imide-aryl ether ketone block copolymers were prepared and their morphology and thermal and mechanical properties investigated. Two aryl ether ketone blocks were incorporated; the first was an amorphous block derived from bisphenol–A and the second block was a semi-crystalline poly(aryl ether ether ketone) prepared from a soluble and amorphous ketimine precursor. Bis(amino) aryl ether ketone and aryl ether ketimine oligomers were prepared via a nucleophilic aromaic substitution reaction with molecular weights ranging from 6,000 to 12,000 g/mol. The oligomers were co-reacted with 4,4′-oxydianiline (ODA) and pyromellitic dianhydride (PMDA) diethyl ester diacyl chloride in N-methyl–2-pyrrolidone (NMP) in the presence of N-methylmorpholine. The copolymer compositions, determined by H-NMR, of the resulting amic ester based copolymers ranged from 8 to 50 wt % aryl ether ketone or ketimine content. Prior to imide formation, the ketimine moiety of the aryl ether ketimine block was hydrolyzed (p-toluene sulfonic acid) to the ketone form producing the aryl ether ether ketone block. Compositions of this block were maintained low to retain solubility. Solutions of the copolymers were cast and cured to effect imidization, producing clear films with high moduli (ca. 2200 MPa) and elongations (33–100%). The copolymers displayed good thermal stability with decomposition temperatures in excess of 450°C. Multiphase morphologies were observed irrespective of the co-block type, block length or composition. © 1992 John Wiley & Sons, Inc.     

New Fluorinated Poly(imide siloxane) Random and Block Copolymers with Variation of Siloxane Loading

Several new random and block copoly(imide siloxane)s have been prepared by the solution polycondensation of commercially available 4,4′-oxydianiline (ODA) and amino-propyl terminated polydimethylsiloxane (APPS) with 4,4′-(hexafluoro-isopropylidene)diphthalic anhydride (6FDA). The siloxane loading was kept to 10, 20, 30, 40 and 50 wt% in the copolymers. The random copolymers were prepared by a one pot solution imidization technique, and two pot solution imidization technique was adopted for the synthesis of the block copolymers. The diamine ODA and the dianhydride 6FDA composed the hard block segment, while APPS and 6FDA composed the soft block segment. The hard block length was kept constant while the soft block lengths were varied by varying the siloxane loading. Accordingly, block copoly(imide siloxane)s were prepared on increasing the soft block lengths (DP) from 3 to 6, 10, 18 and 36 for fixed hard block length of 22. The resulting polymers have been well characterized by IR, NMR and GPC techniques. Thermal and mechanical properties of the random and block copolymers were compared with the already reported homopolyimide without siloxane moiety.