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Waterborne trifunctionalsilane-terminated polyurethane nanocomposite with silane-modified clay
Subramani, Sankaraiah,Lee, Jun-Young,Choi, Sung-Wook,Kim, Jung Hyun Wiley Subscription Services, Inc., A Wiley Company 2007 Journal of polymer science Part B, Polymer physics Vol.45 No.19
<P>Trifunctional organosilane-modified clay was synthesized and used to prepare waterborne trifunctionalsilane-terminated polyurethane (WSPU)/clay nanocomposite dispersions in this study. Qualitative evidence of the presence of chemically attached silane molecules on clay were confirmed by Fourier transform infrared spectroscopy. The grafted amount and the grafting yield were determined by thermogravimetric analysis and the obtained results were in good agreement with the cation exchange capacity of pristine clay. X-ray diffraction and transmission electron microscopy examinations indicated that the clay platelets are mostly intercalated or partially exfoliated in the SPU matrix with a d-spacing of ∼2.50 nm. Clay does not influence the location and peak broadness of the glass transition temperature of soft segment as well as hard segment domains in the WSPU/clay films. WSPU/clay dispersion with higher clay content exhibits a marginal increase in the average particle size, but silane modified clay has a pronounced effect compared with Cloisite 20A-based nanocomposites. In addition, the incorporation of organophilic clay can also enhance the thermal resistance and tensile properties of WSPUs dramatically through the reinforcing effect. The improvement in water and xylene resistance of the silane modified clay nanocomposites proved that trifunctional organosilane can be used as effective modifiers for clays. Storage stability results confirmed that the prepared nanocomposite dispersions were stable. This method provides an efficient way to incorporate silane modified clay in SPU matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2747–2761, 2007</P>
Subramani Sankaraiah,Lee Jung Min,Kim Jung Uyun,Cheong In Woo The Polymer Society of Korea 2005 Macromolecular Research Vol.13 No.5
One-pack cross-linkable nanocomposites of waterborne methyl ethyl ketoxime (MEKO)-blocked aromatic polyurethane dispersion (BPUD) reinforced with organoclay (quaternary ammonium salt of Cloisite 25A) were synthesized by the acetone process using 4,4'-methylenedi-p-phenyl diisocyanate (MDl), poly(tetramethylene) glycol (PTMG), dimethylol propionic acid (DMPA), and methyl ethyl ketoxime (MEKO). Particle size, viscosity, and storage stability of these nanocomposites were investigated. TEM and XRD studies confirmed that the silicate layers of organophilic clay were exfoliated and intercalated at a nanometer-scale in the BPUD matrix.
One-Step Synthesis of Photoluminescent Core/Shell Polystyrene/Polythiophene Particles
정연재,김중현,이승모,Subramani Sankaraiah,정인우,최성욱 한국고분자학회 2011 Macromolecular Research Vol.19 No.11
Photoluminescent polystyrene (PS)/polythiophene (PTh) particles with a core/shell structure were synthesized via a one-step process using radical polymerization for styrene and Fe^3+-catalyzed oxidative polymerization for thiophene. Water-soluble potassium persulfate (KPS) and iron chloride (FeCl_3) were used as intitiators for the polymerization of styrene and thiophene, respectively. Sodium dodecyl sulfate (SDS) served as a polymierization site in the form of a micelle as well as a collodial stabilizer. Analyzing the samples using field-emission scanning electron microscopy (FE-SEM) and Fourier transform infrared (FTIR) spectroscopy at different times revealed a plausible mechanism for the formation of the PS/PTh particles. In the mechanism of particle formation, the sulfate (OSO_3^- ) groups of SDS electrostatically induced Fe^3+ ions to the perimeter of the micelle; thus, the polymerization of thiophene was carried out mainly at the perimeter of the SDS micelle, eventually forming small PTh aggregates within the SDS micelles. The styrene oligomers or monomers that shifted into the preformed PTh aggregates were polymerized in the core domain of the aggregates; thus, the particle size gradually increased until all the styrene monomers were consumed, resulting in core/shell PS/PTh particles. The core/shell structure of the PS/PTh particles was confirmed by observing their crumpled morphology after selective dissolution of the PS core using a solvent. The photoluminescence (PL) intensity of the particles was found to be higher than that of pure PTh particles, attributable to the core/shell structure.
Thermal Decomposition Behavior of Blocked Diisocyanates Derived from Mixture of Blocking Agents
Lee Jung Min,Subramani Sankaraiah,Lee Young Soo,Kim Jung Hyun The Polymer Society of Korea 2005 Macromolecular Research Vol.13 No.5
To improve the performance and reduce raw material costs, blocked isocyanates were prepared with mixture of blocking agents in many industries. Three blocked isocyanates (adducts) namely $\varepsilon$-caprolactam/benzotriazole-blocked 4,4'-diphenylmethane diisocyanate (MDI), toluene-2,4-diisocyanate (TDI) and 4,4'-dicyclohexyl-methane diisocyanate ($H_{12}$MDI) were synthesized. Six reference adducts were also prepared by blocking MDI, TDI, and $H_{12}$MDI with $\varepsilon$-caprolactam ($\varepsilon$-CL) or benzotriazole. The reactions were carried out in acetone medium and dibutyltin dilaurate (DBTDL) was used as a catalyst. The progress of the blocking reaction was monitored by IR spectroscopy. De-blocking temperatures (dissociation temperatures) of these adducts were studied using DSC and TGA and the results were correlated. As expected, the thermal analysis data showed that de-blocking temperature of blocked aromatic isocyanates was lower than that of the blocked aliphatic isocyanates. The low de-blocking temperature of blocked aromatic isocyanate could be due to electron withdrawing benzene ring present in the blocked isocyanates. It was also found that benzotriazole-blocked adducts de-blocked at higher temperature compared with $\varepsilon$-CL-blocked adducts.
Govindaiah, Patakamuri,Lee, Jung-Min,Lee, Seung-Mo,Kim, Jung-Hyun,Subramani, Sankaraiah The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.11
Polycarbonate (PC)/sulfonated polystyrene (SPS) ionomer/organoclay nanocomposites were prepared by a solution intercalation process using the SPS ionomer as a compatibilizer. The effect of an organoclay on the melt crystallization behavior of the ionomer compatibilized PC were examined by differential scanning calorimetry (DSC). The melt crystallization behavior of PC was dependent on the extent of organoclay dispersion. The effect of the ionomer loading and cation size on intercalation/exfoliation efficiency of the organoclay in PC/SPS ionomer matrix was also studied using wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). Dispersion of the organically modified clay in the polymer matrix improved with increasing ionomer compatibilizer loadings and cation size. The SPS ionomer compatibilized PC/organoclay nanocomposite showed enhanced melt crystallization compared to the SPS ionomer/PC blend. Well dispersed organoclay nanocomposites showed better crystallization than the poorly dispersed clay nanocomposites. These nanocomposites also showed better thermal stability than the SPS ionomer/PC blend.