Fabrication of superhydrophilic poly(styrene-alt-maleic anhydride)/silica hybrid surfaces on poly(vinylidene fluoride) membranes

Superhydrophilic organic/inorganic hybrid surfaces have been fabricated on blend membranes of poly(vinylidene fluoride) (PVDF) and poly(styrene-alt-maleic anhydride) (SMA). The blend membranes were prepared from PVDF/SMA mixed solution with N,N-dimethylacetamide (DMAc) as solvent by immersion-precipitation phase inversion process. The gained blend membranes were immersed into γ-aminopropyltriethoxysilane (APTS) solution to generate SMA/silica hybrid surfaces by the reaction between anhydrides and APTS. The hybrid surfaces chemical compositions, morphologies and hydrophilicity were investigated in detail. It demonstrates that the hybrid surfaces possess micro-nano hierarchical structure and display superhydrophilicity property and good stability. Finally, the reaction and formation mechanism of the superhydrophilicity hybrid surface was discussed.     

Modification of poly(styrene-alt-maleic anhydride) with 1,3,4-oxadiazole units for electroluminescent devices

New copolymers of poly(styrene-alt-maleic anhydride) (PSMA) modified with 2-(4-aminophenyl)-5-(biphenyl-4-yl)-1,3,4-oxadiazole and hexylamine were prepared. The copolymers, characterized by UV-vis and FT IR spectroscopy, reached 1.22 mol % of the oxadiazole units relative to anhydride groups at the maximum (PSMA-4). Electric and optical properties of the copolymers were studied. The currents obtained depend strongly on the content of oxadiazole units in the copolymers. Currents measured in PSMA-4 were more than two orders of magnitude higher than those measured in the copolymers without oxadiazole. Using polymer blends made of poly(9,9-dihexadecylfluorene-2,7-diyl) and PSMA-4, blue light-emitting devices were fabricated and their photoluminescence and electroluminescence spectra were measured.     

Improved protein-adsorption resistance of polyethersulfone membranes via surface segregation of ultrahigh molecular weight poly(styrene-alt-maleic anhydride)

A styrene-maleic anhydride (SMA) alternating copolymer with ultrahigh molecular weight (M_w > 10⁶) synthesized in super critical carbon dioxide (SC CO₂) medium was used as hydrophilic polymeric additive in the preparation of polyethersulfone (PES) membranes. The PES/SMA blend membranes were prepared by immersion precipitation process. X-ray photoelectronic spectroscopy (XPS) measurements confirmed that the hydrolyzed SMA preferentially segregated to membrane–coagulant interface during membrane formation. For the PES/SMA blend membranes, no big change was observed in the cross-sectional structure and the mechanical properties were well maintained after SMA addition except that a thicker top layer was formed. The surface morphology analysis by atomic force microscopy (AFM) showed that the membrane surface roughness increased with the added SMA amount. The results of water contact angle, water absorbance measurements and static protein adsorption experiments revealed that the surface enrichment of SMA endowed PES/SMA blend membranes with significantly improved surface hydrophilicity and protein-adsorption resistance.     

Oligo(p-phenylene-ethynylene)s with backbone conformation controlled by competitive intramolecular hydrogen bonds

A series of conjugated oligo(p-phenylene-ethynylene) (OPE) molecules with backbone conformations (that is, the relative orientations of the contained phenylene units) controlled by competitive intramolecular hydrogen bonds to be either co-planar or random were synthesised and studied. In these oligomers, carboxylate and amido substituents were attached to alternate phenylene units in the OPE backbone. These functional groups were able to form intramolecular hydrogen bonds between neighbouring phenylene units. Thereby, all phenylene units in the backbone were confined in a co-planar conformation. This planarised structure featured a more extended effective conjugation length than that of regular OPEs with phenylene units adopting random orientation due to a low rotational-energy barrier. However, if a tri(ethylene glycol) (Tg) side chain was appended to the amido group, it enabled another type of intramolecular hydrogen bond, formed by the Tg chain folding back and the contained ether oxygen atom competing with the ester carbonyl group as the hydrogen-bond acceptor. The outcome of this competition was proven to depend on the length of the alkylene linker joining the ether oxygen atom to the amido group. Specifically, if the Tg chain folded back to form a five-membered cyclic structure, this hydrogen-bonding motif was sufficiently robust to overrule the hydrogen bonds between adjacent phenylene units. Consequently, the oligomers assumed non-planar conformations. However, if the side chain formed a six-membered ring by hydrogen bonding with the amido NH group, such a motif was much less stable and yielded in the competition with the ester carbonyl group from the adjacent phenylene unit. Thus, the hydrogen bonds between the phenylene units remained, and the co-planar conformation was manifested. In our system, the hydrogen bonds formed by the back-folded Tg chain and amido NH group relied on a single oxygen atom as the hydrogen-bond acceptor. The additional oxygen atoms in the Tg chain made a negligible contribution. A bifurcated hydrogen-bond motif was unimportant. From our results, in combination with the results from an independent study by Meijer et al., it is evident that intramolecular hydrogen bonds involving back-folded oligo(ethylene glycol) moieties may differ in their structural details. Absorption spectroscopy served as a convenient yet sensitive technique for analysing hydrogen-bonding motifs in our study.     

A novel covalent functionalisation of poly (styrene-alt-maleic anhydride) with 4-amino benzo-9-crown-3 ether

The grafting of 4-amino benzo-9-crown-3 ether to poly (styrene-alt-maleic anhydride) has been described. The covalent grafting of crown ether has led to a considerable increase in the solubility of polymer in organic solvents such as dimethyl sulphoxide, dimethylformamide and tetrahydrofuran. The highest solubility was attained in DMF and DMSO. The covalently bonded 4-benzo-9-crown-3 ether allowed the hosting of Li⁺. The covalently grafted crown ether to polymer was identified by infrared spectroscopy and thermogravimetric analysis methods.     

(1-Naphthyl)(trifluoromethyl) O-carboxy anhydride as a chiral derivatizing agent: eclipsed conformation enforced by hydrogen bonding

The preparation of the (1-naphthyl)(trifluoromethyl) O-carboxy-anhydride 1 and its use as a chiral derivatizing agent with several alpha-chiral primary amines are reported. The very large Delta delta(RS) values observed in (1)H NMR have been correlated with a marked preference of the corresponding alpha-hydroxy-amides for the eclipsed conformation. In comparison, the related O-methylated amides are shown to adopt staggered conformations, which substantiates the critical role of intramolecular hydrogen bonding in maximizing the anisotropic effect.     

Destruction of hydrogen bonds of poly(N-isopropylacrylamide) aqueous solution by trimethylamine N-oxide

Trimethylamine N-oxide (TMAO) is a compatible or protective osmolyte that stabilizes the protein native structure through non-bonding mechanism between TMAO and hydration surface of protein. However, we have shown here first time the direct binding mechanism for naturally occurring osmolyte TMAO with hydration structure of poly(N-isopropylacrylamide) (PNIPAM), an isomer of polyleucine, and subsequent aggregation of PNIPAM. The influence of TMAO on lower critical solution temperature (LCST) of PNIPAM was investigated as a function of TMAO concentration at different temperatures by fluorescence spectroscopy, viscosity (η), multi angle dynamic light scattering, zeta potential, and Fourier transform infrared (FTIR) spectroscopy measurements. To address some of the basis for further analysis of FTIR spectra of PNIPAM, we have also measured FTIR spectra for the monomer of N-isopropylacrylamide (NIPAM) in deuterium oxide (D(2)O) as a function of TMAO concentration. Our experimental results purportedly elucidate that the LCST values decrease with increasing TMAO concentration, which is mainly contributing to the direct hydrogen bonding of TMAO with the water molecules that are bound to the amide (-CONH) functional groups of the PNIPAM. We believed that the present work may act as a ladder to reach the heights of understanding of molecular mechanism between TMAO and macromolecule.     

Thermoresponsive nanostructures by self-assembly of a poly(N-isopropylacrylamide)-lipid conjugate

The synthesis and purification of a poly(N-isopropylacrylamide)-lipid conjugate and its use in the preparation of a thermoresponsive lipid mesophase is described. Specifically, poly(N-isopropylacrylamide) with a single carboxyl group at one end was activated with dicyclohexylcarbodiimide/N-hydroxysuccinimide to form an active ester. This N-hydroxysuccinimide ester was then used to form a dimyristoyl-sn-glycero-3-phosphoethanolamine conjugate with poly(N-isopropylacrylamide) via an amide bond, rendering the conjugate amphiphilic. Quaternary phases comprising the conjugate, a phosopholipid, dimyristoylphosphatidylcholine, and a cosurfactant, N,N-dimethyldodecylamine-N-oxide, dispersed in water were found to self-assemble at room temperature to form liquid crystalline gels, adopting an expanded lamellar structure. A modest increase in temperature triggered the reversible conversion of the aggregate to a collapsed lamellar structure, while a modest reduction in temperature resulted in its conversion to a nonlamellar phase. The phases were characterized by polarized optical microscopy and small-angle X-ray scattering (SAXS).     

Anion-dependent self-assembly of silver(I) and diaminotriazines to coordination polymers: non-covalent bonds and role interchange between silver and hydrogen bonds

New coordination polymers have been obtained by the self-assembly of silver salts AgX (X = BF 4, PF 6, CF 3SO 3) and 2,4-diamino-6-R-1,3,5-triazines L (R = phenyl and p-tolyl) of formulas AgLX ( 1- 6). A complex of different stoichiometry, [Ag 3L 2(H 2O)(acetone) 2](BF 4) 3, 7 (R = phenyl), has also been synthesized. The three-dimensional structures of five compounds have been determined by X-ray diffraction studies. For the AgLX complexes, when X = BF 4 and R = phenyl or p-tolyl, chiral chains with alternating Ag and L are formed. The chains are cross-linked by the counteranions in a three-dimensional fashion through hydrogen bonds and weak Ag...F interactions giving rise to a structure with solvent-filled channels. Different and more compact structures have been found when the counteranion is CF 3SO 3 (OTf). When R = phenyl, sheets are formed which consist of [Ag 2(OTf) 2L 2] units with double triflate bridges and which contain columns of pi-pi stacked arenes. Hydrogen bonds connect the sheets. When AgOTf is used and R is p-tolyl, a different and unusual ladderlike structure is obtained in which the rungs are double asymmetric bridges consisting of the triflate groups bonded to Ag in kappa (2) O,mu 2- O and kappa (1) O,mu 2- O fashion. The ladders are parallel to each other and are mutually linked by N-H...N hydrogen bonds to give a 3D architecture. A very similar ladderlike structure has been found for 7 but with a water molecule and a BF 4 (-) group acting as bridges. The role played by the hydrogen bonds in complex 6 to form the 3-D structure is played in 7 by [Ag(acetone) 2] fragments. The noncovalent interactions play an important role in the different solid-state 3D structures. The behavior of the new derivatives in solution has also been analyzed. A new species has been detected at low temperatures, and this exhibits restricted rotation of the phenyl ring.     

Collapsed conformation of poly(methacrylic acid) chain containing nonionic hydrophilic units

Copolymers of methacrylic acid (MAA) and a nonionic hydrophilic monomer N-vinylpyrrolidone (NVP) were synthesized by polymerization in aqueous solution in the absence of metal ions. The NVP content of the copolymers ranged from 2 to 36 mole % with sequences of MAA interrupted at random by a single unit of NVP at all compositions. The pH-induced conformational transition of these copolymers was followed by potentiometric titration and viscosity studies and the results were compared with those of pure poly(methacrylic acid) (PMAA). The negative free energy of transition from the un-ionized compact from to expanded structure showed a gradual decrease with increasing NVP content, and the collapsed conformation observable for PMAA at low degrees of ionization (0 < α < 0.3) disappeared at NVP contents greater than 15 mole%. These findings are supported by viscosity data. The results suggest that long-range methyl–methyl hydrophobic contacts still possible in higher NVP content copolymers are not sufficient to bring about the collapse of the molecule and a minimum average sequence length of about 20 MAA units is required to compact the molecule. Hydrophilic “shielding” of MAA chains by NVP segments could also partly destabilize the collapsed structure.     

Linear distortion of octahedral metal centres by multiple hydrogen bonds in modular ML(4) systems

A series of compounds of the type [M(1)(4)(H(2)O)(2)]SO(4)[middle dot]2H(2)O containing a simple urea-based pyridyl ligand have been synthesised and characterised by X-ray crystallography. The enclathrated water exists within discrete linearly stacked cavities and causes significant distortions in the M-OH(2) bonds due to the presence of a strongly hydrogen bonded water square.     

Reinforced self-assembly of hexa-peri-hexabenzocoronenes by hydrogen bonds: from microscopic aggregates to macroscopic fluorescent organogels

Hexa-peri-hexabenzocoronene derivatives (HBCs) that have hydrogen-bonding functionalities (either amido or ureido groups) adjacent to the aromatic cores have been synthesized to study the effects of intracolumnar hydrogen bonds on the self-assembly behavior of HBCs. The hydrogen bonds effectively increased the aggregation tendency of these compounds in solution. In the bulk state, the typical columnar supramolecular arrangement of HBCs was either stabilized substantially (1 a, 1 b, 2 a, and 2 b), or suppressed by dominant hydrogen-bonding interactions (3). For some of the compounds (1 a, 2 a, and 2 b), the supramolecular arrangement adopted in the liquid-crystalline state was even retained after annealing, presumably owing to the reinforcement of the pi-stacking interactions by the hydrogen bonds. Additionally, the combined effect of the hydrogen bonds and pi-stacking of the aromatic moieties led to the formation of fluorescent organogels, whereby some derivatives were further investigated as novel low molecular-mass organic gelators (LMOGs).     

支化型交替聚(苯乙烯-alt-马来酸酐)自组装胶束的制备及其乳化性能

利用支化型交替聚(苯乙烯-alt-马来酸酐)(BPSMA)在选择性溶剂DMF-H_2O中自组装制备球形胶束,以该胶束作为新型颗粒乳化剂稳定油-水体系,探讨胶束浓度和pH对BPSMA胶束乳化性能的影响。用紫外分光光度计(UV-Vis)追踪了聚合物溶液自组装过程;粒径及Zeta电位分析仪和透射电子显微镜(TEM)表征了BPSMA胶束的基本性质;利用光学显微镜分析了乳液性质,扫描电子显微镜(SEM)观察了胶束在固化后的油滴表面的形貌。结果表明:BPSMA胶束具有优异的乳化效率,在极低的质量浓度下(0.25~1.00 mg/mL)亦可长期稳定乳液;BPSMA胶束所稳定的乳液具有明显的pH响应性,当pH≤6时,胶束呈球形颗粒状吸附并稳定于油水界面,当pH6时,胶束从油水界面脱离,乳液破乳;此外,BPSMA胶束作为颗粒乳化剂还具备良好的普适性,可以长效稳定碳酸二辛脂、辛酸丙基庚酯、硅油、棕榈酸异辛酯和润肤油脂等。     

Structure of poly(maleic anhydride)

The bulk polymerization of maleic anhydride initiated with acylperoxides, di-tert-butyl peroxide, AIBN, or pyridine proceeds with evolution of CO₂. The amount of CO₂ generated depends on the nature and the concentration of the initiator. With peroxide initiators, less than 5% of the polymerized maleic anhydride is decarboxylated. ¹H-NMR spectra, obtained on the benzoyl peroxide-initiated polymer and its methyl ester, are consistent with the unrearranged poly(maleic anhydride) structure and rule out the polycyclopentanone structure proposed by Braun and co-workers. Base-initiated polymaleic anhydride is substantially decarboxylated, and the resulting polymer has anhydride and carboxyl groups. Elemental analyses and ¹H-NMR spectra obtained on the pyridine-initiated polymer and its methyl ester refute both the cis-poly(vinylene ketoanhydride) structure suggested by Schopov and the polycylopentanone structure proposed by Braun and co-workers.     

Further studies of the preferred chain conformation of crystalline poly(vinylidene chloride)

The polymer chain conformation of crystalline poly(vinylidene chloride) (PVDC) has been the subject of controversy for the past three decades. In this study, a combination of techniques has been employed in an attempt to elucidate the preferred conformation of PVDC. Conformational models containing two monomers per translational repeat distance have been considered. Calculations of the translational repeat distance and the nonbonded Cl ?Cl contact distance between two adjacent CCl₂ groups have been performed for each of the models. By comparing these results with those derived from x-ray analysis and a theoretical estimation of the minimum nonbonded Cl ?Cl contact distance, an initial judgment of the structural feasibility of the models has been gained. A symmetry analysis has been performed for each conformational model and theoretical estimations of the polarization and intensity of the C? Cl and C? H stretching vibrations have been obtained. These results have been compared with experimental infrared and Raman spectra. It is concluded that a TXTX′ (where X and X′ are torsional angles of equal value but opposite sign) chain-conformational model for PVDC is favored.     

IR investigation of hydrogen bonds in weakly hydrated films of poly(vinyl alcohol)

A system of hydrogen bonds in weakly hydrated PVA films containing up to ≤8.5 wt % water is investigated via IR spectroscopy. It is shown that water molecules bind to only part of the hydroxyl groups of the polymer that are available for hydration and form the first hydrating layer. In a completely dehydrated film, practically every hydroxyl group of PVA forms hydrogen bonds with two other hydroxyl groups and serves as both a proton donor and a proton acceptor. In the hydrated film, one to three water molecules directly bind with one hydroxyl group of PVA.     

Removal of Heavy Metal Ions from Aqueous Solutions Using Modified Poly(styrene-alt-maleic anhydride) Copolymer as a Chelating Resin

Russian Journal of Applied Chemistry - the work, 3-(4-hydroxy phenyl)cyclopropane-1,1,2,2-tetramethyleneamine (HPCA) was synthesized. Poly(styrene-maleic anhydride) (SMA) copolymer was modified...     

Infrared spectroscopic study of stereo-controlled poly(N-isopropylacrylamide) with an extended chain conformation induced by adsorption on a gold surface

Poly(N-isopropylacrylamide) (PNiPAM) compounds with various diad tacticities were prepared, and the molecular interaction properties in a thin film deposited on a gold surface were analyzed using infrared spectroscopy. The intramolecular and intermolecular interactions were found to depend on the tacticity, and only atactic (diad ratio 46 %) PNiPAM exhibits poor molecular interaction even in the bulk sample. On the other hand, the same series of compounds dissolved in an acetone solution were spread on a gold surface to form a thin film. In the dissolution process, the polymer molecules are relaxed via solvation, and they are bound to the gold surface by a molecular interaction to form a submonolayer thin film. In the thin film, the molecular interaction with the gold surface via the N–H group was monitored in the infrared spectra only for a nearly isotactic (m?=?90) PNiPAM by an apparent shift of the N–H stretching vibration band. This shift was confirmed by changing the degree of hydrophilicity of the gold surface: a larger shift is found on a gold surface with stronger hydrophilicity. As a result, the conformation of a nearly isotactic molecule is found to be extended by the interaction with the gold surface, which works to immobilize the molecule.