Novel azobenzene polyelectrolytes have been used to fabricate biocompatible self-assembled multilayer (SAMU) thin films of variable absorbance, thickness, organization, and morphology. The prepared SAMU films are useful for directed cell growth, and this application relies directly on control of contact and surface energy, and requires the ability to tune the surface characteristics which are critical to their development. The azo polyelectrolytes employed here were similar in their degree of polymerization and repeat unit composition of acrylic acid monomer and azo monomers, and only differ from each other due to the presence of different substituted head R-groups present on the p-position of the aromatic ring of the azo chromophores. Possession of characteristics of both the self-assembly due to acrylic acid groups, and photoswitchability of the azo monomer enable the azobenzene functionalized polyelectrolytes to exhibit novel photo-reversible applications. The azo polyelectrolytes with the substituted R-group pairs of shorter-ionized hydrophilic COOH and SO3H, shorter-non-ionized hydrophobic H and OC2H5, and larger-nonionized hydrophobic octyl C8H17 and C8F17 were used as polyanions and counter charge PDAC used as polycation to fabricate the layer-by-layer SAMU films onto glass and silicon substrates. The fabricated SAMU films were also characterized by various techniques. The UV absorption maxima, λmaxp of the SAMU films move to lower wavelength relative to solution to exhibit a blue shift for the hydrophobic R-groups, while this behaviour was not observed for the hydrophilic R-groups. Similarly, the thickness, organization, morphology and other properties of the thin films were found to be dependent on the type of substituted R-groups of the azo polyelectrolytes due to the inter-related factors of ionization, hydrophobicity/hydrophilicity, solubility, and aggregation of azo PEL in the dipping solutions used for fabrication of the SAMU films. Understanding and controlling the adsorption characteristics of azo multilayer thin–film of switchable functionalities are vital to explore their potential for the development and application of new devices in diverse areas of biosensor, drug delivery systems, on-chip microscale chemical process and microfluidics systems. 相似文献
A novel set of light-responsive polyelectrolytes has been developed and studied, to control and tune surface wettability by introducing various types of substituted R head-groups of azo polyelectrolytes in self-assembled multilayer (SAMU) films. As part of a larger project to develop polymer surfaces where one can exert precise control over properties important to proteins and cells in contact, photo-reversibly, we describe here how one can tune quite reliably the contact angle of a biocompatible SAMU, containing a photo-reversible azo chromophore for eventual directed cell growth. The azo polyelectrolytes described here have different substituted R head-group pairs of shorter-ionized hydrophilic COOH and SO3H, shorter non-ionized hydrophobic H and OC2H5, and larger non-ionized hydrophobic octyl C8H17 and C8F17, and were employed as polyanions to fabricate the SAMU onto silicon substrates by using the counter-charge polycation PDAC. The prepared SAMU films were primarily characterized by measurement of their contact angles with water. The surface wetting properties of the thin films were found to be dependent on the type of substituted R-groups of the azo polyelectrolytes through their degree of ionization, size, hydrophobicity/hydrophilicity, solubility, conformation, and inter-polymeric association and intra-polymeric aggregation. All these factors appeared to be inter-related, and influenced variations in hydrophobic/hydrophilic character to different extents of aggregates/non-aggregates in solution because of solvation effects of the azo polyanions, and were thus manifested when adsorbed as thin films via the SAMU deposition process. For example, one interesting observation is significantly higher contact angles of 79° for SAMU films of larger octyl R groups of PAPEA-C8F17 and PAPEA-C8H17 than for others with contact angles of 64° observed for non-polar R-groups of OC2H5 and H. Furthermore, lower contact angle values of 59° for SAMU films with polar R-groups of COOH and SO3H relative to that of non-polar R-groups are in accordance with their expected order of the hydrophilicity or hydrophobicity. It is possible that the large octyl groups are more effective in shielding the ionic functional groups on the substrate surface, and contributed less to the water drop-molecule interactions with ionic groups of the PDAC and/or AA groups. In addition, higher hydrophobicity of the SAMU films may be due to the incorporation of bulky and hydrophobic groups in these polyelectrolytes, which can produce aggregates on the surfaces of the SAMU films. Through understanding and controlling the complex aggregation behavior of the different substituted R-groups of these azo polyelectrolytes, and hence their adsorption on substrates, it appears possible to finely tune the surface energy of these biocompatible films over a wide range, enhance the photo-switching capabilities of the SAMU films, and tailor other surface properties for the development and application of new devices in diverse areas of microfluidics, specialty coatings, sensors, and biomedical sciences. 相似文献
The synthesis of cationic cyclopentadienyliron-containing polymers with pendent azobenzene chromophores was accomplished via metal-mediated nucleophilic aromatic substitution reactions. All of the desired polymers were isolated as vibrantly coloured materials and displayed excellent solubility in polar aprotic solvents. Cationic and neutral cyclopentadienyliron polymers incorporating azo dyes in the backbone were also prepared. Reactions of azo dyes with dichlorobenzene complexes allowed for the isolation of cationic cyclopentdienyliron (CpFe+) complexes with azo dye chromophores. These complexes were then reacted with 1,1′-ferrocenedicarbonyl chloride to produce the trimetallic monomers with terminal chloro groups. These monomers contained two pendent CpFe+ cations and a neutral iron moiety in the backbone. Nucleophilic substitution reactions of these monomers with oxygen and sulfur containing dinucleophiles gave rise to a new class of polymeric materials. The pendent CpFe+ moieties could also be cleaved from the polymer backbones using photolysis to afford novel ferrocene based polymers. The UV-vis spectra of the organoiron monomers and polymers display similar wavelength maxima however incorporating azobenzene chromophores with electron-withdrawing substituent into the polymer chains resulted in bathochromic shifts of the λmax values. 相似文献
The formation of cyclophosphazenes containing several ligands or substituent groups gives rise to an attractive derivative set, for development of novel applications, with variable properties. Here, it is possible to unravel the role of different functional groups attached to the N3P3 backbone, to reach a better understanding of the bonding character in the cyclic [─P─N─] skeleton. We employed the extended transition state-natural orbital for the chemical valence scheme to unravel the σ and π orbital kernels that are involved in the assembling of such structures, by varying the acceptor-donor characteristics of the ─CF3, ─NO2, ─COOH, ─CN, ─NH2, ─OH, and ─OCH3 groups, where ─NO2 behaves as a stronger electron-withdrawing substituent rather than ─CF3, ─COOH, and ─CN, denoting that the nature of the ligand-phosphazene interaction contributes to some degree to the bond strength of the cyclic [─P─N─] backbone. Our results reveal that the electron-withdrawing ─NO2 group leads to higher σ and π [─P─N─] orbital-energy contributions, which is reflected in a shortening of the [─P─N─] distance, contrasting with the case of electron-donating groups such as ─NH2, ─OH, and ─OCH3 within the phosphazene set. These insights allow further variation and modulation of the bonding in the [─P─N─] ring. 相似文献
Titanium(IV) complexes of the general formula TiL(OPri)2 [where LH2 = R CH3 where R = ─C6H5, ─C6H4Cl(p)] were prepared by the interaction of titanium isopropoxide with sterically hindered Schiff bases derived from heterocyclic β -diketones in 1:1 molar ratio in dry benzene. The complexes TiL(OPri)2 were used as versatile precursors for the synthesis of other titanium(IV) complexes. Titanium(IV) complexes of the type TiLL'(OPri) (where L'H═R1R2C═NOH, R1 = R2 = ─CH3; R1 = ─CH3,R2 = ─C6H5; R1 = ─COC6H5, R2 = ─C6H5) were synthesized by the reaction of TiL(OPri)2 with ketooximes (L'H) in equimolar ratio in dry benzene. Another type of titanium(IV) complexes having the general formula TiLGH(OPri) (where GH2═HO─G─OH, G = ─CH2─CH2─) have been prepared by the reaction of TiL(OPri)2 with glycol in 1:1 molar ratio in dry benzene. Plausible structures of these new titanium(IV) complexes have been proposed on the basis of analytical data, molecular weight measurements, and spectral studies. 相似文献
N,N-Dimethylformamide (DMF)/H2O mixtures were used as solvents to fabricate azo polyelectrolyte (PEAPH)/poly(diallyldimethyl ammonium chloride)(PDAC) self-assembled
multilayers with the layer-by-layer electrostatic adsorption technique. PEAPH is a copolymer of acrylic acid and azobenzene-containing
acrylate. The effect of the ratio of DMF to water on the multilayer growth, structure and surface morphology was studied in
some details. Results show that DMF/H2O mixtures are proper media for PEAPH/PDAC multilayer fabrication. The ratio of DMF to water in the mixture has significant
influence on the multilayer structure and surface morphology. With the increase of DMF content, the multilayer thickness has
a better linear growth relationship with the bilayer number, and the multilayer surface becomes smoother. Moreover, azo chromophores
show less H-aggregation when the multilayers are fabricated from DMF/H2O mixtures with higher DMF contents. These studies demonstrate that using organic solvent and water mixtures is an effective
way to control the multilayer construction by adjusting the media properties. This method can be applied to multilayer fabrication
of other water-insoluble polyelectrolytes.
__________
Translated from Acta Polymerica Sinica, 2005, (4) (in Chinese) 相似文献
4-Vinylpyridinium trifluoromethanesulfonate monomers substituted at nitrogen with H, O, CH3, C2H5, C6H13, and C12H25 were synthesized and characterized spectroscopically. Thermal analyses (DSC and TGA) were carried out on all the compounds. The solid monomers (N? H, N? CH3, N? C6H13, and N? C12H25) exhibited endothermic melting followed by exothermic polymerization and exothermic decomposition (>400°C). Liquid N? C2H5 monomer revealed only exothermic polymerization and decomposition. The N? O polymer underwent thermal decomposition below 300°C. The N–C12H25 homopolymer, prepared from monomer in the DSC or in bulk, displayed an unusual thermal transition at 250°C, which has been attributed to a polymer backbone reorientation leading to side-chain ordering of the dodecyl groups. 相似文献
2,6‐Diaminopyridine (26‐DAP, C5H7N3) is a common intermediate in the synthesis of aromatic azo chromophores, which are widespread in the dyes and pigments industry. Sublimation of commercial 26‐DAP powder yielded a new polymorph, denoted Form II, which grew as colorless orthorhombic needles. Recrystallization from acetone or toluene also yielded Form II as the major phase. Thermal analysis shows that Form II is a less stable polymorph and it converts upon heating at 335 K to the previously reported Form I. 相似文献
Crystals of the title compound, [Zn(C45H28N4O2)(H2O)]·2C6H5NO2, consist of multiporphyrin supramolecular assemblies sustained by intermolecular COOH⋯COOH and Zn(H2O)⋯COOH hydrogen bonds. One of the two nitrobenzene solvent molecules hydrogen bonds peripherally to these arrays. 相似文献
Several kinds of novel azobenzene-containing polyelectrolytes with special molecular design have been developedfrom acryloyl chloride or epoxy based precursor polymers. The acryloyl chloride based precursor polymer, poly(acryloylchloride), was prepared by free radical polymerization of acryloyl chloride. The azo polyelectrolytes were prepared by anesterification reaction between the precursor polymer and corresponding azo chromophores containing a reactive hydroxylgroup, followed by hydrolysis of the unreacted acyl chloride groups. The epoxy based precursor polymer was prepared by thereaction between 1,4-cyclohexanedimethanol diglycidyl ether and aniline, and postfunctionalized by azo coupling reaction toform azo polymers containing chromophores with ionizable groups. The polyelectrolytes were characterized by elementalanalysis, ~1H-NMR, IR and UV-Vis spectroscopy. The photodynamic and photoresponsive properties, as well as self-assemblyof these azo polyelectrolytes are reported in this paperp. 相似文献
Azophenols with various substituents at the para position of the phenyl ring were enzymatically polymerized in the presence of H2O2. Structural characterization of the synthesized polymers by FTIR, FT-Raman, and NMR (1H and 13C) spectroscopy confirms our previous observation that this enzymatically catalyzed coupling reaction occurs primarily at the ortho positions, with some substitution at the meta position of the phenol ring. The strong constraint and poor packing of the azobenzene chromophores in the polymer leads to a significant blue shift of the π-π* transition absorption and slow photoisomerization and thermal relaxation in comparison to the monomers. Surface relief gratings (SRG) with large surface modulation have been fabricated on these enzymatically synthesized polymer films. 相似文献
In this work,surface-relief-grating formation behavior was studied by using two hyperbranched azo polymers.The hyperbranched polymers containing pseudo-stilbene type azo chromophores throughout the hyperbranched structure were synthesized by step-growth polycondensation of AB2 type monomers.The AB2 monomer,4-(4’-(bis(2-chloroethyl)amino)-phenylazo) benzoic acid(BAA),was prepared through azo-coupling reaction between N,N’-bis(2-chloroethyl)aniline and 4- aminobenzenic acid.The another AB2 monomer,4-(4’-(bis(2-chloroethyl)amino)phenylazo)-3-nitro-benzoic acid(BANA), was prepared through azo-coupling reaction between N,N-bis(2-chloroethyl)aniline and 3-nitro-4-aminobenzcnic acid.The hyperbranched polymers(PBAA and PBANA) were prepared through nucleophilic substitution reaction of BAA and BANA, respectively.The polymers synthesized were characterized by using spectroscopic methods and thermal analysis.The photoinduced dichroism and photo-induced surface-relief-grating(SRG) formation of the hyperbranched polymers were investigated upon irradiation with Ar+ laser at 488 nm.PBAA shows typical photoinduced dichroism SRG formation behavior.On the contrary,PBANA does not show the photoresponsive properties.The results indicate that the nitro at the ortho position of azo group of PBANA shows the effect of inhibiting the photoinduced variations.The effect can be attributed to the blockage of the trans-cis isomerization of the azobenzene moieties by the steric hindrance. 相似文献
Summary: A new class of macromolecules containing neutral and cationic organoiron moieties with arylazo chromophores in their backbones has been prepared. Photolysis of these polymers resulted in the removal of the cationic iron moieties leading to new polyferrocenes with azo dyes in their backbones. UV-vis studies showed λmax around 419 nm in DMF with a bathochromic shift to around 530 nm upon the addition of HCl.
Organoiron macromolecules containing azo dye moieties prepared in this study. 相似文献
By using the copolymerizations of N-methyl-N-phenyl-2-aminoethyl methacrylate (I) and 4-dimethylaminostyrene (II) with styrene initiated with 2,2′-azoisobutyronitrile (AIBN) and with CCl3COOH, the copolymerization parameters and Alfrey-Price copolymerization constants e and Q were determined for I and II. The only product of polymerizations initiated with CCl3COOH and CH3COOH in mixtures of II with vinyl monomers was a homopolymer of II. The order of homopolymerization of II in benzene initiated with CCl3COOH at 50° was 0.99 with respect to [II] and 1.10 with respect to [CCl3COOH]; the temperature dependence of homopolymerization in the range 25–40° was 63 ± 5 kJ mol?1. The rate of homopolymerization of II in solution in C6H6 at 50° was virtually unaffected by inhibitors. In the polymerization initiated with carboxylic acids, the radical character of propagation centres was proved for I, but not for II. 相似文献