Various Types Of Poly Research Articles

Charge transfer and catalytic properties of various PEDOTs as Pt-free counter electrodes for dye-sensitized solar cells

Despite the high electrocatalytic activity of Pt and the fact it is a champion catalyst for the counter electrode (CE) of state-of-art dye-sensitized solar cells (DSSCs), its high cost, rarity, and the concern about its possible deterioration by the iodine-based redox electrolyte, has compelled the search for suitable and low-cost catalysts for CEs. To circumvent this issue, efforts were directed to exploring the suitability of various types of poly(3,4-ethylenedioxythiophene)(PEDOT)-based conducting polymers as the most suitable electrocatalysts for low-cost CEs. Amongst various types of PEDOT explored as CEs, micelle directed electropolymerized PEDOT:SDS (:sodium dodecyl sulfate) exhibited not only excellent catalytic activity (>Pt), as confirmed by cyclic voltammetry and electrical impedance spectroscopy investigations, but also fairly good photovoltaic performance exhibiting photoconversion efficiency of 5.8%, which is only slightly lower than the performance shown by Pt-based CE for the DSSCs fabricated under similar experimental conditions. Further improvement for the PEDOT:SDS-based CE surpassing the Pt-based CE is envisioned by morphological control and making their suitable composites with carbon-based nanomaterials.

Fabrication of high-density array of barnacle-like porous structures using polystyrene colloidal particle monolayer and poly(vinyl alcohol) coating

A high-density array of barnacle-like porous structures was fabricated using monolayers of polystyrene spheres and various types of poly(vinyl alcohol). We first prepared the polystyrene sphere monolayer as a close-packed hexagonal array on a glass substrate. The monolayer was then etched using a plasma treatment to isolate each sphere. Next, we spin-coated the isolated spheres with a water solution of poly(vinyl alcohol). After drying, we applied a second short plasma treatment to the substrate before immersing it in a toluene bath, which promoted opening formation due to polystyrene swelling. As a result, a high-density array of barnacle-like porous structures was homogenously formed on the substrate. These porous structures are expected to be used for various applications including functional coatings, protective cell cultures, and sensor chips.

Polyisoprene modified poly(alkyl acrylate) foam as oil sorbent material

ABSTRACTBiorenewable polyisoprene latex obtained from natural rubber, Hevea brasiliensis, was used to prepare the reusable polyisoprene–poly(alkyl acrylate) foam for petroleum‐based liquid absorption. The foam was produced via latex vulcanization and cured by steaming. The effect of various types of poly(alkyl acrylate) such as poly(methyl methacrylate) (PMMA), poly(butyl methacrylate) (PBMA), and poly(butyl acrylate) (PBA) on oil sorption capacity of the foam were studied. Scanning electron microscope (SEM) images showed interconnected open‐cell macrostructure with the foam porosity greater than 75% and good compression set. The oil sorption capacity of the foam was in the range of 2.0–16.6 g g−1. The addition of poly(alkyl acrylate) enhanced hydrophobicity and oil sorption capacity of the foam. The absorbed oil was easily recovered by squeezing and the foam can be reused up to 30 sorption–desorption cycles and still preserve high quality sorption. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42688.

Assessment of cell proliferation in knitting scaffolds with respect to pore‐size heterogeneity, surface wettability, and surface roughness

ABSTRACTIn this study, various types of poly(ε‐caprolactone) (PCL) knitting scaffolds were fabricated and analyzed to assess the cell‐culturing characteristics of knitting scaffolds with respect to pore‐size heterogeneity, surface wettability, and surface roughness. First, control knitting scaffolds were fabricated using 150‐µm‐diameter PCL monofilaments. Using chloroform and NaOH, PCL knitting scaffolds with varying roughness, pore‐size heterogeneity, and surface wettability were fabricated. Cell‐culture assessments were performed on these six types of PCL knitting scaffolds. Saos‐2 cells were used for cell assessments and cultured for 14 days on each scaffold. Consequently, heterogeneous pore‐size distribution and high surface wettability were found to enhance cell proliferation in knitting scaffolds. In addition, for highly hydrophobic knitting scaffolds exhibiting water contact angles greater than 110 degrees, smaller surface roughness was found to enhance cell proliferation. According to this study, in the case of knitting scaffold, NaOH‐treated knitting scaffold, without any control for the pore‐size homogenization, could be a candidate as the optimal knitting scaffold. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42566.

Modeling cloud point of soluble polymers in supercritical carbon dioxide fluid using PCP-SAFT equation of state – An application in enhanced oil recovery

The phase behavior of the soluble polar polymers in supercritical carbon dioxide fluid has been already measured through determination of the cloud point pressure against the weight fraction of the polymer. In recent years, a few works have been carried out to investigate the solubility of some polar polymers in the supercritical carbon dioxide so that most of them have focused on the synthesis method of the polymers and measurements of their cloud point pressure. However, there is a lack of a proper thermodynamic model for prediction of the solution cloud point pressure of such systems. In this work, we model the cloud point pressure of the various types of poly(lactic acid) (PLA) with the different molar masses and end chemical groups; and various types of poly(1-O-(vinyloxy) ethyl-2,3,4,6-tetra-O-acetyl-β-d-glucopyranoside) (P(AcGlcVE)) with the different molar masses and the same end chemical groups. The Perturbed-Chain Polar Statistical-Associating-Fluid-Theory (PCP-SAFT EoS) of Gross, J. AIChE, 51 (2005) 2556–2568, is applied here through its modification for the present polymer–CO2 systems. We account the quadrupole–quadrupole term in the PC-SAFT EoS to represent the interaction energy between carbon dioxide molecules and polymer segments. Using the cloud point pressure data of the present polymer–CO2 systems, the parameters of the PCP-SAFT EoS are obtained for these polymers. The results show the present equation of state can correlate with the experimental cloud point data accurately so that the deviation of the experimental data with the calculated results is low.

Synthesis and evaluation of poly(diol citrate) biodegradable elastomers

Herein, we report the synthesis and evaluation of a novel family of biodegradable and elastomeric polyesters, poly(diol citrates). Poly(diol citrates) were synthesized by reacting citric acid with various diols to form a covalent cross-linked network via a polycondensation reaction without using exogenous catalysts. The tensile strength of poly(diol citrates) were as high as 11.15±2.62 MPa and Young's modulus ranged from 1.60±0.05 to 13.98±3.05 MPa under the synthesis conditions that were investigated. Elongation was as high as 502±16%. No permanent deformation was found during mechanical tests. The equilibrium water-in-air contact angles of measured poly(diol citrates) films ranged from 15° to 53°. The mechanical properties, degradation and surface characteristics of poly(diol citrates) could be controlled by choosing different diols as well as by controlling the cross-link density of the polyester network. Various types of poly(diol citrate) scaffolds were fabricated to demonstrate their processing potential. These scaffolds were soft and could recover from deformation. In vitro and in vivo evaluation using cell culture and subcutaneous implantation, respectively, confirmed cell and tissue compatibility. The introduction of poly(diol citrates) will expand the repertoire of currently available biodegradable polymeric elastomers and should help meet the requirements of tissue engineering applications.

Biodegradable microspheres alone do not stimulate murine macrophages in vitro, but prolong antigen presentation by macrophages in vitro and stimulate a solid immune response in mice

The purpose of this study was to analyze the potential of various types of biodegradable microspheres (MS) (i) to activate in vitro cell line-derived macrophages (RAW 264.7, Mϕ), and primary peritoneal and bone marrow-derived mouse Mϕ, to prolong the release and presentation of microencapsulated synthetic malaria antigens by Mϕ after uptake of antigen-loaded MS, and (ii) to stimulate an immune response in mice against a microencapsulated synthetic malaria antigen. The MS were made of various types of poly(lactide-co-glycolide) (PLGA) or chitosan cross-linked with tripolyphosphate. PLGA, but not chitosan MS, were efficiently ingested by Mϕ. Upon exposure to the various MS types, Mϕ increased only the production of reactive oxygen intermediates (ROI), while the production of nitric oxide (NO), tumor necrosis factor alpha (TNF-α), and the expression of cyclooxigenase-2 (COX-2), inducible NO synthase (iNOS), the cell surface markers MHC class I and II, and CD 86 remained unaffected. In vitro release of the microencapsulated antigen from PLGA50:50 MS followed a pulsatile pattern and extended over 14 weeks. This prolonged antigen release was also mirrored in the significantly prolonged antigen presentation over more than 7 days by Mϕ after uptake of antigen-loaded PLGA MS. Finally, antigen-loaded PLGA MS induced a solid immune response in mice after a single s.c.-injection, which was only slightly inferior to the antibody titers measured with the control formulation with Montanide ISA720. These results suggest that MS are well tolerated by Mϕ. The prolonged antigen presentation by Mϕ, as measured in vitro, along with the capacity to induce a strong immune response in animals emphasize that biodegradable MS are a very promising delivery system for both preventive and immunotherapeutic vaccines.

Surface Restructuring Behavior of Various Types of Poly(dimethylsiloxane) in Water Detected by SFG

Surface structures of several different poly(dimethylsiloxane) (PDMS) materials, tetraethoxysilane-cured hydroxy-terminated PDMS (TEOS-PDMS), platinum-cured vinyl-terminated PDMS (Pt-PDMS), platinum-cured vinyl-terminated poly(diphenylsiloxane)-co-poly(dimethylsiloxane) (PDPS-co-PDMS), and PDMS-co-polystyrene (PDMS-co-PS) copolymer in air and water have been investigated by sum frequency generation (SFG) vibrational spectroscopy. The SFG spectra collected from all PDMS surfaces in both air and water are dominated by methyl group stretches, indicating that all the surfaces are mainly covered by methyl groups. Other than surface-dominating methyl groups, some -Si-CH2-CH2- moieties on the Pt-PDMS surface have also been detected in air, which are present at cross-linking points. Information about the average orientation angle and angle distribution of the methyl groups on the PDMS surface has been evaluated. Surface restructuring of the methyl groups has been observed for all PDMS surfaces in water. Upon contacting water, the methyl groups on all PDMS surfaces tilt more toward the surface. The detailed restructuring behaviors of several PDMS surfaces in water and the effects of molecular weight on restructuring behaviors have been investigated. For comparison, in addition to air and water, surface structures of PDMS materials mentioned above in a nonpolar solvent, FC-75, have also been studied. By comparing the different response of phenyl groups to water on both PDPS-co-PDMS and PS-co-PDMS surfaces, we have demonstrated how the restructuring behaviors of surface phenyl groups are affected by the structural flexibility of the molecular chains where they are attached.

Microencapsulation of water-soluble macromolecules with acrylic terpolymers by the Wurster coating process for colon-specific drug delivery

The aim of this work is to explore a microcapsule formulation applicable for a peroral colon-specific delivery of water-soluble macromolecules such as peptide drugs, based on our previous delayed-release formulations using self-made colloidal terpolymers of ethyl acrylate, methyl methacrylate and 2-hydroxyethyl methacrylate (poly(EA/MMA/HEMA)). Peptides are thermally unstable and less permeable through a polymeric membrane in general. Thus, the present work was intended to establish the acrylic terpolymers having the following characteristics: an excellent film-formability even at a low process-temperature of 40 °C to preserve the stability of heat-sensitive drugs and a desired permeability allowing a delayed-release profile of macromolecular drugs. Using various types of poly(EA/MMA/HEMA) synthesized with different monomer molar ratios, microencapsulation of the particles consisting of a lactose core and a surface-layer of water-soluble fluorescence-labeled dextran (FITC-Dex, Mw 9500), a model of macromolecular solute, was carried out by the Wurster process. The release profiles of FITC-Dex were highly dependent on the terpolymer compositions. The increased EA content made the poly(EA/MMA/HEMA) films flexible and less permeable, leading to significant decrease in release rate of FITC-Dex. Contrary, it was found that the increase in HEMA content enhanced the FITC-Dex release due to the enhanced hydration of the films, as expected from its higher hydrophilicity than the other monomers. Among a series of poly(EA/MMA/HEMA) prepared here, the poly(EA/MMA/HEMA) with the molar ratio of 95:85:40 exhibited a good film-formability in the post-thermal curing process at 40 °C. The established coating films allowed delayed-release of the microencapsulated FITC-Dex; the profile was characterized by a lag time and subsequent rapid release. This delayed-release was probably due to time-dependent change of the semi-permeable nature of the hydrated coating films as a consequence of anomalous film-deformation arising from the osmotic pressure inside the microcapsules. Moreover, the release profiles of FITC-Dex were found to be pH-independent. Based on our findings, the use of poly(EA/MMA/HEMA) with molar ratio of 95:85:40 could be proposed as a feasible way to prepare a delayed-release microcapsule containing water-soluble macromolecules by the Wurster coating process, toward the future application to colon-specific delivery of peptide drugs.

Drug-release behavior of polymeric prodrugs of ibuprofen with PEG and its derivatives as polymeric carriers

We have synthesized various types of poly(ethylene glycol) (PEG)-ibuprofen conjugates by nucleophilic substitution of bromo-terminated PEG with ibuprofen-Cs salt. The conversion of the terminal hydroxyl groups to bromo-termini was quantitative, as was the drug conjugation process, which suggests that the present synthetic method is very useful for the preparation of PEG-based prodrugs from pharmaceuticals having carboxyl functionalities. The drug-release behavior of the prodrugs was examined in both phosphate buffer (PBS, pH 7.4) and rat plasma. From the drug-release behavior in PBS, we determined that each prodrug has high storage stability. The drug-release rate was observed to be much faster in rat plasma than in buffer solution as a result of the acceleration effect provided by enzymes present in the plasma. The drug-release rate in rat plasma depends on the degree of molecular aggregation of the prodrugs, which can be changed effectively by the nature of their spacer groups or by the use of Pluronic as the polymer carrier.

Synthesis of various polymeric prodrugs of ibuprofen with PEG and its derivative as polymeric carriers

We have synthesized various types of poly(ethylene glycol) (PEG)-ibuprofen conjugates by the nucleophilic substitution of bromo-terminated PEG with ibuprofen-Cs salt; PN (Pluronic) was also used in place of PEG. All the bromo-terminated PEGs and PN were obtained in high yield. Conversions of the terminal hydroxyl groups to bromotermini were quantitative, as were the drug conjugation processes. TheI 1/I 3 values obtained from solutions of the ibuprofen-conjugated prodrugs are summarized in relation to those of ibuprofen in water and in aqueous solutions of the original PEG, PN, and several ordinary surfactants. We believe that the fully hydrophilic PEG is completely hydrated and forms no hydrophobic pocket by segment aggregation. These results indicate that the probe environment is significantly hydrophobic, particularly in the solution of prodrug PN, for which the ratio is similar to that obtained from typical micelles of surfactants. The results suggest, therefore, that the present synthetic method is very useful for preparing PEG-based prodrugs from pharmaceuticals having carboxyl functionalities.

Structural Analysis for PET Fiber using Laser Raman Microprobe Spectroscopy.

Polarized Raman spectra for the various types of poly(ethylene terephthalate) fibers were measured using microprobe spectroscopy changing the optical systems, and the conditions suitable for the estimation of density and molecular orientation of the fibers were discussed. For the estimation of density, the full width at a half maximum of 1730 cm-1 band measured under the laser polarization direction parallel to and Raman polarization direction perpendicular to the fiber axis was most convenient. For the estimation of molecular orientation, the parameter using the ratio of relative Raman intensities, that is (I1615 / I632)/(I1615 / I1730) which showed the highest correlation coefficient against birefringence, was suitable: Here, I1730, I1615 and I632 are the intensity of 1730cm-1, 1615cm-1 and 632cm-1 bands, respectively. The relative intensity, I1615 / I632, was measured under both laser polarization and Raman polarization in the direction parallel to the fiber axis, and I1615 / I1730 was measured under both laser polarization and Raman polarization in the direction perpendicular to the fiber axis.

Relationships between Structure and Properties of Poly(aspartic acid)s

Various types of poly(aspartic acid)s, which were poly(α-l-aspartic acid), poly(α-d-aspartic acid), poly(β-l-aspartic acid), and poly(α,β-d,l-aspartic acid)s, were prepared, and their biodegradabilities using the OECD 301C method and calcium ion chelating abilities were measured to clarify the relationship between the structure of poly(aspartic acid)s and these properties. Distinct tendencies were found both between the number of amide protons and biodegradability and between the ratio of the dicarboxylic acid end groups to the dicarboxylic acid end group plus succinimide end group and biodegradability. The chirality of the aspartic acid unit and the type of amide linkage in poly(aspartic acid) had no apparent effect on the biodegradability of poly(aspartic acid). The result of repetitive biodegradability analyses for poly-aspartic acid suggested the complete biodegradation is possible. Regarding the calcium ion chelating ability, only the type of amide linkage affected the calcium ion chelating ability. ...

Melt Stability Study of Various Types of Poly(l-lactide)

Poly(l-lactide) (PLLA) prepared by ring-opening melt polymerization using tin−octoate as catalyst undergoes a rapid melt degradation. The melt stability of PLLA was evaluated by using a Haake melt rheometer at various temperatures. The degradation rate constants were calculated from the changes in the melt viscosity for as-polymerized, precipitated, and acid treated PLLA. Furthermore, stability measurements were performed for as-polymerized PLLA modified with various types of peroxides (hydroperoxide, dialkyl peroxide, peroxy ester, and diaroyl peroxide). The energy of activation for the melt degradation of as-polymerized PLLA was calculated to 119.4 kJ/mol at temperatures between 180 and 210 °C. Precipitation of PLLA gave a reduction of the tin catalyst content in the polymer, and this also reduced the extent of the melt degradation. A further reduction of the tin content, and accordingly a reduction in the melt degradation, was achieved after acid treatment of the polymer. Addition of peroxide in open a...

Crystal chemical aspect of synthesis of laser crystals with garnet structure in Ln2O3−Sc2O3−M2O3 systems (Ln=Y, Gd; M=Ga, Al)

Regions of existence were determined for various types of poly- and monocrystalline solid solutions (Ln3[ScyM2−y]M3O12; {Ln3−xScx}[ScyM2−y]M3O12; Ln3[LnzScyM2−y−z] M3O12; Ln=Y, Gd; M=Ga, Al) by analyzing the diagrams rVIII−rVI (rVI are weighted mean dodecahedral and octahedral radii, respectively). We found the position of congruently melting compositions in rVIII−rVI coordinates and optimal compositions for obtaining Nd3+- and Cr3+-doped crystals. The structure of the congruently melting composition was found to be formed of “equilibrium” polyhedra, which need not be stabilized. It is shown that a congruently melting composition, which is absent in the original matrix, may be achieved by isomorphous substitutions at certain positions of the structure. The most probable mechanisms of formation of poly- and monocrystalline solid solutions with garnet structure are suggested using the calculated binodal curves of decomposition.

Synthesis and Characterization of Some Novel Poly(nitroarylates)

AbstractVarious types of poly(nitroarylates) (8–17) were prepared using interfacial polycondensation (IPC) and solution polycondensation (SPC) of 5‐nitroiso‐phthaloyl chloride (la) and 2‐nitroterephthaloyl chloride (2a) with different bisphenols: hydroquinone (3), resorcinol (4), 4.4′‐dihydroxydiphenyl (5), 2,2‐bis(4‐hydroxyphenyl) propane (6) and bis(4‐hydroxyphenyl) sulfone (7). A nitro group was introduced in the polymeric chain in order to improve the properties, solubility and thermal stability of these polymers. Some of the factors affecting the IPC were studied, such as the effect of concentration of the initial components and the role of the solvent. The structures of the poly(nitroarylates) (8–17) were confirmed by elemental analysis, infrared and proton magnetic resonance spectrometry. Thermomechanical analysis (TMA) and thermogravimetric analysis (TGA) of the synthesized polymers were also studied.

Determination of the density dispersion of suspension poly(vinyl chloride) by the method of kinetic density curves

AbstractA new method has been developed for the evaluation and comparison of quality of various types of poly(vinyl chloride) (PVC) powder with respect to their density homogeneity. The method consists in the determination of the dependence of the volume of a specifically heavier fraction of PVC powder on the density or concentration of testing aqueous NaNO3 solutions after a chosen time of contact between the powder and the testing solutions. Compared with the method of determination of density distribution using densitometric titration, the new method simplifies and extends possibilities of comparison of polymers and improves the density characterization.

Evolved gas analysis of poly(methyl methacrylate)

The thermal decomposition of various types of poly(methyl methacrylate) under vacuum was investigated by evolved gas analysis with a mass spectrometer. Though the volatilized product is mainly methyl methacrylate due to unzipping, four steps of volatilization were observed, and decompositions depend on the molecular weight and the polymerization process. The mechanisms of these four steps are elucidated by comparison of the amount of the volatilized product found at each step with the molecular weight and the polymerization process. The first step is a depolymerization initiated at the weak bond of copolymerized oxygen, and the second and third steps consist of depolymerization initiated at the chain ends, which occur due to disproportionation in propagating radical termination during polymerization. The fourth and final step is a depolymerization initiated by random scission in the main chain.