Polymer Mass Research Articles

Investigation of redox activity in the napthalenediimide-poly(3,4-ethylenedioxythiophene) cross-linked polymers

Electroactive polymers, based on the concept of linking a redox-active core to a backbone with high electronic conductivity, are a class of interesting materials because of the possibility to independently control different properties like electrochromic contrast, conductivity, charge capacity and redox potential window by the proper choice of the two distinct components employed. In this regard, we recently developed a new napthalenediimide-poly(3,4-ethylenedioxythiophene) crosslinked polymer, which was applied in electrochromic and energy storage devices. In this paper the electrochemical characterization of the polymer by cyclic voltammetries and electrochemical quartz crystal microbalance investigations is described. The redox process of the polymer backbone shows the characteristic features of p-doping conducting polymers while the napthalenediimide redox units have a bi-electronic molecular like electrochemistry that strongly depends on the electrolyte cation. The polymer mass change during the voltammetric cycles reveals the role of the solvent in balancing the mass flux across the layer.

Composites Based on Polyfluoroalkylacrylate Nanodispersions for Chemical Fiber Surface Modification

A method for preparing composites for chemical fiber surface modification that was based on nanodispersions of polyfluoroalkylacrylate and an industrial coarsely dispersed system was examined. The colloidal chemical properties of composites prepared by mixing the two dispersions in different polymer mass ratios were studied. The optimum conditions for modifying fibers with composites of latexes LFM-N and SKD-1S were found using mathematical experiment planning and process optimization.

Tuning Structure and Rheology of Silica–Latex Nanocomposites with the Molecular Weight of Matrix Chains: A Coupled SAXS–TEM–Simulation Approach

The structure of silica-latex nanocomposites of three matrix chain masses (20, 50, and 160 kg/mol of poly(ethyl methacrylate)) are studied using a SAXS/TEM approach, coupled via Monte Carlo simulations of scattering of fully polydisperse silica nanoparticle aggregates. At low silica concentrations (1 vol. %), the impact of the matrix chain mass on the structure is quantified in terms of the aggregation number distribution function, highest mass leading to individual dispersion, whereas the lower masses favor the formation of small aggregates. Both simulations for SAXS and TEM give compatible aggregate compacities around 10 vol. %, indicating that the construction algorithm for aggregates is realistic. Our results on structure are rationalized in terms of the critical collision time between nanoparticles due to diffusion in viscous matrices. At higher concentrations, aggregates overlap and form a percolated network, with a smaller and lighter mesh in the presence of high mass polymers. The linear rheology is investigated with oscillatory shear experiments. It shows a feature related to the silica structure at low frequencies, the amplitude of which can be described by two power laws separated by the percolation threshold of aggregates.

Evaluating Lignins as Enzyme Substrates: Insights and Methodological Recommendations from a Study of Laccase-Catalyzed Lignin Polymerization

Lignin preparations from kraft and sulfite pulping, steam explosion, and enzyme saccharification processes were assessed as substrates for lignin polymerization catalyzed by Trametes hirsuta laccase (ThL). Oxygen consumption associated with laccase catalyzed oxidation of the selected lignins was measured using a microplate-based oxygen assay. Laccase-induced changes in the molecular masses of the lignin polymers were assessed with aqueous-alkaline size exclusion chromatography (SEC) and changes in monomeric phenolics by reverse-phase high pressure liquid chromatography (HPLC). Obtaining consistent results in the lignin-laccase assay system required careful pH monitoring and control. All lignin preparations were oxidized by ThL, the rate being highest for steam-exploded eucalypt and lowest for enzyme-saccharified lignin. Comparing lignins, higher lignin-laccase reactivity was correlated with lower lignin molecular mass and higher amounts of monomeric phenolics. Solubility was not an indicator of reactivity. Steam-exploded and lignosulfonate-treated pine preparations were further fractionated by ultrafiltration to determine what molecular mass fractions were the most reactive in ThL catalyzed oxidation. Both retentate (> 3kDa), and to a lesser degree permeate (< 3kDa), fractions were reactive.

Transgenic expression of a functional fragment of harpin protein Hpa1 in wheat induces the phloem-based defence against English grain aphid.

The harpin protein Hpa1 has multiple beneficial effects in plants, promoting plant growth and development, increasing crop yield, and inducing resistance to pathogens and insect pests. For these effects, the 10-40 residue fragment (Hpa1₁₀₋₄₂) isolated from the Hpa1 sequence is 1.3- to 7.5-fold more effective than the full-length protein. Here it is reported that the expression of Hpa1₁₀₋₄₂ under the direction of an insect-induced promoter induces the phloem-based defence to English grain aphid, a dominant species of wheat aphids. The expression of Hpa1₁₀₋₄₂ was found to compromise the colonization preference of aphids on the plant and further inhibit aphid reproduction in leaf colonies. In Hpa1₁₀₋₄₂-expressing wheat lines, moreover, aphid feeding from the phloem was repressed in correlation with the phloem-based defence. This defensive mechanism was shown as enhanced expression of wheat genes encoding phloem lectin proteins (PP2-A1 and PP2-A2) and β-1,3-glucan synthase-like enzymes (GSL2, GSL10, and GSL12). Both PP2-A and β-1,3-glucan formed high molecular mass polymers to block phloem sieve plate pores and therefore impede aphid feeding from the phloem. However, the phloem-based defence was impaired by treating plants with ethylene signalling inhibitors, suggesting the requirement for the ethylene signalling pathway. In addition, if Hpa1₁₀₋₄₂-expressing plants were subjected to attack by a small number of aphids, they newly acquired agriculturally beneficial characters, such as enhanced vegetative growth and increased tiller numbers and grain output values. These results suggest that the defensive and developmental roles of Hpa1₁₀₋₄₂ can be integrated into the germplasm of this agriculturally significant crop.

Modeling of pneumatic melt drawing of polypropylene super-thin fibers in the Laval nozzle

Abstract Melt spinning of the fibers by supersonic air jet in the Laval nozzle is a novel, efficient and energy saving method of formation of super-thin fibers. In the process, polymer melt is extruded from a row of orifices and fast drawn by the pneumatic forces. In the modelling, air velocity, temperature and pressure distributions are computed from the k-! aerodynamic model. Computations of the polymer air-drawing dynamics are based on the mathematical model of melt spinning in a single-, thin-filament approximation and Phan-Thien/Tanner non-linear viscoelasticity of the polymer melt. Axial profiles of the polymer velocity, temperature, tensile stress and rheological extra-pressure are computed. Influence of the Laval nozzle geometry, initial air compression, an initial melt temperature, a polymer mass output and the diameter of the melt extrusion die is discussed. The role of the polymer molecular weight, melt viscosity and relaxation time is considered. Example computations show the influence of important processing and material parameters. In the supersonic process, a high negative internal extra-pressure is predicted in the polymer melt under high elongation rates which may lead to cavitation and longitudinal burst splitting of the filament into a high number of sub-filaments. A hypothetical number of sub-filaments at the splitting is estimated from an energetic criterion. The diameter of the sub-filaments may reach the range of nano-fibers. A substantial influence of the Laval nozzle geometry is also predicted.

Novel co-axial prilling technique for the development of core–shell particles as delayed drug delivery systems

In this study, biocompatible double layered beads consisting of pectin core and alginate shell were prepared through a single step manufacturing process based on prilling apparatus equipped with co-axial nozzles. The core was loaded with piroxicam (PRX) as model non-steroidal anti-inflammatory drug (NSAID). Morphology, size distribution and shape of the double layered beads varied depending on the operative conditions and polymer concentrations. Co-axial nozzles size, applied vibration frequency, gelling conditions and, mainly, polymers mass ratio were identified as critical variables. Particularly, the relative viscosity of polymeric feed solutions inside the nozzle was the key parameter to obtain homogeneous and well-formed coated particles. The produced beads were investigated for the release kinetic in different media. Once PRX was encapsulated within the pectin core, a controlled release pattern was observed. Particularly, beads produced with 4:1 core/shell ratio (F4) released less than 30% of PRX in simulated gastric fluid (SGF) while total liberation of the drug was achieved during the next 3h in simulated intestinal fluid (SIF). More interesting, F4 tested in SIF was able to release drug in a delayed and sustained manner at established time points (2h_8.2%, 3h_32.2%, 4h_70.1% and 5h_about 100%). Based on the above results, co-axial prilling approach is expected to provide success in manufacturing systems with delayed drug release profiles. Such systems may be potentially useful in targeting diseases which are affected by the circadian rhythm, such as chronic inflammation.

Dissolution rate enhancement of the anti-inflammatory drug diflunisal by coprecipitation with a biocompatible polymer using carbon dioxide as a supercritical fluid antisolvent

Dissolution rate enhancement of the anti-inflammatory drug diflunisal was achieved using for the first time a supercritical fluid technology. The supercritical fluid antisolvent (SAS) method was applied to precipitate diflunisal alone and to coprecipitate the drug together with the biocompatible polymer polyvinylpyrrolidone (PVP K-30 and K-10). The untreated and SAS processed diflunisal, and the coprecipitates were characterized in terms of size, morphology, crystallinity, compositions, drug-polymer interactions, and drug release. SAS processed diflunisal exhibited a polymorphic form different from that of the untreated drug. Diflunisal crystallinity disappeared in the coprecipitates. Three different drug: polymer mass ratios were studied: 75:25, 50:50, and 25:75. Microparticle size decreased and aggregation disappeared as the relative amount of polymer increased. The 25:75 coprecipitate consisted of loose spherical particles exhibiting mean particle size of 410 nm while the 75:25 coprecipitate consisted of bigger aggregated particles. The SAS method was shown to be a suitable technology to form solid dispersions of a poorly soluble drug.

Toward residual-layer-free nanoimprint lithography in large-area fabrication

In the paper, residual-layer-free nanoimprint lithography for large-area fabrication is reviewed. In order to remove the residual layer during the imprint process, polymer resists and mold materials should be designed with the aspects of surface chemistry and mold geometries in mind. Various approaches for residual-layerfree nanoimprint lithography are discussed including incomplete filling by polymer mass, reverse imprint methods, self-removal techniques, and the employment of elastomeric mold deformation. In addition, issues that must be overcome to enable large-area roll-to-roll nanoimprinting without a residual layer are presented.

A diffusion limited sorption–desorption noise model for polymer coated SAW chemical sensors

The paper presents a new model for the sorption–desorption noise in polymer-coated SAW chemical sensors. The model visualizes the sorption and desorption phenomena in polymer coatings similar to the activated gaseous adsorption and desorption on solid surfaces, however, the interpretations of the activation energy and the attempt frequency in the two cases are fundamentally different. In the case of gaseous adsorption/desorption on the solid surfaces the activation energies are associated with discrete surface sites (or traps) having potential well or barrier like character for the adsorbates. The adsorption is modeled as a succession of discrete random events of entrapment for the gas molecules striking the surface, and the desorption as a thermally activated escape from the traps by overcoming the potential barrier. The stochastic nature of these processes generates instantaneous fluctuation in the gaseous load on the surface. In contrast, the present model visualizes the change in free energy associated with the partitioning of analytes from the vapor phase into the polymer coating as the activation energy for both the sorption and desorption processes. The attempt frequency for desorption is determined by the analyte diffusion time across the polymer coating thickness. In equilibrium, the average rates for sorption and desorption are equal. The instantaneous fluctuation of the vapor load in the polymer coating generates noise in the sensor response. The model predicts an exponential autocorrelation function for the polymer mass density fluctuation with variance in proportion to the average mass loading. This results in Lorentzian phase noise spectrum for the SAW sensor oscillators with bandwidth determined by the inverse diffusion time. The paper presents some numerical results for the analyte concentration resolution and limit of detection and the phase noise spectrum by assuming typical sensing conditions. A possibility for enhancing sensor performance by stochastic resonance is also proposed by utilizing nonlinear interaction between sorption–desorption noise and a modulating signal generated by modulation of vapor concentration.

Various aspects of ultrasound assisted emulsion polymerization process

In this paper, the effects of ultrasonic (US) power, pulse ratio, probe area and recipe composition were investigated on two process responses namely, monomer (methyl methacrylate, MMA) conversion and electrical energy consumption per mass of product polymer (PMMA). Pulsed mode US is more suitable than continuous mode US for emulsion polymerization. The probe (tip) area has little effect on the yield of polymerization when comparing 19 and 13mm probes, 13mm probe performing slightly better for high conversion levels. Meanwhile, large probe area is beneficial for high conversion efficiency of electric energy to US energy as well as for high radical generation yield per energy consumed. The conversion increased slightly and electrical energy consumption decreased substantially by using a recipe with high SDS and monomer concentrations. Conclusions presented in this paper may be useful for scale-up of US assisted emulsion polymerization.

Semicontinuous Heterophase Polymerization of Methyl and Hexyl Methacrylates to Produce Latexes with High Nanoparticles Content

The semi-continuous heterophase polymerization (SHP) under monomer-starved conditions of methyl methacrylate and hexyl methacrylate is reported, at various monomer addition rates to elucidate the effect of monomer solubility on the mechanism of particle nucleation and growth. Polymer particles in the nanometer range from both monomers were obtained, which decreased in size as monomer addition rate was decreased. Molar masses of both polymers also diminished as monomer addition rate was slowed down. The propagation rate constant dictates how fast the starved condition is achieved rather than the monomer solubility in the aqueous phase. A slow particle rate of growth helps to obtain a narrower PSD.

Interaction of N-(2-hydroxypropyl)methacrylamide based homo, random and block copolymers with primary immune cells.

Polymer nanoparticles (NP), e.g., polymeric micelles, represent a promising platform for drug delivery including the field of immune modulation. In respect to this potential application, identification of chemical and structural properties that affect interaction of polymers with immune cells is an important step in their preclinical characterization. A series of well-defined, fluorescently labeled homopolymers, random as well as block copolymers based on the clinically approved N-(2-hydroxypropyl)methacrylamide (HPMA) were prepared to study the influence of polymer architecture on the interaction of polymers with primary human und murine immune cells systematically. The number average of the molar mass (M(n)) for all polymers was set to the range of 4-14 kDa with a varying ratio of hydrophilic and hydrophobic units and dispersities (D) in the range of 1.17-1.29. Cell uptake greatly depended on the polymer molecular weight and micro structure: Comparison of polymers of the same molar mass but varying ratio of hydrophilic and hydrophobic units revealed a strict dependency of cellular uptake on the size of the hydrophobic block. HPMA-ran-LMA copolymers with high amounts of lauryl side chains (15 and 20% LMA content) had highest internalization rates into human and mouse immune cells (monocytes, granulocytes, B and T cells). Our findings underline the role of particle size and composition of polymeric carriers in the field of nanomedicine.

Preparation of Composite Materials of Waste Clay and Polymethyl Methacrylate Using Mechanochemial Polymerization in an Organic Solvent

In order to use a waste clay effectively and to investigate mechanochemical polymerization as preparation method of the inorganic-organic composite materials, the mechanochemical polymerization of methyl methacrylate (MMA) was carried out by grinding the waste clay in n-heptane solvent. The waste clay was a halloysite with 16.2m2/g in specific surface area. The grinding operation was performed using a vibrating ball mill with a laboratory scale. The effect of monomer concentration in n-heptane solvent on the polymerization rate and the molecular mass of polymer were examined. As a result, the mechanochemical polymerization of MMA also proceeded by the grinding of the clay in n-heptane solvent. It was found that the polymerization rate increased with the increase of MMA concentration and that the conversion of MMA reached than 90%. Although the number average molecular mass of resulting polymer was in the order of 104 to 105, the molecular mass was decreased with the grinding time due to the scissions of polymer chains by the mechanical action. This polymerization mechanism was found to be radical reaction from the investigation of polymer tacticity. As for the composite of clay and PMMA obtained by the mechanochemical polymerization, a die molding was possible directly without kneading process.

Evaluation of 4-substituted styrenes as functional monomers for the synthesis of theophylline-specific molecularly imprinted polymers.

Six novel functional monomers: 4-(4-vinylphenyl)pyridine (M1), 4′-vinylbiphenyl-4-ol (M2), N,N-dimethyl-4′-vinylbiphenyl-3-amine (M3), (4′-vinylbiphenyl-4-yl)methanol (M4), 4′-vinylbiphenyl-4-carboxylic acid (M5) and 4-hydroxy-5-methyl-4′-vinylbiphenyl-3-carboxylic acid (M6), were examined for their ability to imprint theophylline (1). Using a molecular modelling-NMR titration approach, M2 and M6 were predicted to give rise to the most specific molecularly imprinted polymers (MIPs). Rebinding analysis suggests that no imprinting effect resulted from the polymerisation of monomers M1, M5 and M6, but modest to good levels of imprinting were evident from monomers M2, M3 and M4 with IF values ranging from 1.1 (MIPM3, 20 mg) to 45 (MIPM2, 10 mg). The selective recognition of 1 varied as a function of polymer mass used. At low polymer loadings MIPM2 gave the very high IF of 45, reducing to IF = 4.1–2.3 at 20–40 mg polymer loading. With monomer M2, microwave synthesised MIP (MW-MIPM2) was examined. The MW-MIPM2 displayed lower specific rebinding than its conventionally produced counterpart (MIPM2) with IF values ranging from 1.6–2.3 (cf., MIPM2 IF 2.3–45), but significantly higher levels of rebinding with 25–52% of 1 rebound from a 0.080 mM CH3CN solution of 1 (cf., MIPM2 5–25%). MW-MIPM2 displayed a lower BET surface area than MIPM2 (185 m(2) g(−1)vs. 240 m(2) g(−1)), and lower surface (zeta) potential (−13.1 ± 8.22 mV vs. −31.4 ± 4.84 mV). Freundlich isotherm analysis revealed that MW-MIPM2 possessed higher affinity binding sites for 1 than MIPM2 with Kd values of 1.38 and 2.31 respectively. In addition, MW-MIPM2 also exhibits a higher number of binding sites (NT) compared to MW-NIPM2 (0.72 and 0.41 mg g(−1), respectively). In specificity studies using caffeine (2), MIPM2 displayed a two-fold preference for rebinding of 1 and MW-MIPM2 a five-fold preference for 1 over 2. The quantity of 2 bound in both cases was consistent with non-specific binding events. In competitive rebinding experiments, increased discrimination in favour of 1 over 2 was observed.

A Study on the Morphology of a Dispersed Particle Gel Used as a Profile Control Agent for Improved Oil Recovery

To achieve in-depth profile control of injection water and improve oil recovery, a new profile control agent, termed as dispersed particle gel (DPG), has been developed and reported. In this paper, the morphology of DPG and the factors that influence its morphology are systematically investigated using atomic force microscopy (AFM). The AFM studies show that DPG is composed of small pseudospherical particles and that their sizes can be controlled by adjusting the shearing rate, the initial polymer mass concentration, and the salinity. Dynamic light scattering (DLS) is used to study the effects of the initial polymer mass concentration, the shearing rate, the salinity, and the high-temperature aging on the particle size of DPG. The aggregation ability of DPG is explained using the DLVO theory and space stability theory. This work provides a scientific basis and technical support for the formula design of DPG and its application in the oil and gas field.

Efficient Scheme for Chemical Flooding Simulation

In this paper, we investigate an efficient implicit scheme for the numerical simulation of chemical enhanced oil recovery technique for oil fields. For the sake of brevity, we only focus on flows with polymer to describe the physical and numerical models. In this framework, we consider a black oil model upgraded with the polymer modeling. We assume the polymer only transported in the water phase or adsorbed on the rock following a Langmuir isotherm. The polymer reduces the water phase mobility which can change drastically the behavior of water oil interfaces. Then, we propose a fractional step technique to resolve implicitly the system. The first step is devoted to the resolution of the black oil subsystem and the second to the polymer mass conservation. In such a way, jacobian matrices coming from the implicit formulation have a moderate size and preserve solvers efficiency. Nevertheless, the coupling between the black-oil subsystem and the polymer is not fully resolved. For efficiency and accuracy comparison, we propose an explicit scheme for the polymer for which large time step is prohibited due to its CFL (Courant-Friedrichs-Levy) criterion and consequently approximates accurately the coupling. Numerical experiments with polymer are simulated : a core flood, a 5-spot reservoir with surfactant and ions and a 3D real case. Comparisons are performed between the polymer explicit and implicit scheme. They prove that our polymer implicit scheme is efficient, robust and resolves accurately the coupling physics. The development and the simulations have been performed with the software PumaFlow [PumaFlow (2013) Reference manual, release V600, Beicip Franlab].

Designing multi-responsive polymers using latent variable methods

The design of stimulus-responsive materials, particularly those intended to respond to more than one stimulus, is an inherently challenging and typically trial-and-error process involving multiple synthesis/characterization iterations in the laboratory. In this work, latent variable models are applied to existing, “failed” polymer formulations and characterizations to facilitate the rational design of materials with specific, targeted properties and to predict responsive polymer properties before synthesizing the materials in the laboratory. The models are capable of simultaneously predicting three targeted polymer properties (cloud point, molecular weight, and % recovery of polymer mass) for poly(N-isopropylacrylamide)-based materials that can be reversibly photo-crosslinked. Model inversion and optimization are used to identify new polymer formulations that exhibit significantly improved properties relative to the formulations developed by chemical intuition based on available literature. This model-based design approach moves away from the traditional trial-and-error approach to save time, energy, and resources in the production of novel materials while at the same time generating responsive polymers with improved properties.

&lt;b&gt;Solid-liquid equilibrium measurements for the ternary system PCL + chloroform + nonsolvents (n-hexane, ethanol, methanol, isopropanol) at 303.15 K&lt;/b&gt; - doi: 10.4025/actascitechnol.v36i1.16615

This work reports experimental data of polycaprolactone (PCL) polymer solubility in chloroform as solvent and n-hexane, methanol, ethanol and isopropanol as nonsolvents, at atmospheric pressure (about 1,0 bar) and temperature of 303.15 K. It was used PCL with 70000-90000 and 2000 molar mass (MM). The experiments of solubility were performed using a jacketed-cell with temperature controlled by an ultrathermostatic bath, in which a turbidity method was adopted and used. From the obtained results it should be observed that the n-hexane presented a more pronounced anti-solvent effect in the PCL solubility, where the heterogeneous region (solid phase presence) was broader than when other nonsolvent. It was also observed that the binodal curves measured with the high molar mass polymer showed similar results compared to the low molar mass one.

Optimization of the synthesis procedure of microparticles containing gold for the selective oxidation of glycerol

Microencapsulation of gold particles was carried out by means of in situ polymerization of urea and formaldehyde. The influence of the amount of organic solvent (dimethyl sulfide) and the gold precursor to polymer mass ratio (Au/PUF) on the encapsulation process and the physical properties of the resulting catalysts have been studied. The amount of DMS has a marked influence on the morphology of the microparticles, affecting to both the porosity outer surface and the encapsulated gold particle size. Synthesized poly(urea-formaldehyde) microparticles containing gold were tested in the liquid phase selective oxidation of glycerol. Obtained results showed that both the amount of DMS and the Au/PUF mass ratio played an important role in the deposition of the gold particles and, consequently, in its catalytic response.