Influences of solution property and charge density on the self-assembly behavior of water-insoluble polyelectrolyte sulfonated poly(sulphone) sodium salts

Two sulfonated poly(sulphone) sodium salts (SPSF) with different molecular weights and ionic exchange capacities in a N,N-dimethyl formamide/water (DMF-H2O) mixed solvent with various DMF contents were selected as a model system for investigating the influences of solvent composition, solution properties, and charge density of polyelectrolytes on the layer-by-layer (LbL) self-assembly of water-insoluble polyelectrolytes. Poly(dimethyldiallylammonium chloride) (PDDA) in aqueous solution was used as the counterpart. The PDDA/SPSF multilayer films grew nearly linearly with the layer numbers regardless of the volume fraction of DMF, phiDMF, in the SPSF solutions. The total absorption amount of the PDDA/SPSF multilayer films was strongly dependent on the charge density of the SPSF molecules and the phiDMF value of the SPSF solutions. Minimum values of absorption amount were observed at phiDMF = 0.6 to approximately 0.7. The surface hydrophobicity and roughness of the multilayer films can be tuned by varying phiDMF. These observations were rationalized in terms of the chain dimension and the ionization degree of the SPSF molecules as a function of phiDMF, which was characterized by the intrinsic viscosity ([eta]SPSF) and conductivity (LSPSF) of the SPSF solutions. The results indicate that the molecular structures of the DMF-H2O mixed solvent strongly affect the solution properties of SPSF, which in turn determine the growth behavior and physical properties of the PDDA/SPSF multilayer films.     

Polyelectrolyte blend multilayer films: surface morphology, wettability, and protein adsorption characteristics

We report the influence of polyelectrolyte (PE) multilayer films prepared from poly(styrene sulfonate)-poly(acrylic acid) (PSS-PAA) blends, deposited in alternation with poly(allylamine hydrochloride) (PAH), on film wettability and the adsorption behavior of the protein immunoglobulin G (IgG). Variations in the chemical composition of the PAH/(PSS-PAA) multilayer films, controlled by the PSS/PAA blend ratio in the dipping solutions, were used to systematically control film thickness, surface morphology, surface wettability, and IgG adsorption. Spectroscopic ellipsometry measurements indicate that increasing the PSS content in the blend solutions results in a systematic decrease in film thickness. Increasing the PSS content in the blend solutions also leads to a reduction in film surface roughness (as measured by atomic force microscopy), with a corresponding increase in surface hydrophobicity. Advancing contact angles (theta) range from 7 degrees for PAH/PAA films through to 53 degrees for PAH/PSS films. X-ray photoelectron spectroscopy measurements indicate that the increase in film hydrophobicity is due to an increase in PSS concentration at the film surface. In addition, the influence of added electrolyte in the PE solutions was investigated. Adsorption from PE solutions containing added salt favors PSS adsorption and results in more hydrophobic films. The amount of IgG adsorbed on the multilayer films systematically increased on films assembled from blends with increasing PSS content, suggesting strong interactions between PSS in the multilayer films and IgG. Hence, multilayer films prepared from blended PE solutions can be used to tune film thickness and composition, as well as wetting and protein adsorption characteristics.     

Hydrogen-bonding-directed layer-by-layer assembly of poly(4-vinylpyridine) and poly(4-vinylphenol): effect of solvent composition on multilayer buildup

This paper describes the buildup of hydrogen-bonding-directed poly(4-vinylpyridine)/poly(4-vinylphenol) (PVPy/PVPh) multilayer film that was fabricated by layer-by-layer (LbL) assembly of PVPy and PVPh from an ethanol solution. UV-visible spectroscopy and Fourier transform infrared (FT-IR) spectroscopy revealed a uniform deposition process. The interaction between PVPy and PVPh was identified as hydrogen bonding through FT-IR spectroscopy and temperature-dependent IR spectral changes of the hydrogen-bonded multilayer. Notably, we discussed the effect of solvent conditions on the growth of PVPy/PVPh multilayer films monitored by UV-visible spectroscopy. It was found that increasing the ratio of N,N-dimethylformamide (DMF) in the mixed ethanol/DMF solvents resulted in a marked decrease of the amount of polymers adsorbed, which was attributed to the increased polarity of the adsorption solutions. Furthermore, the solvent stability of PVPy/PVPh multilayer film in mixed ethanol/DMF solvents with different DMF ratios was also investigated. As a result, a new method for tuning the structure of hydrogen-bonding-directed multilayer film was developed.     

Construction and deconstruction of multilayer films containing polycarboxybetaine: effect of pH and ionic strength

The influences of pH and NaCl concentration of dipping solutions and the pH and NaCl concentration of disintegration solutions on the disintegration behaviors of poly(4-vinylpyridiniomethanecarboxylate) (PVPMC)/poly(sodium 4-styrenesulfonate) (PSS) (PVPMC/PSS) multilayer films were investigated by ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FT-IR), quartz crystal microbalance (QCM) and atomic force microscopy (AFM). It was found that the disintegration rates and degrees of PVPMC/PSS multilayer films in neutral water could be well controlled by changing pH of dipping solutions and immersion time during the disintegration process. Furthermore, PVPMC/PSS multilayer films could be disintegrated completely and rapidly in pH 8 alkali solution or physiological condition (i.e., 0.15 M NaCl solution). The controllable disintegration of PVPMC/PSS multilayer films was then utilized to fabricate PEC/PSS free-standing multilayer films, in which PEC was a positively charged polyelectrolyte complex made from excessive poly(diallyldimethylammonium) (PDDA) and PSS. The experimental results indicated that the disintegration rates of PVPMC/PSS sacrificial sublayer strongly affected the integrity of the resultant PEC/PSS free-standing multilayer films. Only free-floating PEC/PSS was released from neutral water by disintegrating PVPMC/PSS multilayer sublayers. However, large size flat and tube-like PEC/PSS free-standing multilayer films with good mechanical properties were obtained facilely from pH 8 alkali solution and 0.15 M NaCl solution, respectively. The preparation of such free-standing films at physiological condition may be useful in the biological or medical application.     

Oriented polymers from solution. IV. Polyethylene/polypropylene blend films

Work on the surface-growth method of producing blend films from mixed solutions of two polymers has exposed a random fluctuation in both growth rate and composition of the blend film with time of deposition. The effects are explained by heterogeneous separation of the two polymer components in the solution induced by the stirring action of the rotor of the Couette apparatus used. The solution is thus converted to a colloidal sol which on cooling forms a gel which exhibits syneresis at room temperature. The sol-to-gel transition is thermally reversible.     

Layer-by-layer assembly of two temperature-responsive homopolymers at neutral pH and the temperature-dependent solubility of the multilayer film

We fabricated a layer-by-layer (LbL) film of temperature-responsive homopolymers at neutral pH and studied its temperature-dependent solubility. We first measured the cloud point of mixed solutions of temperature-responsive polymers. The significant decrease of cloud point suggested that the intermolecular interaction between two polymer chains of different kinds was stronger than that between two polymer chains of the same kind. Strong intermolecular interaction between two polymer chains of different kinds is a prerequisite for LbL assembly. On the basis of the decrease of cloud point of mixed solutions of temperature-responsive homopolymers, we selected poly(N-vinylcaprolactam) (PVCL) and poly(2-hydroxypropyl acrylate) (PHPA) for LbL assembly. LbL films of the two polymers were fabricated at neutral pH at a constant temperature. When the film was immersed in purified water at a temperature lower than the assembly temperature, it can be partially dissolved with a diffusion-limited dissolution process. The temperature-responsive solubility of the LbL film is closely connected to the phase behavior of mixed solutions of the two polymers. Additionally, as compared to multilayer films of neutral polymers and poly(carboxylic acid)s, the PVCL/PHPA multilayer film is relatively stable when it was immersed in buffer solutions near physiological pH at the assembly temperature. Such LbL films with temperature-responsive solubility might be used as a dissolvable film or a smart capsule.     

Physicochemical properties of quaternized poly(amidoamine) dendrimers with alkyl groups and of their mixtures with sodium dodecyl sulfate

The physicochemical properties of quaternized poly(amidoamine) dendrimers (generation 4) with methyl or octyl groups and of their mixtures with sodium dodecyl sulfate (SDS) in aqueous solutions have been investigated using several techniques including surface tension, fluorescence of pyrene, and dynamic light scattering. In the single systems of the dendrimers, the dendrimer with octyl groups shows lower surface tension and lower micropolarity than the dendrimer with methyl groups. The hydrodynamic radii of two quaternized poly(amidoamine) dendrimers are considerably large, indicating the formation of aggregates. In the mixed systems of quaternized poly(amidoamine) dendrimers and SDS, the dendrimer with octyl groups-SDS mixed system shows very low surface tension and low micropolarity even in the presence of extremely low SDS concentration compared to those of the dendrimer with methyl groups-SDS mixed system. Maximum turbidity for both systems is observed at around the mixed molar ratio of dendrimer:SDS=1:1.5 where distinct changes have also been confirmed by surface tension, fluorescence of pyrene, and electrical conductivity measurements.     

Organic vapor detection by quartz crystal microbalance modified with mixed multilayer Langmuir-Blodgett Films

Mixed chloroform solution of Polysiloxane PS-264 and stearic acid was made into multilayer Langmuir-Blodgett (LB) films on the surface of quartz crystal microbalance (QCM). The condition for forming mixed multilayer LB films is discussed in this paper. In addition, PS-264, stearic acid and their mixture (molar ratio 1:1) were coated on the surface of QCM sensors by a spin coating method. The above modified crystals were exposed to different concentrations of various organic vapors, including related chlorinated hydrocarbons and alcohol vapors. The results of frequency changes corresponding to concentration change of the above vapors were compared. The linear regression coefficients of the QCM with LB film had better values (0.9881相似文献   

Molecular dynamics simulations of multilayer films of polyelectrolytes and nanoparticles

We performed molecular dynamics simulations of multilayer assemblies of flexible polyelectrolytes and nanoparticles. The film was constructed by sequential adsorption of oppositely charged polymers and nanoparticles in layer-by-layer fashion from dilute solutions. We have studied multilayer films assembled from oppositely charged polyelectrolytes, oppositely charged nanoparticles, and mixed films containing both nanoparticles and polyelectrolytes. For all studied systems, the multilayer assembly proceeds through surface overcharging after completion of each deposition step. There is almost linear growth in the surface coverage and film thickness. The multilayer films assembled from nanoparticles show better layer stratification but at the same time have higher film roughness than those assembled from flexible polyelectrolytes.     

Equilibrium surface adsorption behavior in complex anionic/nonionic surfactant mixtures

Neutron reflectivity (NR) and small angle neutron scattering (SANS) have been used to investigate the equilibrium surface adsorption behavior and the solution microstructure of mixtures of the anionic surfactant sodium 6-dodecyl benzene-4 sulfonate (SDBS) with the nonionic surfactants monododecyl octaethylene glycol (C12EO8) and monododecyl triiscosaethylene glycol (C12EO23). In the SDBS/C12EO8 and SDBS/C12EO23 solutions, small globular mixed micelles are formed. However, the addition of Ca2+ ions to SDBS/C12EO8 results in a transition to a vesicle phase or a mixed vesicle/micellar phase for SDBS rich compositions. In contrast, this transition hardly exists for the SDBS/C12EO23 mixture, and occurs only in a narrow composition region which is rich in SDBS. The adsorption of the SDBS/C12EO8 mixture at the air-solution interface is in the form of a mixed monolayer, with a composition variation that is not consistent with ideal mixing. In water and in the presence of NaCl, the nonideality can be broadly accounted for by regular solution theory (RST). At solution compositions rich in SDBS, the addition of Ca2+ ions results in the formation of multilayer structures at the interface. The composition range over which multilayer formation exists depends upon the Ca2+ concentration added. In comparison, the addition of a simple monovalent electrolyte, NaCl, at the same ionic strength does not have the same impact upon the adsorption, and the surface structure remains as a monolayer. Correspondingly, in solution, the mixed surfactant aggregates remain as relatively small globular micelles. In the presence of Ca2+ counterions, the variation in surface composition with solution composition is not well described by RST over the entire composition range. Furthermore, the mixing behavior is not strongly correlated with variations in the solution microstructure, as observed in other related systems.     

Influence of solvent quality on the growth of polyelectrolyte multilayers

The effect of solvent conditions on the growth of polyelectrolyte (PE) multilayer films comprising poly(allylamine hydrochloride) (PAH) and poly(styrenesulfonate sodium salt) (PSS) on planar substrates was investigated by means of surface plasmon resonance spectroscopy (SPRS), quartz crystal microbalance (QCM), and atomic force microscopy techniques. The solvent quality was varied by the addition of ethanol to the PE solutions used for deposition of the layers, thus tuning the relative strength of electrostatic and secondary intermolecular and intramolecular interactions. Experiments were performed with PE solutions both without added electrolyte and containing 0.5 M NaCl. Decreasing the solvent quality (i.e., increasing the amount of ethanol in the adsorption solution) resulted in a marked increase of both the multilayer film thickness and mass loading, as determined from the SPRS spectra and QCM frequency shifts, respectively. With the solution composition approaching the precipitation point, thick PAH/PSS films were formed due to the screening of the electrostatic intra- and interchain repulsions and enhanced hydrophobic interactions between the polyelectrolyte chains. However, the films formed from water/ethanol mixtures remained stable upon subsequent exposure to water or salt-containing solutions: no significant film desorption occurred after up to 24 h of exposure to water or 0.5 M NaCl solutions. In addition, the effect of postdeposition exposure to water/ethanol mixtures was investigated for PE multilayers assembled from aqueous solutions. In this case, the optical thickness of the films was determined during exposure to water/ethanol mixtures, and instead of swelling, the polyelectrolyte films collapse to the surface as a result of the unfavorable segment-solvent interactions.     

Investigations of Thin Films with Amphiphilic Dendrimers Bearing Peripheral Fullerene Subunits

In spite of a molecular mass of 7704.6 g mol(-1), third-generation compound G3 (shown schematically; Z=C(8)H(17)) is able to form stable Langmuir films. In a systematic study, the amphiphilic properties of the corresponding dendrimers of first (G1) and second generation (G2), with one and two peripheral fullerene units, respectively, were investigated and a model could be proposed for the multilayer films obtained from G1.     

Anomalous thickness evolution of multilayer films made from poly-L-lysine and mixtures of hyaluronic acid and polystyrene sulfonate

Using a mixture of polyanions or polycations offers a new way to control the properties of polyelectrolyte multilayer (PEM) films. The central issue of PEM films made from blended polyelectrolyte solutions is the relation between the properties of the blended architecture and the properties of the films made from each pure component. Two situations are possible: either (i) the properties of the blended films are intermediate between those corresponding to the single components or (ii) new effects may emerge leading, for instance, to improved mechanical properties. Situation (i) is expected when the chemical natures of both polyelectrolytes from the blended mixture are close, whereas situation (ii) is more probable when the polyelectrolytes from the blend are very different. In this study, we focus on the buildup of PEM films made by the alternate spray deposition of a polyanion blend [a mixture of polystyrene-4-sulfonate (PSS) and hyaluronic acid (HA) in different mass fractions] and a polycation solution of poly-L-lysine (PLL). Whereas (HA-PLL) films exhibit a strong exponential growth with the number of deposition steps, the (PSS-PLL) system is only weakly exponential. We find that when the composition of the polyanion blend ranges from pure (HA-PLL) to pure (PSS-PLL), the films can always be constructed. However, the polyanion composition of the films is far from that of the polyanion solutions used for the buildup. One observes a strong preference for the incorporation of PSS over HA into the films. Moreover, the most striking feature is that the film thickness does not evolve monotonously with the polyanion solution composition but passes through a sharp minimum for a polyanion solution containing 90-95% HA. A possible mechanism for this peculiar finding is proposed.     

Electrochemical and Surface Properties of Multilayer Films Based on a Ru2+ Metallodendrimer and the Mixed Addenda Dawson Heteropolyanion

The successful formation of organized multilayer assemblies, formed from the Dawson type mixed addenda heteropolyanion, [P₂W₁₇ V^IVO₆₂]^8?, and a Ru²⁺ pentaerythritol based metallodendrimer, [RuDen]⁸⁺, has been achieved on carbon electrode surfaces. Cyclic voltammetric studies of the assembly across a wide pH domain, namely, 2 to 7 was possible. Upon redox switching, the redox couples associated with the Ru^III/II redox system, of the cationic metallodendrimer, and both the V^IV/V and the tungsten‐oxo framework of the heteropolyanion, were clearly evident. The multilayer assembly exhibited good stability towards both redox cycling and soaking over extended periods of time in aqueous buffer solutions. In addition, the constructed multilayer films were found to be quite compact in nature. The films were further characterized by X‐ray photoelectron spectroscopy (XPS) to determine their elemental composition. Surface morphology of the multilayer films was determined by atomic force microscopy (AFM). The electrocatalytic reduction of iodate by the multilayer film was also investigated.     

Use of a ruthenium-containing conjugated polymer as a photosensitizer in photovoltaic devices fabricated by a layer-by-layer deposition process

Multilayer polymer films composed of a ruthenium terpyridine complex containing poly(p-phenylenevinylene) (Ru-PPV) and sulfonated polyaniline (SPAN) were prepared by a layer-by-layer electrostatic self-assembly deposition. The deposition process was carried out from SPAN solution in water and Ru-PPV in dimethylformamide (DMF). Optical-quality multilayer thin films were obtained. The film growth process was monitored by quartz crystal microbalance, and the surface morphology of the films was studied by atomic force microscopy. It was found that the properties of the multilayer films were dependent on deposition conditions such as the pH of the SPAN solution, the presence of salt in the polymer solutions, and the post-film-forming thermal annealing process. Cross-section transmission electron microscopic images suggested that there was no stratified structure formed in the multilayer films. Photovoltaic cells were fabricated by sandwiching the multilayer films between indium-tin-oxide and aluminum electrodes. The device performances were examined by illumination with AM 1.5 simulated solar light. The power conversion efficiencies of these devices were on the order of 10(-3)%. The maximum incident photon-to-electron conversion efficiency (IPCE) of the devices was found to be approximately 2% at 510 nm, which is consistent with the absorption maximum of the ruthenium complex. This indicates that the photosensitization process is due to the electronic excitation of the ruthenium complex.     

Synthesis and photophysical properties of triphenylamine-based dendrimers with 1,3,5-triphenylbenzene cores

Two new conjugated dendrimers bearing a triphenylamine moiety as dendrons and 1,3,5-triphenylbenzene as a core have been synthesized through a convergent synthetic strategy. These conjugated dendrimers have high fluorescence quantum yields and exhibit similar absorption and emission behaviors in solutions and in solid films, which demonstrate that these dendrimers form good amorphous states.     

Compositional and structural engineering of DNA multilayer films

We report the layer-by-layer (LbL) preparation of multilayered thin films that consist solely of DNA. The properties of the films were varied by assembling the layers from different oligonucleotide building blocks, which are composed of repeating homopolymeric units of nucleotides [adenosine (A), cytosine (C), guanine (G), and thymidine (T)] or "random" sequences. Films assembled from oligonucleotides with a single complementary unit did not show continual layer buildup. To form a repeating multilayer system, it was necessary for single-stranded DNA to be available for subsequent layers to hybridize. By using oligonucleotides with multiple nucleotide units, multilayer films were successfully assembled. We demonstrate that the thickness and swellability of the films can be controlled by the extent of hydrogen bonding (the G/C content of the oligonucleotide) and orientation of the oligomers. We have examined the stability and swellability of the films in solutions of varying salt concentration as well as in a denaturing urea solution. Stable, hollow DNA capsules were also formed by preparing the films on sacrificial colloidal templates, followed by removal of the core. The assembly of propagating structures through DNA hybridization paves the way for the engineering of DNA films with tailored composition, structure, and permeability, making them likely to find application in drug/gene delivery and biomolecular sensing.     

A facile convergent procedure for the preparation of triphenylamine-based dendrimers with truxene cores

A simple convergent procedure has been developed for the preparation of triphenylamine dendrons containing an alkene at the center, which can be coupled in a single step to give dendrimers that contain truxene for the core without any protection-deprotection chemistry. These conjugated dendrimers exhibit similar absorption and emission behaviors in solutions and in thin films, which are indicative of the high isolation effect of well-organized three-dimensional dendrimers. They also have high fluorescence quantum yields and high glass transition temperatures, which indicate that these dendrimers are candidates for the application in OLED as light emitting materials.     

Correlation in the properties of aqueous single films and foam containing a nonionic surfactant and organic/inorganic electrolytes

Correlation of the behavior of foam from aqueous solutions of C(10)E(8) + TPeAB mixtures with the properties of the single foam films is sought through a theoretical analysis based on experimental data. The state in the adsorption layer on the air/solution interface has been determined from the surface tension experimental data by applying the Frumkin adsorption isotherm for mixed surfactants. Diverse parameters of the adsorption layer have been calculated. Values of the surface potential, estimated from the electrostatic disjoining pressure in the films, are found to be in good agreement with those calculated through the Grahame equation for the air/water interface. The energy of interaction (attraction) in the mixed adsorption layers is determined. The behavior of a foam body produced from solutions of the same composition, is also investigated in two independent ways using the stationary foam column and the foam life-time (decay rate) methods. Both techniques gave similar results with respect to foam stability.     

Surface properties of the binary mixed systems of alkylpyridinium halides and sodium alkylsulfonates

Surface properties of the binary mixed systems of decyl- and dodecylpyridinium chloride or bromide and sodium pentyl- and heptylsulfonate have been investigated. The surface tension of solutions of equimolar mixtures of surfactants and individual surfactants was measured, and the composition of mixed monolayers and surface interaction parameter β were calculated with the regular solution theory. Our results indicate that the properties of mixed films depend on both ionic strength and the kind of added inorganic electrolyte. With the increase of inorganic electrolyte concentration, the content of more surface active ions in the adsorption films enhances and is the highest in the presence of NaI and the smallest when solutions contain NaCl. Mutual interactions in mixed adsorbed films were found to be attractive. However, the strength of interaction weakens with the increase of ionic strength and depends on the kind of inorganic ions in the order: Cl⁻>Br⁻>I⁻.