Fire- and heat-resistant polymer based on maleimido-substituted 2,2-bis(anilino)-4,4,6,6-tetrakis-(4-aminophenoxy)-cyclotriphosphazene

A fire- and heat-resistant polymer was obtained by the thermal polymerization of bismaleimido-substituted 2,2-bis(anilino)-4,4,6,6-tetrakis-(4-Aminophenoxy)-cyclotriphosphazene. The thermal stabilities of the polymer were evaluated in nitrogen and in air by thermogravimetric analysis. This polymer was stable to 345°C and had char yields of 78% at 800°C in nitrogen and of 71% at 700°C in air. The structures of cyclotriphosphazene precursors and the polymer were characterized using Fourier-transform infrared and proton nuclear magnetic resonance spectroscopy.     

Relaxation of liquid‐crystalline polymer fibers in polycarbonate–liquid‐crystalline polymer blend system

The relaxation of liquid‐crystalline polymer (LCP) fibers in the polycarbonate (PC)/LCP blend was examined under various conditions on a hot‐stage microscope. LC5000 is a thermotropic LCP consisting of 80/20 hydroxybenzoic acid and poly(terephthalate). The geometry of the fibers is not an important factor in the relaxation process. Fibers of different aspect ratios and lengths relaxed at the same rate and exhibited identical onset times. Increasing the temperature caused the fibers to relax faster, especially near the nematic‐transition temperature. The fibers relaxed almost immediately when subjected to a temperature of 285 °C. At 280 °C the fibers were stable for 43 min, whereas at 270 °C no noticeable relaxation was evident. Addition of compatibilizer stabilized the fibers by enhancing the interfacial adhesion between the fibers and the PC matrix. Consequently, LCP fibers in the compatibilized system relaxed at a much higher temperature (294 °C) as compared with the uncompatibilized system (275–280 °C). © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2307–2312, 2003     

New polymer syntheses 16. LC-copolyesters of 3-(4-hydroxyphenyl) propionic acid and 4-hydroxy benzoic acids

The polycondensation of 3-(4-hydroxy phenyl)-propionic acid, 4-Hypp, by means of acetanhydride or acetylchloride was conducted either in the presence or in the absence of a liquid reaction medium. DSC measurements, polarizing microscope, and X-ray diffraction studies indicate poly(4-Hypp) possesses at about 215°C a reversible first order transition between two solid phases. Copolyesters containing various mole ratios of 4-Hypp and 4-hydroxy benzoic acid, 4-Hybe, were prepared by bulk condensation with acetanhydride at 320°C. At 4-Hypp/4-Hybe ratios less than 1.0:1.5 the reaction product was heterogeneous, containing crystals of pure poly(4-Hybe). Neither increasing the reaction time nor the variation of the transesterification catalyst resulted in an entirely homogeneous copolyester. However, for 4-Hypp/4-Hybe ratios greater than 1.0:1.5, ¹³C NMR spectra indicate perfectly random sequences. Also, terpolyesters containing 3-chloro-4-hydroxy- or 3,5-dichloro-4-hydroxy-benzoic acid were heterogeneous with less than 30 mol % 4-Hypp. DSC measurements revealed for all polyesters a glass transition in the range of 55–78°C. Temperature dependent X-ray diffraction studies confirm that the solid phase is a s.c. LC-glss. Correspondingly low heat distortion temperatures were found by thermomechanical analyses. The copolyesters display under the polarizing microscope LC-phase up to temperatures of 450–480°C, where rapid thermal degradation prevents further investigations. In the case of the 4-Hypp/4-Hybe 1:1 copolyester, the LC-phase extends over a temperature range of about 400°C. TGA measurements indicate beginning thermal degradation at temperatures between 350 and 380°C.     

Influencing polymer properties by regiospecific complexation

ABA block-copolymers in which the A segments are capable of forming complexes and B is a non-complexing segment, have been used to prepare polymer materials with properties that can be changed by adding a complexing agent. The complex forming segments were poly(ethylene oxide) (PEO), linear polyethylenimine (LPEI) and poly(N-tert-butylethylenimine) (PTBEI). Commercially available liquid ABA block-copolymers, in which A is PEO and B is poly(propylene oxide), were investigated with high molar mass poly(acrylic acid) (PAA) as the complexing agent for PEO. It was found that the mixtures containing 3 to 7 wt.-% of PAA, showed a marked shear-thickening behavior leading eventually to gelation. This was attributed to the transformation of intramolecular polymer complexes, at low shear rates, to intermolecular complexes, at high shear rates, due to the chain stretching of PAA. ABA copolymers in which A is LPEI or PTBEI and B polytetra-hydrofuran (PTHF), were prepared. Complexation of these copolymers with low molecular weight poly-acids or PAA in polar and non-polar solvents as well as in bulk have been investigated. ABA copolymers in which A is PEO and B a PTHF segment were prepared. These block-copolymers show two melting points: one at appr. 55°C, due to the PEO segments, and one at appr. 30°C due to the PTHF. Upon addition of alkali metal salts such as sodium iodide or sodium thiocyanate, complexes with PEO are formed and as a consequence, the melting point of the PEO segments shifts to appr. 160°C. The complexed materials behave as thermoplastic elastomers up to that temperature.     

Thermal analysis of the pyrolytic behaviors of a highly crosslinked polymer

Thermogravimetric-mass spectrometric (TG/MS) and differential scanning calorimetric (DSC) techniques were used in the characterization of oxidative and nonoxidative degradation reactions of a highly crosslinked divinylbenzene/styrene copolymer. When the copolymer was subjected to a temperature-programmed air environment, four exothermic reactions were detected. The initial small exothermic reaction, starting at ca. 125°C and reaching its maximum at ca. 180°C, was presumed to result from the decomposition of peroxides. The second exothermic reaction, which overlapped with the initial one and peaked at ca. 270°C, was attributed to oxidation with a significant amount of oxygen uptake and liberation of some gaseous products such as CO₂, styrene, benzaldehyde, ethylstyrene, and ethylbenzaldehyde. The strongest exothermic reaction took place at ca. 290–380°C and had its peak at ca. 360°C. Associated with this reaction was the generation of many gaseous pyrolysates, as given above. The exothermic reaction continued at a relatively constant rate from ca. 380°C to the maximum temperature of the experiment (500°C) with the release of only one gaseous product (CO₂). The initial exothermic reaction can be eliminated by controlled thermal decomposition of peroxides; therefore, a more thermally stable polymer can be obtained. Exothermic reactions, starting at ca. 170°C, were observed. Pyrolytic reactions in an inert gas were also studied.     

Crosslinking of polyimides via spirodilactone unit in polymer backbone

A new approach for the crosslinking of polyimides via the lactamization of spirodilactone unit in polyimide backbone was studied by two means: model reaction and the comparison of the properties of the polyimide precursors to those of the crosslinking polymers. Polyimides 4 and 5 were soluble in N,N′dimethylacetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO), N′-methylpyrrolidone (NMP), and other common organic solvents, whereas their corresponding crosslinking polymers were insoluble in these solvents. The glass transition temperatures for polyimide 5 and its crosslinking polymer were 262°C and 291°C, whereas those for polyimide 4 and its crosslinking polymer were 265°C and 360°C. The weight-loss rate of the crosslinking polymers was apparently slower than that of the precursors when the temperature was > 400°C. The 10% weight-loss temperature for the polyimides 4 and 5 was < 500°C, whereas that for the crosslinking polymers was close to or above 600°C. The results indicate that this type of crosslinking polymer has good thermal properties. The temperature for the formation of lactam was above 180°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3680–3686, 1999     

Synthesis of polyvinylpyrrolidone and its nanosilver-based polymer composites in supercritical carbon dioxide

Polyvinylpyrrolidone is synthesized in supercritical carbon dioxide at a pressure of 20 MPa and a temperature of 65°C. Polyvinylpyrrolidone films are impregnated with the organic complex silver 1,5-(cyclooctadiene)-1,1,1,5,5,5-hexafluoroacetyl acetonate, and the metal is subsequently reduced by hydrogen. The chemical structure and structure of nanometallopolymer composites are investigated by SAXS, transmission electron microscopy, FTIR and UV spectroscopy, and X-ray fluorescent analysis. It is shown that the impregnation with the complex and the reduction of the complex give rise to Ag(0) nanoparticles with a predominant size on the order of 1 nm.     

Stability of electrical properties of conducting polymer composites

The effect of slow cycle heating and cooling on the stability of electrical properties of two polymer composites‐ polypropylene/polypyrrole (PP/PPy) and polypropylene/carbon black (PP/CB) ‐ was investigated. Conductivity in composites was measured in heating/cooling cycles in the temperature range from 16°C to 105°C in PP/PPy and to 125°C in PP/CB, respectively. It was found that the thermal treatment caused the decrease of PP/PPy conductivity while in case of PP/CB the treatment increased the electrical conductivity. The positive effect was explained by increased crystallinity in the thermally treated composite.     

THE CRYSTAL STRUCTURES OF TWO IMINO-1,2,4- DITHIAZOLES FORMED BY THERMAL DECOMPOSITION OF 5-(DIALKYLAMINO)-3-(SUBSTITUTED IMINO)-1,2,4-DITHIAZOLES

Abstract

The thermal decomposition products of two substituted imino-1,2,4-dithiazoles have been studied by single crystal x-ray analysis. Both products crystallize in space group P2^1/c with four molecules per unit cell. The first product, obtained from 5-(dimethylamino)-3-(methylimino)-1,2,4-dithiazole has cell dimensions of a=9.922(8) Å, b=12.052(11) Å, c=13.358(12) Å and β=104.9(1)°. The molecule is made up of two planar segments related by an extremely large twist (?154°) about a C?N double bond. The results from this study have also contributed further information in the area of nonbonded interactions between ring and thione sulfur atoms. The second product, from 5-(dimethylamino)-3(phenylimino)-1,2,4-dithiazole was shown to be an ordered 1:1 complex of the starting material and one of its isomers. The cell dimensions are a=12.420(6) Å, b=8.840(9) Å, c=22.276(22) Å and β= 112.2(1)°. The different molecules are linked by an inter molecular NH… N hydrogen bond.     

Free volumes in liquid-crystalline main-chain polymer probed by positron annihilation

Free volumes in a copolymer consisting of p-hydroxybenzoic acid (HBA) and poly(ethylene terephthalate) (PET) were probed by positron annihilation technique. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured in the temperature range between 30 and 230°C. Above the glass transition temperature (ca. 60°C), the lifetime of ortho-positronium (o-Ps) annihilated in the free volumes and its annihilation probability were found to increase with increasing specimen temperature. These facts were attributed to the increase both in the size of the free volumes and in the concentration of such regions due to rearrangements of molecules. From the observed lifetime of o-Ps, it was found that the size of the free volumes increases from 0.05 nm³ to 0.1 nm³ in the temperature range between 30 and 230°C. At solid-mesophase transition temperature (150–220°C), the size of the free volumes monotonously increases, while the increase in the concentration of such regions saturates at 174°C. The clear relationship between the data obtained by the positron annihilation and those obtained by differential scanning calorimetry was confirmed. ©1995 John Wiley & Sons, Inc.     

Thermodynamic properties of some concentrated polymer solutions

Solubilities of several solvents were measured in four molten polymers by using an isobaric vapor-pressure apparatus. Solvent concentration ranged from 0.5 to 15 wt-%. The systems polyisoprene–benzene and polyisobutylene–benzene were studied at 80.0°C; polyisobutylene–cyclohexane was studied at 100.0°C; ethylene–vinyl acetate copolymer (EVA)–cyclohexane, EVA–isooctane, and poly(vinyl acetate)–isooctane were studied at 110.0°C. Of six polymer–solvent systems studied, all except poly(vinyl acetate)–isooctane appear to exhibit hysteresis in a single sorption–desorption cycle starting with dry polymer. The desorption curves of solvent activity plotted versus solvent weight fraction show an inflection point, suggesting localized adsorption of solvent molecules. Experimental data were analyzed with a theory which takes into account adsorption of solvent by polymer in addition to differences in free volumes and intermolecular forces. The theory gives a semiquantitative representation of the experimental data.     

New polymer syntheses. 60. Thermostable polymers of 2-(hydroxyaryl)benzoxazole-5-carboxylic acids

Tristrimethylsilyl-3-amino-4-hydroxybenzoic acid was condensed with various aromatic acetoxy carboxylic acid chlorides in Marlotherms-S® at 20–350°C. Under these conditions formation of an amide group, ring closure to benzoxazole groups and polycondensation occur step by step in a “one-pot procedure”. The crude polyesters were hydrolyzed to yield pure 2-(hydroxyaryl) benzoxazole-5-carboxylic acids which were acetylated and polycondensed. The pure polyesters obtained in this way were characterized by viscosity and DSC measurements, WAXS-powder patterns, and thermogravimetric analyses. The polyester of 2-(4-hydrophenyl) benzoxazole-5-carboxylic acid has a degree of crystallinity > 90% and a short term in thermostability in air up to 500°C.     

New polymer syntheses. LXVI. Copolyester of 4-hydroxybenzoic acid and 3-(4'-hydroxyphenoxy)benzoic acid or 4-(3'-hydroxyphenoxy)benzoic acid

Copolyesters of 4-hydroxybenzoic acid (HBA) and 3-(4'-hydroxyphenoxy)benzoic acid were prepared by two different procedures. Either the acetyl derivatives were polycondensed in bulk at temperatures up to 300°C or they were polycondensed in an inert reactions medium (Marlotherm-S) at 340°C. Two analogous series of copolyesters were synthesized from 4-acetoxybenzoic acid (4-HBA) and 4-(3'-acetoxyphenoxy)benzoic acid. The copolyesters were characterized by elemental analyses, inherent viscosities, ¹H- and ¹³C-NMR spectroscopy, WAXS and DSC measurements, and by optical microscopy. All copolyesters synthesized in solution were highly crystalline materials which were neither meltable nor soluble. Part of the copolyesters prepared by polycondensation in bulk were semi-crystalline, meltable, and soluble. The copolyester derived from 3-(4'-hydroxyphenoxy)benzoic acid proved to be thermotropic forming a nematic melt, whereas the isomeric copolyesters of 4-(3'-hydroxyphenoxy)benzoic acid only formed isotropic melts. © 1993 John Wiley & Sons, Inc.     

Polyethylene glycol grafted cotton as phase change polymer

Thermal storage cotton possessing solid–solid phase change properties was prepared by direct grafting of polyethylene glycol (PEG) on cotton fiber/cloth. Attempt has been made to characterize intermediates so that desired grafting could be obtained. The grafting was done by using urethane linkage and the grafted cotton was found to undergo solid–solid phase transition. The modified cotton was characterized by using Fourier transform infrared spectroscopy (FT-IR), ¹³C CPMAS, polarizing optical microscopy, differential scanning calorimetry (DSC) and thermogravimetry respectively. The DSC study revealed quite good storage effect of grafted cotton and the enthalpy of melting was found to be 55–59 J/g with a peak appearing at around 60 °C. During cooling scan, the crystallization peak appeared at around 38 °C. Further, thermogravimetric analysis confirmed good thermal stability up to 300 °C. Appreciable improvement of mechanical properties of cotton has been observed after grafting. The polarizing optical micrograph clearly showed change of morphology after grafting, i.e., the grafted PEG adhering to fiber surface.     

3,3,6,6-四甲基-9-对氯苯基-1,8-二氧代-2,3,4,5,6,7-六氢氧杂蒽的合成和晶体结构

标题化合物C2 3H2 5O3Cl是由对氯苯甲醛与 5,5 二甲基 1 ,3环己二酮在乙二醇中反应而得。结构通过单晶X 射线衍射法测定 ,其晶体属于单斜晶系 ,空间群P2 1 /n ,a =6.0 4 8(1 ) ,b =1 9.543(3) ,c =1 7.42 0 (3) ,β =97.2 9(1 )° ,V =2 0 4 2 .2 (6) 3,Mr=384.90 ,Dc=1 2 52 g/cm3,Z =4,μ(MoKα) =2 .0 6cm- 1 ,F(0 0 0 ) =81 6。晶体结构用直接法解出 ,经用全矩阵最小二乘法对原子参数进行修正 ,最终的偏离因子为R =0 .0 39,Rw=0 .0 4 7。X 射线衍射分析表明 :平面 1 (C(8) -C(9) -C(1 9) )与平面 2 (C(1 0 ) -C(1 1 ) -C(1 2 ) )之间的两面角为1 6.2 4° ;平面 1与平面 3(C(7) -C(8) -C(9) )之间的两面角为 1 77.37° ;平面 1与平面 4(C(1 )-C(5) -C(6) )之间的两面角为 98.2 1°;平面 2与平面 3之间的两面角为 1 61 .1 2° ;平面 2与平面 4之间的两面角为 81 .98°;平面 3与平面 4之间的两面角为 79.1 5°     

Higher aliphatic polyaldehydes. II. Polymer structure and polymer stability of poly(n-heptaldehyde)

Poly(n-heptaldehyde) has been prepared by anionic and cationic polymerization at ?60°C in methyl cyclohexane. The anionic polymer is more crystalline and of a higher degree of isotactic structure than the somewhat rubbery but still crystalline cationic polymer. The polymers have been acetate-endcapped to improve their thermal stability. Cationic polymer, when endcapped and purified, begins to degrade above room temperature; even crystalline anionic polymer degrades at a reasonable rate at 100°C. The crystallinity of poly(n-heptaldehyde) is caused by crystallization of the acetalic main chain as well as the side chain. Two regions of melting have been recognized by DSC analysis and by microscopic observations. The low melting region between 80 and 100°C has been identified as the melting of the paraffinic side chains of poly(n-heptaldehyde). It consists of three clearly definable endotherms at 78, 87, and 101°C.     

Excluded-volume effects in dilute polymer solutions. IV. Polyisobutylene

Statistical radii of gyration, second virial coefficients, and intrinsic viscosities of sharp fractions (M?_w/M?_n ≈ 1.1) of polyisobutylene (PIB) covering a wide range of molecular weight (1.6 × 10⁵ to 4.7 × 10⁶) were determined in isoamyl isovalerate (IAIV) at a number of temperatures ranging from 20 to 60°C, in n-heptane at 25°C, and in cyclohexane at 25°C by light-scattering and viscosity measurements. It was found that IAIV at 22.1°C is a theta solvent for PIB. Analysis of the data by the methods described in preceding papers of this series indicated that, except for minor differences, the conclusions derived from similar studies with polychloroprene, polystyrene, and poly-p-methylstyrene hold equally for solutions of the typical linear polymer investigated here. In particular, no decisive evidence for the drainage effect was found.     

New solid polymer electrolytes based on polyester diacrylate for lithium power sources

New solid polymer electrolytes are developed for a lithium power source used at the temperatures up to 100°C. Polyester diacrylate (PEDA) based on oligohydroxyethylacrylate and its block copolymers with polyethylene glycol were offered for polymer matrix formation. The salt used was LiClO₄. The ionic conductivity of electrolytes was measured in the range of 20 to 100°C using the electrochemical impedance method. It is shown that the maximum conductivity in the whole temperature range is characteristic of the electrolyte based on the PEDA copolymer and polyethylene glycol condensation product (2.8 × 10^?6 S cm^?1 at 20°C, 1.8 × 10^?4 S cm^?1 at 95°C).     

Kristall- und Molekülstruktur von 6-Ethoxy-12,12-dimethyldibenzo[d,g]-1,3,2,6-dioxaphosphasilocin-6-oxid

Synthesis and Crystal Structure of the Bis(amidinatochelate) Complex ClSb[Ph? C(NSiMe₃)₂]₂ The antimony(III) amidinato complex ClSb[Ph? C(NSiMe₃)₂]₂ was obtained by the reaction of antimony trichloride and N,N,N′-tris(trimethylsilyl)benzamidine in dichloromethane in form of pale-yellow, moisture sensitive crystals. X-ray crystal structure determinations were performed at 20°C and at ?93°C. Crystal data at 20°C: space group P1 , Z = 2, a = 1160.3(2), b = 1305.4(2), c = 1336.5(2) pm, α = 68.32(1), β = 79.79(1), γ = 71.47(1)°; at ?93°C the lattice vectors are 1.20 to 0.85% shorter. In the molecule two Ph? C(NSiMe₃)₂ groups are attached with their N atoms in a chelate manner to the Sb atom. Together with the Cl atom they form an irregular coordination polyhedron about the Sb atom with a stereochemically strongly effective lone electron pair. The SiMe₃ groups show considerable twisting vibrations about the N? Si axes even at ?93°C.     

Alternating ethylene–alkyl acrylate copolymers. I. polymer preparation

High molecular weight alternating ethylene–ethyl acrylate copolymers were prepared by using boron trifluoride to complex the acrylate ester. The polymerizations were run under mild conditions (25–50°C, 6–20 atm ethylene) in dichloromethane or dichloroethane solution with free-radical initiation. At lower ethylene pressures or at less than stoichiometric levels of BF₃, the polymers are acrylate-rich. This is due to ethyl acrylate homopolymerization competing with the copolymerization reaction. The effect of other polymerization variables is also discussed.