Papers by Keyword: Micelle

Abstract: We have shown how different micellar (SDBS) vs. polyelectrolytic (PSSA) supramolecular assemblies in post-CMP cleaning solutions differ in their tribological performance when used in a novel PVA scrubber for 300-mm silicon dioxide wafer cleaning. Significant differences in real-time shear force and coefficient of friction data from the wafer-solution-brush interface (both in time domain as well as frequency domain) have been attributed to differences in each supramolecule’s chemical functionality and structure, which in turn, have been correlated to wafer-level defects. The work has underscored the importance of measuring the tribological attributes of post-CMP cleaning processes in an effort to improve cleaning performance.

Abstract: Micelles are particles of colloidal dimension and it is known that in an aqueous phase can solubilize water insoluble molecules (hydrophobic biologically active substances) in their inner core. However surfactants may have adverse effects on biological structures. Association of micelles with suitable bioacceptable molecules (e.g. hyaluronan) may lead to enhance their biocompatibility, decrease the nanoparticles cytotoxicity and also to target to the specific receptors in a human body. In this study, results of the research of electrostatic coating of cationic micelle with hyaluronan are reported. The cationic micelle/hyaluronan complexes were studied using turbidimetry and dynamic light scattering method and were evaluated to determine their structure, average size and zeta potential as a function of the amount of the both component in the system. Turbidimetric titration was chosen as indicator of the loss of intensity of transmitted light due to the scattering effect of particles associated from hyaluronan and surfactant in it. Dynamic light scattering measurement provided information about size distribution and zeta potential during mixing of component. Pilot solubilization experiments were performed to evaluation of stability and solubilization ability of the complexes. Results of turbidimetry revealed that aggregates formation (turbidity increasing) depends especially on hyaluronan concentration while surfactant concentration (above critical micelle concentration) affects interaction insignificantly. Dynamic light scattering experiments indicate that hyaluronan molecular weight has insignificant effect on isoelectric point of the systems. It was found that solubilization ability of the complexes is influenced by molecular weight of hyaluronan.

Abstract: In this study, we synthesized carboxymethyl chitosan-graft-poly(ε-caprolactone) (CMCS-g-PCL) by grafting ε-CL onto the hydroxyl groups of CMCS via ring-opening polymerization. The graft copolymers were characterized by ¹H NMR spectroscopy and thermogravimetric analysis (TGA). Then use the graft copolymer to produce the micelle by solvent-evaporation method. The DLS and TEM were utilized to evaluate the particle size and morphology and showed that the micelles were in a well-defined spherical shape with a uniform size distribution. The results indicated that the size of range is below 200 nm and could be used as drug carrier and have better active cellular uptake.

Abstract: A surface properties of a sulfobetaine–type zwitterionic gemini surfactant with the structure of 1,2-bis [N-methyl-N-(3-sulfopropyl) -dodecylammonium] ethane betaine (ZGS12), were investigated in aqueous solution . The critical micelle concentration (CMC) of the gemini surfactant at different temperatures and mixed micelle properties of ZGS12 and sodium dodecyl benzene sulfonate (SDBS) were investigated. The results show that cmc of the gemini surfactant (ZGS12) decreases with raising temperature, Gibbs free energy changes and entropy changes are negative and postive, respectively, indicating the formation of micelle is spontaneous and driven mainly by entropy. According to the theory of regular solution , interaction parameters between the zwitterionic gemini surfactant ZGS12 and the anionic surfactant SDBS indicate strong attractive interaction and great degree of synergism in micelle formation due to weakening of the electrostatic head group repulsion.

Abstract: Different compositions of surfactant systems give rise to a rich variety of structures of aggregates. At higher concentrations of surfactant in water, the surfactant molecules aggregate to form lyotropic liquid crystals [1]. In the present work we have prepared two surfactant systems consisting of (i) 20% of cetyl-trimethyl-ammonium-bromide (CTAB) in water, and (ii) 30% of tetra-decyl-trimethyl-ammonium-bromide (TTAB) in water. Both the systems exhibit various lyotropic liquid crystal structures when an increasing amount of co-surfactant is added as third component [2, 3]. These liquid crystalline structures are very sensitive to the solution conditions such as co-surfactant concentration, temperature, ionic strength, counter ion polarizability etc. In this study, positron life time spectroscopy and conductivity measurement have been employed to locate various phases exhibited by the lyotropic liquid crystals. In addition to delineating various phase boundaries of the systems, positron annihilation technique has also yielded new findings.

Abstract: In this study, a amphiphilic copolymer, poly ((N-isopropylacrylamide)-co-acrylamide-co- (octadecylacrylate)-co-(Falate-(polyethyleneglycol)-(acrylicacid)))(P(NIPA-co-AAm-co-ODA-co-FPA)) micelles was synthesized by free radical random copolymerization. The obtained amphiphilic copolymers were self-assembled into micelles, which exhibited thermally sensitivity. LCST of the micelles was detected by uv-vis spectrophotometer. The diameter and morphology of micelles were determined by laser particle size analyzer (LPSA) and transmittance electron microscope (TEM), respectively. The micelle with a diameter of 60 nm and LCST of 40 oC was obtained by utilizing of ODA and the feed ratio of NIPA and AAm, respectively, which is satisfied for drug delivery in living body. The maximum DLC was achieved with the amount of ODA (180mg).

Abstract: The block copolymer poly (ε-caprolactone)-b-poly (N-isopropyl acrylamide) (PCL-b-PNIPAM) is synthesized via the combination of ring-opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT). PCL-b-PNIPAM can self-assemble into the micelles taking PCL as the cores and PNIPAM as the shells. Add α-CD into the micelles, because the inclusion complexation of α-CD to PCL chains and phenols is stronger than that to PCL, to regulate the hydrophilic and hydrophobic features of PCL chain. So PCL-b-PNIPAM block copolymers have potential application in drug delivery and gene transfection.

Abstract: Block copolymers D,L-Polylactide-b-poly(poly(ethylene glycol) methyl ether acrylate) (D,L- P(LA)-b-P(PEGMA)) were prepared via ring-opening polymerization and reversible addition fragmentation chain transfer (RAFT) polymerization. The block polymers generated in the reaction reveal the living behavior with the molecular weight increasing with time. The copolymer D,L-P(LA)200-b-P(PEGMA)₂₂₅ was synthesized successfully with D,L-P(LA) macro-RAFT agent, and was self-assembled in an aqueous environment, leading to the formation of self-assembly micelles. A distinct critical micelle concentration (CMC) was observed of the self-assembly system. The size of it was characterized by both DLS and TEM.

Abstract: Formation of layered nanosheets and micro-spheres from a simple self-assembly and polycondensation of n-octadecylsilane (PODS) in water and toluene is demonstrated, respectively. The structure of the micro-spheres was characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). According to the TEM images, it was firstly confirmed that the micro-spheres consist of stacks of bilayered polymerized n-octadecylsilane with head-to-head arrangements. The co-effects of water and solvent were proposed to control the octadecyltrichlsilane hydrolysis process and eventually the morphology of the micro-spheres. A micelle formation mechanism for the formation of the PODS micro-spheres under the co-effects of water and solvent were firstly proposed.

Abstract: A series of amphiphilic block copolymers mPEO-b-PCL with different PCL molecular weight were successfully prepared by combination of anionic ring-opening polymerization with coordination-insertion ring-opening polymerization. Firstly, the linear mPEO was prepared by anionic ring-opening copolymerization of EO with 2-(2-methoxyethoxy) ethoxide potassium as the small molecule initiators, then the mPEO as the macroinitiator was used to initiate the ring-opening polymerization of CL, in the absence of Sn(Oct)₂ as the catalyst, and amphiphilic block copolymers mPEO-b-PCL were obtained. By changing the ratio of monomer and macroinitiator, prepared a series of different molecular weight mPEO-b-PCL. The structure of intermediates and final products were characterized by ¹H NMR and GPC. The critical micelle concentration (cmc) of the final copolymer was measured. In addition, the sizes and morphologies of the obtained micelles at different PCL chains were studied with Laser nano-particle size analyzer and transmission electron microscopy (TEM).