Chiral Poly Research Articles

Synthesis and characterization of a chiral copoly(ether sulfone) with high molecular weight

A series of chiral poly(ether sulfone)s containing (S)-binaphthyl unit were synthesized via nucleophilic substitution polycondensation. The as-synthesized polymers were characterized by NMR. The molecular weights of these polymers were calculated by viscosity and gel permeation chromatography. The thermal stability was measured by TGA. The optical activities of the polymers were studied by circular dichroism and optical rotation. It was found that introducing more reactive 2,2′-biphenol monomer to partly substitute the binaphthol monomer could increase the molecular weight of the polymer from 4.1 × 104 to 9.8 × 104 g mol−1. Meanwhile, the thermal stability increased and the decomposition temperature rose from 447 to 518 °C, with the optical activity of the polymer well preserved. However, the value of the specific optical rotation decreased with increasing biphenol to binaphthol molar ratio. In addition, the optical rotation direction of the polymer was contrary to that of the pristine binaphthol monomer, which indicated that the chiral polymers formed a secondary structure. © 2013 Society of Chemical Industry

Construction and characterization of poly(amide-ester-imide) nanocomposites containing N-trimellitylimido-l-leucine toughened with a combination of bioactive surface-grafted TiO2

This paper addressed production and characterization of novel type copolyester/titania (TiO2) nanocomposites (NCs). First, the surface of TiO2 was modified by chiral diacid monomer, N-trimellitylimido-l-leucine (TMIL) (1) as a coupling agent to form organomodified TiO2 (O-TiO2) nanoparticles (NPs). Fourier transform infrared (FT-IR) spectroscopy confirmed the presence of coupling agent groups on the surface. Thereafter, a novel chiral poly(amide-ester-imide) (PAEI) was synthesized by step-growth polymerization of diacid monomer 1 with diol, N,N′-(1,3,5,7-tetraoxo-5,7-dihydropyrrolo[3,4-f]isoindole-2,6(1H,3H)-diyl)bis(4-hydroxybenzamide) (2) via tosyl chloride, pyridine and N,N-dimethyformamide as a condensing agent. The incorporation of O-TiO2 NPs into the obtained PAEI provided an opportunity for the construction of polymer-based NCs with novel and powerful properties. The obtained NCs were premeditated using transmission electron microscopy (TEM), FT-IR spectra, thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), X-ray diffraction; also the optical properties of the NCs were studied using ultraviolet-visible spectroscopy. The TEM and FE-SEM results showed that the NPs were dispersed homogeneously in PAEI matrix on the nanoscale. TGA data confirmed that the heat stability of the aforementioned NCs in the presence of O-TiO2 NPs was improved.

Design and Characterization of Chiral and Thermally Stable Nanostructure Poly(amide-imide)s Containing Different Trimellitylimido-Amino Acid-Based Diacids and 4,4′-Methylenebis(3-chloro-2,6-diethylaniline) Units

In this study new chiral nanostructure poly(amide-imide)s (PAI)s were synthesized via direct polycondensation of different trimellitylimido-amino acid-based diacids and 4,4′-methylenebis(3-chloro-2,6-diethylaniline), using tetra-n-butylammonium bromide and triphenyl phosphite as a green media. The formation of these nanostructure PAIs was confirmed by 1H-NMR, Fourier transform infrared spectroscopy, specific rotation, elemental analysis, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and thermo gravimetric analysis techniques. The FE-SEM micrographs and XRD patterns showed that, the obtained PAIs are nanostructured with different shapes and noncrystalline polymers.

Effect of Surface Functionalized Nano-ZnO Structure on Morphology and Properties of Poly(amide-imide) Nanocomposites Containing N-trimellitylimido-L-leucine and 5-(2-benzimidazole)-1,3-phenylenediamine

The authors report the construction of the nanostructure chiral poly(amide-imide) (PAI) with flexible chiral unit in the backbone and benzimidazole pendant group, from an optically active synthesized N-trimellitylimido-L-leucine (V), and 5-(2-benzimidazole)-1,3-phenylenediamine (IV) via direct polycondensation in tetrabuthylammonium bromide as a green media. Then, hybrid organic-inorganic nano-ZnO/PAI composites were prepared with different amount of modified ZnO nanoparticles via ultrasonic process. The surface of nano-ZnO was modified with 3-aminopropyltriethoxysilane due to the homogeneous distribution of ZnO in polymer matrix. The properties, including thermal properties, morphological study and spectroscopy analysis of the nanocomposites were investigated.

Reinforcement of poly(vinyl alcohol) with chiral poly(amide-imide)s nanoparticles containing S-valine under simple ultrasonic irradiation method

Nanostructured amino acid containing poly(amide-imide) (PAI) was synthesized from the direct polycondensation reaction of 2–(3,5–diaminophenyl)–benzimidazole and N,N′–(pyromellitoyl)–bis–phenylalanine diacid under green condition by using tetrabutylammonium bromide as molten ionic liquid. Field emission scanning electron microscopy images show that the average diameter of polymeric nanoparticles with spherical shape was around 20–35 nm. In the next step, these polymeric nanoparticles were used as nano-fillers for reinforcement of poly(vinyl alcohol) (PVA) for the first time. Bionanocomposite of PVA and various compositions of PAI nanoparticles were produced through ultrasound-assisted technique. Fourier transform infrared spectroscopy, x-ray diffraction, field emission scanning electron microscopy, and thermogravimetric analysis were utilized to characterize the obtained hybrid materials, morphology, and properties. Results of thermal properties indicated that the thermal stability is enhanced. The improvement of thermal properties was attributed to the homogeneous and good dispersion of PAI nanoparticles in the PVA matrix and the strong hydrogen bonding between O–H groups of PVA and the carbonyl of amide and imide groups of the used PAI nanoparticles.

Investigating the nanostructure and thermal properties of chiral poly(amide-imide)/Al2O3 compatibilized with 3-aminopropyltriethoxysilane

Novel chiral poly(amide-imide) (PAI)/Al2O3 nanocomposites were prepared via incorporating surface modified Al2O3 nanoparticles into polymer matrices for the first time. In the process of preparing the nanocomposites, severe aggregation of Al2O3 nanoparticles could be reduced by surface modification and γ-aminopropyltriethoxysilane. The optically active PAI chains were formed from the polycondensation reaction of N,N′-(pyromellitoyl)-bis-phenylalanine diacid with 2-(3,5-diaminophenyl)-benzimidazole in green condition. The obtained polymer and inorganic metal oxide nanoparticles were used to prepare chiral PAI/Al2O3 nanocomposites through ultrasonic irradiation. The resulting nanoparticle filled composites were also characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis (TGA) techniques. TGA thermographs confirmed that the heat stability of the prepared nanoparticle-reinforced composites was improved. Mechanical properties showed that the film containing 10wt% of modified Al2O3 had a tensile strength of the order of 83.6MPa, relative to the 64.3MPa of the pure PAI.

Investigating thermophysical properties of novel chiral nanostructured poly(amide-ester-imide)s containing different amino acids based on biological active N, N′-(pyromellitoyl)-bis-l-amino acids and diol

Preparation of potentially biodegradable poly(amide-ester-imide)s (PAEI)s with different amino acids was described. For the first time, the synthesis of diol N, N′-(1,3,5,7-tetraoxo-5,7-dihydropyrrolo[3,4-f]isoindole-2,6(1H,3H)-diyl)bis(4-hydroxybenzamide) (diol 4) was recounted. The diol 4 was supplied by Vitas-M Laboratory, Ltd (Moscow, Russia). The key monomer applied in this project was diol 4. The direct polycondensation reaction of several chiral diacids (3A–3D) with aromatic diol 4 was carried out in a system of tosyl chloride, pyridine, and N,N-dimethyformamide. All the above PAEIs were characterized by proton nuclear magnetic resonance, Fourier transform infrared (FT-IR), elemental analysis, specific rotation techniques, x-ray diffraction, and field emission scanning electron microscopy (FE-SEM). Thermogravimetric analysis was used to study thermal properties of PAEIs. The FE-SEM of the aforementioned PAEIs indicated that these polymers were nanostructured particles. These polymers contain bioactive amino acids and diol units possibly with potential applications as biodegradable and biocompatible agents.

Facile synthesis of nanocomposite materials by intercalating an optically active poly(amide-imide) enclosing (l)-isoleucine moieties and azobenzene side groups into a chiral layered double hydroxide

The use of layered inorganic solids as host materials for the creation of inorganic–organic host–guest supramolecular structures is of increasing interest. In the present investigation, the nanocomposites of chiral poly(amide-imide) (PAI) and different amount of modified layered double hydroxide (LDH) were prepared via solution intercalation method for the first time. Chiral organically-modified chiral LDH was prepared via ion exchange reaction of LDH in a solution of N,N′-(pyromellitoyl)-bis-l-isoleucine diacid in distilled water. Novel diamine with azo side group was synthesized from the reaction of 4-aminoazobenzene and 3,5-dinitrobenzoyl chloride followed by reduction of dinitro with iron oxide hydroxide catalyst and hydrazine monohydrate. An optically active PAI was prepared by direct polyamidation of the chiral diacid with azo diamine under green condition using molten tetra-n-butylammonium bromide with good yield and moderate inherent viscosity. The obtained polymer and organically-modified chiral LDH were used to prepare chiral and high performance hybrid materials. The effect of LDH contents on thermal, physicomechanical, and morphological properties of PAI was investigated by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy techniques. Thermogravimetric analysis results confirmed that the heat stability of the prepared nanoparticle-reinforced composites was improved.

Enantiopure Chiral Poly(glycerol methacrylate) Self‐Assembled Monolayers Knock Down Protein Adsorption and Cell Adhesion

Chirality plays a fundamental role not only in biological systems, but also in synthetic materials intended for bio-applications. Self-assembled monolayers (SAMs) are prepared on gold surfaces through a "grafting to" method from racemic or enantiopure chiral poly(glycerol methacrylate)s (PGMA(rac), PGMA(R), and PGMA(S)), having a thiol endgroup. Such SAMs constitute a chemically and structurally well-defined model substrate for studying protein adsorption and cell adhesion as a function of the polymer chirality. Surface plasmon resonance measurements reveal that PGMA SAMs greatly reduce the adsorption of bovine serum albumin (BSA) compared to bare gold surfaces. Interestingly, enantiopure SAMs based on PGMA(R) or PGMA(S) show a significantly larger reduction in BSA adsorption than PGMA(rac)-covered surfaces. Studies with the monocytic cell line THP-1 show a similar relationship between enantiopurity of PGMA SAMs and the extent of cell adhesion. Ellipsometry and Raman spectroscopy measurements indicate that SAMs formed by PGMA(rac) have a higher grafting density compared to SAMs of PGMA(R) and PGMA(S). This seems to be due to the ability of PGMA(rac) to form more intermolecular hydrogen bonds among polymer chains compared to the enantiopure PGMAs. Circular dichroism spectroscopy provide evidence that enantiopure polymers adopt a chiral ordered conformation, most likely helical, in aqueous solutions. It is concluded that a higher water content of SAMs formed by enantiopure PGMA(S) and PGMA(R) SAMs arises from the macromolecular chiral conformation adopted by their enantiopure PGMA chains, and it is the decisive reason for the reduced BSA adsorption and cell adhesion as compared to PGMA(rac) SAMs.

Preparation of new polymer nanocomposites based on chiral poly(amide-imide)/surface-modified ZnO nanoparticles containing 4,4′-methylene bis(3-chloro-2,6-diethylaniline) linkages via ultrasonication-assisted process

In the present investigation, a novel chiral poly(amide-imide) (PAI) was synthesized via direct polycondensation reaction of chiral diacid monomer with 4,4′-methylene bis(3-chloro-2,6-diethylaniline) in molten tetrabutylammonium bromide as a green solvent. Then PAI-based bionanocomposites (BNC)s have been successfully prepared via ultrasonic irradiation method using zinc oxide (ZnO) nanoparticles functionalized by γ-aminopropyltriethoxysilane as a coupling agent to decrease aggregation of nanoparticles in polymer matrix. The physicochemical and morphology properties of the neat PAI and BNCs were studied using 1H-NMR, FT-IR spectroscopy, specific rotation, elemental analysis, X-ray diffraction, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). FT-IR and TEM depicted that the ZnO nanoparticles function as a physical cross-linking agent with PAI through hydrogen bonding between the OH on the ZnO nanoparticles and the C=O of the amide and imide groups. Also, TEM and FE-SEM images revealed that ZnO nanoparticles were dispersed in PAI matrix with particle size between 15 and 25 nm. Thermogravimetric analysis data showed an improvement of thermal stability of new BNCs in comparison with the pure PAI.

In vitro studies on biodegradable chiral nanostructure poly(amide-imide)s containing different natural amino acids in green medium

α-Amino acids, as one type of the major building blocks of living systems, are the principal components of all naturally occurring peptides and proteins. The aim of this paper was to synthesize and characterize of novel chiral nanostructured poly(amide-imide)s (PAIs) that are biologically active and biodegradable under a natural environment. PAIs were prepared from the polycondensation reaction of optically active diacids monomers containing different natural amino acids with 4,4′-methylene bis(3-chloro-2,6-diethylaniline) in molten tetrabutylammonium bromide as a green solvent. In vitro fungal colonization and weight loss studies showed that the synthetic polymer having alanine amino acid is biologically more active compared to the other components, nontoxic to microbial growth and could be classified as biodegradable compounds. The synthesized PAIs were characterized by different techniques. The field-emission scanning electron microscopy showed that the obtained PAIs were nanostructured polymers.

Development of novel chiral poly(amide–imide)/bionanocomposites containing N,N′-(pyromellitoyl)-bis-phenylalanine units reinforced by organoclay and modified TiO2

In the present investigation, novel optically active poly(amid–imide) (PAI)/organoclay (OC)/titanium dioxide (TiO2) bionanocomposite (BNC) films were prepared by solution intercalation method. These BNCs were synthesized by blending the chiral OC and modified TiO2 nanoparticles (NPs) with the PAI solution. An optically active PAI containing l-phenylalanine amino acid was synthesized via direct polycondensation reaction of N, N′-(pyromellitoyl)-bis-phenylalanine diacid 4 with 4,4′-diaminodiphenylsulfone 5 in the presence of molten tetrabutylammonium bromide as a green solvent. This polymer was end capped with amine end groups of diamine in the final polymerization process. Cloisite Na+ and protonated form of l-phenylalanine amino acid were used for the preparation of the chiral OC via ion-exchange reaction. The surface of TiO2 NPs was fictionalized by KH550 (γ-aminopropyltriethoxyl) coupling agent under ultrasonic irradiation. Finally, PAI/OC/TiO2 BNC films containing 5 wt% of the OC and 5, 10 and 15 wt% of modified TiO2 were prepared via solution intercalation technique. The resulting hybrid materials were subjected to Fourier transform infrared spectroscopy, thermogravimetric analysis techniques and x-ray diffraction. The morphology of the obtained materials was examined by transmission electron microscopy and field emission scanning electron microscopy techniques.

High-performance nanostructure chiral poly(amide–imide)s containing benzamide and amino acid linkages: Preparation, characterization and ultrasonic effect on the morphology

In this research work, several novel optically active nanostructure poly(amide–imide)s (PAIs) were synthesized from the direct polycondensation reaction of 3,5-diamino- N-(pyridin-3-yl) benzamide with chiral diacids based on trimellitic anhydride-derived dicarboxylic acids containing different natural amino acids such as l-methionine, S-valine, l-alanine and l-isoleucine in green medium consisting of molten tetrabutylammonium bromide. The diamine was synthesized by a two-step reaction. At first, 3,5-dinitro- N-(pyridin-3-yl)benzamide was prepared from the reaction of one equimolar of 3-amino pyridine and one mole of 3,5-dinitrobenzoyl chloride. In the next step, the obtained dinitro was reduced by Pd/C and hydrazine hydrate. The new thermally stable optically active PAIs with inherent viscosity ranging from 0.31 to 0.46 dL g−1 were obtained with high yield. The synthesized polymers were characterized with Fourier transform infrared, proton-nuclear magnetic resonance spectroscopy, specific rotation measurements, thermogravimetric analysis, x-ray diffraction, field emission scanning electron microscopy (FE-SEM) and elemental analysis techniques. Morphological study by FE-SEM showed that these new PAIs were noncrystalline and nanostructure polymers with particle size between 50 and 70 nm. The effect of ultrasonic radiation on the obtained nanostructured polymers showed that the size of polymeric nanoparticles was reduced to about 30–45 nm.

Novel chiral poly(amide-imide) nanocomposites reinforced with silicate layers and TiO2 nanoparticles based on N-trimellitylimido-l-isoleucine

In the present investigation, the goal was the preparation, characterization, and surface morphology of poly(amide-imide)/TiO2/oganoclay nanocomposites. At first, an optically active poly(amide-imide) was synthesized from the polymerization reaction of N-trimellitylimido-l-isoleucine diacid with 4,4′-methylenebis(3-chloro-2,6-diethylaniline). The obtained polymer and TiO2 nanoparticles were used to prepare poly(amide-imide)/TiO2 nanocomposites through ultrasonic irradiation. Then, different amounts of organoclay were added to the poly(amide-imide)/TiO2 nanocomposite system to obtain poly(amide-imide)/TiO2/oganoclay nanocomposite. The resulting hybrids materials were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis techniques.

The effects of reactive organoclay on the thermal, mechanical, and microstructural properties of polymer/layered silicate nanocomposites based on chiral poly(amide-imide)s

Considering the importance of the nanocomposites, the present work focuses on some new hybrid materials prepared by introducing reactive organoclay (OC) into the chiral poly(amide-imide) (PAI) matrix. At first, Cloisite Na+ was modified with protonated l-isoleucine amino acid. Then, PAI containing phenylalanine was synthesized via solution polycondensation of chiral diacid chloride with 4,4′-diaminodiphenylsulfone and was characterized with Fourier transform infrared (FTIR) and 1H NMR techniques. At last, PAI/OC nanocomposite films containing 2, 5, 10, and 15 % of OC were prepared via solution intercalation method. The effect of OC dispersion and the interaction between OC and polymer chains on the properties of nanocomposites were investigated using FTIR, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, tensile testing of thin films, and thermogravimetry analysis techniques. The thermal stability of hybrids such as the decomposition temperature and mass residue at 800 °C was improved. Mechanical data indicated improvement in the tensile strength of the nanocomposites with OC loading up to 10 wt%. The transparency of the hybrid films was investigated by means of UV–Vis spectra.

Cross‐Linked Helically Chiral Poly‐(γ‐benzyl‐L‐glutamate) as Enantiodiscriminating Alignment Medium

The best of both worlds: By crosslinking poly-(γ-benzyl-L-glutamate) (PBLG), an alignment medium, which combines the scalability of cross-linked polymer gels (strain-induced-alignment media) with the enantiodiscriminating properties of helically chiral PBLG, was obtained. Spectra of excellent quality and residual dipolar couplings (RDCs) of the perfect size can be obtained for small organic compounds (see scheme; Bn = benzyl).

Synthesis of novel nanostructured chiral poly(amide-imide)s containing dopamine and natural amino acids

Four new thermally stable and optically active poly(amide-imide)s (PAI)s with good inherent viscosities were synthesized from the direct polycondensation reaction of N,N′-(pyromellitoyl)-bis-L-α-amino acids with 3,5-diamino-N-(3,4-dihydroxy-phen-ethyl)benzamide in a medium consisting of a molten salt, tetrabutylammonium bromide, and triphenyl phosphite as the activator. The polymerization reactions produced a series of novel PAIs containing dopamine segment in the side chain in high yield with inherent viscosities between 0.33 and 0.49 dL/g. The obtained polymers were typically characterized by means of FT-IR, 1H NMR spectroscopy, elemental analyses, powder X-ray diffraction, field emission scanning electron microscopy, inherent viscosity, and solubility tests. Thermal properties and flame retardant behaviour of the PAIs were also investigated using thermal gravimetric analysis (TGA and DTG) and limiting oxygen index (LOI). Data obtained by thermal analysis revealed that these polymers showed good thermal stability. Furthermore, high char yield in TGA and good LOI values indicated that the obtained polymers were capable of exhibiting good flame retardant properties.

Microwave‐Assisted Synthesis and Morphological Characterization of Chiral Poly(amide–imide) Nanostructures in Molten Ionic Liquid Salt

ABSTRACTIonic liquids (ILs) are outstanding microwave‐absorbing agents due to their high ionic conductivity and polarizability, thus leading to a high heating rate and considerably shortened reaction time. In this study, a series of novel chiral poly(amide–imide) (PAI) nanostructures with hydroxyphenyl pendant units in the side chain were prepared with excellent yields via a simple microwave heating method using molten tetrabutylammonium bromide (TBAB) as a molten IL and triphenyl phosphite as the condensing agent. The polymerization proceeded well in molten TBAB and PAIs were obtained with high yields and moderate inherent viscosities ranging from 0.32 to 0.49 dL/g. The obtained PAIs were characterized using Fourier transform infrared spectroscopy, specific rotation, powder X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), thermogravimetric analysis, elemental analysis, and in some cases by 1H NMR technique. The FE‐SEM micrographs and XRD showed that the synthesized PAIs were nanostructured and amorphous polymers that nanosize particles are in the range of 66–78 nm. The effect of ultrasonic irradiation on the size of polymer particles was also investigated. The transparent and flexible thin films based on PAI nanostructures were obtained by a casting technique, and their properties were studied. © 2012 Wiley Periodicals, Inc. Adv Polym Techn 2013, 32, 21333; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21333

Chiral and water‐soluble poly(2‐oxazoline)s

AbstractWe describe the synthesis and characterization of the first water‐soluble and chiral poly(2,4‐disubstituted‐2‐oxazoline)s. While poly(2,4‐dimethyl‐2‐oxazoline)s are water soluble up to 100 °C, aqueous solutions of poly(2‐ethyl‐4‐methly‐2‐oxazoline) exhibit a lower critical solution temperature. This is discussed in context with its constitutional isomers poly(2‐oxazoline)s and poly(2‐oxazine)s. Circular dichroism spectroscopy revealed strong Cotton effects, which are also responsive to temperature in aqueous solution. It is therefore hypothesized that structures, comparable to polyproline helices, are formed in aqueous solution. In contrast to polyproline, poly(2,4‐disubstituted‐2‐oxazoline)s are highly water soluble and therefore represent very interesting pseudo‐polypeptides that may be useful to develop responsive biomimetic biomaterials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Novel, thermally stable and chiral poly(amide-imide)s derived from a new diamine containing pyridine ring and various amino acid-based diacids

In this investigation, several novel optically active and potentially biodegradable poly(amide-imide)s were synthesized through direct polycondensation reaction. First, a new aromatic diamine compound including pyridine ring was synthesized, which was reacted with diimide dicarboxylic acids containing different natural amino acids such as l-alanine, l-leucine, l-isoleucine and l-methionine under green condition, using molten tetrabutylammonium bromide. These new chiral macromolecules were characterized using Fourier transform infrared spectroscopy, proton and carbon nuclear magnetic resonance, field emission scanning electron microscopy (FE-SEM), x-ray diffraction (XRD) and elemental and thermogravimetric analysis techniques. They show high solubility in polar organic solvents, such as N, N′-dimethylacetamide, N-methyl-2-pyrrolidone and dimethyl sulfoxide at room temperature. XRD and FE-SEM studies show that all the obtained polymers exhibit noncrystalline and nanostructure morphology. Due to the existence of amino acids in their structures, these polymers can show a potential biodegradability and biocompatibility behavior.