Polymer Solutions Of Poly Research Articles

Preparation of various morphological films at nanoscale by phase separation method

A film consisting of nanopore and nanopillar structures was produced from a binary immiscible polymer solution of poly(amic acid) (PAA) and polyimide (PI), which can be used as a potential light extraction layer or flexible substrate in organic light-emitting diode (OLED) devices. A phase separation method was applied to create uniform and random pattern structures in nanoscale via a simple spin-coating technique. Firstly, the binary immiscible polymer solutions of PAA and PI whose precursor is carbazole-based dianiline were prepared with various volume ratios, and then the polymer mixtures were spin-coated onto substrates to form transparent films with various morphologies and dimensions, as observed by a field emission scanning electron microscope technique. In addition, after annealing PAA/PI films at 300 °C, the homogenous and flexible characteristic of nanopore and nanopillar structures could be achieved.

The use of doped conductive bionic muscle nanofibers in a tennis racket–shaped optical fiber humidity sensor

This study introduces a unique method for the production of a highly sensitive tennis racket-shaped optical fiber humidity sensor consisting of a U-shaped probe and electrospun functional nanofibers. Functional nanofibers of the racket consist of conjugated polymers prepared through a mixture of two kinds of polymer molecules electrospun in an electric field of about 1.7 kV/cm. Interpenetrating polymer networks were fabricated through electrospinning, for which a polymer solution of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) doped in polyvinyl alcohol (PVA) was used. The hydrogen-bonding interaction of the interpenetrating polymer networks/H2O plays a major role in increasing the sensitivity of the humidity sensor. The sensitivity of the sensor was found to be −0.990 nm/%RH, which was 16.02 % greater than that of undoped PEDOT:PSS PVA nanofibers.

Determination of Concentration-Dependent Diffusion Coefficients in Polymer–Solvent Systems: Analysis of Concentration Profiles Measured by Raman Spectroscopy during Single Drying Experiments Excluding Boundary Conditions and Phase Equilibrium

Diffusion coefficients in polymer solutions are strongly dependent on composition and temperature. In many cases sufficient data are not available due to time-consuming measurements and a high number of material systems of interest. In this work a new method is proposed that allows determination of concentration-dependent diffusion coefficients directly from spectroscopic data of single film drying experiments. The quantitative data of concentration profiles in the sample are used to calculate diffusion coefficients by Fick’s law. The results are independent of boundary conditions in the gas phase. Two polymer solutions of poly(vinyl acetate) (PVAc) and the solvents methanol and toluene are investigated. The results are compared to diffusion data from the literature. Experimental proof of the independence from boundary conditions is provided. Diffusion coefficients down to values of approximately 10–14 m2 s–1 are accessible. The diffusion data are in good agreement with literature data and suitable for mo...

Fabrication of Polymer Nanopeapods in the Nanopores of Anodic Aluminum Oxide Templates Using a Double-Solution Wetting Method

Although one-dimensional polymer nanomaterials can be prepared by approaches such as the template method, the control over the morphologies of one-dimensional polymer nanomaterials containing multiple components is still a great challenge. In this work, we investigate the formation of polymer nanopeapods using a novel double-solution wetting method in the nanopores of anodic aluminum oxide (AAO) templates. A polystyrene (PS) solution in dimethylformamide (DMF) is first introduced into the nanopores of the AAO templates. Then a second polymer solution of poly(methyl methacrylate) (PMMA) in acetic acid is infiltrated into the nanopores. Because of the stronger interaction between acetic acid and aluminum oxide than that between DMF and aluminum oxide, the PMMA solution preferentially wets the pore walls of the templates and the PS solution is isolated in the center of the nanopores. After the evaporation of the solvent, peapod-like PS/PMMA nanostructures are obtained, where the shell and the core are composed of PMMA and PS, respectively. The compositions of the polymer nanopeapods are confirmed by removing PS or PMMA selectively. The formation mechanism of the nanostructures is related to the Rayleigh-instability-type transformation and further studied by changing experimental parameters such as the polymer concentration or the polymer molecular weight. This work not only provides a simple approach to prepare multicomponent polymer nanomaterials with controlled morphologies and sizes, but also contributes to a deeper understanding of polymer–solvent interactions in confined geometries.

Electrospun Porous Mats for High Efficiency Filtration

Submicron size fibers (so-called nanofibers) are easily produced with an electrospinning apparatus from polymer solutions of poly(ethylene oxide), poly(vinyl alcohol), and polyamide-6. Electrospinning seems the most powerful tool for fabricating polymer nanofibers. Fibers were directly deposited in the form of random fiber webs with high area-to-volume ratio and small porous size on ordinary nonwoven filters of PET microfibers. Morphology and diameter distribution of the electrospun filaments were characterized by SEM investigations. The flow resistance of the produced composite filters are evaluated by means of air permeability measurements. The electrospun fibers have diameters ranging from about 70—500 nm and are interconnected each other to form thin webs that have very small pore size. After the electrospinning treatment, the air permeability of the filter media decreases 6—17 times showing a significant change of flow resistance that can be controlled by the thickness of nanofibers layer and the pore size. High efficiency nano-microfibers composite filters could be used in a wide range of applications, ranging from air cleaning for automotive to environment conditioning or liquid filtration.

In Vivo Chondrogenesis of Mesenchymal Stem Cells in a Photopolymerized Hydrogel

Surgical options for cartilage reconstruction can be significantly improved through advances in cartilage tissue engineering, whereby functional tissue replacements are created by growing cells on polymer scaffolds. The objective of this study was to use a photopolymerizable hydrogel to implant bone marrow-derived mesenchymal stem cells subcutaneously in a minimally invasive manner and promote cartilage tissue formation by the cells in vivo. Athymic nude mice were injected subcutaneously with polymer solutions of poly(ethylene) oxide diacrylate containing mesenchymal stem cells and placed under a UVA lamp to transdermally photopolymerize (solidify) the injected liquid. Experimental groups included polymer solutions with hyaluronic acid (HA), transforming growth factor (TGF)-beta3, or both. After 3 weeks of implantation, cartilage formation was evaluated by gene expression analysis and histologic techniques. Hyaluronic acid increased the viscosity of the polymer solutions, which helped maintain the injections at the desired site during photopolymerization. Mesenchymal stem cells in hydrogels containing both HA and TGF-beta3 produced the highest quality cartilage, based on expression of the cartilage-specific genes and production of proteoglycan and collagen II. When used independently, TGF-beta3 and HA alone induced cartilage-specific gene expression and collagen type II production; however, TGF-beta3 was essential for proteoglycan production. HA enhanced proteoglycan production when combined with TGF-beta3 and reduced expression and production of collagen I. This study is the first to demonstrate the minimally invasive implantation and subsequent chondrogenic differentiation of mesenchymal stem cells in the subcutaneous environment. This lays the foundation for further optimization of a novel and practical technology for cartilage reconstruction.

Pressure−Volume−Temperature Properties for 1-Octanol + Acetophenone, Poly(Propylene Glycol) + 1-Octanol + Acetophenone, and Poly(Ethylene Glycol) + Poly(Ethylene Glycol Methyl Ether) + Anisole

Pressure−volume−temperature (P−V−T) properties were measured for 1-octanol + acetophenone, the polymer solutions of poly(propylene glycol) (PPG) with the mixed solvents of 1-octanol and acetophenone, and the polymer blends of poly(ethylene glycol) (PEG)/poly(ethylene glycol methyl ether) (PEGME) with anisole at temperatures from 298.15 K to 348.15 K and pressures up to 50 MPa. The Tait equation represents accurately the pressure effect on the liquid densities over the entire pressure range. The experimental-specific volumes of the constituent binary systems were correlated with the Flory−Orwoll−Vrij and the Schotte equations of state to determine the binary interaction parameters. By use of these determined binary parameters, the equations of state predicted the specific volumes to average absolute deviations of better than 0.13% for the ternary mixtures composed of PPG with the mixed solvents and the polymer blends of PEG/PEGME with anisole.

Flow of mixtures of poly(ethylene oxide) and hydrolyzed polyacrylamide solutions through opposed jets

In this work, the porous media flow of polymer solutions of poly(ethylene oxide) (PEO), hydrolyzed polyacrylamide (HPAA), and their blends is investigated. Aqueous solutions of PEO exhibit critical extension thickening when flowing through porous media. HPAA solutions also exhibit critical extension thickening in excess salt environments, but their behavior changes to a more gradual extension thickening when dissolved in deionized water. The mixtures of solutions of HPAA and PEO therefore vary its porous media flow behavior, depending on the ionic environment. In deionized water, a critical extension thickening similar to that obtained with PEO is still observed when HPAA is mixed in at concentrations low enough so that its apparent viscosity does not mask the influence of PEO. In the presence of salt, only a critical extension thickening is observed, which is attributed to transient network formation of both PEO and HPAA molecules. The mixtures generally exhibit a less critical behavior and display a lower than expected sensitivity of the onset Reynolds number for extension thickening with concentration. The results presented herein indicate that interspecies molecular interactions through transient network formation and the associated flow modification play a major role in determining the complex non-Newtonian flow behavior of these polymer solutions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 783–795, 1999

Genetic typing by capillary electrophoresis with the allelic ladder as an absolute standard.

We demonstrate a genetic typing method based on capillary electrophoresis/laser-induced fluorescence (CE-LIF). VNTR polymorphism in the human D1S80 locus was studied. A pooled allelic ladder, which contains the 27 most common human alleles, was used as the absolute standard. Extracted genomic DNA from an individual was amplified by polymerase chain reaction (PCR). Typing can be accomplished by co-injection of the PCR product and the D1S80 ladder and then running CE. Separation by a polymer solution of poly(ethylene oxide) in uncoated fused-silica capillaries allows high-resolution, repeated runs in the same capillary. Sensitive detection with minimal sample preparation is possible by using ethidium bromide as the intercalating dye. Statistical analysis of the data indicates a high level of confidence in matching the bands despite variations in the injection process or in the CE system. Future adaptation to a multiple-capillary array system should allow high-speed, high-throughput operation.

Cyclopolycondensation. XIII. New synthetic route to fully aromatic poly(heterocyclic imides) with alternating repeating units

AbstractFully aromatic poly(heterocyclic imides) of high molecular weight were prepared by the cyclopolycondensation reactions of aromatic diamines with new monomer adducts prepared by condensing orthodisubstituted aromatic diamines with chloroformyl phthalic anhydrides. The low‐temperature solution polymerization techniques yielded tractable poly(amic acid), which was converted to poly(heterocyclic imides) by heat treatment to effect cyclodehydration at 250–400°C under reduced pressure. In this way, the polyaromatic imideheterocycles such as poly(benzoxazinone imides), poly(benzoxazole imides), poly(benzimidazole imides) and poly(benzothiazole imides) were prepared, which have excellent processability and thermal stability both in nitrogen and in air. The poly(amic acids) are soluble in such organic polar solvents as N,N‐dimethyl‐acetamide, N‐methylpyrrolidone, and dimethyl sulfoxide, and the films can be cast from the polymer solution of poly(amic acids) (ηinh = 0.8–1.8). The film is made tough by being heated in nitrogen or under reduced pressure to effect cyclodehydration at 300–400°C. The polymerization was carried out by first isolating the monomer adducts, followed by polymerization with aromatic diamines. On subsequently being heated, the open‐chain precursor, poly(amic acid), undergoes cyclodehydration along the polymer chain, giving the thermally stable ordered copolymers of the corresponding heterocyclic imide structure.

Cyclopolycondensations

AbstractFully aromatic polyquinazolinediones of high molecular weight were prepared by the cyclopolycondensation reaction of 4,4′‐diamino‐3,3′‐biphenyldicarboxylic acid with aromatic diisocyanates. The poly(phosphoric acid) solution polymerization techniques yielded tractable poly(urea acid), which was converted to polyquinazolinediones by thermal cyclodehydration at 300–400°C. under reduced pressure. The polyquinazolinediones thus obtained have excellent thermal stability both in nitrogen and in air. The poly(urea acid) is soluble in dimethyl sulfoxide, and films can be cast from the polymer solution of poly(urea acid) (ηinh = 0.8 to 1.8). The films are made tough by being heated in nitrogen or under reduced pressure at 300–400°C. The polymerization mechanism of the cyclopolycondensation reaction was studied, and it was established that the polymerization proceeded through the formation of tractable poly(urea acid), Structure (I), of high molecular weight, followed by cyclodehydration, yielding poly(1,2‐dihydro‐2‐imino‐4H‐3,1‐benzoxazin‐4‐one), Structure (II). On subsequently being heated this undergoes intramolecular rearrangement along the polymer chain, giving the thermodynamically stable polyquinazolinedione, Structure (III).