PAA Content Research Articles

Cure Behavior and Thermal Properties of Poly (Amide-Amidic Acid) Modified Diglycidyl Ether of Bisphenol-A/4,4′-Diaminodiphenylsulfone

Poly (amide-amidic acid) (PAA) was selected to modify diglycidyl ether of bisphenol-A (DGEBA)/4,4′-diaminodiphenylsulfone (DDS). The cure behavior was studied by means of nonisothermal differential scanning calorimeter (DSC) analysis, indicating that PAA played a role of catalyst during the process of the curing reaction. Results of Fourier transform infrared spectroscopy (FT-IR) analysis showed that the PAA acted as a co-curing agent when the PAA content was 3.2–38.4 phr and also as a modifier when the PAA content was 12.8–38.4 phr. The glass transition temperature (Tg ) decreased with the increase of PAA content. The thermal stability improved when the PAA content was 3.2–6.4 phr because of the catalytic effect of PAA. The flexural strength improved for the varying PAA content studied in this work, with the highest flexural strength being obtained when the PAA content was 6.4 phr. The fracture surface morphology was observed using scanning electron microscopy (SEM); the morphologies varied with changing...

Adsorption and adhesion of poly(vinyl alcohol) and poly(ammonium acrylate) as organic additives for wet mold processing of Al2O3

Abstract Adsorption and adhesion of polyvinyl alcohol (PVA) molecules on Al2O3 surfaces in pH 3–10 or 0–0.1 mass% poly(ammonium acrylate) (PAA) aqueous solution was examined using the AFM colloidal probe method. The PVA behavior on the solid surface was estimated using force curve measurements obtained using colloidal probe AFM. Extensions originating from the bridging of PVA between the solid surfaces were observed primarily at less than approximately 200 nm in the pH 3 aqueous solution. The extensions, which were observed at more than approximately 600 nm for pH 6 and 10 aqueous solutions, resulted from different conformations of the PVA molecules. In the PVA–PAA system, the number of extensions decreased by increasing the PAA content. This was not observed in a PAA aqueous solution of greater than 0.1 mass%, which indicates that PAA was adsorbed selectively onto the solid surface. The force curve showed that PAA was more effective than PVA.

Pervaporative separation of isopropyl alcohol/water mixtures: effects of the operation conditions

Abstract Isopropyl alcohol/water mixture was separated by an environmentally friendly membrane process: pervaporation. Pervaporation experiments were carried out with a polymer blend membranes of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) at different temperatures. PVA/PAA cross-linked membranes were prepared with different blend ratios. The influence of PVA/PAA ratio and of liquid mixture composition were investigated. The apparent activation energies were calculated at different temperatures. With increasing PAA content in the membranes fluxes decreased and selectivities increased. The flux increased with increasing operation temperature, as selectivity decreased. The studies showed that isopropylalcohol/water mixtures can be separated by pervaporation which is an energy efficient technology using the prepared membranes.

An investigation of cure and thermal stability of poly(amide‐amidic acid) modified tetraglycidyl 4,4′‐diaminodiphenylmethane/4,4′‐diaminodiphenylsulfone

AbstractIn this work, poly(amide‐amidic acid) (PAA) was used to modify tetraglycidyl 4,4′‐diaminodiphenylmethane (TGDDM)/4,4′‐diaminodiphenylsulfone (DDS) system. Results of non‐isothermal differential scanning calorimetry analysis indicated that PAA played a role of catalyst during the process of the curing reaction. The curing mechanism was studied by Fourier transform infrared spectroscopy, showing that the PAA acted as a co‐curing agent in the system. The glass transition temperature decreased firstly and then increased with the increase of the PAA content. PAA equally rendered TGDDM more fire resistant with higher char yield. On examining the fracture surface morphology using scanning electron microscopy, it was observed that there was no obvious phase separation when the content of PAA was less than 20 phr (per hundred weight of TGDDM/DDS resin), however, phase separation was observed when the content of PAA was 25 and 30 phr. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Interchain Hydrogen Bonding Interaction Induced phase Behaviors of Poly(ethylene oxide)-b-poly(N-vinylcarbazole)/Poly(acrylic acid) Blend

In this paper, we study an αβ/C blend system composed of a diblcok copolymer of poly(ethylene oxide)113-b-poly(N-vinylcarbazole)77 (PEO113-b-PVK77) and a homopolymer of poly(acrylic acid) (PAA) with a weight-average molecular weight of 1900 g/mol. The phase behavior of the blend was characterized using various techniques including Fourier transform infrared spectroscopy, differential scanning calorimetry, small-angle X-ray scattering, and transmission electron microscopy. The experimental results indicate that while the PEO and PVK blocks are miscible in bulk state, adding PAA into the diblock can lead to microphase separation of the blend due to the interchain hydrogen bonding complexation between PEO and PAA. The phase morphology of the blend is strongly dependent on the PAA composition. Only with sufficiently high weight fraction of PAA (wtPAA), the blends can present ordered microphase-separated structures, although the long-range order is not well developed. For 40% < wtPAA < 70% (corresponding to the PVK volume fraction between 44% and 22%), the ordered phase is changed from lamella to cylinder to cubic phase with increasing wtPAA. Further increase of PAA content results in spheres with the core of PVK dispersed in the matrix of PAA. The diameters of the PVK cores of cylinders and spheres are very close to the twice of the unperturbed end-to-end distance of the PVK block, indicating that the rather rigid PVK block is hard to be deformed during microphase separation. The PAA composition dependence of the blend phase behavior illustrates that the degree of PEO/PAA complexation dominates the segregation strength. After the microphase separation occurs, the phase morphology can be adjusted by varying the PAA content.

Preparation of poly(vinyl alcohol)-based membranes with controllable surface composition and bulk structures and their pervaporation performance

Abstract Poly(vinyl alcohol)-based membranes with controllable surface structures and bulk characteristics were prepared by casting PVA/poly(acrylic acid) (PAA) solutions onto different substrates. Four kinds of surfaces, namely the air-side 1 and glass-side surface (a glass plate used as substrate), the air-side 2 and PTFE-side surface (a polytetrafluoroethylene (PTFE) plate used as substrate), were formed. At any a given content of PAA in PVA casting solution, the air-side 1 and PTFE-side surfaces of the resulting membranes were less hydrophilic than the corresponding glass-side and air-side 2. Interestingly, there was similar surface composition between the air-side 1 and PTFE-side, and between the glass-side and air-side 2. Furthermore, the membranes prepared on a PTFE plate exhibited higher crystallinity than those formed on a glass plate. By an induction of the underlying substrates, the surface composition and bulk characteristics of those PVA-based membranes could be tuned. Pervaporation experiments for separating acetic acid/water mixtures through those membranes were carried out, and the results indicated that the permselectivity was mainly dependent on membrane surface composition, whereas the permeability was more significantly governed by membrane bulk characteristics. This provides a feasible method for the structure optimization of a high-efficient membrane and mechanism exploration in pervaporation separation.

New chitosan/poly (acrylic acid) composite membrane for application in pervaporation dehydration of caprolactam solution

To improve caprolactam pervaporation (PV) separation dehydration process, composite membrane was investigated using chitosan (CS) and poly (acrylic acid) (PAA) blending membrane as active layer and a polyacrylonitrile (PAN) ultrafiltration membrane as substrate. The composite membranes were characterized by FTIR, SEM, and XRD measurements to assess the intermolecular interactions membranes of morphology, and observe the crystallinity, respectively. The effect of the ratio of PAA and CS in the composite membranes on the PV performance was investigated. The flux was decreased and the separation factor was increased by the PAA content increase in the range of 10–30 wt.%. Besides, operating temperature and feed composition on PV performances were investigated. Data showed that PAA/CS composite membranes displayed good swelling and PV performance, and the composite membranes had superior separation performances for dehydration of ɛ-caprolactam solution, that the highest separation factor could reach 7,804 at 313 K, for 70 wt.% caprolactam. The evaluated results revealed that the separation performances of CS/PAA composite membranes were strongly related to their reaction degree and intrinsic structure as well as the operating parameters.

Cure and thermal stability of poly(amide‐amidic acid)—cured tetraglycidyl 4,4′‐diaminodiphenylmethane

AbstractA novel curing agent, poly (amide‐amidic acid) (PAA), was used to cure tetraglycidyl 4,4′‐diaminodiphenylmethane (TGDDM). The initial cure and exothermic peak temperatures increased with increase in PAA content. The mechanism for the cure of TGDDM/PAA was proposed which involved, besides TGDDM cure, PAA imidization in the system. Examination of the morphology of the fractured surface using scanning electron microscopy showed that curing with PAA improved more the fracture toughness as compared to the conventional 4,4′‐diaminodiphenylsulfone (DDS), and rendered TGDDM more fire resistant with higher char yield. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Tethering methoxy polyethylene glycols to improve the antifouling property of PSF/PAA‐blended membranes

AbstractPoly(acrylic acid) (PAA) was used as an additive to fabricate blended polysulfone (PSF) ultrafiltration (UF) membranes. Hexanediamine was used as a crosslinking agent to react with PAA and formed an active surface with amine group. Then, an end carboxyl group methoxy polyethylene glycol (MPEG) was grafted on the membrane surface via an amidation reaction. Water contact angle measurement indicated that the surface hydrophilicity of PSF/PAA‐blended membranes and MPEG‐modified membranes remarkably increased. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FTIR) was used to confirm the existence of PAA in the blended membranes and the change of chemical composition. Membrane surface and cross‐sectional morphologies were observed by scanning electron microscope. The flux of pure water increased slightly after modification, while the rejection to bovine serum albumin had no obvious change. The improvement of antifouling property for MPEG‐modified membrane was accordant with the increase of PAA content in PSF/PAA‐blended membranes. Protein UF experiments revealed that membrane fouling, especially irreversible membrane fouling, was remarkably reduced due to the incorporation of MPEG. The long‐term protein UF experiment demonstrated the improvement of recycling property and the reliability of modification. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Electrochemical polymerization of aniline in the presence of poly(acrylic acid) and characterization of the resulting films

Conducting films composed of polyaniline (PANI) and poly(acrylic acid) (PAA) were prepared by electrochemical polymerization of aniline in the presence of PAA. The PAA content in the films (PANI/PAA films) was controlled by the concentration of PAA in polymerization solution, and the properties of the films were investigated in relation to the PAA content. It was demonstrated by means of scanning electron microscopy and cyclic voltammetry that the surface morphology and electrochemical property of the films were affected significantly by the PAA content. In contrast, the conductivity of the films was found hardly dependent on the PAA content up to 18 wt %. The cyclic voltammetry gave an interesting result that the PANI/PAA films showed an electroactivity in neutral solution, which was not observed for the PANI film without PAA, and the electroactivity was closely related to the PAA content in the PANI/PAA films.

The effect of pH and ionic strength on the dispersion of carbon nanotubes in poly(acrylic acid) solutions

AbstractThe dispersion of three kinds of acid‐treated carbon nanotubes (CNTs) in poly(acrylic acid) (PAA) aqueous solution of different pH and ionic strengths (varied by NaCl, KCl and ZnCl2) was investigated by visual observation, zeta potential, particle size analysis, transmission electron microscopy and scanning electron microscopy. Visual observation revealed that the dispersion of CNTs acid treated at 60 °C for 3 h and at 80 °C for 2 h was poor in aqueous solutions with pH &lt; 2 or pH &gt; 12. The poor dispersion of acid‐treated CNTs may be improved by adding PAA. In particular, PAA improved the dispersion of CNTs with greater COOH content. In a low pH solution (pH 1.5), a higher PAA content resulted in poorer CNT dispersion while in a high pH solution (pH 12.5), a higher PAA content led to better CNT dispersion. For superior dispersion in a basic aqueous solution (pH 12.5), experimental data showed that a greater atomic radius or a higher cationic charge of the added salt may result in faster aggregation and thus precipitation of CNTs. Copyright © 2011 Society of Chemical Industry

Preparation and Characterization of pH Sensitive Microgels with Semi-Interpenetrating Polymer Network Structure

The microgels with semi-interpenetrating polymer network (semi-IPN) structure based on cross-linked poly(N-isopropylacrylamide) (PNIPAM) and linear poly(acrylic acid) (PAA) were fabricated by one-step precipitation polymerization technique. The chemical composition of the microgels was determined by Fourier transformation infrared spectroscopy and elemental analysis. It was found that the PAA content inside the microgels decreased as the pH value of reaction media increased. The semi-IPN structure of the microgels was confirmed by transmission electron microscopy using uranyl acetate staining method. The pH dependent hydrodynamic diameters obtained by dynamic light scattering revealed that these microgels can reversibly shrink and swell in the pH range from 4.0 to 6.0. The semi-IPN microgels synthesized at pH 3.0 could undergo about 120 times volume change in the pH range.

A new approach for patterning epiclon-based polyimide precursor films using a lyotropic liquid crystal template

Blends of hydroxypropyl cellulose (HPC) in lyotropic phase have been prepared with a new epiclon-based poly(amic acid) (PAA) in different ratios. The detailed surface morphology of the PAA/HPC films was examined by polarized light microscopy (PLM) and atomic force microscopy (AFM). Besides the specific interactions, such as the hydrogen bonds between PAA and the liquid crystalline component, a slight cross-linking produced in the PAA structure by UV irradiation stabilized the resulting morphology. The effect of UV exposure and the influence of the HPC component weight ratio on the morphology developed by the PAA/HPC blends were investigated. The band texture, typical for lyotropic HPC solutions, evidencing different intensities and dimensions, is observed from atomic force microscopy images in PAA/HPC, being distinguished even at high PAA content and is also maintained after HPC removal with a selective solvent, namely acetone. These results lie at the basis of future investigations concerning high performance mixed alignment layers used in display devices or cell culture substrates with tuned morphology.

PH-Induced Antireflection Coatings Derived From Hydrogen-Bonding-Directed Multilayer Films

Hydrogen-bonding-directed layer-by-layer assembled films, based on polystyrene-block-poly(acrylic acid) (PS-b-PAA) block copolymer micelles and poly(4-vinylpyridine) (P4VP), were successfully fabricated in methanol. Varying the PAA content in the PS-b-PAA micelles afforded control over the film growth properties, especially the multilayer film thickness. Interestingly, antireflection films with refractive indices that could be tuned between 1.58 and 1.28 were obtained by treatment with an aqueous HCl solution (pH 2.27), and the transmittance obtained was as high as 98.4%. In acid solution, the pyridine group was protonated, destroying the hydrogen bonding between P4VP and PAA. A concomitant pH-induced polymer reorganization in the multilayers resulted in a porous honeycomb-like texture on the substrate.

Self-Assembly in Thin Films of Mixtures of Block Copolymers and Homopolymers Interacting by Hydrogen Bonds

We report on the self-assembling behavior in thin films of mixtures of polystyrene-block-poly(ethylene oxide) copolymers (PS-b-PEO), having PEO cylindrical microdomains, with poly(acrylic acid) homopolymers (PAA). We study the effect of adding PAA of different molecular weights, specifically interacting with the PEO block by hydrogen bonding, on the thin film characteristics: morphology, microdomain orientation and spacing. It is found that the addition of PAA induces an orientation of the cylindrical microdomains perpendicularly to the film surface. The lattice spacing increases with the amount of PAA added until a transition toward lamellar morphology is observed. This transition occurs at lower PAA content for PAA of small molecular weight. The experiments also reveal that the PAA homopolymer is localized in the center of the PEO microdomains. The trends observed in the experiments were validated by self-consistent field theory calculations using a newly and specifically developed model.

The role of hydrogen-bonding interaction in poly(vinyl alcohol)/poly(acrylic acid) blending solutions and their films

The aim of this work is to investigate the hydrogen-bonding interaction in poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAA) blending system and its influence on rheological properties in solution and the physical properties in solid state. Introducing PAA into PVA solutions resulted in a thickening behavior of blend solutions. The viscosity of the solutions increased with PAA content increasing, and a maximum viscosity could be obtained when the ratio of PVA/PAA was 70/30. The intermolecular hydrogen-bonding and miscibility between PVA and PAA in solid state were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and mechanical measurements. The results displayed the great influence of introducing PAA on the properties of blending films. The tensile strength increased from 89.31 MPa to 119.8 MPa and Young’s modulus improved by over 300% with increasing PAA concentration compared with those of pure PVA films. By systematically studying the rheological behaviors of solutions and the physical properties of films, the influence of hydrogen-bonding in solutions and solid states were discussed.

Self-Assembly of PEGylated Peptide Conjugates Containing a Modified Amyloid β-Peptide Fragment

The self-assembly of PEGylated peptides containing a modified sequence from the amyloid beta peptide, FFKLVFF, has been studied in aqueous solution. PEG molar masses PEG1k, PEG2k, and PEG10k were used in the conjugates. It is shown that the three FFKLVFF-PEG hybrids form fibrils comprising a FFKLVFF core and a PEG corona. The beta-sheet secondary structure of the peptide is retained in the FFKLVFF fibril core. At sufficiently high concentrations, FFKLVFF-PEG1k and FFKLVFF-PEG2k form a nematic phase, while PEG10k-FFKLVFF exhibits a hexagonal columnar phase. Simultaneous small angle neutron scattering/shear flow experiments were performed to study the shear flow alignment of the nematic and hexagonal liquid crystal phases. On drying, PEG crystallization occurs without disruption of the FFKLVFF beta-sheet structure leading to characteristic peaks in the X-ray diffraction pattern and FTIR spectra. The stability of beta-sheet structures was also studied in blends of FFKLVFF-PEG conjugates with poly(acrylic acid) (PAA). While PEG crystallization is only observed up to 25% PAA content in the blends, the FFKLVFF beta-sheet structure is retained up to 75% PAA.

Membranes Prepared from a Blend of Poly(acrylic Acid) and Natural Rubber-Graft-Poly(vinyl Alcohol) (PAA/NR-g-PVA)

The blend membranes from PAA and NR-graft-PVA were prepared. By introducing potassium persulfate (KPS) initiator, PVA can be chemically attached to the NR latex particles which was confirmed by FT-IR spectroscopy. Most of added-PVA was grafted on the NR latex particles as indicated by the almost-linear increasing of grafting percentage. The swelling of the PAA/NR-g-PVA blend membranes was performed in different concentrations of water-ethanol solutions. For the water concentration lesser than 30 vol.%, all membranes showed almost no-swelling but beyond 30 vol.% water, the degree of swelling revealed the substantial swelling with the degree of swelling increased as PAA content in the membrane increased.

PH/TEMPERATURE DUAL STIMULI RESPONSIVE MICROGELS BASED ON INTERPENETRATING POLYMER NETWORK STRUCTURE

The microgels with interpenetrating polymer network(IPN) structure based on(poly(N-)isopropylacrylamide)(PNIPAM) and poly(acrylic acid)(PAA) were synthesized by seed-emulsion polymerization,using redox initiator at room temperature and the less crosslinked PNIPAM microgels as seeds.The microgels were determined to be composed of PNIPAM and PAA by Fourier transform infrared spectrometer(FTIR),and the IPN structure in the microgels was confirmed by transmission electron microscopy(TEM).The results obtained by dynamic laser light scattering(DLLS) showed that the microgels had good pH/temperature dual stimuli responsiveness without any marked interaction.In the case of the pH of the aqueous media 5.5,the PAA component in the microgels had no effect on their volume phase transition temperature,but when the pH of the aqueous media was 4.0,their volume phase transition temperature was slightly decreased due to the formation of hydrogen bonds between PNIPAM and PAA.The pH stimuli responsiveness of the microgels was enhanced by the PAA content within the microgels.

Natural rubber/poly(acrylic acid) semi‐interpenetrating polymer network membranes for the pervaporation of water–ethanol mixtures

AbstractPervaporation membranes for the dehydration of water–ethanol mixtures were prepared from a semi‐interpenetrating polymer network (semi‐IPN) of natural rubber (NR) and crosslinked poly(acrylic acid) (PAA). The swelling studies revealed that hydrophilic PAA present in the semi‐IPN membranes caused the membranes to swell greatly in water. The swelling degree of the membranes in water was significantly affected by the amount ratio between the hydrophobic NR and the hydrophilic PAA. The sorption experiments of the NR/PAA membranes in various concentrations of water–ethanol mixtures suggested the preferential sorption to water. However, for the membrane with high PAA content, the water sorption selectivity decreased considerably at high water concentration of water–ethanol mixtures because the membrane was in the highly swollen state. Pervaporation separations of water–ethanol mixtures using NR/PAA membranes were performed and it was found that at low water concentrations of feed mixtures, increasing the PAA content of the membrane can enhance both water permeation flux and selectivity. Additionally, under low feed water concentration, increasing the feed temperature would increase the water flux with the decreasing of the ethanol flux. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009