02613nas 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<p>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</p>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-001011nas a2200133   4500008004100000245003800041210003800079300001100117490000700128520062200135100002200757700002500779856007300804       2014                        eng d00aHydrophobically Modified Chitosan0 aHydrophobically Modified Chitosan  a91-1020 v193 a<p>Hydrophobically modified chitosan was prepared using the hydrophobic compound derived from natural resource material such as cashew nut shell liquid. Chitosan was modified using 3-pentadecyl cyclohexane carbaldehyde to different extents (2, 3, and 5 mol%). Solution properties of hydrophobically modified chitosan were studied by rheology and light scattering. These indicated the aggregation behavior above the critical association concentration. Further, it was concluded that above the critical association concentration, the dynamics of the network formed due to the associations slowed down significantly.</p>1 aShedge, Aarti, S.1 aBadiger, Manohar, V.  uhttps://library.ncl.res.in/content/hydrophobically-modified-chitosan02081nas a2200181   4500008004100000245008100041210006900122260000800191300001400199490000600213520144700219100002701666700002201693700002501715700002801740700002101768856011001789       2017                        eng d00aThermo-reversible sol-gel transition of aqueous solutions of patchy polymers0 aThermoreversible solgel transition of aqueous solutions of patch  cJAN  a5101-51100 v73 aWhile aqueous solutions of several amphiphilic thermo-reversible polymers show gelation upon heating, there are fewer examples of polymer solutions that exhibit gelation when cooled. This paper reports an interesting phenomenon of abrupt thermoreversible gelation of aqueous solutions of a hydrophobically modified polymer upon cooling. A high molecular weight precursor copolymer (PCP, (M-w) over bar approximate to 5 x 10(6) g mol(-1)) of N, N-dimethylacrylamide (70 mol%) and acrylic acid (30 mol%) was modified by reacting 10 mol% of the acrylic acid groups with n-dodecyl amine to form a hydrophobically modified copolymer (HMCP). The composition of the copolymer was ascertained using NMR spectroscopy. Cooling the solution of PCP at a controlled rate resulted in a gradual increase in its low shear viscosity as dictated by the flow activation energy. In contrast, cooling the solution of HMCP under identical conditions resulted in an abrupt and large non-Arrhenius increase in viscosity at a specific transition temperature, which decreased with decrease in polymer concentration. Fluorescence measurements and dynamic light scattering data showed that abrupt gelation happened upon cooling, when polymer coils percolate accompanied with concomitant transition in chain conformation from compact micellar coils formed by intra-chain hydrophobic associations to swollen polymer coils connected by inter-chain hydrophobic interactions.1 aParmar, Indravadan, A.1 aShedge, Aarti, S.1 aBadiger, Manohar, V.1 aWadgaonkar, Prakash, P.1 aLele, Ashish, K.  uhttps://library.ncl.res.in/content/thermo-reversible-sol-gel-transition-aqueous-solutions-patchy-polymers