Synthesis of homoveratric acid-imprinted polymers and their evaluation as selective separation materials

A bulk polymerization method was used to easily and efficiently prepare homoveratric acid (3,4-dimethoxyphenylacetic acid)-imprinted polymers from eight basic monomers: 2-vinylpyridine, 4-vinylpyridine, 1-vinylimidazole, N-allylaniline, N-allylpiperazine, allylurea, allylthiourea, and allylamine, in the presence of homoveratric acid as a template in N,N-dimethylformamide as a porogen. The imprinted polymer prepared from allylamine had the highest affinity to the template, showing an imprinting factor of 3.43, and allylamine polymers MIP8/NIP8 were selected for further studies. Their binding properties were analyzed using the Scatchard method. The results showed that the imprinted polymers have two classes of heterogeneous binding sites characterized by two pairs of K(d), B(max) values: K(d)(1) = 0.060 μmol/mL, B(max)(1) = 0.093 μmol/mg for the higher affinity binding sites, and K(d)(2) = 0.455 μmol/mL, B(max)(2) = 0.248 μmol/mg for the lower affinity binding sites. Non-imprinted polymer has only one class of binding site, with K(d) = 0.417 μmol/mL and B(max) = 0.184 μmol/mg. A computational analysis of the energies of the prepolymerization complexes was in agreement with the experimental results. It showed that the selective binding interactions arose from cooperative three point interactions between the carboxylic acid and the two methoxy groups in the template and amino groups in the polymer cavities. Those results were confirmed by the recognition studies performed with the set of structurally related compounds. Allylamine polymer MIP8 had no affinity towards biogenic amines. The obtained imprinted polymer could be used for selective separation of homoveratric acid.     

Amino-functionalized monolithic spin-type columns for high-throughput lectin affinity chromatography of glycoproteins

Hydrophilic poly(ethylene glycol)-based monoliths were synthesized in the spin-tip format for high-throughput applications via pulsed electron beam irradiation. Monoliths with a homogeneous porous structure and a total porosity of 69% were obtained. The cross-linked polymeric structure was further mechanically stabilized via the incorporation of silica nanoparticles. Amino-functionalization of the monoliths was accomplished by a straightforward, water-based, one-step approach that entailed the electron-beam irradiation-induced grafting of poly(allylamine). The amine functionalized spin columns showed very low unspecific protein adsorption and were successfully applied as adsorbents in lectin affinity chromatography for the purification of ovalbumin. The novel columns also outperformed a commercially available system.     

Adsorption of amyloid beta-peptide at polymer surfaces: a neutron reflectivity study.

The adsorption of amyloid beta-peptide at hydrophilic and hydrophobic modified silicon-liquid interfaces was characterized by neutron reflectometry. Distinct polymeric films were used to obtain noncharged (Formvar), negatively (sodium poly(styrene sulfonate)) and positively charged (poly(allylamine hydrochloride)) hydrophilic as well as hydrophobic surfaces (polystyrene and a polysiloxane-dodecanoic acid complex). Amyloid beta-peptide was found to adsorb at positively charged hydrophilic and hydrophobic surfaces, whereas no adsorbed layer was detected on hydrophilic noncharged and negatively charged films. The peptide adsorbed at the positively charged film as patches, which were dispersed on the surface, whereas a uniform layer was observed at hydrophobic surfaces. The thickness of the adsorbed peptide layer was estimated to be approximately 20 A. The peptide formed a tightly packed layer, which did not contain water. These studies provide information about the affinity of the amyloid beta-peptide to different substrates in aqueous solution and suggest that the amyloid fibril formation may be driven by interactions with surfaces.     

Glassy state of polystyrene sulfonate/polyallylamine polyelectrolyte multilayers revealed by the surface force apparatus

The interactions between two poly(allylamine)/poly(styrene sulfonate) multilayers made of 4.5 and 5 bilayers are investigated by the surface force apparatus (SFA). As the two surfaces approach, one reaches a threshold point where a repulsion sets in, until they become barely compressible. Repetitive load/unload cycles show that, once compressed, the films remain almost in their compressed state. This indicates that the poly(allylamine)/poly(styrene sulfonate) films are in a glassy state, in marked difference with the SFA findings on poly-(L-lysine)/poly-L-glutamic acid) multilayers. These results are discussed in the light of linearly and exponentially growing films.     

Mechanically responsive films of variable hydrophobicity made of polyelectrolyte multilayers

Mechanically responsive surfaces that allow to switch reversibly from a hydrophobic to a hydrophilic substrate are reported. The surfaces are constituted of polyelectrolyte multilayers deposited on modified charged silicone sheets. n bilayers of poly(allylamine)-Nafion (PAH-Naf) and m bilayers of poly(allylamine)-poly(acrylic acid) (PAH-PAA) composed the multilayers. A (PAH-Naf)(n) film possesses a water contact angle of around 105 degrees, whereas the contact angle of a (PAH-Naf)(4)-(PAH-PAA)(m) multilayer is around 50 degrees. When such a film with m < 5 and terminated by PAA is stretched out, its water contact angle increases up to around 100 degrees. Successive elongation/retraction cycles allow the water contact angle to alternate reversibly between 100 and 57 degrees indicating the reversible mechanical responsive nature of the film.     

Facile fabrication of robust multilayer films: visible light-triggered chemical cross-linking by the catalysis of a ruthenium(II) complex

Highly stable covalently attached multilayer films were constructed by visible-light irradiation of hydrogen-bonding directed multilayer films of poly(allylamine) and poly(4-vinylphenol).     

Amphoteric poly(vinyl alcohol) gel as a force generator: Observation of microporous gel formation with cryo-SEM

Amphoteric PVA hydrogels were made from mixed aqueous solutions of poly(acrylic acid), poly(allylamine) hydrochloride and poly(vinyl alcohol) by repetitive freezing and thawing. The hydrogen bond induced gelation produced an elastic and tough microporous hydrogel which generated tension as high as 0.3MPa corresponding to the solvent exchange from water to acetone. In this paper we show the microscopic structure of hydrogels determined by means of cryo-SEM technique and X-ray analysis.     

Dynamics of ion exchange between self-assembled redox polyelectrolyte multilayer modified electrode and liquid electrolyte

A probe beam deflection (PBD) study of ion exchange between an electroactive polymer poly(allylamine)-bipyridyl-pyridine osmium complex film and liquid electrolyte is reported. The PBD measurements were made simultaneously to chronoamperometric oxidation-reduction cycles, to be able to detect kinetic effects in the ion exchange. Layer-by-layer (LbL) self-assembled redox polyelectrolyte films with osmium bipyridyl complex covalently attached to poly(allylamine) (PAH-Os) and poly(styrene sulfonate) (PSS) have been built by alternate electrostatic adsorption from soluble polyelectrolytes. The ionic exchange during initial conditioning of the film ("break-in") undergoing oxidation-reduction cycles and recovery after equilibration in the reduced state have shown an exchange of anions and cations with time lag between them. The effect of the nature of cation on the ionic exchange has been investigated with dilute HCl, LiCl, NaCl, and CsCl electrolytes. The ratio of anion to cation exchanged at the film-electrolyte interface has a strong dependence on the nature of charge in the topmost layer, that is, when negatively charged PSS is the capping layer, a larger proportion of cation exchange is observed. This demonstrates that the electrical potential distribution at the redox polyelectrolyte multilayer (PEM)/electrolyte interface determines the ionic flux in response to charge injection in the film.     

Proton conductivity in the dry membrane of poly(sulfonic acid) and polyamine layer-by-layer complex

A layer-by-layer assembled and molecular-complexed polymer membrane was prepared by the simple combination of poly(4-styrenesulfonic acid) and poly(allylamine) on a comb-shaped gold electrode: it displayed a very high proton conductivity of 10(-3) S cm(-1) under a dry condition at 120 degrees C.     

Poly(allylamine) beads as selective sorbent for preconcentration of formaldehyde and acetaldehyde in high-performance liquid chromatographic analysis

Formaldehyde and acetaldehyde in water were determined by preconcentration with poly(allylamine) beads, derivatization with 2,4-dinitrophenylhydrazine (DPH) and analysis by HPLC. Poly(allylamine) beads (0.5 g) were used to adsorb formaldehyde and acetaldehyde at 1.2-150 microg l(-1) and 3.5-220 microg l(-1) from water (1 l). The concentration factor is 50 fold. The aldehydes were eluted and derivatized with 2 mM DPH in 0.5 M H2SO4 (10 ml). The time of analysis was 1 h. The detection limits (S/N=3) for formaldehyde and acetaldehyde were 0.6 and 2 microg l(-1), respectively.     

Construction of positively-charged layered assemblies assisted by cyclodextrin complexation

A beta-cyclodextrin dimer is found to be effective in preparing a layer-by-layer architecture of positively charged ferrocene-appended poly(allylamine) presumably on the basis of strong beta-cyclodextrin-ferrocene host-guest interaction.     

Direct Electron Transfer Reactivity of Hemoglobin in Cationic Gemini Surfactant–Poly (Allylamine) Hydrochloride Composite Film on Glassy Carbon Electrode

A new composite film comprising cationic gemini surfactant butane-α,ω-bis(dimethyl dodeculammonium bromide) (BDDA, C₁₂-C₄-C₁₂) and poly (allylamine) hydrochloride(PAH) have been prepared. The composite film showed good biocompatibility and could promote the direct electron transfer between hemoglobin (Hb) and glassy carbon (GC) electrode. The immobilized Hb exhibited a pair of well-defined, quasi-reversible, and stable redox peaks with a formal potential of ?0.158 V (vs. SCE) in 0.10 M pH 7 phosphate buffer solutions, and showed high affinity to hydrogen peroxide. The cathodic peak current of the electrode was linear with increasing concentration of H₂O₂ in the range of 5.14 to 200 μM.     

Covalent gluing and postgluing of Langmuir-Blodgett monolayers at hydrocarbon surfaces

Langmuir-Blodgett (LB) monolayers of 5,11,17,23,29,35-hexaformyl-37,38,39,40,41,42-hexakis(1-n-octyloxy)calix[6]arene (2), deposited onto silylated silicon wafers, were cross-linked (i.e., "covalently glued") via Schiff base formation with poly(allylamine). Direct evidence for imine formation was obtained from X-ray photoelectron spectroscopy and from attenuated total reflection IR spectroscopy. These modified surfaces could be removed from the aqueous subphase into air with retention of the assembly and its orientation relative to the surface, as evidenced by atomic force microscopy, water contact angle measurements, and film thickness determinations by ellipsometry. Similar assemblies were also synthesized via a postgluing procedure, in which the substrate containing the LB monolayer was removed from the subphase and rapidly immersed into an aqueous solution containing poly(allylamine). The potential of combining postgluing methods with continuous LB film deposition as a surface modification technique is briefly discussed.     

Structural characterization of a spin-assisted colloid-polyelectrolyte assembly: stratified multilayer thin films

The assembly of polyelectrolytes and gold nanoparticles yields stratified multilayers with very low roughness and high structural perfection. The films are prepared by spin-assisted layer-by-layer self-assembly (LbL) and are characterized by X-ray reflectivity (XRR), UV-vis spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy (TEM). Typical structures have four repeat units, each of which consists of eight double layers (DL) of poly(sodium 4-styrenesulfonate)/poly(allylamine hydrochloride), one monolayer of gold nanoparticles (10 nm diameter), and another layer of poly(allylamine hydrochloride). XRR scans show small-angle Bragg peaks up to seventh order, evidencing the highly stratified structure. Pronounced Kiessig fringes indicate a low global roughness, which is confirmed by local AFM measurements. TEM images corroborate the layered structure in the growth direction and nicely show the distinct separation of the individual particle layers. An AFM study reveals the lateral gold particle distribution within one individual particle layer. Interestingly, the spin-assisted deposition of polyelectrolytes reduces the roughness induced by the particle layers, leading to self-healing of roughness defects and a rather perfect stratification.     

层层自组装聚烯丙胺盐酸盐/Pd纳米复合薄膜的制备及其电催化特性

利用层层静电自组装技术将聚烯丙胺盐酸盐(PAH)和四氯合钯酸根离子( )交替沉积在基底上, 然后用硼氢化钠还原, 构筑了含钯纳米粒子的PAH/Pd纳米复合薄膜. 通过紫外-可见吸收光谱(UV-Vis)、扫描电子显微镜(FESEM), X射线光电子能谱(XPS)和循环伏安(CV)等手段对复合膜的组装、成分、微结构、表面形貌和光学性能进行了测试分析. FESEM图形显示膜表面有一定的粗糙度, 膜上生成了粒径在50～100 nm 范围的钯纳米粒子; UV-Vis结果显示多层膜在特征吸收峰处的吸光度数值随膜双层数增加逐渐增大, 呈良好的线性关系, 表明多层膜是均匀组装的; XPS结果证实了复合膜上有Pd生成, CV结果说明复合薄膜对尿酸的氧化具有较好的电催化活性, 有望用于电化学传感器.     

Urea photosynthesis inside polyelectrolyte capsules: effect of confined media

The influence of the restricted volume of poly(styrene sulfonate)/poly(allylamine hydrochloride) capsules of different size (2.2, 4.2, and 8.1 microm) on the TiO2-assisted photosynthesis of urea from inorganic precursors (CO2 and NO(3-)) in aqueous solution was demonstrated. Poly(vinyl alcohol) was employed as electron donor to facilitate the photosynthetic process. Decreasing the size of the confined microvolume of polyelectrolyte capsules accelerates the NO(3-) photoreduction, which is a limiting stage of the urea photosynthesis and, correspondingly, increases the efficiency of urea production. The highest yield of urea photosynthesis (37%) was achieved for Cu-modified TiO2 nanoparticles encapsulated inside 2.2 microm poly(styrene sulfonate)/poly(allylamine hydrochloride) capsules.     

Effect of process parameters on the polymer mediated synthesis of silica at neutral pH

We report herein the synthesis of well-defined silica structures atneutral pH and ambient conditions using poly(allylamine hydrochloride)(PAH), a cationically charged synthetic polymer, as a catalyst/template.Tetramethoxysilane (TMOS) was used as the precursor and the synthesisprocess parameters varied include TMOS pre-hydrolysis time(t_P), reaction time (t_R), buffer, molecular weightof the polymer, TMOS concentration, polymer concentration andperturbation of the reaction mixture. It was found that the TMOSpre-hydrolysis time was an important parameter governing the resultingsilica morphology along with the reaction time and the TMOSconcentration. Characterization of the silica was performed using SEM,FTIR, EDS and XRD. The poly(allylamine hydrochloride), which was thecatalyst/template, was found to be incorporated into the silicaparticles. These findings are of importance for understanding the roleof polypeptides, in nature, and macromolecules, in general, that arecapable of forming similar silica structures.     

HPLC analysis of synthetic polymers on short monolithic columns

Ultrashort monolithic columns (disks) were thoroughly studied as efficient stationary phases for precipitation–dissolution chromatography of synthetic polymers. Gradient elution mode was applied in all chromatographic runs. The mixtures of different flexible chain homopolymers, such as polystyrenes, poly(methyl methacrylates), and poly(tert‐butylmethacrylates) were separated according to their molecular weights on both commercial poly(styrene‐co‐divinylbenzene) disks (12 id × 3 mm and 5 × 5 mm) and lab‐made monolithic columns (4.6 id × 50 mm) filled with supports of different hydrophobicity. The experimental conditions were optimized to reach fast and highly efficient separation. It was observed that, similar to the separation of monoliths of other classes of (macro)molecules (proteins, DNA, oligonucleotides), the length of column did not affect the peak resolution. A comparison of the retention properties of the poly(styrene‐co‐divinylbenzene) disk‐shaped monoliths with those based on poly(lauryl methacrylate‐co‐ethylene dimethacrylate), poly(butyl methacrylate‐co‐ethylene dimethacrylate), and poly(glycidyl methacrylate‐co‐ethylene dimethacrylate) supports demonstrated the obvious effect of surface chemistry on the resolution factor. Additionally, the results of the discussed chromatographic mode on the fast determination of the molecular weights of homopolymers used in this study were compared to those established by SEC on columns packed with sorbent beads of a similar nature to the monoliths.     

Ultrasonically induced opening of polyelectrolyte microcontainers

The effect of ultrasonic treatments of different intensity and duration on the integrity and permeability of polyelectrolyte capsules was investigated both in poly(allylamine)/poly(styrene sulfonate) and Fe(3)O(4)/poly(allylamine)/poly(styrene sulfonate) polyelectrolyte capsules. Ultrasonic treatment of polyelectrolyte capsules induces the destruction of the polyelectrolyte shell and the release of the encapsulated material even at short (5 s) sonification times. The presence of magnetite nanoparticles significantly improves the efficiency of the ultrasonically stimulated release of the encapsulated compounds and enables magnetically controlled delivery to the desired site before ultrasonic treatment. Release of the encapsulated compound induced at ultrasonic power comparable to those of ultrasonic generators applied in medicine, demonstrating practical application of the ultrasonically triggered capsule opening in medicine.     

Electrostatic long-range and short-range interactions in linear poly(allylamine hydrochloride) chains

The efficiencies of two azo initiators in the polymerization of allylamine salts in water and organic solvents were compared. The hydrodynamic and molecular characteristics of poly(allylamine hydrochloride) in 0.1 M NaCl in the molecular mass range M×10^?3=18?65 were studied, and the scaling relationships were derived for the intrinsic viscosity ([η]=7.65×10^?3 M ^0.8±0.1), translational diffusion coefficient (D ₀=2.41×10^?4 M ^{?(0.59±0.05)}), and velocity sedimentation coefficient (s ₀=2.77×10^?15 M ^0.41±0.05). The hydrodynamic data were interpreted in terms of electrostatic long-range and short-range interactions. The equilibrium rigidity of poly(allylamine hydrochloride) chains in 0.1 M NaCl and its structural and electrostatic constituents were quantitatively estimated. It was shown that the conformation of poly(allylamine hydrochloride) chains in pure water is close to rodlike.