PAA Films Research Articles

Direct patterning of poly(acrylic acid) on polymer surfaces by ion beam lithography for the controlled adhesion of mammalian cells

Poly(acrylic acid) (PAA)-patterned polystyrene (PS) substrates were prepared by ion beam lithography to control cell behaviors of mouse fibroblasts and human embryonic kidney cells. Thin PAA films spin-coated on non-biological PS substrates were selectively irradiated with energetic proton ions through a pattern mask. The irradiated substrates were developed with deionized water to generate negative-type PAA patterns. The surface characteristics of the resulting PAA-patterned PS surface, such as surface morphology, chemical structure and composition and wettability, were investigated. Well-defined 100 μm PAA patterns were effectively formed on relatively hydrophobic PS substrates by ion beam lithography at higher fluences than 5 × 10(14) ions/cm(2). Moreover, based on the in vitro cell culture test, cells were adhered and proliferated favorably onto hydrophilic PAA regions separated by hydrophobic PS regions on the PAA-patterned PS substrates, and thereby leading to the formation of well-defined cell patterns.

Imidization induced structural changes of 6FDA-ODA poly(amic acid) by two-dimensional (2D) infrared correlation spectroscopy

Two-dimensional (2D) gradient mapping method and 2D correlation analysis of in situ FTIR spectra were used to probe the thermal imidization-induced spectral changes in 6FDA-ODA poly(amic acid) (PAA) films prepared by a reaction of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 4,4′-oxydianiline (ODA) in N,N′-dimethylacetamide. Large spectral changes in the in situ FTIR spectra of 6FDA-ODA PAA film were observed in the range, 130–230°C. The thermal imidization of 6FDA-ODA PAA films strongly affects the spectral changes in amic acid groups in the PAA unit. The spectral change in the amic acid groups occurred before those of the imide ring. The cyclic anhydrides, isoimdes and intermolecular links are present together with the imide ring in the thermally-cured 6FDA-ODA PAA films.

Synthesis and Characterization of Polybenzoxazinone and its Prepolymer Using Gas Separation

Polybenz‐3,1‐oxazinone‐4 (PBOZ) films are prepared via the thermal rearrangement of poly[(methylene‐bis‐anthranilamide) 4,4′‐diphenyloxidicarboxylic acid] (PAA) films by heating to 300 °C. PAA is synthesized by low‐temperature polycondensation. The PBOZ film exhibits excellent mechanical properties and a high glass‐transition temperature. Conversion of PAA to PBOZ leads to an increase in the fractional free volume as a result of thermal dehydration and cyclization during membrane formation and due to the removal of residual solvent. The excess free volume in the PBOZ film is approximately 3–4% of the total volume. The gas permeability and selectivity of the PBOZ film is higher than that of the PAA film. The thermal rearrangement of polymers is recognized as a suitable method to improve separation efficiency. image

Enhanced mechanical and thermal properties of polyimide/organically modified montmorillonite hybrid film based on stable poly(amic acid) ammonium salt

In this study, polyimide/organically modified montmorillonite (PI/OMMT) hybrid film was prepared by in situ polymerization from the stable poly(amic acid) ammonium salt/OMMT (PAAS/OMMT) precursor hybrid. PAAS was obtained by incorporating calculated triethylamine into terpolymer poly(amic acid) (PAA), which was synthesized by pyromellitic dianhydride (PMDA), 4,4′-oxydianiline and p-phenylenediamine in dimethylacetamide (DMAc). OMMT as a type of layered clays was prepared through surface treatment of montmorillonite (MMT) with 1-hexadecylamine. Mechanical property measurements of PI/OMMT hybrid film indicated that the addition of 5 wt% of OMMT increased the Young's modulus of PI film up to 11.24 GPa, which is 58% higher than the pristine PI film from PAAS. Besides, the tensile strength increased to 168.36 MPa, which was higher than that of PI film derived from PAA (164.3 MPa) and PI film derived from PAAS (145.2 MPa). Moreover, the thermal stabilities of PI/OMMT hybrid film with appropriate OMMT content were also better than those of original PI films. POLYM. COMPOS., 34:2076–2081, 2013. © 2013 Society of Plastics Engineers

Contribution of polymeric swelling to the overall response of capacitive gas sensors

A new method for investigation of the swelling of polymers on exposure to gas or vapour has been devised and tested. It uses an optical profilometer (based on the chromatic aberration of a lens system) which is integrated into a computer-controlled gas-dosing and mixing setup. Gas and/or vapour concentration-dependent measurements have been carried out for thick layers of the polymers commonly used in gravimetric and capacitive gas sensors: poly(acrylic acid) (PAA), poly(vinyl pyrrolidone) (PVP), poly(ether urethane) (PEUT), and polydimethylsiloxane (PDMS). The thickness of PAA, PVP, and PEUT films changed significantly on exposure to humidity. These data have been used to derive the sorption isotherms of the respective polymers, which were found to be Henry or Flory-Huggins isotherms. Comparison of the geometrical (swelling) responses with capacitive responses revealed a strong correlation. The correlation, which occurs because both types of response are proportional to the water content of the polymer, is also valid for polymers with nonlinear gas responses. Finally the geometrical and electrical characteristics of the capacitive samples were used to explain the dependence of the capacitive response of different polymers on the concentration of the target gas or vapour. In this way was deduced that PDMS, which does not swell on exposure to humidity, swells in the presence of 2,3-dimethylpentane, for which no profilometer evaluations are yet available.

Catalytic Dechlorination of Monochloroacetic Acid by Film–Supported Pd/Fe Bimetallic Nanoparticles

Three novel kinds of support film, including PVDF-PAA film, PVDF·TiO2–PAA film and PVDF–g–AA film, were synthesized and used to immobilize the Pd/Fe bimetallic nanoparticles (NPs). The immobilized Pd/Fe bimetallic NPs systems were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, contact angle analysis, and X-ray photoelectron spectroscopy. The dechlorination efficiency of the immobilized bimetallic NPs systems were tested and discussed by dechlorinating monochloroacetic acid (MCAA). Comparing with free suspended Pd/Fe NPs, bimetallic NPs with support films appeared better catalytic dechlorination efficiency, and the dechlorination efficiencies of 10 mg/L MCAA in 120 min by Pd/Fe NPs immobilized in PVDF–PAA film, PVDF·TiO2–PAA film and PVDF–g–AA film were 56.33%, 71.01% and 75.51%, respectively.

Optically transparent and colorless polyimide hybrid films with various clay contents

Poly(amic acid) (PAA) was prepared by the reaction of 4,4-(hexafluoroisopropylidene)diphthalic anhydride with m-xylylenediamine in N,N-dimethylacetamide. Hybrid films were obtained from solutions of the precursor polymer blended with varying amounts of pristine saponite (SPT) clay (0–25 wt%). The cast PAA film was heat-treated at different temperatures to create polyimide (PI) hybrid films, which showed excellent optical transparencies and were almost colorless. The wide-angle X-ray diffraction and transmittance electron microscopy results for the PI hybrid films showed a substantial increase in the agglomeration of the clay particles as the clay loading was increased from 10–25 wt%. This finding suggests that in hybrid materials with low clay contents, the clay particles are better dispersed in the matrix polymer and do not agglomerate significantly. The addition of some amount of clay was sufficient to improve the thermal and oxygen barrier properties of the PI, with a maximum improvement observed at 20 wt% SPT. Open image in new window

Characterization of Films of Weak Polyelectrolytes Incorporated with Poly(vinyl-pyrrolidone)-Stabilized Gold Nanoparticles

The incorporation process of gold nanoparticles (Au NPs) into self-assembled films was obtained using the layer-by-layer (LbL) technique where two weak polyelectrolytes, i.e., poly(allylamine hydrochloride) (PAH) as polycation and poly(acrylic acid) (PAA) as polyanion, were sequentially adsorbed. To evaluate this process, the films of PAH and PAA were immersed in gold solutions containing different sizes of Au NPs (6 nm and 10 nm) stabilized with poly(vinyl-pyrrolidone) (PVP) before and after treatment with a 0.1 mol L(-1) solution of hydrochloric acid. The systems were analyzed using a multi-method approach involving UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), atomic force (AFM) and transmission electron microscopy (TEM). The results showed that the self-assembled polyelectrolyte films that were not treated by acid showed greater incorporation and better distribution of Au NPs.

Morphology of nanoimprinted polyimide films fabricated via a controlled thermal history

Fabricating nanopatterns on polyimide (PI) films directly by nanoimprint lithography (NIL) is difficult owing to the high glass transition temperature (Tg). In this study, a nanopatterned PI film was successfully obtained by nanoimprinting poly(amic acid) (PAA) film and curing it afterward. Differential scanning calorimetry, thermogravimetry and dynamic mechanical analysis were carried out to study the state of thermal molecular motion in PAA thick films that have the same content of residual solvent as the PAA thin films used in NIL. The thermal and dynamic mechanical behaviors of PI thick films were studied for comparison. An appropriate nanoimprinting process was proposed based on an understanding of the thermal and dynamic mechanical properties of PAA and PI films. Atomic force microscopy showed that the line pattern was transferred without distortion from the PAA film to the PI film, even though a larger shrinkage took place during the hard baking. The surface of polyimide (PI) film was successfully patterned by nanoimprinting poly(amic acid) (PAA) film and then hard baking. An appropriate nanoimprinting process was established through the study of the thermal and dynamic mechanical properties of PAA and PI film. Atomic force microscopy revealed that line pattern was transferred from silicon mold to PI film successfully and the nanostructures remain undamaged even though a larger shrinkage took place during the hard baking.

Formation of high-capacity protein-adsorbing membranes through simple adsorption of poly(acrylic acid)-containing films at low pH.

Layer-by-layer polyelectrolyte adsorption is a simple, convenient method for introducing ion-exchange sites in porous membranes. This study demonstrates that adsorption of poly(acrylic acid) (PAA)-containing films at pH 3 rather than pH 5 increases the protein-binding capacity of such polyelectrolyte-modified membranes 3-6-fold. The low adsorption pH generates a high density of -COOH groups that function as either ion-exchange sites or points for covalent immobilization of metal-ion complexes that selectively bind tagged proteins. When functionalized with nitrilotriacetate (NTA)-Ni(2+) complexes, membranes containing PAA/polyethylenimine (PEI)/PAA films bind 93 mg of histidine(6)-tagged (His-tagged) ubiquitin per cm(3) of membrane. Additionally these membranes isolate His-tagged COP9 signalosome complex subunit 8 from cell extracts and show >90% recovery of His-tagged ubiquitin. Although modification with polyelectrolyte films occurs by simply passing polyelectrolyte solutions through the membrane for as little as 5 min, with low-pH deposition the protein binding capacities of such membranes are as high as for membranes modified with polymer brushes and 2-3-fold higher than for commercially available immobilized metal affinity chromatography (IMAC) resins. Moreover, the buffer permeabilities of polyelectrolyte-modified membranes that bind His-tagged protein are ~30% of the corresponding permeabilities of unmodified membranes, so protein capture can occur rapidly with low-pressure drops. Even at a solution linear velocity of 570 cm/h, membranes modified with PAA/PEI/PAA exhibit a lysozyme dynamic binding capacity (capacity at 10% breakthrough) of ~40 mg/cm(3). Preliminary studies suggest that these membranes are stable under depyrogenation conditions (1 M NaOH).

Formation of double‐surface‐silvered polyimide films via a direct ion‐exchange self‐metallization technique: The case of BPADA/ODA and [Ag(NH3)2]+

AbstractDouble‐surface‐silvered polyimide (PI) films have been successfully fabricated via a direct ion‐exchange self‐metallization method using silver ammonia complex cation ([Ag(NH3)2]+) as silver resource and bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride/4,4′‐oxydianiline (BPADA/ODA)‐based poly(amic acid) (PAA) as the PI precursor. The alkaline characteristic of the silver precursor dramatically improves the efficiency of the ion exchange and film metallization process. By using an aqueous [Ag(NH3)2]+ solution with a concentration of only 0.01M and an ion‐exchange time of only 5 min, metallized films with desirable performance could be easily obtained by simply heating the silver(I)‐doped PAA films to 300°C. The strong hydrolysis effect of the basic [Ag(NH3)2]+ cations on the flexible and acidic BPADA/ODA PAA chains was observed during the ion exchange process by the quantitative evaluation of the mass loss of PAA matrix. Nevertheless, under the present experimental conditions, the final metallized film essentially retained the basic structural, thermal, and mechanical properties of the pristine PI, which make it a truly applicable material. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

The Microstructure of Zinc Oxide Films Prepared by Hydrothermal Method

In the solutions which are prepared by mixing zinc nitrate hexahydrate, strong ammonia and methenamine in water bath at 90 Centigrade, lamellate and granular zinc oxide films have grown on different substrates such as B270 glass, glass based PAA films, pure aluminum foil and aluminum based PAA films. Films microstructures were characterized by scanning electron microscope (SEM). The influences of substrate and pH on the films microstructure were analyzed. Results reflect that: Ammonia plays an important role in the growing competition of grainy crystal; the more concentration of ammonia, the more zinc oxide crystals grow into granular. Because of the high specific area and adsorption capacity, lacunaris zinc oxide films have great application perspective in gas sensor, catalyzed sorption and biochemistry.

Interrelations between charging, structure and electrokinetics of nanometric polyelectrolyte films

Streaming current, surface conductivity and swelling data of poly(acrylic acid) (PAA) and poly(ethylene imine) (PEI) thin films are analyzed on the basis of the theory for diffuse soft interfaces (J.F.L. Duval, R. Zimmermann, A.L. Cordeiro, N. Rein, C. Werner, Langmuir 25 (2009) 10691). Focus is put on ways to unravel the electroosmotic and migration contributions of the measured surface conductivity, which is crucial for appropriate electrokinetic analysis of films carrying high densities of dissociable groups. Results demonstrate that the osmotically-driven swelling of the PAA films with increasing pH is accompanied by an increase in diffuseness for the interphasial polymer segment density distribution. This heterogeneity is particularly marked at low ionic strength with a non-monotonous dependence of the streaming current on pH and the presence of a maximum at pH∼6.5. The analysis of the PEI films evidences heterogeneous swelling with lowering pH, i.e. upon protonation of the amine groups. The characteristic decay length in the interphasial PEI segment density distribution is found to be nearly independent of the pH, which is in line with the moderate swelling determined by ellipsometry. A critical discussion is given on the strengths and limitations of electrokinetics/surface conductivity for quantifying the coupled electrohydrodynamic and structural properties of moderately to highly swollen polyelectrolyte thin films.

Colorless polyimide nanocomposite films containing hexafluoroisopropylidene group

AbstractPoly(amic acid) (PAA) was prepared by the reaction of 4,4'‐(hexafluoro‐isopropylidene)diphthalic anhydride (6FDA) with 2,2'‐bis[4‐(4‐aminophenoxy)phenyl] hexafluoropropane (BAPP) in N,N‐dimethylacetamide (DMAc). Hybrid films were obtained from blend solutions of the precursor polymer and the organoclay Cloisite 15A, varying the organoclay content from 0 to 3.0 wt%. The cast PAA film was heat‐treated at different temperatures to create polyimide (PI) hybrid films, which showed excellent optical transparencies and were almost colorless. The intercalation of PI chains in the organoclays was examined by means of wide‐angle X‐ray diffraction (XRD) and electron microscopy (SEM and TEM). In addition, the thermo‐mechanical properties were tested using a differential scanning calorimeter (DSC), a thermogravimetric analyzer (TGA), and a universal tensile machine (UTM). In the XRD, SEM, and TEM results for the PI hybrid films, a substantial increase in the agglomeration of the clay particles was observed as the clay loading was increased from 0.5 to 3.0 wt%. This suggests that in the hybrid materials with low clay content, the clay particles are better dispersed in the matrix polymer and do not agglomerate significantly. We found that the addition of a small amount of organoclay is sufficient to improve the thermal and mechanical properties of the PI, with the maximum enhancement being observed at 1.0 wt% Cloisite 15A. Copyright © 2009 John Wiley & Sons, Ltd.

Direct Growth of Highly Ordered Crystalline Zirconia Nanowire Arrays with High Aspect Ratios on Glass by a Tailored Anodization

We report a facile approach to fabricate highly ordered zirconia nanowire arrays with controllable dimensions of φ25–40 nm in diameter, 100–550 nm in length, and 3–20 in aspect ratio by a tailored two-step anodization from superimposed Al/Zr layers sputter-deposited on glass substrates. A porous-type Al anodization in a constant potential mode was performed on the Al layer on Zr/glass in strong acidic electrolytes to form highly ordered porous alumina films with different pore sizes and intervals. Successively, a barrier-type Zr anodization in a constant current mode, at a low-critical-current density of 2 A m−2 with open potentials up to 70–500 V in different acidic electrolytes, was carried out on the underlying Zr film via the overlying PAA films, thereby allowing direct growth of the zirconia nanowires within the alumina nanopores on glass. The as-anodized zirconia nanowires were crystalline, comprising a mixture of monoclinic and orthorhombic ZrO2. In particular, the orthorhombic phase in the zirconia nanowires becomes more predominant with increasing terminal anodizing potentials and exhibits a preferential crystalline orientation in the (002) facet. The formation of anodic zirconia nanowires could be ascribed to the enhancement of the transport number of Zr cations in crystalline zirconia affected by the low-critical-current density and the impurities in the initial Zr film.

Photoluminescent inkjet ink containing ZnS:Mn nanoparticles as pigment

An inorganic nanoparticle suspension, for use in an inkjet ink, has been prepared using chemically synthesised ZnS:Mn nanoparticles with acrylic acid (AA) as a dispersant. AA was also used as a polymeric binder for the jetted ink, by heat-initiated polymerisation of the AA monomer into solid poly(acrylic acid) (PAA). The AA/ZnS:Mn nanoparticle suspension was mixed with surfactant and two co-solvents to achieve the appropriate rheological properties for jetting. The AA suspension, inks, and jetted films of PAA and ZnS:Mn showed strong orange-red photoluminescence (PL) at 600 nm under ultraviolet laser excitation. The emission colour of the ZnS:Mn nanophosphors was tunable over a wide range of wavelengths by using different excitation wavelengths. The most intense PL was observed for jetted inks containing approximately 0.8 w/w% ZnS:Mn nanoparticles. Addition of a cross-linking agent to the inks significantly improved the mechanical resilience of the polymerised films. All suspensions, inks and films were prepared using simple wet chemical methods and low-temperature processing, making them an inexpensive alternative to semiconductive conjugated polymers and suitable for use on temperature-sensitive substrates, such as polymers and paper.

Synthesis and In Vitro Biocompatibility Assessment of a Poly(amic acid) Derived from Ethylenediaminetetraacetic Dianhydride

Poly(amic acid) (PAA) derived from ethylenediaminetetracetic dianhydride shows great potential as a biomaterial suitable for biomedical applications. To evaluate this polymer class further, in vitro cell toxicity (WST-1/ECS, ELISA based) and cell compatibility (cell adhesion and cell proliferation) tests were conducted to establish structure–toxicity relationships. PAAs with a number-average molecular weight ranging between 100 to 200 kg/mol were synthesized at 37°C after 24 h. Porcine radial artery cells (RACs) and descending aorta endothelial cells (ECs) were seeded independently in a 96-well cell culture plate at a cell density of 5000 cells/cm2 to observe toxic effects. Similarly, RACs and ECs were seeded independently onto PAA coated and uncoated cover slips at a cell density of 7000 cells/cm2 to observe growth patterns. Our results showed no toxicity after 96 h of incubation and in addition, both RACs and ECs adhered and proliferated on the PAA films, preserving their phenotype during this time. The tested synthetic material seems promising as a future biomaterial and should elicit a desired cellular response upon implantation.

Photoluminescence-induced oscillations in porous anodic aluminum oxide films grown on Si: Effect of the interface and porosity

We report that porous anodic alumina (aluminum oxide: Al2O3) (PAA) thin films directly grown on Si show clear oscillations in their photoluminescence (PL) spectra which are ascribed to PL-induced interferences within the Fabry–Pérot optical cavity formed by the PAA film on Si, that involve the air/oxide and oxide/Si interfaces. The existence of the PL-induced oscillations is indicative of the high quality of the interface of the PAA film with Si, which is both planar and smooth. We show that by using these oscillations we can develop a sensitive optical method of measuring the porosity of PAA thin films on Si if we know the film thickness. The method is based on the calculation of the effective refractive index of the PAA film derived from the PL-induced oscillations, which is then introduced into the Bruggeman equation in order to derive the porosity of the film.

Enhanced interlayer interaction in cellulose single nanofibre and poly( l-lactic acid) layered films by plasma-initiated surface grafting of poly(acrylic acid) onto poly( l-lactic acid) films

The surface of a poly( l-lactic acid) (PLLA) film was modified with poly(acrylic acid) (PAA) by plasma-initiated polymerization to increase the interaction between PLLA and cellulose single nanofibres (CSNF). The surface wettability of the PAA grafted PLLA film (PLLA–PAA film) was investigated by contact angle measurements. Modification of the PLLA film with PAA decreased the contact angle from 61° to 50°. The surface morphologies of the PLLA film, PLLA–PAA film and CSNF-coated PLLA–PAA film were studied by atomic force microscopy. The interaction between the CSNF and PLLA layers was strengthened by incorporation of a PAA layer onto the PLLA films and it is higher than 2N as proved by a peeling test. This is probably because the carboxyl groups of PAA form hydrogen bonds with the hydroxyl groups of CSNF.

Heat-induced cross-linking of nylon-like weak polyelectrolyte multilayer films: UV–visible studies of methylene blue loading and rates of release

Heat-induced cross-linking of poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) films was studied as a potential method for controlling the rate of release of an absorbed dye, methylene blue (MB), from the film. Alternating layers of PAA and PAH films were prepared, loaded with MB and cured at different temperatures/times. Our studies identified the conditions best controlling both the amount of MB loading and its rate of release from PAA/PAH films to be curing at 150 °C for 10 min. In general, curing temperatures both above and below 150 °C showed slower rates of release as well as lower amounts of MB loading.