Interaction Of Poly Research Articles

Synthesis and application of polymer-clay nanocomposite-supported dichromate oxidizing agent

A hybride polymer–clay nanocomposite supported dichromate reagents was prepared. Direct interaction of poly(styrene-co-N-methyl-4-vinylpyridinium) iodide with sodium montmorillonite (MMT) through ion exchange between sodium cations in MMT and pyridinium ions in the copolymer afforded a polymer–clay nanocomposite (3). The resulting nanocomposite was reacted with potassium dichromate to form the nanocomposite-supported reagents (4). The structure of the resulting nanocomposite was characterized by elemental analysis, infrared spectroscopy, X-ray diffraction and transmission electron microscopy. The dispersion of the MMT particles in the polymer matrix was confirmed using scanning electron microscopy. X-ray mapping for silicon in the nanocomposite revealed uniform distribution of Si in the polymer matrix. The effectiveness of these materials has been tested for oxidation of saturated primary, secondary and benzylic alcohols to their corresponding aldehydic and ketonic compounds in addition to oxidation of quinol to the corresponding quinone. Importantly, there is almost no formation of side-product of this process. POLYM. COMPOS., 36:2066–2075, 2015. © 2014 Society of Plastics Engineer

Novel charge-transfer complexes of 4-hexylamino-1,8-naphthalimide-labelled PAMAM dendrimer with some acceptors: a spectrophotometric study

Poly(amidoamine) dendrimers are very interesting macromolecules with highly branched structures and globular-shaped branched polymeric architectures. They are widely used for drug and gene delivery applications. In order to provide important insight into the interactions of poly(amidoamine) dendrimers with some organic acceptors, the binding of small molecules to 4-hexylamino-1,8-naphthalimide-labelled PAMAM dendrimer (PD) have been studied by spectrophotomeric method. The acceptors used in this research include chloranilic acid (CLA), p-chloranil (CHL), 2,6-dichloroquinone-4-chloroimide (DCQ), 2,6-dibromoquinone-4-chloroimide (DBQ), 7,7ʹ,8,8ʹ-tetracyanoquinodimethane (TCNQ), picric acid (PA), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and iodine monobromide (IBr). The spectrophotometric measurements proved that all the charge-transfer (CT) complexes are formed via a stoichiometry (PD: acceptor) of 1:2 (except for IBr acceptor). Accordingly the obtained complexes could be formulated as [(PD)(CLA)2], [(PD)(DCQ)2], [(PD)(DBQ)2], [(PD)(TCNQ)2], [(PD)(PA)2], [(PD)(CHL)2], [(PD)(DDQ)2] and [(PD)(IBr)4]. Benesi–Hildebrand and its modification methods were applied to estimate the spectroscopic and physical data.

Lithium ion conduction and ion-polymer interaction in poly(vinyl pyrrolidone) based electrolytes blended with different plasticizers

Poly(ethylene oxide), poly(vinyl pyrrolidone) (PEO/PVP), lithium perchlorate salt (LiClO4) and different plasticizer based, gel polymer electrolytes were prepared by the solvent casting technique. XRD results show that the crystallinity decreases with the addition of different plasticizers. Consequently, there is an enhancement in the amorphousity of the samples responsible for the process of ion transport. FTIR spectroscopy is used to characterize the structure of the polymer and confirms the complexation of plasticizer with host polymer matrix. The ionic conductivity has been calculated using the bulk impedance obtained through impedance spectroscopy. Among the various plasticizers, the ethylene carbonate (EC) based complex exhibits a maximum ionic conductivity value of the order of 2.7279 × 10−4 S cm−1. Thermal stability of the prepared electrolyte films shows that they can be used in batteries at elevated temperatures. PEO (72%)/PVP (8%)/LiClO4 (8%)/EC (12%) has the maximum ionic conductivity value which is supported by the lowest optical band gap and lowest intensity in photoluminescence spectroscopy near 400–450 nm. Two and three dimensional topographic images of the sample having a maximum ionic conductivity show the presence of micropores.

Interactions of poly(dimethylsiloxane) with nanosilica and silica gel upon cooling–heating

To control the properties of poly(dimethylsiloxane) (PDMS, Oxane 1000) as a bio-inert material, the characteristics of Oxane 1000 were compared for PDMS alone and interacting with silica gel Si-100 and nanosilica PS400. Low-temperature 1H NMR spectroscopy, applied to static samples at 200–300K, and differential scanning calorimetry (DSC) at 153–393K were used to analyze the properties of PDMS and composites. The NMR study shows that liquid and solid-like fractions of PDMS co-exist over a broad temperature range. The cooling–heating cycles give hysteresis loops of intensity of 1H NMR signals of methyl groups of a liquid fraction of PDMS vs. temperature depending on the silica type. The loop width differs for PDMS alone and bound to silicas, and the samples preheated at 420K are characterized by much narrower loops. DSC measurements of the samples show a significant difference in the thermograms on the first and second DSC scans that depend on the silica type. For PDMS confined in pores of silica gel, 3D spatial structure of the polymers can be more ordered than that of PDMS located in thin layers at a surface of nanosilica. Therefore, both melting endotherms and crystallization exotherms are observed for PDMS/silica gel. However, for PDMS/nanosilica, both thermal features are much weaker and observed during only the first DSC scan.

Determination of thermodynamic properties of poly (cyclohexyl methacrylate) by inverse gas chromatography.

In this work, some thermodynamic properties of poly (cyclohexyl methacrylate) were studied by inverse gas chromatography (IGC). For this purpose, the polymeric substance was coated on Chromosorb W and which was filled into a glass column. The retention times (t(r)) of the probes were determined from the interactions of poly (cyclohexyl methacrylate) with n-pentane, n-hexane, n-heptane, n-octane, n-decane, methanol, ethanol, 2-propanol, butanol, acetone, ethyl methyl ketone, benzene, toluene and o-xylene by IGC technique. Then, the specific volume (Vg(0)) was determined for each probe molecule. By using (1/T; lnVg(0)) graphics, the glass transition temperature of poly (cyclohexyl methacrylate) was found to be 373 K. The adsorption heat under the glass transition temperature (deltaH(a)), and partial molar heat of sorption above the glass transition (deltaH1(S)), partial molar free energy of sorption (deltaG1(S)) and partial molar entropy of sorption (deltaS1(S)) belonging to sorption for every probe were calculated. The partial molar heat of mixing at infinite dilution (deltaH1(infinity)), partial molar free energy of mixing at infinite dilution (deltaG1(infinity)), Flory-Huggins interaction parameter (chi12(infinity)) and weight fraction activity coefficient (a1/w1)(infinity) values of polymer-solute systems were calculated at different column temperatures. The solubility parameters (delta2) of the polymer were obtained by IGC technique.

Interaction of poly(ether imide) films with early immune mechanisms

With the worldwide increase of atherosclerosis, the need for new engineered patient specific implants such as stents or vascular grafts is still emerging. Recently, very smooth poly(ether imide) (PEI) films were, based on their hemocompatibility and compatibility with endothelial cells, suggested as potential biomaterial for cardiovascular applications. In atherosclerosis, immune mechanisms such as complement activation, but also cellular responses such as monocytes and neutrophils activation, can mediate the inflammatory response. Therefore, it is important that the implant material itself does not trigger the inflammatory response. Early immune mechanisms - e.g. macrophage activation, complement induction, generation of reactive oxygen species (ROS), and the secretion of inflammatory cytokines by leukocytes - could potentiate the inflammatory responses, and may thereby alter endothelial cells behaviour or facilitate platelet activation. Therefore, it is important to evaluate the immuno-compatibility of PEI-films. The PEI-films were fabricated from commercially available PEI, which was dissolved in dichloromethane and pulled out on a cleaned, smooth glass surface and subsequently, solvent residues were removed during the drying procedure. Using a murine macrophage reporter cell line possible material bound microbial contaminations and material intrinsic immuno-stimulatory properties were investigated. The macrophages were viable after adhering on the PEI-films and did not show signs of activation, indicating that the used PEI-film was free of microbial contaminations. To determine whether PEI-films induced complement activation, the release of C5a in pooled human plasma was analyzed. The detected C5a levels did not differ between PEI-films and tissue culture plates (TCP), which served as control material. Furthermore, in whole human blood, the generation of ROS as well as the cytokine production were investigated by flow cytometry and by multiplex bead arrays, respectively. The production of IL-6 and TNF-α as well as the generation of ROS by immune cells of the whole blood was not induced upon contact with PEI-films. The immunological evaluation of PEI-films revealed that no substantial activation of the investigated early immune mechanisms occurred. Altogether, this data demonstrate that PEI is immuno-compatible and from that perspective may be a suitable biomaterial for cardiovascular applications.

Theoretical Study of Binding and Permeation of Ether-Based Polymers through Interfaces

We present a molecular dynamics simulation study on the interactions of poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), and their ABA-type block copolymer, poloxamers, at water/n-heptane and 1,2-dimyristoyl-sn-glycero-3-phospatidycholine (DMPC) lipid bilayer/water interfaces. The partition coefficients in water/1-octanol of the linear polyethers up to three monomers were calculated. The partition coefficients evidenced a higher hydrophobicity of the PPO in comparison to PEO. At the water/n-heptane interface, the polymers tend to adopt elongated conformations in agreement with similar experimental ellipsometry studies of different poloxamers. In the case of the poloxamers at the n-heptane/water interface, the stronger preference of the PPO block for the hydrophobic phase resulted in bottle-brush-type polymer conformations. At lipid bilayer/water interface, the PEO polymers, as expected from their hydrophilic nature, are weakly adsorbed on the surface of the lipid bilayer and locate in the water phase close to the headgroups. The free energy barriers of permeation calculated for short polymer chains suggest a thermodynamics propensity for the water phase that increase with the chain length. The lower affinity of PEO for the hydrophobic interior of the lipid bilayer resulted in the spontaneous expulsion within the simulation time. On the contrary, PPO chains and poloxamers have a longer residence time inside the bilayer, and they tend to concentrate in the tail region of the bilayer near the polar headgroups. In addition, polymers with PPO unit length comparable to the thickness of the hydrophobic region of the bilayer tend to span across the bilayer.

Polymer–Pendant Interactions in Poly(pyrrol-3-ylhydroquinone): A Solution for the Use of Conducting Polymers at Stable Conditions

While various organic molecules have been suggested as environmentally friendly alternatives to inorganic electrode materials for lithium ion batteries, most of them suffer from slow kinetics as well as capacity fading due to dissolution. Herein we present the synthesis of poly(pyrrol-3-ylhydroquinone) (PPyQ), a polypyrrole (PPy) derivative with pending hydroquinone groups, for investigation of the use of a conducting polymer to immobilize redox active quinone units. This strategy eliminates dissolution of the active material while also increasing the conductivity. The quinone pending groups in PPyQ cycle reversibly in the potential region where the polymer backbone is conducting and chemically stable. In situ spectroelectrochemistry on PPyQ films reveals UV/vis transitions inherent to PPy, as well as quinone centered transitions, allowing detailed investigation of the interplay between the polymer doping process and the quinone redox conversion. Intriguingly, it is found that the charging of the PPy back...

The interaction of poly(ethylene glycol) with bovine serum albumin studied with low-field nuclear magnetic resonance

The interaction of poly(ethylene glycol) with bovine serum albumin studied with low-field nuclear magnetic resonance

Interaction of a double hydrophilic block copolymer with lipid monolayers at the air–water interface

The interaction of poly(N,N-dimethylacryl-amide)-b-poly(N,N-diethylacrylamide) (PDMA207-b-PDEA177), (DHBC), with 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (sodium salt) (DPPG) and stearic acid (SA), was investigated at the air–water interface. The π−A isotherms of DHBC/DPPC and DHBC/DPPG binary mixtures are nearly the sum of the contribution of components weighted by the molar composition, — the additive rule. The π−A curves of the mixtures show a plateau at ~7mNm−1, owing to the immersion of the hydrophilic block PDMA, and other at ~27mNm−1 attributed to the immersion of the less hydrophilic PDEA block. Differently, the binary mixtures of DHBC/SA and PDEA homopolymer/SA do not follow the additive rule of the components showing an expanding effect at low surface pressures. Brewster angle microscopy images show that both DHBC and PDEA polymers interact with lipid monolayers, strongly disturbing their morphology.

Structure, properties and interfacial interactions in poly(lactic acid)/polyurethane blends prepared by reactive processing

Polyurethane elastomers are promising candidates for the impact modification of PLA producing blends for example for biomedicine. Poly(lactic acid) (PLA)/polyurethane elastomer (PU) blends were prepared by reactive processing and physical blending as comparison. The blends were characterized by a number of techniques including microscopy (scanning electron microscopy, SEM, and atomic force microscopy, AFM), rotational viscometry, thermal (dynamic mechanical analysis, DMA), and mechanical (tensile) measurements. The analysis and comparison of the structure and properties of physical and reactor blends proved the successful coupling of the phases. Coupling resulted in more advantageous structure and superior mechanical properties compared to those of physical blends as confirmed by morphology, macroscopic properties and the quantitative estimation of interfacial interactions. Structural studies and the composition dependence of properties indicated the formation of a submicron, phase-in-phase structure which positively influenced properties at large PU contents. The results strongly support that reactive processing is a convenient, cost-effective and environmentally friendly technique to obtain blends with superior properties.

Chemical Degradation of Polymers (Polyurethanes, Polycarbonate and Polyamide) by Esters of H-phosphonic and Phosphoric Acids

A review of the research efforts on the development of pathways for the degradation of polymer–wastes of polyurethanes, polycarbonates and polyamides by esters of H-phosphonic and phosphoric acids is presented. Our group has made it clear, thanks to a vast research program devoted to this subject, that alkyl esters of H-phosphonic and phosphoric acids can be used as very effective degrading agents for polymers. Products and mechanism of polyurethanes degradation by treatment with phosphonates are reviewed in this work. The interest of phosphorus-containing degradation products lies on the fire retardant properties that these phosphorous moieties introduce in the recovered molecules. Most of these phosphorilated molecules can be easily reapplied as reactive intermediates by treatment with propylene oxide and used for the preparation of rigid polyurethane foams. The interaction of poly[2,2-bis(4-hydroxyphenyl)-propanecarbonate] (PC) with H-phosphonic acid dialkyl esters [(RO)2P(O)H, where R = CH3 or CH2CH3], or with triethyl phosphate (CH3CH2O)3P(O) yielded interesting phosphorus-containing oligocarbonates. Polyamide-6 can be converted into functional reactive oligomers with new properties by treatment with diesters of the H-phosphonic acid.

Interactions of Pluronic block copolymers with lipid monolayers studied by epi-fluorescence microscopy and by adsorption experiments

The interactions of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymers, i.e. Pluronics F87, F88 and F127, with monolayers composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) were investigated with different monolayer techniques. Surface pressure–area isotherms were recorded of co-spread Pluronic/lipid mixtures with different Pluronic content to determine the influence of the polymers on the monolayer phase transitions. The squeeze-out pressure of the polymers upon film compression was dependent on the PPO block length. The monolayer compression experiments were coupled with fluorescence microscopy to visualize the phase separation into polymer-rich and lipid-rich domains and to monitor morphological changes of the lipid domains in the monolayer. Extensive phase separation was observed in the coexistence region between liquid-expanded (LE) and liquid-condensed (LC) lipid phases, where pure polymer domains coexisting with round LE-domains containing polymer, and polymer-free LC-domains were seen. We also investigated the adsorption of Pluronics to a lipid monolayer after injecting a polymer solution underneath a pre-formed lipid monolayer by following the change in pressure at constant area. The results show that polymer adsorption is a superposition of two individual processes with different kinetics. Pluronics with a higher hydrophobicity and with a smaller molecular weight adsorb faster and the type and phase state of the lipid determines the surface pressure where no further Pluronic molecules adsorb to the interface. This critical surface pressure depends on the PPO block length, whereas the strength of the interaction with the lipids is determined by the relative PEO content. This indicates that also interactions between the PEO blocks and the lipid headgroup region are occurring. The interactions with the unsaturated lipid POPC in the liquid-expanded phase turn out to be stronger than for lipids in the liquid-condensed phase, where the polymers are excluded.

Host–Guest Interactions in Poly(N-isopropylacrylamide) Hydrogel Seen by One- and Two-Dimensional 1H CRAMPS Solid-State NMR Spectroscopy

Host–guest interactions in poly(N-isopropylacrylamide) (PNIPA) hydrogels with pyrocatechol were investigated by 1H single-pulse as well as one- and two-dimensional combined rotation and multiple-pulse spectroscopy (CRAMPS) 1H solid-state NMR techniques. Differential scanning calorimetry (DSC), swelling measurements, and density functional theory (DFT) calculations were used as supplementary methods. The results are compared with the phenol–PNIPA system to explore possible similarities or differences in the effects of the two phenolic guest molecules on the temperature-induced volume phase transition of the hydrogel. Both small molecules shift the lower critical solution temperature (LCST) of the hydrogel, but with phenol the transition is broader. This observation may reflect changes in the 1H signal from residual water trapped in cavities in the hydrogel above the LCST. Although in the pyrocatechol-containing hydrogel only two signals are observed, the phenol-containing hydrogel displays numerous signals...

Intramolecular CH/π interaction of Poly(9,9-dialkylfluorene)s in solutions: interplay of the fluorene ring and alkyl side chains revealed by 2D 1H–1H NOESY NMR and 1D 1H-NMR experiments

The existence of intramolecular CH/π interaction of four soluble polyfluorenes (PFs) and molecular di-n-octylfluorene in chloroform-d1 at 20 °C was first revealed by cross-peaks of the ring with several protons of alkyl groups in 1H–1H NOESY NMR and marked upfield shift of several alkyl proton signals in 1H-NMR spectra. Only the PF bearing β-branched chiral groups at 9,9-positions among three chiral PFs in chloroform at 20 °C showed intense circular dichroism bands in the π−π* region because of the intramolecular CH/π interaction. Conflex7 and Gaussian 03 MP2 calculation results supported this idea.

N→π* interactions in poly(lactic acid) suggest a role in protein folding

Poly(lactic acid) (PLA) is a versatile synthetic polyester. We noted that this depsipeptide analog of polyalanine has a helical structure that resembles a polyproline II helix. Using natural bond orbital analysis, we find that n→π* interactions between sequential ester carbonyl groups contribute 0.44 kcal mol(-1) per monomer to the conformational stability of PLA helices. We conclude that analogous n→π* interactions could direct the folding of a polypeptide chain into a polyproline II helix prior to the formation of hydrogen bonds between backbone amides.

Morphology control of nanofillers in poly (phenylene sulfide): A novel method to realize the exfoliation of nanoclay by SiO2 via melt shear flow

We for the first time report a novel method to achieve the morphology control of two kinds of dimensional different nanofillers, the platelike nanoclay and globelike SiO2, by using their “filler to filler” interaction in poly (phenylene sulfide) (PPS). The strong interaction between layered nanoclay and rigid SiO2 is obtained by their different response to shear flow in PPS melt processing. As a result, the exfoliation structure of nanoclay and well-dispersed nano-SiO2 are realized simultaneously. With this successful morphology control, the reinforcement effect of nanofillers in PPS is improved with very little addition. Moreover, with the restriction of exfoliated clay and nano-SiO2 particles, the mobility of PPS molecular chains is confined, leading to the significant change in crystalline behaviors of PPS.

The thermosensitivity of pH/thermoresponsive microspheres activated by the electrostatic interaction of pH‐sensitive units with a bioactive compound

pH/thermosensitive hydrogels whose thermosensitivity is activated by the electrostatic interaction of the pH-sensitive units with a hydrophobic bioactive compound are proposed here as sensor-based self-regulated drug delivery systems. Poly(N-isopropylacrylamide-co-acrylamide-co-aminoethylacrylamide) (poly(NIPAAm-co-AAm-co-AEAAm)) was prepared as a new pH/thermoresponsive polymer by hydrolysis of poly(N-isopropylacrylamide-co-acrylamide (poly(NIPAAm-co-AAm)) at high temperature (120°C) in the presence of ethylenediamine. Owing to the hydrophilicity of the inserted amine, the copolymers lose the thermosensitivity at physiological temperature and have a slow-phase transition at temperatures much higher than that of the human body. However, when the positively charged amine groups of the pH-sensitive units bind electrostatically with the negatively charged drug diclofenac, the copolymers retrieve the thermosensitivity. Poly(NIPAAm-co-AAm-co-AEAAm) was transformed into pH/thermoresponsive stable microspheres by an original approach based on crosslinking of the amine groups of aminoethylacrylamide (AEAAm) with glutaraldehyde at a temperature slightly below the lower critical solution temperature. The swelling/deswelling processes of microspheres occur only after the interaction of poly(NIPAAm-co-AAm-co-AEAAm) with the negatively charged drug diclofenac. The pH/temperature-sensitive microgels and dicofenac act as sensors and as the triggering agent, respectively. Conductometric titration reveals that the thermosensitivity of poly(NIPAAm-co-AAm-co-AEAAm) is retrieved when just half of its amino groups are complexed with diclofenac.

Association of nicotinic acid with a poly(amidoamine) dendrimer studied by molecular dynamics simulations

The interaction of poly(amidoamine)-G3 (PAMAM-G3) dendrimer with nicotinic acid (NA) was investigated by using molecular dynamics (MD) simulations. First, sample free energy profiles of NA crossing PAMAM-G3 at pH 6 and 3 were computed using the adaptive biasing force (ABF) method. We found that PAMAM-G3 provides a more appropriate environment for NA inclusion when internal tertiary amine groups are unprotonated (at pH 6). However, when internal tertiary amine groups are protonated (at pH 3), the PAMAM cavities are less hydrophobic; therefore the drug–dendrimer interactions become similar to drug–solvent interactions. Traditional MD simulations were also performed to investigate the structural stability of the PAMAM–NA complexes near the free energy minima at pH 6. We found that association of NA and PAMAM adopts a preferred binding mode around the surface of PAMAM, where hydrogen bond (HB) interactions with the amino and amide NH groups of the nearby monomers are established. These interactions are very stable whether additional van der Waals interactions between pyridine ring of NA and methylene groups of the more external monomers of PAMAM are established.

Interactions of Poly(ethylene oxide), Poly(methyl methacrylate), and Polystyrene with Ionic Liquid Adspecies

Surface mobility of polystyrene (PS), poly(methylmethacrylate) (PMMA), and poly(ethylene oxide) (PEO) has been investigated via interactions with an ionic liquid adspecies, 1-ethyl-3-methylimidazol...