Facile fabrication of large area of aggregated gold nanorods film for efficient surface-enhanced Raman scattering

An effective and facile method for fabrication of large area of aggregated gold nanorods (AuNRs) film was proposed by self-assembly of AuNRs at a toluene/water interface for the first time. It was found that large area of aggregated AuNRs film could be formed at the interface of toluene and water due to the interfacial tension between the two phases. The obtained large area of aggregated AuNRs film exhibits strong surface-enhanced Raman scattering (SERS) activity with 4-aminothiophenol (4-ATP) and 2-aminothiophenol (2-ATP) as the probe molecules based on the strong electromagnetic coupling effect between the very adjacent AuNRs.

Reversed micelle formation in a model liquid-liquid extraction system

The formation of reversed micelles and the roles of extractant and extracted complexes were investigated in the Cyanex923/n-heptane/H2SO4 system. Interfacial tension (gamma), electrical conductivity (kappa), and water content measurements showed that Cyanex923 had a tendency to self-assemble, forming reversed micelles. The changes in electrical conductivity with concentration of H2SO4 in the organic phase (CH2SO4,(0)) exhibited an S-type curve: a correlation was found between the change in electrical conductivity and the water content as a function of CH2SO4,(0),.

Reactive compatibilization of LLDPE/PS blends with a new type of Lewis acid as catalyst

The reactive compatibilization of LLDPE/PS (50/50 wt%) was achieved by Friedel-Crafts alkylation reaction with a combined Lewis acids (Me3SiCl and InCl3 center dot 4H(2)O) as catalyst. The graft copolymer at the interface was characterized by Fourier transform infrared spectroscopy and the morphology of the blends was analysized by scanning electron microscopy. It was found that the combined Lewis acids had catalytic effect on Friedel-Crafts alkylation reaction between LLDPE and PS, and the catalytic effect was maximal when the molar ratio of InCl3 center dot 4H(2)O to Me3SiCl was 1:5. The graft copolymer LLDPE-g-PS was formed via the F-C reaction and worked as a tailor-made compatibilizer to reduce the interfacial tension. The mechanical properties of reactive blend with combined Lewis acids as catalyst was notably improved compared to that of physical LLDPE/PS blend and serious degradation had been decreased compared to the reactive blend system with AlCl3 as catalyst; we interpreted the above results in term of acidity of combined Lewis acids.

Online study of the formation of PA6 droplets in PP matrix under shear flow

Breakup process of polyamide 6 (PA6) in polypropylene (PP) matrix under shear flow was online studied by using a Linkam CSS 450 stage equipped with optical microscopy. Both tip streaming and fracture breakup modes of PA6 droplets were observed in this study. It was reported that the droplet would break up by tip streaming model when the radio of the droplet phase viscosity to the matrix phase viscosity (n(r) = n(d)/n(m)) is smaller than 0.1 (Taylor, Proc R Soc London A 1934, 146, 501; Grace, Chem Eng Commun 1982, 14, 225; Bartok and Mason, J Colloid Sci 1959, 14, 13; Rumscheidt and Mason, J Colloid Sci 1961, 16, 238; de Bruijn, Chem Eng Sci 1993, 48, 277). However, the tip streaming model was observed even when the viscosity ratio was much greater than 0.1 (n(r) = 1.9). In this study for the tip streaming mode, small droplets were ruptured from the tip of the mother droplet. On the other hand, the mother droplet was broken into two or more daughter droplets with one or several satellite droplets between them for the fracture mode. It was found that PA6 droplet was much elongated at first, and then broke up via tip streaming or fracture to form daughter droplets or small satellite droplets with the shape of fiber or ellipse.

Reactive blending of modified polypropylene and polyamide 12: Effects of compatibilizer content on crystallization and blend morphology

The crystallization behavior and morphology of nonreactive and reactive melt-mixed blends of polypropylene (PP) and polyamide (PA12; as the dispersed phase) were investigated. It Was found that the crystallization behavior and the size of the PA12 particles were dependent on the content of the compatibilizer (maleic anhydride-modified polypropylene) because an in situ reaction occurred between the maleic anhydride groups of the compatibilizer and the amide end groups of PA12. When the amount of compatibilizer was more than 4%, the PA12 did not crystallize at temperatures typical for bulk crystallization. These finely dispersed PA12 particles crystallized co-incidently with the 1313 phase. The changes in domain size with compatibilizer content were consistent with Wu's theory. These investigations showed that crystallization of the dispersed phase Could not be explained solely by the size of the dispersion. The interfacial tension between the polymeric components in the blends may yield information on the fractionation of crystallization.

Surface morphology control of immiscible polymer-blend thin films

The effects of the molecular weights (molecular weight of polystyrene, M-w,M-PS, varying from 2.9 to 129 k) on the surface morphologies of spin-coated and annealed polystyrene/poly (methyl methacrylate) (PS/PMMA = 50/50, w/w) blend films were investigated by atomic force microscopy and X-ray photoelectron spectroscopy. For the spin-coated films, when the M-w,M-PS varied from 2.9 to 129 k, three different kinds of surface morphologies (a nanophase-separated morphology, a PMMA cellular or network-like morphology whose meshes filled with PS, a sea-island like morphology) were observed and their formation mechanisms are discussed, respectively. Upon annealing, two different morphology-evolution processes were observed. It is found that a upper PS-rich phase layer is formed when M-w,M-PS < 4 k, and this behavior is mainly attributed to the low interfacial tension between PS and PMMA component. When M-w,M-PS > 4 k, the PS-rich phase forms droplets on top of the PMMA-rich phase layer which wets the SiOx substrate. These results indicate that the surface morphology of the polymer blend films can be controlled by the polymer molecular weight and annealing conditions.

Rheology and morphology of reactively compatibilized PP/PA6 blends

This work aims to use the Palierne emulsion type model to describe the relationship between the rheological response to small amplitude oscillatory deformation and morphology of polypropylene/polyamide 6 (PP/PA6) blends compatibilized with maleic anhydride grafted polypropylene (PP-g-MAH). It was found that the Palierne emulsion type model could describe very well the linear viscoelastic responses of binary uncompatibilized PP/PA6 blends and failed to describe the ternary compatibilized PP/PP-g-MAH/PA6 blends. These features could be attributed to the fact that the morphology of the ternary blends was not of the emulsion type with the PA6 particles dispersed in the PP matrix but of an emulsion-in-emulsion type, i.e., PA6 particles dispersed in the PP matrix themselves contained PP or PP-g-MAH inclusions. By consideration of PP-in-PA6 particles as pure PA6 particles, where the volume fraction of the PA6 phase was increased accordingly, the Palierne emulsion type model could work very well for a ternary blending system. Preshear at low frequencies modified the morphology of both binary and ternary blends. The particles of the dispersed phase (PA6) became more uniform. These results suggested that the Palierne emulsion type model could be used to extract information on rheological properties and interfacial tension of polymer blends from known morphology and vice versa.

Thermally crosslinkable poly(phenylene sulfide)/poly (ether sulfone)/polymerization of monomer reactant-polyimide blends

The effects of thermally crosslinkable polymerization of monomer reactant-polyimide (POI) on the miscibility, morphology, and crystallization of partially miscible poly(ether sulfone) (PES)/poly(phenylene sulfide) (PPS) blends were investigated with differential scanning calorimetry and scanning electron microscopy. The addition of POI led to a significant reduction in the size of PPS particles, and the interfacial tension between PPS and crosslinked POI was smaller than that between PES and crosslinked POI. During melt blending, crosslinking and grafting reactions of POI with PES and PPS homopolymers were detected; however, the reaction activity of POI with PPS was much higher than that with PES. The crosslinking and grafting reactions were developed further when blends were annealed at higher temperatures. Moreover, POI was an effective nucleation agent of the crystallization of PPS, but crosslinking and grafting hindered the crystallization of PPS. The final effect of POI on the crystallinity of the PPS phase was determined by competition between the two contradictory factors. The crosslinking and grafting reactions between the two components was controlled by the dosage of POI in the blends, the premixing sequence of POI with the two components, the annealing time, and the temperature.

Morphology, crystallization behaviors, and mechanical properties of PA1010/HIPS and PA1010/HIPS-g-MA blends

The binary blends of polyamide 1010 (PA1010) with the high-impact polystyrene (HIPS)/maleic anhydride (MA) graft copolymer (HIPS-g-MA) and with HIPS were prepared using a wide composition range. Different blend morphologies were observed by scanning electron microscopy according to the nature and content of PA1010 used. Compared with the PA1010/HIPS binary blends, the domain sizes of dispersed-phase particles in PA1010/HIPS-g-MA blends were much smaller than that in PA1010/HIPS blends at the same compositions. It was found that the tensile properties of PA1010/HIPS-g-MA blends were obviously better than that of PA 1010/HIPS blends. Wide-angle xray diffraction analyses were performed to confirm that the number of hydrogen bonds in the PA1010 phase decreased in the blends of PA1010/HIPS-g-MA. These behaviors could be attributed to the chemical interactions between the two components and good dispersion in PA1010/HIPS-g-MA blends.

Effect and mechanism in compatibilization of poly(styrene-b-2-ethyl-2-oxazoline) diblock copolymer in poly(2,6-dimethyl-1,4-phenylene oxide) poly(ethylene-ran-acrylic acid) blends

The compatibilization effect of poly(styrene-b-2-ethyl-2-oxazoline) diblock copolymer, P(S-b-EOx), on immiscible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and poly(ethylene-co-acrylic acid) (EAA) is examined in terms of phase structure and thermal, rheological and mechanical properties, and its compatibilizing mechanism is investigated by Fourier-transform infrared spectroscopy. The block copolymer, synthesized by a mechanism transformation copolymerization, is used in solution blending of PPO/EAA. Scanning electron micrographs show that the blends exhibit a more regular and finer dispersion on addition of a small amount of P(S-b-EOx). Thermal analysis indicates that the grass transition of PPO and the lower endothermic peal; of EAA components become closer on adding P(S-b-EOx), and the added diblock copolymer is mainly located at the interface between the PPO and EAA phases. The interfacial tension estimated by theological measurement is significantly reduced on addition of a small amount of P(S-b-EOx). The tensile strength and elongation at break increase with the addition of the diblock copolymer for PPO-rich blends, whereas the tensile strength increases but the elongation at break decreases for EAA-rich blends. This effect is interpreted in terms of interfacial activity and the reinforcing effect of the diblock copolymer, and it is concluded that the diblock copolymer plays a role as an effective compatibilizer for PPO/EAA blends. The specific interaction between EAA and polar parts of P(S-b-EOx) is mainly hydrogen bonding. (C) 1998 Elsevier Science Ltd. All rights reserved.

Compatibilizing effect of polystyrene-block-poly(4-vinylpyridine) for poly(2,6-dimethyl-1,4-phenyleneoxide) chlorinated polyethylene blends

The compatibilizing effect and mechanism of compatibilization of the diblock copolymer polystyrene-block-poly(4-vinylpyridine) P(S-b-4VPy) on immiscible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)/chlorinated polyethylene (CPE) were studied by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), mechanical properties and FTIR measurements. The block copolymer was synthesized by sequential anionic polymerization and melt-blended with PPO and CPE. The results show that the P(S-b-4VPy) added acts as an effective compatibilizer, located at the interface between the PPO and the CPE phase, reducing the interfacial tension, and improving the interfacial adhesion. The tensile strength and modulus of all blends increase with P(S-b-4VPy) content, whereas the elongation at break increases for PPO-rich blends, but decreases for CPE-rich blends. The polystyrene block of the diblock copolymer is compatible with PPO, and the poly(4-vinylpyridine) block and CPE are partially miscible.

Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with poly(butadiene-block-methyl methacrylate)

Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with butadiene-methyl methacrylate diblock copolymers has been investigated by transmission electron microscopy. When the diblock copolymers are added to the blends, the size of PB particles decreases and their size distribution gets narrower. In PB/PMMA7.6K blends with P(B-b-MMA)25.2K as a compatibilizer, most of micelles exist in the PMMA phase. However, using P(B-b-MMA)38K as a compatibilizer, the micellar aggregation exists in PB particles besides that existing in the PMMA phase. The core of a micelle in the PMMA phase is about 10 nm. In this article the influences of temperature and homo-PMMA molecular weight on compatibilization were also examined. At a high temperature PB particles in blends tend to agglomerate into bigger particles. When the molecular weight of PMMA is close to that of the corresponding block of the copolymer, the best compatibilization result would be achieved. (C) 1998 John Wiley & Sons, Inc.

Effects of the compatibilizer PP-g-GMA on morphology and mechanical properties of PP/PC blends

Effects of the compatibilizer polypropylene grafted with glycidyl methacrylate(PP-g-GMA) on the morphology, thermal, rheological and mechanical properties of polypropylene and polycarbonate blends (PP/PC) were studied. It was found that the addition of PP-g-GMA significantly changed their morphology. The mean size of domains reduced from 20 mu m to less than 5 mu m. The dispersed domain size is also strongly dependent upon the content of PP-g-GMA. The interfacial tension of PP/PC/PP-g-GMA (50/30/20) is only about one-tenth of PP/PC (70/30). The crystallization temperature of PP in PP/PC/PP-g-GMA is 5-8 degrees C higher than that of PP in PP/PC blends. Characterization studies based on mechanical properties, differential scanning calorimetry, rheology and morphological evidence obtained by using scanning electron microscopy support the hypothesis that an in-situ copolymer PP-g-PC was formed during the blending process. (C) 1997 Elsevier Science Ltd.

New catanionic surfactants based on 1-alkyl-3-methylimidazolium alkylsulfonates, [C(n)H(2n+1)mim][CmH2m+1SO3]: mesomorphism and aggregation

Anionic and cationic alkyl-chain effects on the self-aggregation of both neat and aqueous solutions of 1-alkyl-3-methylimidazolium alkylsulfonate salts ([C(n)H(2n+ 1)mim][CmH2m+1SO3]; n = 8, 10 or 12; m = 1 and n = 4 or 8; m = 4 or 8) have been investigated. Some of these salts constitute a novel family of pure catanionic surfactants in aqueous solution. Examples of this class of materials are rare; they are distinct from both mixed cationic-anionic surfactants (obtained by mixing two salts) and gemini surfactants (with two or more amphiphilic groups bound by a covalent linker). Fluorescence spectroscopy and interfacial tension measurements have been used to determine critical micelle concentrations (CMCs), surface activity, and to compare the effects of the alkyl-substitution patterns in both the cation and anion on the surfactant properties of these salts. With relatively small methylsulfonate anions (n = 8, 10 and 12, m = 1), the salts behave as conventional single chain cationic surfactants, showing a decrease of the CMC upon increase of the alkyl chain length (n) in the cation. When the amphiphilic character is present in both the cation and anion (n = 4 and 8, m = 4 and 8), novel catanionic surfactants with CMC values lower than those of the corresponding cationic analogues, and which exhibited an unanticipated enhanced reduction of surface tension, were obtained. In addition, the thermotropic phase behaviour of [C(8)H(18)mim][C8H18SO3] (n = m = 8) was investigated using variable temperature X-ray scattering, polarising optical microscopy and differential scanning calorimetry; formation of a smectic liquid crystalline phase with a broad temperature range was observed.

On the self-aggregation and fluorescence quenching aptitude of surfactant ionic liquids

The aggregation behavior in aqueous solution of a number of ionic liquids was investigated at ambient conditions by using three techniques: fluorescence, interfacial tension, and H-1 NMR spectroscopy. For the first time, the fluorescence quenching effect has been used for the determination of critical micelle concentrations. This study focuses on the following ionic liquids: [C(n)mpy]Cl (1-alkyl-3-methylpyridinium chlorides) with different linear alkyl chain lengths (n = 4, 10, 12, 14, 16, or 18), [C(12)mpip]Br (1-dodecyl-1-methylpiperidinium bromide), [C(12)mpy]Br (1-dodecyl-3-methylpyridinium bromide), and [C(12)mpyrr]Br (1-dodecyl-1-methylpyrrolidinium bromide). Both the influence of the alkyl side-chain length and the type of ring in the cation (head) on the CMC were investigated. A comparison of the self-aggregation behavior of ionic liquids based on 1-alkyl-3-methylpyridinium and 1-alkyl-3-methylpyridinium cations is provided. It was observed that 1-alkyl-3-methylpyridinium ionic liquids could be used as quenchers for some fluorescence probes (fluorophores). As a consequence, a simple and convenient method to probe early evidence of aggregate formation was established.