02531nas a2200193   4500008004100000022001400041245012400055210006900179260007100248300001600319490000700335520176400342100002102106700001802127700002502145700002402170700002802194856011502222       2010                        eng d  a0024-929700aAbrupt shear thickening of aqueous solutions of hydrophobically modified poly(N,N `-dimethylacrylamide-co-acrylic acid)0 aAbrupt shear thickening of aqueous solutions of hydrophobically   a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcDEC  a10055-100630 v433 a<p>We report some new and interesting observations on the abrupt and large shear-induced thickening of aqueous solutions of hydrophobically modified poly(N,N'-dimethylacrylamide-co-acrylic acid). High molecular weight copolymer was prepared by free radical copolymerization of N,N'-dimethylacrylamide [DMA] and acrylic acid [AA] and was subsequently modified to different extents using a hydrophobic compound, namely, 3-pentadecylcyclohexylamine [3-PDCA], which is derived from a renewable resource material, cashew nutshell liquid [CNSL]. The structural elucidation of the base copolymer and the hydrophobically modified copolymers was performed by (1)H and (13)C NMR spectroscopy. The zero shear viscosities [eta(0)] of the hydrophobically modified polymers were lower than that of the precursor poly(N,N'-dimethylacrylamide-co-acrylic acid) until some critical polymer concentration, which increased with increase in hydrophobic modification. Above the critical concentrations, the eta(0) of the hydrophobically modified copolymers surpassed that of the precursor at the same concentration. At moderate shear rates some of these hydrophobically modified copolymers exhibited an abrupt shear-induced thickening in which the viscosity of the samples increased severalfold. We show here from creep experiments that thickening occurs only when the shear rate reaches a critical value, (gamma) over dot(crit), and that the thickened samples can be trapped in different metastable states by controlling the applied stress. Interestingly, the shear thickened samples showed further thickening upon decreasing the applied stress. Eventually, the metastable samples revert to their equilibrium states at characteristic time that depends on (small) probe stress.</p>1 aLele, Ashish, K.1 aShedge, Aarti1 aBadiger, Manohar, V.1 aWadgaonkar, Prakash1 aChassenieux, Christophe  uhttps://library.ncl.res.in/content/abrupt-shear-thickening-aqueous-solutions-hydrophobically-modified-polynn-002042nas a2200277   4500008004100000022001100041245009300052210006900145260000800214300001200222490000800234520107600242653004901318653002101367653007401388653001301462653002001475100001701495700001801512700001801530700002101548700002601569700002401595700002501619856012001644       2018                        eng d  a32386100aThermo thickening behavior of MPEG-b-PCL grafted poly(acrylic acid): a molecular insight0 aThermo thickening behavior of MPEGbPCL grafted polyacrylic acid   cJUL  a138-1480 v1483 a<p>We report on the synthesis and characterization of a new thermothickening polymer (PAA-g-(MPEG-b-PCL)) based on the grafting of a block copolymer of mono methoxy poly (ethylene glycol)–b-poly (caprolactone) (MPEG-b-PCL) onto poly (acrylic acid) (PAA). Rheological experiments reveal that aqueous solutions of PAA-g-(MPEG-b-PCL) exhibit interesting irreversible thermothickening behavior above a certain polymer concentration and critical temperature. Light scattering experiments show that increasing temperature induces hydrophobic associations and subsequent aggregation leading to gel formation which is irreversible. The mechanism of thermo thickening was examined at the molecular level by NMR methods which indicated unassembled and assembled environments of the MPEG-b-PCL grafts. On heating, interactions between the graft side chains are significantly enhanced and molecular mobility in the assembled microdomains is reduced. The stable well ordered microdomains that are formed on heating are retained on cooling thus, leading to irreversible gelation.</p>10aHydrophobically modified poly (acrylic acid)10aLight scattering10aMethoxy polyethylene glycol-b-polycaprolactone (MPEG-b-PCL) copolymer10aRheology10aThermo gelation1 aTiwari, Neha1 aShedge, Aarti1 aFayis, K., P.1 aBhat, Suresh, K.1 aRavindranathan, Sapna1 aRajamohanan, P., R.1 aBadiger, Manohar, V.  uhttps://library.ncl.res.in/content/thermo-thickening-behavior-mpeg-b-pcl-grafted-polyacrylic-acid-molecular-insight