Synthesis of inherently dissymmetric polyamides,

The preparation of polyamides from derivatives of optically active biphenic acid is described. The diacid chlorides chosen were 2,2′-dinitro-6,6′-dimethylbiphenyl-4,4′-dicarbonyl chloride and 2,2′-dichloro-6,6′-dimethylbiphenyl-4,4′-dicarbonyl chloride, the diamines were phenyldiamines (o-, m-, p-) piperazine, trans-2,5-dimethylpiperazine, and 1,2-piperaazolidine. Polymerization was carried out by the method of interfacial polycondensation. The polymers of aromatic diamines were insoluble in common organic solvents but soluble in dimethylformamide containing 5% lithium chloride, triesters of phosphoric acid, and methanesulfonic acid. The polymers of aliphatic diamines were also insoluble in common organic solvents but soluble in trifluoroethanol. All polymers had melting points higher than 280°C.     

The amide-aromatic-ring system : An inherently dissymmetric chromophore

Two cyclic peptide like compounds, cyclo-anthranoyl-L- prolyl (1) and cyclo-homoanthranoyl-L-prolyl (2) have been synthesized and investigated by UV spectroscopy and measurement of circular dichroism. Compound 1 of entirely rigid conformation with two N-CO groups conjugated to the aromatic ring, Ar-NH-CO left handed helical, Ar-CO-N right handed helical, shows a very strong positive Cotton effect centered around 250 nm and a strong negative one centered around 227 nm. Compound 2, which has only one conjugated skewed electron system, Ar-NH-CO, can exist in two different stable conformations, one of them being left handed, the other one right handed helical. It also shows a strong positive Cotton effect centered around 235 nm. Since from earlier ¹³C NMR data the latter was concluded to be the preferred conformation, a right handed helical sense of the amide bond-aromatic ring system is likely to correlate with a positive Cotton effect of this inherently dissymmetric chromophore.     

Optical properties and conformations of asymmetric polyamides derived from optically active trans-1,2-cyclopropanedicarboxylic acid

Optical properties and conformations, in solution, of optically active polyamides derived from (+)(S)-trans-1,2-cyclopropanedicarboxylic acid with secondary diamines such as trans-2,5-dimethylpiperazine (DMPIP), piperazine (PIP), or N,N′-dimethylethylenediamine (DMED) have been investigated and compared with the corresponding diamide model compounds. The results suggest that the rigid DMPIP and PIP polyamides may exist in ordered conformations in 2,2,2-trifluoroethanol (TFE) and tetramethylene sulfone (TMS), while reversible conformational transitions to highly extended forms may be induced by the addition of methanesulfonic acid (MSA). In MSA/TMS mixtures, a change in the optical properties, and thus possibly in the conformations, can be observed around 0.5 mole fraction of MSA. A study of CD at higher temperature indicates that the conformations of the DMPIP and PIP polymides tend to be randomized on heating in TMS and probably also in MSA. No evidence for salt effects on conformation has been observed. Possible ordered conformations have been proposed.     

Thermal properties of wholly aromatic polyamides

Various wholly aromatic polyamides based on m-and p-phenylene diamines and isophthaloyl and terephthaloyl chloride have been synthesized and their thermal properties and oxygen index values have been studied. The effect of different substituents on the aromatic ring of the diamine have been explored by comparing their differential thermal analysis (DTA) and thermogravimetric analysis (TGA) behavior, their relative char yields at 700°C, and their oxygen indices. The ? Cl, ? NO₂, and ? OH substituted polyamides have been found to produce the highest char yields. The high char yields are probably associated with crosslinking occurring at high temperatures. Attempts at correlating char yield with oxygen index indicated enhancement for the chlorosubstituted aramids.     

Crystallizability and thermal properties of phosphorus-containing polyamides

Bis(2-carb-n-butoxyethyl)methylphosphine oxide was prepared and condensed with 1,2-diaminoethane, 1,6-diaminohexane, 1,8-diaminooctane, 1,10-diaminodecane, and 1,12-diaminododecane to form polyamides with an increasing number of methylene groups between the amide moieties. Polyamides made from the 1,10- and 1,12-diaminoalkanes were shown by x-ray and DSC to be semicrystalline, while those based on the 1,6- and 1,8-diaminoalkanes were amorphous to x-ray and revealed no first-order transitions. The repeat distances of the crystalline polymers were determined, and an extended planar zigzag conformation was excluded as a possible conformation for these polymers. The thermal stability of the phosphorus-containing polyamides, in both oxygen and nitrogen, was studied by TGA and the results were correlated with the chemical structure.     

Preparation and properties of silicon containing polyamides

Silicon containing polyamides were prepared by melt polycondensation method with a 1,3-bis(3-aminopropyl)tetramethyldisiloxane and aliphatic dicarboxylic acids having various numbers of methylene groups. Only one endothermic peak appeared in the DTA curve of the quenched sample for polyamides having an even number of methylene groups in the repeating unit. Two endothermic peaks, however, appeared for the sample kept for a week in dry air at ambient temperature after quenching: the peak at the higher temperature is called peak I; and the peak at the lower one, peak II. By heat treatment at the higher temperature, peak II shifted to a higher temperature and increased its peak area, and peak I decreased its peak area while keeping its temperature unchanged. This behavior suggests the existence of two types of crystalline states. The peak temperature of peak I alternatively decreased with the increase of the number of methylene groups. The Young's modulus and the tensile strength increased with increase of annealing time at ambient temperature. The solubilities in various solvents, the resistance to alkali solution, and the thermal stability were acceptable. Both the permeation coefficient of oxygen (P) and the separation ratio (P/P) increased with the increase of silicon content in the repeating unit.     

Synthesis and properties of polyamides of p-phenylenedioxydiacetic acid

Several polyamides of p-phenylenedioxydiacetic acid (PDDA) were synthesized by the low-temperature solution polycondensation techniques. Six different diamines were condensed independently with p-phenylenedioxydiacetyl chloride (PDC) in a mixture of N-methyl pyrolidone (NMP) and hexamethyl phosphoramide (HMPA). The polymers were obtained in 80–95% yield and possessed inherent viscosities in the range 0.32–0.81 dL/g. The polymers were characterized by infrared (IR) and H¹-NMR spectra. The solubility, density, crystallinity, and thermal stability of the polyamides were also determined. A model diamide (MDA-1) was also synthesized from aniline and PDC to confirm the formation of polyamides from diamines.     

Synthesis and properties of polyamides containing imidazoline rings

The novel polyamide containing an imidazoline ring(PAI) was synthesized by a two-stage melt polymerization of dimethyl terephthalate (DMT) with diethylenetriamine (DETA) or triethylenetetramine (TETA). The heat resistance of PAI was superior to that of polyamide which was synthesized only in the first-stage reaction and didn't contain imidazoline ring. Their chemical structures were identified by infrared spectroscopy and NMR. The optimum condition for production was studied by varying several reaction factors, including the contents of H₂O and H₃PO₄, the reaction temperature and the reaction time at second-stage reaction under vacuum. According to study of the characteristics of solution behavior of PAI, both the viscosity and the degree of cyclization could be described by equation of in m-cresol at 30°C.     

Preparation and properties of polyamides containing thianthrene units

New polyamides containing thianthrene tetraoxide were synthesized from 2,7-dichloroformylthianthrene-5,5′,10,10′-tetraoxide (A) and various diamines by the low temperature solution polycondensation technique. The resulting polyamides were characterized by i.r. and ¹H-NMR spectra and elemental analysis. The polyamides had inherent viscosities of 0.56–1.21 dl/g in DMA at 30°. All the polymers dissolved readily at room temperature in polar aprotic solvents. Density, crystallinity and thermal stability of these polyamides have been determined. In order to characterize the polymers, a model compound was also prepared from A and p-toluidine.     

Preparation and properties of polyamides containing p-terphenyl units

Novel polyamides that contained p-terphenyl units were prepared with inherent viscosities in the range of 0.4–1.7 dL/g by the polycondensation of 4,4″-dichloroformyl-p-terphenyl with aromatic diamines and 4,4″-diamino-p-terphenyl with aromatic dicarbonyl chlorides. Polyamides composed of only paraoriented phenylene units were insoluble in all solvents and showed a high degree of crystallinity. A series of polyamides that contained p-terphenyl units were more thermostable than corresponding polymers with p-phenylene or biphenylene linkages.     

Synthesis and liquid crystal properties of bipyridine-containing aromatic polyamides

A series of novel aromatic polyamides containing 2,2′-bipyridine moiety were synthesized by polycondensation of 2,2′-bipyridine-5,5′-dicarboxylic acid ( 2 ) with various aromatic diamines in hexamethylphosphoramide (HMPA) containing lithium chloride. The resulting polyamide solutions in 98% sulfuric acid and in HMPA-LiCl exhibited lyotropic liquid crystal phases. The phase transition behaviors were studied by polarizing microscopy and X-ray diffraction. The polyamides also formed metal complexes with cis-dichlorobis(bipyridine)ruthenium dihydrate [cis-Ru(bpy)₂Cl₂ · 2H₂O] which was supported by changes in electronic spectra.     

Adsorption and thermodynamic properties of dissymmetric gemini imidazolium surfactants with different spacer length

A series of dissymmetric gemini imidazolium surfactants with different spacer length ([C_mC_sC_nim]Br₂, m + n = 24, m = 12, 14, 16, 18; s = 2, 4, 6) were synthesized and characterized by ¹H NMR and ESI-MS spectroscopy. Their adsorption and thermodynamic properties were investigated by the surface tension and electrical conductivity methods. Consequently, the surface activity parameters (cmc, γ_cmc, π_cmc, pC₂₀, cmc/C₂₀, Γ_max, A_min) and thermodynamic parameters (ΔG_m^θ, ΔH_m^θ, ΔS_m^θ) were obtained. The effects of the dissymmetry (m/n) and the spacer length (s) on the surface activity and micellization process of surfactants have been discussed in detail.     

Enhanced lasing properties of dissymmetric Eu(III) complex with bidentate phosphine ligands

The luminescent and lasing properties of Eu(III) complexes were enhanced by using an dissymmetric Eu(III) complex. The photophysical properties (the emission spectral shapes, the emission lifetimes, the emission quantum yields, and the stimulated emission cross section (SEC)) were found to be dependent on the geometrical structures of Eu(III) complexes. The geometrical structures of Eu(III) complexes were determined by X-ray single crystal analyses. The symmetrical group of Eu(hfa)3(BIPHEPO) (tris(hexafluoroacetylacetonato)europium(III) 1,1'-biphenyl-2,2'-diylbis(diphenylphosphine oxide)) was found to be C1, which was more dissymmetric than Eu(hfa)3(TPPO)2 (tris(hexafluoroacetylacetonato)europium(III) 1,2-phenylenebis(diphenylphosphine oxide): C2 symmetry) and Eu(hfa)3(OPPO)2 (tris(hexafluoroacetylacetonato)europium(III) 1,2-phenylenebis(diphenylphosphine oxide): C2 symmetry). The analytical data were supported by Judd-Ofelt analysis. The most dissymmetrical Eu(III) complex, Eu(hfa)3(BIPHEPO), showed large electron transition probability and large SEC (4.64 x 10(-20) cm2). The SEC of Eu(hfa)3(BIPHEPO) was superior to even the values of Nd-glass laser for practical use (1.6-4.5 x 10(-20) cm2). The lasing properties of Eu(III) complexes in polymer thin film were measured by photopumping of a Nd:YAG laser (355 nm). The threshold energy of lasing oscillation was found to be 0.05 mJ. The increasing rate of the lasing intensity of Eu(hfa)3(BIPHEPO) as a function of the excitation energy was much larger than that of Eu(hfa)3(TPPO)2 and Eu(hfa)3(OPPO)2. The dissymmetrical structure of Eu(hfa)3(BIPHEPO) promoted the enhancement of the lasing property.     

Preparation and properties of polyamides and polyimides containing phenoxathiin units

Novel polyimides and polyimides having phenoxathiin units have been prepared. Polyamides with inherent viscosities in the range of 0.5–2.9 were readily prepared by the polycondensations of phenoxathiin diamines with aromatic diacyl chlorides and of aromatic diamines with new phenoxathiin diacyl chlorides. The polyimides were synthesized from phenoxathiin diamines and pyromellitic dianhydride by using a two-step procedure. The polyamic acids which formed in the first step had inherent viscosities ranging from 1.0 to 1.6, and they were converted to the polyimides by thermal cyclodehydration. Some of the phenoxanthiin-containing polyamides were highly soluble in polar amide solvents and dimethyl sulfoxide. A series of novel polymers containing phenoxathiin units were much more thermostable than the corresponding polymers having open-chain diphenyl ether linkages.     

Synthesis and properties of polyamides and polyesters from neocarboranedicarboxylic dichloride

Polyamides and polyesters based on neocarboranedicarboxylie dichloride and previously not described have been prepared by low-temperature polycondensation in solution and characterized. In preparing the polyamides, the following diamines were used: benzidine, hexamethylenediamine, m-phenylenediamine, p-phenylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfide, and hydroquinone diaminodiphenyl ester. Polyesters were obtained by using the following diols: phenolthalein, hydroquinone, 4,4′-dihydroxydiphenylpropane, 9,9-dihydroxydiphenylfluorene, 1,6-hexanediol, and ethylene glycol. The resulting neocarborane polyesters melt and are easily soluble in tetrahydrofuran, amide solvents, and chloroform. The neocarborane polyamides described do not melt, are readily soluble in tetrahydrofuran and dimethylformamide, and form transparent films; they are thermostable in an inert at mosphere at high temperatures.     

Synthesis and tunable properties of oligoaniline‐functionalized polyamides

Electroactive polyamides containing dense oligoaniline functionalizations (PAs) were synthesized via oxidative coupling polymerization followed by postpolymerization functionalization, and exhibit excellent solubility, good thermal stability and reversible electroactivity. Interesting spectroscopic changes that occurred through chemical oxidation have been shown, which demonstrate the potential of PAs as an electrochromic material. As a result, the electrochromic behaviors of PAs were investigated in detail, exhibiting high contrast value, moderate switching time, and satisfactory coloration efficiency. Tunable conductive and dielectric properties have also been accomplished by varying the incorporation of oligoaniline segments. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3343–3349     

Synthesis and properties of aromatic polyamides containing the cyclohexane structure

1,1-Bis[4-(4-carboxyphenoxy)phenyl]cyclohexane (III) and 1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane (V) were prepared in two main steps starting from the aromatic nucleophilic substitution of p-fluorobenzonitrile and p-chloronitrobenzene, respectively, with 1,1-bis(4-hydroxyphenyl)cyclohexane in the presence of potassium carbonate in N,N-dimethylformamide (DMF). Using triphenyl phosphite and pyridine as condensing agents, two series of polyamides with cyclohexylidene cardo groups were directly polycondensated from dicarboxylic acid III with various aromatic diamines or from diamine V with various aromatic dicarboxylic acids in an N-methyl-2-pyrrolidone (NMP) solution containing dissolved calcium chloride. The polyamides exhibited inherent viscosities in the range of 0.45 to 1.78 dL/g. Almost all of the polymers were readily soluble in polar aprotic solvents such as NMP and N,N-dimethylacetamide (DMAc) and could afford transparent, flexible, and tough films by solution casting. The glass transition temperatures (T_g) of these aromatic polyamides were in the range of 180–243°C by DSC, and the 10% weight loss temperatures in nitrogen and air were all above 450°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3575–3583, 1999