02500nas a2200217 4500008004100000022001400041245013400055210006900189260006800258300001400326490000800340520167400348653000902022653001102031653001502042653003102057653002202088100002502110700002302135856012402158 2008 eng d a0021-899500aEffect of organic modifiers and silicate type on filler dispersion, thermal, and mechanical properties of ABS-Clay nanocomposites0 aEffect of organic modifiers and silicate type on filler dispersi a111 RIVER ST, HOBOKEN, NJ 07030 USAbJOHN WILEY & SONS INCcNOV a2374-23830 v1103 a

Acrylonitrile-butadiene-styrene (ABS)-clay composite and intercalated nanocomposites were prepared by melt processing, using Na-montmorillonite (MMT), several chemically different organically modified MMT (OMMT) and Na-laponite clays. The polymer-clay hybrids were characterized by WAXD, TEM, DSC, TGA, tensile, and impact tests. Intercalated nanocomposites are formed with organoclays, a composite is obtained with unmodified MMT, and the nanocomposite based on synthetic laponite is almost exfoliated. An unintercalated nanocomposite is formed by one of the organically modified clays, with similar overall stack dispersion as compared to the intercalated nanocomposites. T, of ABS is unaffected by incorporation of the silicate filler in its matrix upto 4 wt % loading for different aspect ratios and organic modifications. A significant improvement in the onset of thermal decomposition (40-44 degrees C at 4 wt % organoclay) is seen. The Young's modulus shows improvement, the elongation-at-break shows reduction, and the tensile strength shows improvement. Notched and unnotched impact strength of the intercalated MMT nanocomposites is lower as compared to that of ABS matrix. However, laponite and overexchanged organomontmorillonite clay lead to improvement in ductility. For the MMT clays, the Young's modulus (E) correlates with the intercalation change in organoclay interlayer separation (Delta d(001)) as influenced by the chemistry of the modifier. Although ABS-laponite composites are exfoliated, the intercalated OMMT-based nanocomposites show greater improvement in modulus. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110:2374-2383, 2008

10aclay10afiller10amechanical10astructure characterization10astyrene-butadiene1 aTiwari, Rajkiran, R.1 aNatarajan, Upendra uhttp://library.ncl.res.in/content/effect-organic-modifiers-and-silicate-type-filler-dispersion-thermal-and-mechanical-002004nas a2200157 4500008004100000022001400041245017700055210006900232260007600301300001200377490000700389520127500396100002501671700002301696856012701719 2011 eng d a0032-388800aEffect of blend composition and organoclay loading on the nanocomposite structure and properties of miscible poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) blends0 aEffect of blend composition and organoclay loading on the nanoco aCOMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USAbWILEY-BLACKWELLcMAY a979-9910 v513 a

Organically-modified montmorillonite clay nanocomposites of poly(styrene-co-acrylonitrile) (SAN), poly(methyl methacrylate) (PMMA) and SAN/PMMA miscible blend are investigated. Structure characteristics at the nanoscale and microscale and thermal and tensile properties are studied as a function of polymer blend composition and filler loading fraction. Blend miscibility and T(g) are unaffected by up to 10% by wt. organoclay. Thermal degradation stability increases with SAN content and exhibits an optimum value of clay loading. Stiffness shows significant improvement. Tensile strength and elongation-at-break suffer as a result of nanocomposite formation. Modulus shows a maximum enhancement of 57% (5 +/- 0.06 GPa at 10 wt% filler, 20/80 SAN/PMMA) and varies linearly with clay fraction for all compositions of matrix phase. Predictions of Halpin-Tsai composite model are in excellent agreement with the experimental behavior over full range of polymer blend composition. Fundamental aspects of a polymer blend-clay nanocomposite are clarified, such as lack of additional synergy between clay platelets and matrix, and tensile ductility reduction, compared with polymer-clay system. POLYM. ENG. SCI., 51:979-991, 2011. (C) 2011 Society of Plastics Engineers

1 aTiwari, Rajkiran, R.1 aNatarajan, Upendra uhttp://library.ncl.res.in/content/effect-blend-composition-and-organoclay-loading-nanocomposite-structure-and-properties-002057nas a2200157 4500008004100000022001400041245008700055210006900142260007100211300001400282490000800296520144200304100002001746700002301766856011001789 2011 eng d a1520-610600aEffect of chemical substituents on the structure of glassy diphenyl polycarbonates0 aEffect of chemical substituents on the structure of glassy diphe a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcFEB a1579-15890 v1153 a

Polycarbonates offer a wide variety of physical property behavior that is difficult to predict due to complexities at the molecular scale. Here, the physical structure of amorphous glassy polycarbonates having aliphatic and cycloaliphatic chemical groups is explored through atomistic simulations. The influence of chemical structure on solubility parameter, torsion distributions, radial distribution function, scattering structure factor; orientation distributions of phenylene rings and carbonate groups, and free volume distributions, leading to interchain packing effects, are shown. The effect of the cyclohexyl ring at the isopropylidene carbon as compared to the effect of the methyl groups positioned on the phenylene rings results in a larger reduction in the solubility parameter (delta). The interchain distance estimated for polycarbonates in this work is in the range of 5-5.8 angstrom. The o-methyl groups on the phenylene, rings, as compared to a cyclohexyl ring, lead to higher interchain distances. The highest interchain distance is observed with a trimethylcyclohexylidene group at the isopropylidene carbon. Atomistic simulations reveal two different types of packing arrangement of nearest neighbor chains in the glassy state, one type of which agrees with the NMR experimental data The fundamental insights provided here can be utilized for design of chemical structures for tailored macroscopic properties.

1 aSulatha, M., S.1 aNatarajan, Upendra uhttp://library.ncl.res.in/content/effect-chemical-substituents-structure-glassy-diphenyl-polycarbonates-001856nas a2200229 4500008004100000022001400041245011600055210006900171260008600240300001300326490000700339520098100346653002101327653001601348653003001364653001601394653002101410653002101431100002401452700002301476856012701499 2011 eng d a0022-234800aEffect of composition on chain dimensions of styrene-methylmethacrylate random copolymers under theta condition0 aEffect of composition on chain dimensions of styrenemethylmethac a325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USAbTAYLOR & FRANCIS INCcAPR a996-10050 v503 a

Rotational-isomeric-state (RIS)-Metropolis Monte Carlo simulations are performed on poly(styrene-ran-methylmethacrylate) random copolymers to study the intrinsic unperturbed (theta-condition) dimensions. Mean-squared end-to-end distance (< r(2)>(o)), mean-squared radius of gyration (< s(2)>(o)), and characteristic ratio (C(n)) have been calculated for these copolymers constituted by different overall chemical compositions (styrene fractions 0.29, 0.56, and 0.70). Calculations were carried out with chains of 500 repeating units. With an increase in the styrene content there is an increase in (< r(2)>(o)), `, and C(n), in agreement with experimental observations. An increase in the fraction of trans conformational states in the backbone torsion angles is found to be responsible for the exhibited chain expansion behavior. The dimensions calculated by the Monte Carlo simulations agree well with experimental values reported in the literature.

10achain dimensions10aMonte Carlo10apoly(methyl methacrylate)10aPolystyrene10arandom copolymer10atheta conditions1 aKaryappa, Rahul, B.1 aNatarajan, Upendra uhttp://library.ncl.res.in/content/effect-composition-chain-dimensions-styrene-methylmethacrylate-random-copolymers-under-002288nas a2200229 4500008004100000022001400041245013800055210006900193260008700262300001200349490000700361520139900368653001101767653001401778653001501792653002601807653001901833653003001852100002501882700002301907856012801930 2013 eng d a0892-705700aEffect of organic modification on the intercalation and the properties of poly(phenylene oxide)/polystyrene blend-clay nanocomposites0 aEffect of organic modification on the intercalation and the prop a1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLANDbSAGE PUBLICATIONS LTDcAPR a392-4150 v263 a

Nanocomposites prepared by the dispersion of unmodified and organically modified montmorillonite (MMT) clay into poly(2,6-dimethyl phenylene oxide)/polystyrene miscible blend in the range of 2-10 wt% clay were investigated by wide-angle x-ray diffraction, transmission electron microscopy, differential scanning calorimetry, thermogravimetric analysis and tensile mechanical tests. The systems based on unmodified sodium MMT (Na+MMT) as well as Cloisite 20A, Cloisite 30B and Cloisite 10A organically modified clays showed polymer intercalation. The glass transition temperature (T-g) value was not affected by the volume fraction of clay and chemical nature of the organoclay. The thermal degradation stability of nanocomposites is found to be only slightly better than that of the blend matrix. A percolation threshold of around 4 wt% organoclay loading is observed. An improvement of 35% relative to unfilled polymer blend matrix is observed for the modulus, for Cloisite 20A nanocomposite containing 2 wt% organoclay. The observed modulus improvement with significant retention of elongational tensile strength and tensile ductility in case of unmodified Na-MMT and Cloisite 30B nanocomposites appears promising. The modulus prediction using Halpin-Tsai model is found to be closer to the experimental data when MMT volume fraction rather than the organoclay volume fraction is used.

10afiller10ainterface10ainterphase10amechanical properties10aNanostructures10aPolymer-matrix composites1 aTiwari, Rajkiran, R.1 aNatarajan, Upendra uhttp://library.ncl.res.in/content/effect-organic-modification-intercalation-and-properties-polyphenylene-oxidepolystyrene-0