Aromatic polyamides with pendent acetoxybenzamide groups and thin films made therefrom

Temperature-Controlled Chain Dynamics in Polyimide Doped with CoCl2 Probed Using Dynamic Mechanical Analysis

Cobalt(II) chloride (CoCl2) being in the vicinity of polyimide chains entails modifications in terms of the molecular dynamics, which are mainly governed by the possible presence of amic acid residual groups, by the transition-metal-type characteristics of cobalt and by the CoCl2 content. Polyimide was synthesized using poly(amic acid) according to the reaction of 2,2'-bis(3,4-dicarboxylphenyl)hexafluoropropane dianhydride (6FDA) with 3,3'-dimethyl-4,4'-diaminodiphenylmethane (MMDA) in N,N-dimethylacetamide. CoCl2 was added before the thermal imidization of the poly(amic acid). An experimental approach was designed to establish the interaction between the polyimide and CoCl2 and whether the interaction depends on the quantity of the salt. Evidence for the existence of residual amic acid groups was obtained using second derivative Fourier Transform Infrared Spectroscopy (FTIR) and with the help of 2D correlation spectroscopy (2D-COS). Moreover, FTIR, along with X-ray photoelectron spectroscopy (XPS), revealed the interaction between the polymer and CoCl2, primarily in the form of Co(II)-N coordinated bonds. Nevertheless, the coordination of cobalt with suitable atoms from the amic acid groups is not precluded. The results of dynamic mechanical analysis (DMA) featured a specific relaxation assigned to the presence of CoCl2 in the polymeric film and demonstrated that its (non)reinforcing effect depends on its content in the polyimide.

Corrosion inhibition property of polyester-groundnut shell biodegradable composite

The use of natural fibers as reinforcing materials in thermoplastics and thermoset matrix composites provide optimistic environmental profits with regard to ultimate disposability and better use of raw materials. The present work is focused on the corrosion inhibition property of a polymer matrix composite produced by the use of groundnut shell (GNS) waste. Polyester (PE) was synthesized by condensation polymerization of symmetrical 1,3,4-oxadiazole and pimelic acid using sodium lauryl sulfate as surfactant. The polyester-groundnut shell composite (PEGNS) was prepared by ultrasonication method. The synthesized polyester-groundnut shell composite was characterized by FT-IR, TGA and XRD analysis. The corrosion inhibitory effect of PEGNS on mild steel in 1M H₂SO₄ was investigated using gravimetric method, electrochemical impedance spectroscopy, potentiodynamic polarization, atomic absorption spectroscopy and scanning electron microscopy. The results showed that PEGNS inhibited mild steel corrosion in acid solution and indicated that the inhibition efficiency increased with increasing inhibitor concentration and decrease with increasing temperature. The composite inhibited the corrosion of mild steel through adsorption following the Langmuir adsorption isotherm. Changes in the impedance parameters R_t, C_dl, I_corr, E_corr, b_a and b_c suggested the adsorption of PEGNS onto the mild steel surface, leading to the formation of protective film.

The Influence of Conformational Parameters on Some Physical Properties of Polyamides Containing Pendant Acetoxybenzamide Groups

Conformational parameters of some aromatic polyamides containing pendant acetoxybenzamide groups have been calculated by Monte Carlo method taking into consideration the hindered rotation produced by the side groups. Several physical properties such as solubility, glass transition temperature, initial decomposition temperature and dielectric constant were studied with regard to the rigidity of the chain of these polyamides. It has been shown that glass transition temperature is correlated with chain rigidity, whereas initial decomposition temperature and dielectric constant are not.

Poly(1,3,4-oxadiazole-amide-ester)s and Thin Films Made from Them

Aromatic poly(1,3,4-oxadiazole-amide-ester)s were prepared by polycondensation reaction of diacid chlorides containing preformed ester groups with aromatic diamines containing 1,3,4-oxadiazole units. These polymers were easily soluble in N-methylpyrrolidinone and were cast into flexible films from such solutions. The polymers showed high thermal stability with initial decomposition temperature being above 365 °C and glass transition temperature in the range of 215–260 °C. The weight average molecular weight was in the range of 91 000–257 000 and polydispersity is in the range of 1.64–5. The polymer films showed good mechanical properties with tensile strength in the range of 40–91 MPa, elastic modulus in the range of 2.22–3.98 GPa and elongation at break in the range of 1.85–7.37%.

Properties of some azo-copolyimide thin films used in the formation of photoinduced surface relief gratings

The patterning of the free standing azo-copolyimide films under different irradiation conditions led to the uniform surface relief gratings.

Synthesis and characterization of thermally stable aromatic polyamides and poly(1,3,4-oxadiazole-amide)s nanoparticles containing pendant substituted bezamides

Background

The introduction of pendent bulky groups along the polymer backbone results in a less ordered polymer matrix and increases the solubility characteristics without affecting thermal properties. The inclusion of chromogenic chemical moieties in the chains can give rise to the luminescent converter material which permits the preparation of materials with potential applications. Aromatic polymers containing heterocyclic rings in the main chain are known for their high thermal resistance, good hydrolytic stability, low dielectric and tough mechanical properties. There is currently much research directed towards the discovery of new blue light-emitting polymers, with characteristics of high efficiency and high reliability. Herein, we describe the preparation of aromatic polyamides and poly (1,3,4-oxadiazole-amide)s nanoparticles with pendant structures comprised of m- and p-acetoxybenzamide groups, where the acetoxybenzamide groups act as signaling units due to their fluorescent and chromogenic characteristics.

Results

Aromatic polyamides and poly(1,3,4-oxadiazole-amide)s nanoparticles with pendant structures comprised of m- and p-acetoxybenzamide groups were successfully prepared and characterized using different analytical methods. Most polyamides were obtained as well-separated spherical nanoparticles while aramide containing pyridine produced aggregated particles attributed to the molecular self assembly via H-bond directed organization of molecular precursors. The thermal behavior of all polymers exhibited two major thermal decompositions due to the subsequent breakage of the acetoxy group in the lateral chain and cleavage of the main amide bonds. Photoluminescence studies revealed that the blue emissions for the polyamide derived from benzidine were blue-shifted (shifted to a lower wavelength) compared to that of polyamides containing flexible linkages.

Conclusions

We report the synthesis of aromatic polyamides and poly(1,3,4-oxadiazole-amide)s nanoparticles with pendant structures comprised of m- and p-acetoxybenzamide groups. The thermal behavior of all polymers exhibited two major decompositions due to breakage of the acetoxy group in the lateral chain and cleavage of the main amide bonds. Structure- photoluminescence correlation demonstrated an interesting connection between structural modification and optical properties. The blue emissions for the polyamide derived from benzidine, attributed to the highly conjugation system, was blue shifted with the introduction of flexible linkages. The prepared polymers dissolved in warm polar aprotic solvents. Further investigations to obtain films with reasonably good mechanical properties for different applications are in progress.

High Performance Polyamides based on s-Triazine Ring: Synthesis and Characterization

High-performance polymers based on aromatic rings are desirable not only because of the high primary bond strengths, but also because their rigid (stiff) polymer chains offer increased resistance to deformation and thermal softening. The choice of s-triazine nucleus is based on its high thermal stability derived from its molecular symmetry and aromaticity. It is well known that s-triazine is heat resistant. Modification of monomer structures by introduction of aromatic pendent groups or heterocyclic rings into the polymer backbone provides good solubility and thermal stability. A new set of polyamides with —CO—NH— groups were synthesized by the Yamazaki’s phosphorylation reaction 2-(morpholino)-4,6-bis (6-napthoxy-2-carboxy)-s-triazine with various aromatic diamines. The polyamides had inherent viscosities in the range 0.549—0.685 dL g-1 in dimethylformamide at room temperature (30 °C) and density 1.135—1.208 g cm - 3 . All the polyamides showed good thermal stability and most of them were readily soluble at room temperature in polar solvents such as N,N-dimethylacetamide, 1-methyl-2-pyrrolidone and dimethylformamide. Polyamides were synthesized successfully with the favourable properties of higher thermal stability along-with good processibility.

2-{5-[2-(4-Nitrophenoxy)phenyl]-1-phenyl-1H-pyrazol-3-yl}phenol

In the title compound, C₂₇H₁₉N₃O₄, the phenol and pyrazole rings are almost coplanar [dihedral angle = 0.95 (12)°] due to an intra­molecular O—H⋯N hydrogen bond, whereas the phenyl ring is tilted by 40.81 (7)° with respect to the plane of the pyrazole ring. The aromatic ring with a nitro­phen­oxy substituent makes a dihedral angle of 54.10 (7)° with the pyrazole ring.

Polyimides Containing 1,3,4-Oxadiazole Rings

Two series of polyimides containing 1,3,4-oxadiazole rings in the main chain, one of them having flexible hexafluoropropane-2,2-diyl groups and the other with carbonyl groups, were prepared by polycondensation of aromatic diamines containing 1,3,4-oxadiazole rings with hexafluoropropane-2,2-diyl-bis(phthalic anhydride) or benzophenonetetracarboxylic dianhydride. Their properties, such as solubility in organic solvents, thermal stability, glass transition temperature, photoluminescence and film-forming properties of the two groups of polymers have been studied and compared.

Synthesis and Characterization of Organosoluble Optically Active Poly(ester-imide)s Derived from Trimellitic Anhydride, L-Methionine and Bisphenols

The reaction of thionyl chloride in pyridine as a condensing agent was used for the direct polycondensation of N-trimellitylimido-L-methionine (4) with various aromatic diols such as bisphenol A (5a), phenolphthalein (5b), 1,5-naphthalendiol (5c), 2,6-dihydroxytoluene (5d), hydroquinone (5e), biphenyl-2,2'-diol (5f), 1,4-dihydroxyanthraquinone (5g). This reaction leads to the formation of novel optically active poly(ester-imide)s (PEI)s. The resulting PEIs were obtained in good yields and exhibited low to moderate inherent viscosities ranging from 0.15 to 0.40 dL g-1. All of the PEIs showed good solubility and readily dissolved in solvents such as N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), pyridine and tetrahydrofuran. Thermogravimetric analysis showed that PEI 6b was stable, with 10% weight loss recorded above 370 oC in nitrogen. All of the above polymers were characterized by FTIR, specific rotation, and representative PEIs were also characterized by 1 H NMR, elemental analysis, and thermogravimetric analysis. The structural characterization and physical properties of these new optically active PEIs are reported.