02214nas a2200277 4500008004100000022001400041245010600055210006900161260007700230300001200307490000800319520117400327653004101501653004501542653002301587653002801610653001301638100001901651700002101670700002301691700002301714700001501737700002801752700002501780856013101805 2005 eng d a1022-135200aHydrophobically modified poly(acrylic acid) using 3-pentadecylcyclohexylamine: synthesis and rheology0 aHydrophobically modified polyacrylic acid using 3pentadecylcyclo aPO BOX 10 11 61, D-69451 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcFEB a464-4720 v2063 a

Hydrophobically modified poly(acrylic acid) was synthesized using 3-pentadecylcyclohexylamine (3-PDCA), which was in turn synthesized from 3-pentadecylphenol, one of the components of cashew-nut shell liquid (CNSL), a renewable resource material. H-1 NMR spectra confirmed the incorporation of 3-PDCA onto PAA and a series of HMPs with three different molar concentrations, viz. congruent to 3, 5 and 7 mol-% of 3-PDCA, were synthesized. An increase in viscosity with increasing hydrophobic content was observed by rheological measurements. The critical association concentrations were determined using an Ubbelohde viscometer and a controlled stress rheometer. The stability of HMPs towards temperature and shear was studied. Rheological measurements showed that there was a steady increase in viscosity with increase in hydrophobe content due to the formation of reversible networks. These polymers exhibited gel-like behavior at low concentrations (greater than or equal to2 wt.-%) with an apparent yield stress (ca. 10 Pa) and showed shear thinning properties (non-Newtonian). However, below a critical concentration, c [eta], they showed Newtonian behavior.

10a3-pentadecylcyclohexylamine (3-PDCA)10ahydrophobically modified polymers (HMPs)10apoly(acrylic acid)10areversible associations10aRheology1 aShedge, A., S.1 aLele, Ashish, K.1 aWadgaonkar, P., P.1 aHourdet, Dominique1 aPcrrin, P.1 aChassenieux, Christophe1 aBadiger, Manohar, V. uhttps://library.ncl.res.in/content/hydrophobically-modified-polyacrylic-acid-using-3-pentadecylcyclohexylamine-synthesis-and-102205nas a2200205 4500008004100000022001400041245003400055210003400089260009900123300001200222490000700234520159000241653001901831653001301850653001401863100001701877700001601894700002101910856006801931 2006 eng d a0260-877400aStudies on shrikhand rheology0 aStudies on shrikhand rheology aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLANDbELSEVIER SCI LTDcMAY a169-1770 v743 a

Shrikhand, a popular Indian dessert made from yogurt, is manufactured on an industrial scale using several chemical engineering unit operations such as mixing, filtration and heat transfer. Understanding the rheology of shrikhand is not only relevant for designing large scale mixers but can also provide quantitative means for linking the microstructure of shrikhand to its perception of texture, consistency and taste. We show here that shrikhand exhibits a combination of several rheological properties such as weak gel-like viscoelasticity, an apparent yield stress, thixotropy and long structural recovery time scales. For instance, the elastic modulus is always higher than the loss modulus over the measurable frequency range and that both moduli show only weak frequency dependence that is a characteristic of gel-like consistency. Forward and reverse rate sweep tests show a distinct hysteresis loop, which is a signature of thixotropic character. In an attempt to trace the origins of these rheological properties in shrikhand we characterized its microstructure and showed that there exist two different microstructures: one composed of crystallites of milk fats having a length scale of similar to 50-100 mu m, and the other composed of aggregates of colloidal cascin micelles of similar to 0.5-10 mu m size. Our studies show that while the temperature sensitivity of the viscoelastic parameters is dominated by the semicrystalline milk fat microstructure, the shear sensitivity is largely dictated by the protein network. (c) 2005 Elsevier Ltd. All rights reserved.

10aMicrostructure10aRheology10ashrikhand1 aKulkarni, C.1 aBelsare, N.1 aLele, Ashish, K. uhttps://library.ncl.res.in/content/studies-shrikhand-rheology-001589nas a2200289 4500008004100000020002200041022001400063245004500077210004500122260010600167300001200273490000900285520068300294653002900977653001301006653002101019100002401040700002101064700002801085700001801113700002201131700001101153700001701164700001801181700002101199856007901220 2008 eng d a978-0-7354-0549-3 a0094-243X00aGelation of regenerated fibroin solution0 aGelation of regenerated fibroin solution aMonterey, CA.bAmer Inst Physics, 2 Huntington Quadrangle, STE 1NO1, Melville, NY 11747-4501 USAcAUG a573-5750 v10273 a

Silk fibroin is a high molecular weight multiblock ampiphillic protein known for its ability to form high strength fibers. It is also biocompatible; silk sutures have been traditionally used for many centuries. Recently, there has been much interest in making silk hydrogels for applications ranging from tissue engineering to controlled delivery. Fibroin gels can be formed from aqueous solutions by changing one or more state variables such as pH, temperature and ionic strength. In this work we present our investigations on the gelation of aqueous fibroin solutions derived from Bombyx Mori silk using light scattering, confocal microscopy and rheological techniques.

10adynamic light scattering10aRheology10asilk fibroin gel1 aNagarkara, Shailesh1 aLele, Ashish, K.1 aChassenieux, Christophe1 aNicolai, Taco1 aDurand, Dominique1 aCo, A.1 aLeal, L., G.1 aColby, R., H.1 aGiacomin, A., J. uhttps://library.ncl.res.in/content/gelation-regenerated-fibroin-solution-101937nas a2200229 4500008004100000022001400041245006000055210005700115260006800172300001400240490000800254520118200262653001801444653002301462653001301485653003301498653002301531100002101554700002101575700002401596856008701620 2009 eng d a0021-899500aReactive extrusion of poly(L-Lactic Acid) with glycidol0 aReactive extrusion of polyLLactic Acid with glycidol a111 RIVER ST, HOBOKEN, NJ 07030 USAbJOHN WILEY & SONS INCcMAY a1391-13980 v1123 a

Glycidol modified polylactic acid (PLLA) polymers have been prepared by reactive extrusion. Influences of residence time and the concentration of glycidol on the extent of reaction with different weight average molecular weight (45,000, 65,000, and 100,000) PLLA's were studied. Structure-property relationship has been established by measuring molecular, mesoscopic, and macroscopic properties. Under reactive extrusion conditions glycidol reacted with the end groups of PLLA to initiate chain extension. Low-molecular weight PLLA reacted with glycidol faster than the medium molecular weight PLLA, whereas high-molecular weight PLLA did not show significant reactions. The glass transition temperature, melting temperature, crystallization temperature, and heat of fusion were measured for unmodified and modified PLLA's. Chain extended PLLA had higher T(g) and T(m) than the unmodified samples. Time sweep rheological experiments were performed to test the melt stability of PLLA. Chain extended PLLA's were found to retain viscoelastic properties for much longer time than the unreacted samples. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 1391-1398, 2009

10abiodegradable10areactive extrusion10aRheology10astructure-property relations10aThermal properties1 aDeenadayalan, E.1 aLele, Ashish, K.1 aBalasubramanian, M. uhttps://library.ncl.res.in/content/reactive-extrusion-polyl-lactic-acid-glycidol-002613nas a2200229 4500008004100000022001400041245011300055210006900168260006800237300001400305490000700319520173200326653001602058653004902074653001302123653002702136100002202163700002802185700002102213700002502234856012402259 2010 eng d a0887-626600aHydrophobically modified poly(vinyl alcohol) using alkoxy-substituted methyl gallate: synthesis and rheology0 aHydrophobically modified polyvinyl alcohol using alkoxysubstitut a111 RIVER ST, HOBOKEN, NJ 07030 USAbJOHN WILEY & SONS INCcMAY a1054-10630 v483 a

Hydrophobically modified poly(vinyl alcohol) (HMPVA) polymers were synthesized by potassium t-butoxide-catalyzed reaction of PVA with methyl 3,4,5-tris(n-octyloxy) benzoate (MGC(8))/3,4,5-tris(n-dodecyloxy) benzoate (MGC(12)) and 1,3-propane sultone. The concentration of 1,3-propane sultone was kept constant at 10 mol %. and that of MGC(8) (2, 3, and 4 mol %)/MGC(12) (2 and 3 mol %) was varied to obtain HMPVAs with different hydrophobic contents. The incorporation of MGC(8)/MGC(12) and 1,3-propane sultone onto HMPVA was confirmed by NMR spectroscopy. Rheological properties of aqueous solutions also confirmed the presence of hydrophobic and charged functional groups on HMPVAs. In the semidilute regime, the specific viscosity of HMPVAs followed concentration scaling that is typical of polyelectrolytes. At higher concentrations, the HMPVA solutions with 3 and 4 mol % of MGC(8) exhibited large increase in specific viscosity. Oscillatory experiments on these solutions exhibited gel-like behavior at polymer concentrations of 40-50 g/L. Confocal microscopy images of HMPVA with 4 mol % of MGC(8) clearly indicated the existence of microgels. The tendency of formation of microgels further increased with increasing chain length of the hydrophobe, that is, with MGC(12). These samples exhibited rheological behavior that is typical of soft solids and was therefore probed by the strain-rate frequency superposition technique reported recently in the literature. HMPVAs with improved rheological properties show potential applications as thickeners in cosmetic creams, lotions and as drug carriers in pharmaceutical formulations. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1054-1063, 2010

10agallic acid10ahydrophobically modified poly(vinyl alcohol)10aRheology10awater-soluble polymers1 aShedge, Aarti, S.1 aWadgaonkar, Prakash, P.1 aLele, Ashish, K.1 aBadiger, Manohar, V. uhttps://library.ncl.res.in/content/hydrophobically-modified-polyvinyl-alcohol-using-alkoxy-substituted-methyl-gallate-002046nas a2200265 4500008004100000022001400041245006600055210006600121260005700187300001200244490000700256520123100263653002601494653002001520653000901540653001201549653001401561653001301575653001301588100002201601700001901623700002001642700002101662856009701683 2013 eng d a0035-451100aAscertaining universal features of yielding of soft materials0 aAscertaining universal features of yielding of soft materials a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcNOV a859-8650 v523 a

Many metastable complex fluids, when subjected to oscillatory shear flow of increasing strain amplitude at constant frequency, are known to show a characteristic nonlinear rheological response which consists of a monotonic decrease in the elastic modulus and a nonmonotonic change in the loss modulus. In particular, the loss modulus increases from its low strain value, crosses the elastic modulus, and then decreases with further increase in the strain amplitude. Miyazaki et al. (Europhys Lett 75:915-921, 2006) proposed a qualitative argument to explain the origin of the nonmonotonic nature of the loss modulus and suggested that in fact this response could be universal to all complex fluids if they are probed in a certain frequency window in which the fluid is dominantly elastic in the small strain limit. In this letter, we confirm their hypothesis by showing that a wide variety of complex fluids, irrespective of their thermodynamic state under quiescent conditions, indeed show the aforementioned characteristic nonlinear response. We also show that the maximum relative dissipation during yielding occurs when the imposed frequency resonates with the characteristic beta relaxation frequency of the fluid.

10aColloidal suspensions10aEntangled melts10aGels10aGlasses10aMicrogels10aRheology10aYielding1 aKamble, Samruddhi1 aPandey, Anurag1 aRastogi, Sanjay1 aLele, Ashish, K. uhttps://library.ncl.res.in/content/ascertaining-universal-features-yielding-soft-materials-001568nas a2200229 4500008004100000022001400041245007900055210006900134260005700203300001200260490000700272520079800279653002501077653001801102653001301120653000901133100001701142700002101159700002401180700002101204856011301225 2013 eng d a0035-451100aRheology and microstructural studies of regenerated silk fibroin solutions0 aRheology and microstructural studies of regenerated silk fibroin a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcNOV a833-8400 v523 a

Regenerated silk fibroin solutions (RSF) are produced by dissolving degummed silk fibers in water. We have observed that RSF solutions at a concentration less than 15 % by weight exhibit an unusual gel-like response in conventional shear rheology measurements. At higher concentrations, the response is predominantly viscous (or liquid-like). We have probed this counterintuitive behavior of silk fibroin solutions by using microrheology, and interfacial rheometry. Scattering techniques were also used to understand the microstructure of RSF solutions as a function of the concentration. Our studies suggest that the gel-like response of the RSF solution may result from the formation of an interfacial film at the air-solution interface, which dominates the bulk rheological response.

10aInterfacial rheology10aMicrorheology10aRheology10aSilk1 aNisal, Anuya1 aKalelkar, Chirag1 aBellare, Jayesh, R.1 aLele, Ashish, K. uhttps://library.ncl.res.in/content/rheology-and-microstructural-studies-regenerated-silk-fibroin-solutions-002272nas a2200253 4500008004100000022001400041245006300055210006300118260000800181300001200189490000700201520153700208653002001745653001501765653000801780653001901788653001301807653001701820100002101837700002301858700002101881700002101902856009501923 2020 eng d a0035-451100aMicrostructure and yielding of capillary force induced gel0 aMicrostructure and yielding of capillary force induced gel cMAY a291-3060 v593 a

We have investigated the rheology and structure of a gel formed from a mixture of non-Brownian particles and two immiscible liquids. The suspension of particles in a liquid undergoes gelation upon the addition of a small content of second, wetting liquid which forms liquid bridges between particles leading to a sample spanning network. The rheology of this gel primarily exhibits a yield stress at low shear rates followed by a linear variation of shear stress at high shear rates. The apparent yield stress extracted from the flow curves increases rapidly with volume fraction of the second liquid before saturation, while it exhibits a monotonic increase with increasing particle concentration. Rescaling of the yield stress curves using suitable shift factors results in an empirical expression for the yield stress showing squared dependence on liquid fraction and a rapid increase with particle fraction above a certain value, both combined in a highly non-linear manner. The microstructural variations with changing secondary liquid content and particle fractions are captured using three-dimensional X-ray tomography technique. The microstructure is observed to show increased local compactness with increased liquid content and increased spatial homogeneity with increased particle fractions. The images from X-ray tomography are analysed to obtain the distributions of particle-particle bonds (coordination number) in the system which serve to explain the observed yield stress behaviour in a qualitative manner.

10aCapillary force10aFlow curve10agel10aMicrostructure10aRheology10aYield stress1 aHuprikar, Sameer1 aUsgaonkar, Saurabh1 aLele, Ashish, K.1 aOrpe, Ashish, V. uhttps://library.ncl.res.in/content/microstructure-and-yielding-capillary-force-induced-gel