Linear Polyamides Research Articles

Inhibition of heat shock transcription factor binding by a linear polyamide binding in an unusual 1:1 mode.

Heat shock proteins (HSPs) are known to protect cells from heat, oxidative stress, and the cytotoxic effects of drugs, and thus can enhance cancer cell survival. As a result, HSPs are a newly emerging class of protein targets for chemotherapy. Among the various HSPs, the HSP70 family is the most highly conserved and prevalent. Herein we describe the development of a β-alanine rich linear polyamide that binds the GGA heat shock elements (HSEs) 3 and 4 in the HSP70 promoter in an unusual 1:1 mode and inhibits heat shock transcription factor 1 (HSF1) binding in vitro.

Investigation of melting behaviors and crystallinity of linear polyamide with high‐aliphatic content

AbstractThe melting behaviors and crystal structures of a long alkyl chain polyamide and nylon 18 18, were investigated under annealing and isothermal crystallization conditions. Nylon 18 18 showed multiple melting peaks in differential scanning calorimetry (DSC) thermograms depending on thermal history of the samples. The origin of the multiple melting peaks may be a result of a melting and recrystallization mechanism during DSC scans. Wide‐angle X‐ray diffraction patterns showed two new diffraction peaks, which appeared at 0.44 and 0.37 nm, and are characteristic peaks of α‐form (triclinic structure) of even–even nylons with increasing annealing temperature. The intensities of these peaks increased, and they split further apart, with elevated annealing temperatures. The solid‐state 15N CP/MAS NMR spectra of the nylon 18 18 samples that had been quenched and annealed also confirmed the α‐crystalline form. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The Effects of Substituent Grafting on the Interaction of pH-Responsive Polymers with Phospholipid Monolayers

pH-responsive amphiphilic polymers with suitable graftings have demonstrated highly efficient cell membrane activity and hence are promising applicants for drug-delivery. Grafting the hydrophobic amino acid l-phenylalanine and the hydrophilic methoxy poly(ethylene glycol) amine onto the pendant carboxylic acid moieties of a linear polyamide, poly(l-lysine isophthalamide), can effectively modify the amphiphilicity and conformation of the amphiphilic polymers. Here, the interactions of these polymers with phospholipid monolayers adsorbed on mercury (Hg) electrodes have been studied. AC voltammetry (ACV), rapid cyclic voltammetry (RCV), and electrochemical impedance spectroscopy (EIS) have been applied to monitor phospholipid monolayer associations with different polymer concentrations under different pH values. The polymers interact reversibly with the monolayer shown by altering the monolayer capacitance and inhibiting the phospholipid reorientation in electric field. Polymer grafting enhances the pH-mediated conformational change of the polymers which in turn increases their phospholipid monolayer activity. The most significant monolayer interactions have been observed with the polymer grafted with hydrophobic l-phenylalanine. A low level of PEGylation of the backbone also increases the monolayer activity. The polymer/DOPC interactions have been represented with an impedance model, which takes account of the interaction giving rise to an increase in monolayer capacitance and inhomogeneity and a Debye type dielectric relaxation. The extent of penetration of the polymers into the monolayer is inversely related to the electrical resistance they give rise to during the Debye relaxation. The cell membrane activities of these amphiphilic polymers have been successfully mirrored in this supported DOPC monolayer system, isolating the key parameters for biomembrane activities and giving insight into the mechanism of the interactions. The conclusions from this study provide strategic directions in material design catering to different requirements in biomedical applications.

Direct Synthesis of Polyamides via Catalytic Dehydrogenation of Diols and Diamines

We report a direct synthesis of polyamides via catalytic dehydrogenation of diols and diamines. A PNN pincer ruthenium complex, the Milstein catalyst, was used for this reaction and polyamides with number average molecular weight from ∼10 to 30 kDa could be obtained from a wide variety of diols and diamines bearing aliphatic or aromatic, linear or cyclic spacers. Because of the high catalytic selectivity of primary amine over secondary amine, polyamines could be conveniently incorporated into linear polyamides without tedious protection/deprotection steps. Compared with conventional condensation method, this catalytic system avoids the requirement of stoichiometric preactivation or in situ activation reagents and provides a much cleaner process with high atomic economy.

Novel thin film composite membrane containing ionizable hydrophobes: pH-dependent reverse osmosis behavior and improved chlorine resistance

New polyamide thin film composite membranes were prepared by interfacial polymerization of hexafluoroalcohol (HFA)-containing aromatic diamine and trimesoyl chloride (TMC) on a porous polysulfone support. The surface properties of the resulting membranes were characterized by water contact angle, XPS, and SEM. Additionally, the desalination separation performance was evaluated by the cross-flow filtration of 2000 ppm NaCl solution. Water contact angle and XPS analyses indicated that the HFA-containing polyamide membrane is relatively hydrophobic at neutral conditions but becomes hydrophilic at basic conditions due to ionization of the HFA groups, so we refer to this group as an “ionizable hydrophobe” or “i-phobe”. The membrane showed strongly pH-dependent reverse osmosis behavior with enhanced performance (high water flux and high salt rejection) at high pH (ca. 10). Both the electron withdrawing nature and the steric bulkiness of the HFA functionality are also advantageous in protecting the polyamide membrane from chlorine attack. Based upon NMR studies of model polymers (linear polyamides with and without the HFA functionality) and the membrane performance measured before and after chlorine exposure, the HFA-containing polyamide has improved chlorine stability compared to the reference polyamide made from m-phenylenediamine and TMC.

New sets of solubility parameters of linear and crosslinked aromatic polyamides

As generally accepted, also in the case of pol- yamides linear and crosslinked polymeric materials are believed to be characterized by the same solution properties and, consequently, by the same solubility parameters. How- ever, despite their great practical importance, a thorough study aimed to determine the best solvent media able to dis- solve linear aromatic polyamides has not been performed yet or, at least, has not been published. In this study, we report on our study on the solubility parameters of linear and crosslinked aromatic polyamides. We demonstrate that the assumption of considering these two classes as having the same solubility properties can lead to dramatically erro- neous results. Two new different sets for linear and cross- linked aromatic polyamides are proposed. Namely, linear poly(p-phenylene terephthalamide) is characterized by dp, dd, and dH equal to 8.6, 18.4, and 11.3, respectively; by con- trast, the corresponding values of the crosslinked aromatic polyamides taken into consideration are: 11.5, 16.8, and 10.2.V C 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 3155-3160, 2010

Blends of different linear polyamides with hyperbranched aromatic AB2 and A2 + B3 polyesters

AbstractTo explore the possible applications of hyperbranched polymers for modifying linear polyamides, two hyperbranched aromatic polyesters characterized as high Tg polymers possessing phenolic end groups were used in melt mixing with partly aromatic polyamide and commercially available aliphatic polyamide‐6, respectively. Different amounts of both hyperbranched polyesters (from 1 wt % up to 20 wt %) were added to the polyamides, and the influence of these hyperbranched polyesters on the properties of the polyamides was investigated. The hyperbranched polyester based on an AB2 approach was found to be the most effective modifier. A significant increase of the glass transition temperature of the final blend was detected. However, a remarkable reduction of crystallinity as well as complex melt viscosity of those blends was also observed. The use of an A2+B3 hyperbranched polyester as melt modifier for the polyamides was less effective for changing the thermal properties, and the complex melt viscosity of the final material increased since heterogeneous blends were formed. In contrast to that, generally, the addition of the AB2 hyperbranched polyester to the polyamides resulted in homogeneous blends with improved Tg and processability. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3558–3572, 2009

Cyclic and Linear Polyamides from Polycondensations of Hexamethylenediamine and m-Xylylenediamine with Adipic, Isophthalic, and Terephthalic Acids

Cyclic and linear oligoamides were extracted with methanol in 0.1−0.9% yield from condensation polymers of hexamethylenediamine or m-xylylenediamine with mixtures of adipic, isophthalic, and terephthalic acids. The parent polymers and methanol extracts were analyzed using mass spectrometry, and the extracts, in which the smaller molecules were concentrated by a factor of about 200, were studied by nuclear magnetic resonance (NMR) spectroscopy. Small cyclic oligoamides dominated all of the extract spectra. Cyclic monomers were observed with adipic acid but not with the aromatic acids. Cyclic dimers and trimers predominated and yields of higher cyclics decreased rapidly with increasing ring size, especially in the extracts. The degree of incorporation of the acids into small cyclics was adipic > isophthalic > terephthalic. NMR spectra of extracts from all polymers containing terephthalic and/or isophthalic acid units showed linear oligomers with benzoyl end groups, which presumably arose from thermal decarb...

Synthesis and characterization of dendronized aromatic polyamides with bromomethyl groups in the periphery

AbstractThis paper focused on the synthesis of novel functionalized dendronized aromatic polyamides, which contained a polyamide backbone and polyamide dendrons decorated with bromomethyl groups, by the macromonomer route. The new activating procedure of the synthesis of dendrons and macromonomers using thionyl chloride as an activating agent eliminated the protection/deprotection procedure and reduced side reactions. The structures of the dendrons, macromonomers, and polyamides were confirmed by FTIR, 1H NMR, 13C NMR, and elemental analysis. The properties of the resulting dendronized polyamides, which were compared with that of the linear polyamide (LP), were studied using GPC, XRD, TGA, DSC, inherent viscosity measurement, and solubility experiment. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Discovery of G-quadruplex stabilizing ligands through direct ELISA of a one-bead-one-compound library

We describe the identification of small-molecule G-quadruplex ligands using a direct ELISA screen of a one-bead-one-compound library of unnatural polyamides displayed on a branched linker with a biotin tag. This general purpose parallel screen for small molecule-oligonucleotide interactions was validated by surface plasmon resonance and ELISA of resynthesized compounds. Linear polyamides displayed similar rankings in their affinity for quadruplex as their branched counterparts. Quadruplex affinity as judged by these surface based techniques was a useful predictor of the ability of the ligands to stabilize the quadruplex to thermal unfolding in solution.

Synthesis, thermal and mechanical properties and biodegradation of branched polyamide 4

A series of linear and branched polyamide 4 were prepared and characterized in order to study the effect of the structure on thermal and mechanical properties. Polybasic acid chlorides were effective initiators for the synthesis of the branched polyamide 4. The melting points of the polyamide 4 for the high molecular weight region were near 265 °C and showed no significant difference depending on their chain structure. On the other hand, it was found that the branched polyamide 4 showed remarkable increase of tensile strength, compared to similar molecular weight of the linear polyamide 4 (e.g. four-branched type M w=9.28×10 4, tensile strength=72 MPa).When the initiator having branched structure were used, gel was also formed at the initiator concentration over a certain value (e.g. 3.0 mol% for 4-branched type).The biodegradation of the branched polyamide 4 was evaluated using a standard activated sludge (e.g. four-branched type M w=8.25×10 4, biodegradation 41%).

Investigation of a tartaric acid‐based linear polyamide and dimer as chiral selectors in liquid chromatography

A twin selector for enantioselective liquid chromatography based on O,O'-bis(dimethyl)benzoyl tartaric diamide was synthesized and compared to commercially available Kromasil CHI-DMB (O,O'-bis(dimethyl)benzoyl tartaric diamide). A linear polyamide based on the same tartaric acid derivative was also synthesized, immobilized on silica, and evaluated as stationary phase. The twin selector was immobilized as a brush-type phase, with similar bonding chemistry as in Kromasil CHI-DMB. It was shown to exhibit lower resolution power than Kromasil CHI-DMB. However, retention and separation factors obtained on the respective sorbents were shown to exhibit interdependence. CD spectra of the twin selector give no indication that the respective branches interact in the solvent mixtures employed for chromatography. The linear polyamide showed lower enantioselectivity and higher retention than Kromasil CHI-DMB.

Synthesis and characterization of novel polyamides based on tridecanedioic acid: Nylons 3 13, 5 13, 6 13, 7 13, 9 13, 10 13, 11 13

Abstract Linear polyamides with high aliphatic content were prepared through step-heating melt polycondensation of tridecanedioic acid with various diamines. The synthesized polyamides were characterized comprehensively by means of IR, NMR and Raman spectroscopy. In addition, thermogravimetry, differential scanning calorimetry and dynamic mechanical analysis were used to investigate thermal properties of the obtained polyamides. It was found that melting and crystallization temperatures decrease as the aliphatic content increases. X-ray diffraction was applied to determine the crystal structures of the polyamides.

Synthesis and Characterization of Linear Polyamides Derived from l-Arabinitol and Xylitol

The synthesis and characterization of a new series of AABB-type polyamides based on l-arabinitol and xylitol are described. These linear polyamides were obtained by reaction of the aldaric acids or aliphatic dicarboxylic acids, with sugar-based diamine or aliphatic diamines. The pentaric diacids were activated as their pentachlorophenyl esters, and the diamino sugars were used as dihydrochlorides. Aliphatic diamines were used either as their activated trimethylsilyl derivatives or as the free bases. All the polyamides were soluble in the usual organic solvents, and those fully sugar-based were also soluble in water. All of them were very hygroscopic, especially those based on xylitol. DSC and X-ray powder diffraction studies showed that l-arabinitol-based polyamides were more crystalline than those derived from xylitol.

Linear polyamides from L‐malic acid and alkanediamines

AbstractA series of linear polyamides (PnMLM) derived from O‐methyl‐protected L‐malic acid and 1,n‐alkanediamines with even n values ranging from 4 to 12 were prepared and fully characterized. L‐Malic acid entered in the chain with a random orientation rendering essentially aregic polymers. PnMLM displayed optical rotation consistent with the content of the polymer in malic units, and they all were crystalline with melting points ranging from 158 to 188 °C and glass‐transition temperatures varying from 37 to 70 °C. PnMLM appeared to be fairly stable to heat with thermal decomposition starting close to 300 °C. Hydrolytic degradation of PnMLM at 37 °C was slow, but the process was significantly faster at 70 °C. Thermal degradation took place with the formation of cyclic malimides in the residual polymer and released the 1,n‐alkanediamine. However, hydrolytic degradation took place in a first stage with the formation of open chains of carboxylic‐ and amine‐ended oligomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1566–1575, 2004

Synthesis of novel polyamides starting from ferulic acid dimer derivative

Novel polyamides containing cyclobutane in the main chain were synthesized from a dimmer that was obtained by topochemical [2 + 2] photo-dimerization of O-acetylferulic acid crystals, using two different methods: (1) The dimer was converted into a three-dimensional network polyphenylester on heating, eliminating acetic acid. The network polymer was reacted with a diamine to afford a linear polyamide. (2) The same dimer chloride was submitted to an interfacial polycondensation with a diamine. Although the first method is a unique one to convert a network polymer to a linear polymer, the second method was found to be more practical from the viewpoints of both preparation process and the quality of the polymer obtained. These synthetic procedures into the polyamides and characterization of resulted polymers are described. The phenolic polymer showed an anti-oxidant nature when reacted with a free radical DPPH.

Cyclic Polyamide-6 by Thermal Polycondensation of ε-Caprolactam and ε-Aminocaproic Acid

ε-Caprolactam (ε-CLA) and ε-aminocaproic acid (ε-ACA) were polycondensed with a molar ratio of 90:10 at 250 °C for 2, 4, 6, 8, 17, and 48 h. The molecular weight increased up to a time of 17 h, and the molar ratio of cycles vs linear chains increased accordingly. After 17 h, only cyclic polyamides were detected in the MALDI−TOF mass spectra (detectable up to 10 000 Da). Furthermore, ε-CLA/ε-ACA ratios of 0/100, 50/50, and 80/20 were polycondensed at 250 °C for 17 and 48 h. In all cases, the same maximum molecular weight was obtained, suggesting that the chain growth was limited by cyclization. Heating a 99:1 ε-CLA/ε-ACA mixture yielded a low molar mass product exclusively consisting of cycles. Extraction experiments with various solvents proved that a separation of cyclic and linear polyamides is not feasible in this way. All these results are in perfect agreement with our new theory of thermodynamically controlled polycondensations.

Poly(ether amide) Dendrimers via Nucleophilic Ring-Opening Addition Reactions of Phenol Groups toward Oxazolines: Synthesis and Characterization

The synthesis of aliphatic−aromatic poly(ether amide) dendrimers via ring-opening addition reaction of phenol groups toward oxazoline up to generation 3 is presented. The first and second generation could be prepared both by convergent and divergent approaches. The ring-opening addition reaction was carried out in bulk at temperatures between 140 and 190 °C, followed by hydrogenation of the protecting benzyl ether units with palladium catalyst. The dendrons and dendrimers were characterized by 1H and 13C NMR spectroscopy, MALDI−TOF MS, SEC, and DSC. The synthetic scheme applied allowed to prepare perfect dendrimers having identical structure and end groups as previously described hyperbranched polymers which enabled a direct comparison of the properties. Melt rheology measurements on the dendrimers revealed a predominantly elastic behavior with a relatively high viscosity at low frequency, as was found also for the hyperbranched analogues. The second generation of one of the poly(ether amide) dendrimers was mixed with linear polyamide 6 (PA6) in melt up to an amount of 1 wt % in order to evaluate the influence of dendrimers on the properties of the matrix. The dendrimer was fully miscible with the matrix, but in contrast to the hyperbranched polymers of higher molar mass, it had no influence on the melt rheological behavior of the PA6.

Reactions of Heterocumulenes with Organometallic Reagents: VII. Reactions of Carbanions Derived from Alkoxy- and Alkylthioethenes with Isocyanates as a Simple Route to N-Substituted 2-Alkoxy- and 2-(Alkylthio)acrylamides

Metalated alkoxy- and alkylthioethenes readily add to isocyanates, and subsequent hydrolysis or alkylation of the adducts gives N-mono- and N,N-disubstituted 2-alkoxy- and 2-(alkylthio)acrylamides in up to 86% yield. The reactions with propyl and phenyl isocyanates do not stop at the stage of addition of one isocyanate molecule, and further addition leads to formation of linear and cyclic polyamide structures.

Water‐soluble polymers with tunable temperature sensitivity: Solution behavior

Water‐soluble polymers with tunable temperature sensitivity: Solution behavior