PAA Films Research Articles

Environmentally Friendly Positive- and Negative-tone Photo-patterning Systems of Low-K and Low-CTE Polyimides

A low-K and low-CTE polyimide, CBDA/TFMB (CBDA = 1,2,3,4-cyclobutanetetracarboxylic dianhydride, TFMB = 2,2'-bis(trifluoromethyl)benzidine) was applied to photosensitive materials. Poly(amic acid) (PAA) of this system was modified using imide-containing diamines to control the solubility in alkaline solutions. Copolymerization using them made possible to form positive-tone fine pattern in combination with diazonaphthoquinone. Additionally it was found that this PAA film is quite soluble in some environmentally friendly (biodegradable) solvents, e.g., alcohols, glycols, and their monoalkyl ethers. PAA film containing an ionic bonding-type methacrylate and a photoinitiator gave fine negative patterns. The corresponding PI films cured from these photosensitive PAA films exhibited a low CTE, a low K, a high Tg, and high transparency comparable to the original PI film.

Introduction of copper iodide fine particles into a poly(acrylic acid) matrix via a complex of polymer–polyiodide ions

In this study, an organic–inorganic nanocomposite material of cross-linked poly(acrylic acid) (PAA) doped with fine particles of copper iodide (CuI) was prepared. The preparation method of the composite involved the complexing of PAA film with polyiodide ions such as I3− and I5− by immersion in an iodine–potassium iodide (I2–KI) aqueous solution, and then reaction with CuCl in aqueous hydrochloric acid, resulting in the in-situ formation of CuI fine particles within the PAA matrix. The crystal form of CuI in the composite was identified as γ-CuI using X-ray diffraction, and the amount of CuI could be varied by changing both the concentration of the I2–KI solution and the frequency of performing the doping procedure to introduce CuI into the matrix. This preparation method, using polyiodide ions as a precursor, has an advantage in that a large amount of metal iodide, such as CuI, can be easily formed, and it is regarded as a unique method for the preparation of organic–inorganic composites.

Changes of surface morphology in UV-irradiated poly(acrylic acid)/poly(ethylene oxide) blends

Thin polymer films of PAA, PEO and PAA/PEO blends with different components ratio were obtained by means of casting their aqueous solutions and water evaporation. All samples were then exposed to short-wavelength UV-radiation ( λ=254 nm). The morphology of samples, as observed in polarized light of optical microscope, exhibited the existence of spherulitic structures. Surface properties were studied using the SEM technique and contact angle measurements. It was found that UV-irradiation changes the size of spherulites in pure PEO and in blends containing its major amount. The contact angle measurements indicate that UV-radiation induces some changes of hydrophilicity of samples.

Highly Ion Conductive Poly(ethylene oxide)-Based Solid Polymer Electrolytes from Hydrogen Bonding Layer-by-Layer Assembly

We report the development of a solid polymer electrolyte film from hydrogen bonding layer-by-layer (LBL) assembly that outperforms previously reported LBL assembled films and approaches battery integration capability. Films were fabricated by alternating deposition of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) layers from aqueous solutions. Film quality benefits from increasing PEO molecular weight even into the 10(6) range due to the intrinsically low PEO/PAA cross-link density. Assembly is disrupted at pH near the PAA ionization onset, and a potential mechanism for modulating PEO:PAA ratio within assembled films by manipulating pH is discussed. Ionic conductivity of 5 x 10(-5) S/cm is achievable after short exposure to 100% relative humidity (RH) for plasticization. Adding free ions by exposing PEO/ PAA films to lithium salt solutions enhanced conductivity to greater than 10(-5) S/cm at only 52% RH and tentatively greater than 10(-4) S/cm at 100% RH. The excellent stability of PEO/PAA films even when exposed to 1.0 M salt solutions led to an exploration of LBL assembly with added electrolyte present in the adsorption step. Fortuitously, the modulation of PEO/PAA assembly by ionic strength is analogous to that of electrostatic LBL assembly and can be attributed to electrolyte interactions with PEO and PAA. Dry ionic conductivity was enhanced in films assembled in the presence of salt as compared to films that were merely exposed to salt after assembly, implying different morphologies. These results reveal clear directions for the evolution of these promising solid polymer electrolytes into elements appropriate for electrochemical power storage and generation applications.

Anisotropic in-plane gradients of poly(acrylic acid) formed by electropolymerization with spatiotemporal control of the electrochemical potential.

Laterally varying thickness gradients of poly(acrylic acid) (PAA) were formed by Zn(II)-catalyzed electropolymerization of acrylic acid (AA) in the presence of an in-plane electrochemical potential gradient applied to Au working electrodes. In the static potential gradient (SPG) approach, two ends of a Au working electrode were clamped at distinct potentials for the duration of the electropolymerization process, thereby generating a time-independent in-plane electrochemical potential gradient, V(x). A dynamic potential gradient (DPG) approach was also used, in which the two end potentials were varied in time, while maintaining a constant voltage offset, to generate an in-plane electrochemical potential gradient, V(x,t). Because the kinetics of heterogeneous electron transfer vary with the local overpotential, these two methods produce PAA films with laterally varying thickness gradients, although they exhibit different spatial characteristics. X-ray photoelectron spectroscopy (XPS) and surface plasmon resonance (SPR) imaging were used to characterize the PAA gradients. The in-plane thickness variations of PAA gradients formed by both SPG and DPG approaches agree with predictions of the Butler-Volmer equation at small absolute overpotentials, while at large (negative) overpotentials, mass transport dominates, and the thickness reaches a plateau value independent of local potential. DPG-produced PAA gradients are generally broader than SPG gradients with the same initial potential and comparable effective growth time, indicating that the DPG approach is more suitable for formation of thicker gradients.

Synthesis and photoconductive characteristics of biphenylporphyrin‐containing poly(amic acid)s and polyimides

AbstractThree series of biphenylporphyrin (BPP)‐containing poly(amic acid)s (PAAs) were synthesized and converted into heat‐treated polyimides (HPIs) and chemically treated polyimides (CPIs). Viscosity measurements, UV–vis and IR spectroscopies, as well as thermogravimetric analysis (TGA), were used to characterize the structures of the polymers. UV–vis spectra revealed that the BPP units formed aggregates in PAA and CPI films, rather than in HPI films. Photoinduced discharge was used to characterize the photoconductive properties of these polymer films. It was found that the photosensitivity was greatly enhanced by introducing BPP units into the polymer chains. For these three series of polymers, the photosensitivity increased in the order PAA < HPI < CPI according to the content of BPP in the polymers. The photoconductive characteristics were interpreted by the intrinsic π—π* process of BPP aggregation and the extrinsic process of charge‐transfer complex formation. The best photoconductive performances of the CPIs were attributed to the existence of two charge‐carrier‐generation processes. Copyright © 2004 Society of Chemical Industry

Electrochemical fabrication of novel nanostructures based on anodic alumina

A novel nanostructured sandwich PAA/Al/PAA (PAA: porous anodic alumina) wassuccessfully designed and fabricated by anodic oxidation on both sides of an Al foil. Thepore size of the PAA membranes was controlled by choosing appropriate voltage, lengthof anodic oxidization time, temperature and electrolytes. The thickness of thecentral Al layer was varied by changing the anodic oxidization time. We showthat the nanostructured sandwich PAA/Al/PAA can be used as a template infabricating homogeneous or heterogeneous nanostructured sandwiches by depositingthe same kind of material or different materials into the PAA membranes of thesandwich. We also show that it can be used to prepare nanowires and bipolarelectrodes. In addition, Al nanosheets or Al nanowalls were produced by removingthe PAA films completely or partially. Nanogaps between the PAA films werealso formed by etching away the centre Al layer of the sandwich structures. Thethickness of these nanosheets, nanowalls and nanogaps was controlled by choosingappropriate electrolytes and electrochemical parameters during the anodic oxidationof Al. All these nanostructures offer novel opportunities for both fundamentalresearch and technological applications of low dimensional nanostructure systems.

Electroswitchable Photoelectrochemistry by Cu2+−Polyacrylic Acid/CdS-Nanoparticle Assemblies

CdS nanoparticles are incorporated into a poly(acrylic acid) (PAA) film associated with an Au electrode, and the nanoparticles are covalently linked to the matrix. Cu2+ ions are incorporated into the CdS-nanoparticle−PAA film, and the electroswitchable photocurrent generation by the system, in the presence of triethanolamine as sacrificial electron donor, is demonstrated. The electrochemical reduction of the CdS−Cu2+−PAA state to the CdS−Cu0−PAA state (−0.55 V vs SCE) leads to the formation of conductive metal nanoclusters that facilitate electron transfer of the CdS-conduction-band electrons to the electrode, and the generation of the photocurrent. The oxidation of the Cu0 clusters to Cu2+ ions linked to the carboxylate units of PAA (applied potential +0.55 V vs SCE) switches off the photocurrent. The system not only is active for the reversible electroswitchable photocurrent generation but also acts as a photoelectrochemical detector of Cu2+ ions.

Preparation of acrylic grafted chitin for wound dressing application

Chitin grafted with poly(acrylic acid) (chitin–PAA) was prepared with the aim of obtaining a hydrogel characteristic for wound dressing application. The chitin–PAA films were synthesized at various acrylic acid feed contents to investigate its effect on water sorption ability. Acrylic acid (AA) was first linked to chitin, acting as the active grafting sites on the chain that was further polymerized to form a network structure. The evidences of grafting were found from FTIR and solid state 13C NMR spectra. The TGA results exhibited the high degradation temperature of the grafted product suggesting the formation of a network structure. The degree of swelling (DS) of chitin–PAA films was found in the range of 30–60 times of their original weights depending upon the monomer feed content. The chitin–PAA film with 1:4 weight ratio of chitin:AA, possessed optimal physical properties. The cytocompatibility of the film was investigated with a cell line of L929 mouse fibroblasts. The morphology and behavior of the cells on the chitin–PAA film were determined after different time periods of culture up to 14 days. The L929 cells proliferated and attached well onto the film. These results suggested that the 1:4 chitin–PAA has a potential to be used as a wound dressing.

Crosslinking reaction of poly(vinyl alcohol) with poly(acrylic acid) (PAA) by heat treatment: Effect of neutralization of PAA

AbstractThe crosslinking reaction of poly(vinyl alcohol) (PVA) by esterification using poly(acrylic acid) (PAA) as a crosslinking reagent was investigated to obtain highly insoluble PVA materials. Blend films of PVA and PAA (PVA/PAA = 8/2) were prepared to examine the effect of degree of neutralization (DN) in PAA and heat‐treatment conditions on the degree of crosslinking reaction. The degree of crosslinking reaction varied significantly when the DN of PAA changed. The optimum DN for the crosslinking reaction was in the range of 5 to 10 mol %. In the case of unneutralized PAA, the degree of crosslinking reaction was at most 15 mol % by heat treatment for 20 min at 200°C. Applying partially neutralized PAA (DN = 10 mol %) raised the degree to about 40 mol % under the same heat‐treatment conditions. FTIR analysis revealed that the hydroxyl group of PVA in the film blended with unneutralized PAA was degraded to a greater degree than that with partially neutralized PAA as a result of heat treatment. It was found that heat treatment at a low pH condition enhances the degradation of the hydroxyl group of PVA, resulting in a decrease of the number of crosslinking sites by esterification. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2420–2427, 2003

Photosensitive poly(amic acid)/organoclay nanocomposites

A project was carried out aimed at reducing the coefficient of thermal expansion (CTE) of photosensitive polyimide formulations (photoresists) through the incorporation of small amounts of an organoclay. The organoclay was formed by a cation exchange reaction between a NA+-montmorillonite clay and an ammonium salt of dodecylamine. Two polyimide precursors, a poly(amic ester) (PAE) and a poly(amic acid) (PAA), were used in this study. The PAE was prepared by direct polymerization of 2,2′-bis-(3-amino-4-hydroxyphenyl)hexafluoropropane and bis(n-butyl)ester of pyromellitic acid in the presence of phenylphosphonic dichloride as an activator. The polymer had an inherent viscosity of 0.23dL/g. The PAA copolymer was prepared by polymerization of pyromellitic dianhydride, oxydiphthalic anhydride and oxydianiline. The polymer had an inherent viscosity of 1.00dL/g. Two photosensitive resin/clay formulations were prepared from these two PI precursors using 2,3,4-tris(1-oxo-2-diazonaphthoquinone-5-sulfonyloxy)-benzophenone as the photosensitizer and 3wt% organoclay. The films obtained from the PAA formulation were transparent and tough, while the films prepared from the PAE formulation were opaque and brittle. Both X-ray diffraction and transmission electron microscope analyses showed that, although the organoclay was not dispersed well in the PAE matrix, it was dispersed in the PAA matrix on a nanometer scale. The clay particles remained well dispersed after the PAA film was thermally imidized. The CTE of the polyimide film obtained was 23% lower than that of a similar film that did not contain the organoclay. The temperature at which the polyimide underwent a 5% weight loss when subjected to TGA in nitrogen was also increased by 13%. The photosensitive PAA/clay nanocomposite showed a sensitivity of 301mJ/cm2 and a contrast of 1.66 when a 0.2wt% tetramethylammonium hydroxide developer was used. A line/space pattern with a resolution of 10 μm was obtained from this formulation.

PH-Dependent Growth and Morphology of Multilayer Dendrimer/Poly(acrylic acid) Films

Because hyperbranched poly(amidoamine) dendrimers are relatively well-defined polycations with a high density of charge, they provide unique materials for controlled synthesis of films by alternating electrostatic adsorption of polycations and polyanions. Thicknesses of generation 4 (G4) dendrimer/poly(acrylic acid) (PAA) “bilayers” can be tuned from 2000 A simply by varying deposition pH, while generation 8 (G8) dendrimer/PAA bilayers can be as thick as 4000 A. The highest thicknesses occur when using deposition pH values at which PAA and dendrimers are only partially charged, and the thickest films show high surface roughnesses, which may in part account for the rapid film growth. Deposition of dendrimer/PAA films on porous alumina supports yields highly gas-permeable membranes. This is in sharp contrast to the case of poly(allylamine hydrochloride)/PAA films, which allow little gas flux. Dendrimer/PAA films can also be induced to form microporous coatings through pH- and salt-induced structural...

Synthesis and Characteristics of Poly[N,N‘-diphenyl-N,N‘-bis(4-aminobiphenyl)-(1,1‘-biphenyl)-4,4‘-diamine pyromellitimide] as a Hole Injecting and Transporting Layer for Hybrid Organic Light-Emitting Device

A novel hole injecting and transporting polymer, poly[N,N‘-diphenyl-N,N‘-bis(4-aminobiphenyl)-(1,1‘-biphenyl)-4,4‘-diamine pyromellitimide] (PMDA-DBABBD PI), was obtained by thermal imidization from its poly(amic acid) (PAA) made by the reaction of pyromellitic dianhydride with the DBABBD that was chemically reduced from N,N‘-diphenyl-N,N‘-bis(4-nitrobiphenyl)-(1,1‘-biphenyl)-4,4‘-diamine synthesized through the palladium-catalyzed amination. The materials were characterized by using 1H NMR, 13C NMR, FT-IR, HR GC-MS, EA, and DSC. The characteristics of the PAA or PI thin films were investigated with XPS and an impedance spectroscopy. The hybrid light-emitting devices (HOLEDs) with the PAA and PI thin films were fabricated to examine the performance of the polymeric thin films as a hole injecting and transporting layer. The PI thin film having the glass transition temperature of 200 °C showed stable characteristics in the application for the HOLED whereas the PAA thin film seemed to be unstable. The power ...

Preparation and Modification of Poly(methacrylic acid) and Poly(acrylic acid) Multilayers

By employment of a strategy of post-transfer modification, precursor Langmuir−Blodgett (LB) films of poly(tert-butyl methacrylate) (PtBMA) and poly(tert-butylacrylate) (PtBA) can be converted to poly(methacrylic acid) (PMAA) and poly(acrylic acid) (PAA) through acid-catalyzed hydrolysis in the gas phase. X-ray reflectivity studies show that these films possess surface roughnesses and controllable thicknesses, which are consistent with the retention of the “two-dimensional” configuration of the precursor polymers at the air/water interface. On this basis, the PMAA and PAA films with presumable layered architecture can be obtained, even though PMAA and PAA are too hydrophilic to undergo direct LB-multilayer formation. A combination of infrared spectroscopy, contact angle measurements, and sorption experiments confirms the chemical transformation and increased hydrophilicity of the films. Using the same approach, gas-phase reactions with organic amines convert the reactive carboxylic acid groups to their cor...

Application of a surface plasmon resonance sensor to analyses of amine compounds with the use of a polymer film and an acid-base reaction.

A surface plasmon resonance (SPR) sensor was applied to analyses of some amine compounds (n-butylamine, isobutylamine, aniline, and N,N-dimethylaniline) by using a polymer film and an acid-base reaction in it. Poly(acrylamide) (PAA) was adopted as the polymer film and was immobilized on an Au film to prepare a sensor chip. Pivalic acid was entered into the PAA film as an acid. The PAA film with a thickness of 50 nm gave the highest sensitivity to the SPR sensor. Although water was better concerning the sensitivity for the SPR sensor as the solvent, ethanol was adopted because it dissolves well all of the amine compounds used. The Au film coated with the PAA film gave higher sensitivity for analyses of n-butylamine and isobutylamine, and lower sensitivity for analyses of aniline and N,N-dimethylaniline than an Au film without the PAA film. The PAA film containing pivalic acid gave 4-5 orders of magnitude higher sensitivity to the SPR sensor for analyses of all the amine compounds due to the reaction between pivalic acid and these amine compounds.

Imprinted Poly(acrylic acid) Films on Cadmium Selenide. A Composite Sensor Structure that Couples Selective Amine Binding with Semiconductor Substrate Photoluminescence

Molecularly imprinted films of poly(acrylic acid) (PAA) have been coated onto n-CdSe in order to make the band-edge photoluminescence (PL) of the semiconductor respond selectively to the imprinting analyte. This strategy has been implemented using PAA films deposited in the presence of ammonia and trimethylamine analytes. PAA films have been characterized by IR spectroscopy, which indicates that binding of either analyte nearly reversibly deprotonates the polymer carboxylic acid groups. PL measurements suggest that the imprinted PAA coatings serve as sieves for selective surface binding: In contrast to the bare CdSe surface, which responds both to ammonia and trimethylamine with reversible enhancements in PL intensity, CdSe coated with ammonia-imprinted PAA (AI−PAA) films exhibits reversible PL changes toward ammonia but no response to trimethylamine. The PL changes for the AI−PAA films can be fit to a dead-layer model that indicates that ammonia binding reduces the CdSe depletion width by ∼100 A, an eff...

Ultrathin, Hyperbranched Poly(acrylic acid) Membranes on Porous Alumina Supports

The synthesis of high-flux composite membranes requires deposition of an ultrathin, discriminating layer on a highly permeable support. This paper describes the synthesis, derivatization, and characterization of hyperbranched poly(acrylic acid) (PAA) membranes on porous alumina supports. PAA films as thin as ∼40 nm effectively cover underlying pores without filling them, presumably because of their hyperbranched structure. Synthesis of these films begins by sputtering a thin gold layer on the alumina support and then grafting a layer of PAA to a self-assembled monolayer of mercaptoundecanoic acid on the gold. Graft-on-graft deposition of PAA yields the hyperbranched membrane. FESEM (field-emission scanning electron microscopy) and AFM (atomic force microscopy) images clearly show that hyperbranched PAA films can completely cover the substrate surface without filling underlying pores, thus creating an ultrathin membrane on a porous support. PAA membranes are especially attractive because derivatization permits control over transport properties. Gas transport studies indicate that three-layer PAA films do not show a high selectivity by themselves, but selectivity improves significantly after covalent derivatization of PAA with H2NCH2(CF2)6CF3.

Synthesis and characterization of poly(amide-imide)s and their precursors as materials for membranes

Water soluble diamine amic acids (DAAs) were synthesized by reacting aliphatic diamines with pyromellitic dianhydride. Poly(amide–amic acid)s (PAAs) were prepared by interfacial polycondensation of DAAs in aqueous sodium hydroxide solution with isophthaloyl chloride in dichloromethane. Poly(amide–imide)s (PAIs) containing alternating (amide–amide)–(imide–imide) sequences were obtained by thermal cycloimidization of the PAA films at 175°C for 4 h in a forced air woven. The PAIs were readily soluble in polar aprotic solvents such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, and N-methyl-2-pyrrolidone. The inherent viscosities of the polymers are in the range of 0.97–1.7 dL/g. The polymers were characterized by IR, 1H nuclear magnetic resonance (NMR), and thermogravimetric analysis (TGA). Thin film composite membranes containing PAA ultrathin barrier layer were prepared by in situ interfacial polycondensation of DAA in water with trimesoyl chloride or isophthaloyl chloride in hexane on the surface of a porous polysulfone membrane. The membranes were characterized for water permeability and for the separation of NaCl and Na2SO4. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1721–1727, 2000

Luminescence Studies of Polymer Matrices: 4. Phosphorescence of Benzophenone Dispersed in Acrylic Acid Based Polymer Films

The thermal dependence of the phosphorescence characteristics of benzophenone (BP) dispersed in thin films of poly(acrylic acid), PAA, and acrylic acid-methyl methacrylate, AA-MMA, copolymers is described. At all temperatures (between 77 K and 410 K), and in each of the systems studied, the triplet state decay kinetics of the phosphor are complex: a minimum of three exponential terms is required for adequate modelling of the time dependence of BP phosphorescence. This complexity is considered to reflect the breadth and heterogeneity of the distribution of sites accessed by the probe within each of the polymer matrices. Both phosphorescence intensity and lifetime measurements are affected by the onset of macromolecular relaxations within each of the film samples. However, the temperature dependence of the BP phosphorescence data seems to also reflect the presence of specific interactions between the probe and polymer. Consequently the data do not allow a definitive picture of the relaxation behaviour or phase morphology of the copolymer samples to be derived. The data also illustrate the fact that, in designing a high-performance phosphorescent coding system, trends in the photophysical characteristics of one dopant in a given matrix do not necessarily translate into predictions of the behaviour of another phosphor even in the same matrix.

Luminescence studies of polymer matrices. III. Characterization and evaluation of acrylic acid‐based polymers as hosts for a phosphorescent coding system

The phosphorescence characteristics of naphthyl labelled poly(acrylic acid) film samples have been studied as a function of temperature, with a view to investigating the effect of matrix control on the level of triplet emission observed. Two relaxations, which serve to deactivate the excited triplet states have been detected from phosphorescence lifetime measurements: the α (or glass) and the βtransition (which can be associated with the onset of rotation of the carboxylic acid group). Investigation of the emission from 2-benzoyl naphthalene dispersed within both an acrylic acid-methyl methacrylate copolymer and a PAA film, respectively, has revealed that the more intense, longer-lived phosphorescence results from the modified polymer. This is considered to reflect the existence of (i) hydrogen-bonding interactions induced by the presence of carboxylic acid groups which serve to form a rigid matrix and (ii) intramolecular aggregates of methyl methacrylate units which create hydrophobic-rich pockets, capable of sustaining intense phosphorescence at room temperature. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2127–2136, 1999