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101.
A series of tail-type cationic surface-active monomers with the cationic charge at the -end (1; ST-Cm-AB, m=5, 7, and 9, where ST is a styrenic group, Cm the alkylene chain at the 4-position of styrene, and AB is alkyltrimethylammonium bromide) have been synthesized as a novel cationic polymerizable surfactant. Their fundamental physicochemical properties such as critical micelle concentration (cmc) and weight-average aggregation number of the micelle (Nw(agg)) have been characterized in water at 25 °C by static light-scattering measurements. The cmc values determined for the tail-type surfactant monomers are two-orders of magnitude smaller than those of the corresponding head-type cationic surfactant monomers (2; ST-C1-AC-Cm). The Nw(agg) of ST-Cm-AB is 68 for m=5, 156 for m=7, and 413 for m=9. Free-radical homopolymerization of ST-C7-AB proceeds very rapidly in water as a result of organization in the micelle to afford the corresponding amphiphilic cationic polyelectrolyte with Mw=3.63×106 and 23 nm hydrodynamic radius at 25 °C. Emulsion copolymerization of styrene with ST-Cm-AB also proceeds rapidly to afford very stable cationic polystyrene latex particles of 30–60 nm diameter. The amphiphilic cationic polyelectrolyte of poly(ST-C7-AB) is likely to assume a compact conformation with high segment density in 0.1 mol L–1 NaCl in water. Addition of hydrophobic aromatic counter-anions with an weak acid group, for example potassium hydrogen phthalate (PHK) and sodium salicylate, to a salt-free aqueous solution of poly(ST-C7-AB) induces intermolecular aggregation and increases the solution viscosity substantially, often producing gels and precipitation at high polymer concentration. 相似文献
102.
C.?L.?de?Vasconcelos T.?N.?C.?Dantas M.?R.?Pereira J.?L.?C.?FonsecaEmail author 《Colloid and polymer science》2004,282(6):596-601
Rheological properties of concentrated alumina suspensions using a charged copolymer as the dispersant have been studied. The non-Newtonian behavior of these fluids was characterized and correlated to potential measurements and sedimentation column data, obtained with these dispersions. As a result, a clear relationship between dispersion stability and pseudoplastic/dilatant rheological behavior was established. 相似文献
103.
The binding interaction of the cationic surfactant cetyltrimethylammonium bromide (CTAB) and anionic poly(2-(acrylamido)-2-methylpropanesulfonic
acid) (PAMPS) in dilute aqueous solutions was studied using the excimer fluorescent emission of the cationic probe 1-pyrenemethylamine
hydrochloride (PyMeA·HCl). In the absence of CTAB, the saturation binding of PyMeAH+ on PAMPS is about 2.4 AMPS repeat units for one probe cation as determined by the relative emission intensity, I
E/I
M, of the excimer to monomer. With increasing CTAB concentration, I
E/I
M firstly increases, reaches a maximum, then decreases to zero. The I
E/I
M maximum indicates a critical aggregation concentration (cac) of 10−5 mol/l for CTAB in PAMPS solutions. The CTAB concentration at which I
E/I
M is zero is exactly equal to the PAMPS concentration, indicating that the probe cation is thoroughly excluded from the binding
site of PAMPS by the CTAB cation and the equivalent stoichiometric aggregation is formed between CTAB and PAMPS. The blueshift
of the excimer emission and the excitation spectra shows that the decrease of I
E/I
M with increasing CTAB concentration above the cac is caused mainly by the decrease of the static excimer.
Received: 26 July 2000 Accepted: 23 November 2000 相似文献
104.
Decher等提出的阴阳聚电解质层层组装膜技术(LbL),方便快捷,结构有序,其纳米级可控,可用于生物传感器、杂多酸多层膜修饰电极及天然多糖类功能膜等领域.LbL膜的厚度直接影响其性能,而膜厚度与紫外吸光度(A)成正比.故A是通常用于评价膜厚度的一种简便方法.紫外吸光度与聚电解质溶液浓度(cp)往往呈递增关系,随着溶液中cp的增大,单位面积上吸附聚电解质的量也增加。 相似文献
105.
106.
Terhi HirvikorpiMika Vähä-Nissi Ali HarlinMikko Salomäki Sami ArevaJuuso T. Korhonen Maarit Karppinen 《Applied Surface Science》2011,257(22):9451-9454
Commercial polylactide (PLA) films are coated with a thin (20 nm) non-toxic polyelectrolyte multilayer (PEM) film made from sodium alginate and chitosan and additionally with a 25-nm thick atomic layer deposited (ALD) Al2O3 layer. The double-coating of PEM + Al2O3 is found to significantly enhance the water vapor barrier properties of the PLA film. The improvement is essentially larger compared with the case the PLA film being just coated with an ALD-grown Al2O3 layer. The enhanced water vapor barrier characteristics of the PEM + Al2O3 double-coated PLA films are attributed to the increased hydrophobicity of the surface of these films. 相似文献
107.
《Ultrasonics sonochemistry》2014,21(1):43-49
An efficient cold-mechanical/sonic-assisted extraction technique was developed for extraction of genipin from genipap (Genipa americana) peel. Ultrasound assisted extraction (285 W, 24 kHz) was performed at 5, 10 and 15 °C for 5, 10 and 15 min. After cold-extraction, genipin was separated from pectin and proteins by aid of fungal pectinesterase. The maximum yield of non-cross-linked genipin was 7.85 ± 0.33 mg/g, at 10 °C for 15 min by means of ultrasound extraction. The protein amount in extracts decreased in all samples. If mechanical process is combined with ultrasound assisted extraction the yield is increased by 8 times after the pectinesterase-assisted polyelectrolyte complex formation between pectic polysaccharides and proteins, avoiding the typical cross-linking of genipin. This novel process is viable to obtain non-cross-linked genipin, to be used as a natural colorant and cross-linker in the food and biotechnological industries. 相似文献
108.
Redox ions are deposited on a polyelectrolyte‐coated gold electrode by an electric field to fabricate an ion‐selective thin film electrode. The Fe(CN)${{{4- \hfill \atop 6\hfill}}}$ ions are deposited on a few monolayer‐coated polyelectrolyte gold electrode by a slow periodic potential cycle. The deposition process and electrode properties are quantitatively and simultaneously monitored by cyclic voltammetry and a novel technique, using a Scanning Electrometer for Electrical Double‐layers (SEED). No redox properties are obtained without the electric‐field‐deposition. Owing to the redox mediation and net charge due to the redox ion, the electrode is ion‐selective. We demonstrate the principle to detect 1 µM of dopamine in a mixture with 1 mM of ascorbic acid. 相似文献
109.
In this study we present results of the conductivity and resistance to thermooxidative and condensation reactions of a highly phosphonated poly(pentafluorostyrene) (PWN2010) and of its blends with poly(benzimidazole)s (PBI). This polymer, which combines both: (i) a high degree of phosphonation (above 90%) and (ii) a relatively high acidity (pKa (–PO3H2 ↔ –PO3H−) ∼ 0.5) due to the fluorine neighbors, is designed for low humidity operating fuel cell. This was confirmed by the conductivity measurements for PWN2010 reaching σ = 5 × 10−4 S cm−1 at 150 °C in dry N2 and σ = 1 × 10−3 S cm−1 at 150 °C (λ = 0.75). Furthermore, this polymer showed only 48% of anhydride formation when annealing it at T = 250 °C for 5 h and only 2% weight loss during a 96 h Fenton test. These properties combined with the ability of the PWN2010 to form homogeneous blends with polybenzimidazoles resulting in stable and flexible polymer films, makes PWN2010 a very promising candidate as a polymer electrolyte for intermediate- and high-temperature fuel cell applications. 相似文献
110.
The preparation, characterization and conductivities of poly(2vinylpyridine), P-2VP and its fluoride derivative are reported here. The polymer P-2VP was prepared by thermal polymerization of 2vinylpyridine, 2VP and its salt, by acidification with HF. The formation of P-2VP salt was confirmed by IR and 1H NMR techniques. Conductivities were determined from 30 to 110 °C in solid state. The addition of F− ion increases the ionic conductivity of the polymer dramatically. The P-2VP-HF behaves as an intrinsic conducting polymer. The determination of the molecular mass of P-2VP and P-2VP-HF indicated that 95% of pyridine molecule was hydrofluorinated. 相似文献