@article { ISI:000248062700019, title = {Exhaustive analysis of frontal copolymerization of functionalized monovinyl and divinyl monomers}, journal = {Chemistry-A European Journal}, volume = {13}, number = {20}, year = {2007}, month = {APR}, pages = {5862-5872}, publisher = {WILEY-V C H VERLAG GMBH}, type = {Article}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

A series of copolymers of 2-hydroxyethyl methacrylate (HEMA)/ glycidyl methacrylate (GMA) and ethylene dimethacrylate (EGDM) were synthesized by frontal polymerization (FP). This study was conducted to investigate the effect of crosslink density, type and concentration of initiator, the use of a complex initiator system, porogen, and diluent on the most relevant parameters of FP, such as sustainability of the front, temperature profile, front velocity, and yield. The products were also characterized for intruded pore volume, pore-size distribution, epoxy-functionality number, and surface morphology. Higher crosslink densities (CLDs) and initiator concentration produced higher front velocities, whereas no trend in front temperature was noted. A complex initiation system was effective in stabilizing and increasing the polymerization yield. Relative to suspension polymerization (SP), FP products synthesized without a solvent were microporous, whereas micro-to-macroporous products were obtained in the presence of a solvent (for HEMA-EGDM polymers). We also present, explain, and discuss the exotic patterns observed under a microscope. We observed two basic types of spatial patterns, namely, planar and nonplanar patterns. The type of planar pattern observed under scanning electron microscopy (SEM) has a spatial impulse that appears as a loop followed by regular periodic motion in the radial and axial directions. This behavior gives rise to a repeating pattern that is a few microns thick. Also, nonplanar patterns, namely, layered concentric rings and winding staircase patterns, were observed under SEM.

}, keywords = {copolymerization, patterns, Polymers, porosity}, issn = {0947-6539}, doi = {10.1002/chem.200601428}, author = {Pujari, Narahari S. and Inamdar, Satish R. and Ambekar, Jalindar D. and Kulkarni, B. D. and Ponrathnam, Surendra} } @article { ISI:000244006300011, title = {Water-triggered frontal polymerization}, journal = {Macromolecular Rapid Communications}, volume = {28}, number = {1}, year = {2007}, month = {JAN}, pages = {109-115}, publisher = {WILEY-V C H VERLAG GMBH}, type = {Article}, address = {PO BOX 10 11 61, D-69451 WEINHEIM, GERMANY}, abstract = {

A totally new mode of frontal polymerization (FP) of acrylamide is established which is triggered by the simple addition of a minute, specific volume of water. Experimental conditions under which this mode of polymerization yields linear and water-soluble polyacrylamide were carefully established, paving the way to synthesize commercially pertinent homo- and copolymers. A new redox couple was identified to circumvent the imidization and the ensuing gelation, hitherto associated with FP of acrylamide. Effects of reaction variables such as type and concentration of redox couple and volume of water on measurable parameters of FP such as front velocity, front temperature, shape of front and yield have been studied. Two types of redox couples are reported. Nonplanar frontal regime was observed in few redox couples. We could visually observe helical patterns with naked eyes, while layered patterns were observable under SEM. Additionally, micro-phase separation and heterogeneity in the polymer matrix was observed due to unreacted pockets of monomer which evolve via bulk mode. This nonlinear phenomenon is described.

}, issn = {1022-1336}, doi = {10.1002/marc.200600572}, author = {Pujari, Narahari S. and Inamdar, Satish R. and Ponrathnam, Surendra and Kulkarni, Bhaskar D.} } @article { ISI:000263021000003, title = {Vinyl-2-pyrrolidone derivatized guar gum based aqueous two-phase system}, journal = {Separation and Purification Technology}, volume = {65}, number = {1, SI}, year = {2009}, month = {FEB}, pages = {9-13}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Aqueous two-phase systems (ATPs) are formed when certain combinations of two polymers or polymer and salt are added to water. Phase separation occurs at certain specific concentrations that have similar densities and low interfacial tensions. The present study involves synthesis and application of a novel derivatized guar in aqueous two-phase system. The derivation of guar gum was performed by grafting of 1-vinyl-2-pyrrolidone by a redox reaction in aqueous medium ceric ammonium nitrate (CAN) and potassium Peroxydisulfate(K2S2O8). The ratio of grafting efficiency (\%GE) and ratio of grafting (\%G) was 56\% and 70.1\% respectively. The grafted copolymers were characterized for percent yield and FTIR absorbance. A new aqueous two-phase extraction protocol was established using a mixture of derivatized guar and dextran. A phase diagram was constructed based on the phase separation exhibited by the system at 25 degrees C. The partition coefficient was determined for standard bovine serum albumin (BSA), lactate oxidase (LO) and phytase. The partitioning coefficients were 0.479, 1.981, and 2.586 respectively in the Dextran (2 mill ion)/V-GG/H2O system. The influence of an ionic salt sodium chloride (NaCl) was investigated on the partitioning of BSA. (C) 2008 Elsevier B.V. All rights reserved.

}, keywords = {Aqueous two phase, graft copolymers, Guar gum, Partition coefficient (K), Phase diagram, Vinyl pyrrolidone, viscosity}, issn = {1383-5866}, doi = {10.1016/j.seppur.2008.03.020}, author = {Kautharapu, Kumar and Pujari, Narahari S. and Golegaonkar, Sandeep B. and Ponrathnam, Surendra and Nene, Sanjay N. and Bhatnagar, D.} }