BISHWA BHUSAN Nayak - Academia.edu (original) (raw)

Uploads

Papers by BISHWA BHUSAN Nayak

Research paper thumbnail of Poly(epsilon-caprolactone)/organo-modified montmorillonite nanocomposites by in-situ polymerization

Abstracts of Papers of the American Chemical Society, 2007

Research paper thumbnail of Photocrosslinking of poly(ethylene terephthalate) copolymers containing photoreactive comonomers

Polymer, 2005

Poly(ethylene terephthalate) (PET) copolymers containing 4,4′-, 3,5-, and 2,4-benzophenone dicarb... more Poly(ethylene terephthalate) (PET) copolymers containing 4,4′-, 3,5-, and 2,4-benzophenone dicarboxylate chromophores have been synthesized by transesterification of PET with benzophenone 4,4′-dicarboxylic acid (4,4′-BDA), dimethyl benzophenone 4,4′-dicarboxylate (4,4′-BDE), dimethyl benzophenone 3,5-dicarboxylate (3,5-BDE) and dimethyl benzophenone 2,4-dicarboxylate (2,4-BDE). The benzophenone segments in the backbone induce photocrosslinking upon UV irradiation in the solid state most probably by a hydrogen atom abstraction mechanism. The crosslinking rate depends upon the concentration and the structure of chromophores as evidenced by gel content measurements. The photocrosslinking efficiency of 4,4′-benzophenone dicarboxylate containing polymers is higher than for 2,4- or 3,5-benzophenone dicarboxylate containing polymers. Photocrosslinked PET copolymers show increased glass transition temperatures and broadening of melting transitions.

Research paper thumbnail of A novel photoinimer for the polymerization of acrylates and methacrylates

Journal of Polymer Science Part A: Polymer Chemistry, 2005

A new class of multifunctional photoinitiating system based on 3-(acryloyloxy)-2-hydroxypropyl me... more A new class of multifunctional photoinitiating system based on 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM), N,N,N 0-trimethylethylenediamine (TMED) and 3-benzoylbenzoyl chloride present in the same molecule has been synthesized and characterized by 1 H and 13 C NMR spectroscopy. This self-contained photoinitiator-monomer (photoinimer) was used to efficiently initiate polymerization of acrylates and methacrylates. Both rate of polymerization and percentage conversion increased with increase in initiator concentration. An increment in rate of polymerization observed when the benzophenone moiety was directly attached to the parent molecule (obtained from the Michael addition reaction between AHM and TMED) appears to be due to proximity effect: chemical bonding provides a high local concentration of both components of the photo-activated system involving benzophenone and a hydrogen atom source from an electron-rich tertiary amine. For the three initiating systems investigated, lowering the initiator concentration plays an important role; i.e., the polymerization rate for the chemically linked system was about two times faster than the mixed initiating system.

Research paper thumbnail of Development of graft copolymer flocculating agents based on hydroxypropyl guar gum and acrylamide

Journal of Applied Polymer Science, 2001

Graft copolymers of hydroxypropyl guar gum (HPG) with polyacrylamide (PAM) have been synthesized ... more Graft copolymers of hydroxypropyl guar gum (HPG) with polyacrylamide (PAM) have been synthesized using a ceric ion-induced solution polymerization technique at 28°C. Six graft copolymers have been synthesized with variation in the number and length of grafted PAM chains. The graft copolymers were characterized by viscometry, infrared (IR) spectroscopy, and thermal analysis studies. Flocculation jar tests were carried out in 0.25 wt % kaolin, iron ore, and silica suspensions. Among the series of graft copolymers, the one with fewest but longest PAM chains shows the better performance. The flocculation characteristics of this best performing graft copolymer are compared with various commercially available flocculants in the three suspensions.

Research paper thumbnail of Synthesis and characterization of grafted hydroxypropyl guar gum by ceric ion induced initiation

European Polymer Journal, 2001

A study was made of the ceric-ammonium-nitrate-initiated graft copolymerization of polyacrylamide... more A study was made of the ceric-ammonium-nitrate-initiated graft copolymerization of polyacrylamide onto hydroxypropyl guar gum by solution polymerization technique. Six grades of graft copolymers have been synthesized by varying catalyst and monomer concentrations. The synthesized products were then characterized by various instrumental techniques like viscometry, elemental analysis, IR, thermal, XRD and SEM studies. The percentage of grafting increases with increasing catalyst concentration and decreases with monomer concentration taking other parameters constant.

Research paper thumbnail of Multifunctional photo-initiator for acrylate and methacrylate polymerization

Abstracts of Papers of the American Chemical Society, 2005

Research paper thumbnail of Highly exfoliated poly (ϵ‐caprolactone)/organomontmorillonite nanocomposites prepared by in situ polymerization

Poly(e-caprolactone)/organomodified montmorillonite nanocomposites were prepared by in situ polym... more Poly(e-caprolactone)/organomodified montmorillonite nanocomposites were prepared by in situ polymerization with dibutyltin dimethoxide as an initiator/ catalyst. The montmorillonite was first modified with 1-decyl-2-methyl-3-(11-hydroxyundecyl)imidazolium cation. The hydroxyl functionality was used not only for initiating polymer chains from the surface of the clay platelets but also for grafting polymer chains to the surface by acting as a reversible chain-transfer agent. The molecular weights of the polymer chains were controlled by the ratio of monomer to hydroxyl content. X-ray diffraction and transmission electron microscopy studies confirmed that highly exfoliated nanostructures were formed. The amount of inorganic component did not affect the thermal behavior of the polymer matrix as shown by differential scanning calorimetry or thermogravimetric analysis. The highly exfoliated clay sheets acted as nucleating agents and increased the degree of crystallinity from 51 to 69% at 5 wt %. Dynamic mechanical analysis revealed an enhancement of the storage modulus with increasing clay content above the glass-transition temperature.

Research paper thumbnail of Poly(epsilon-caprolactone)/organo-modified montmorillonite nanocomposites by in-situ polymerization

Abstracts of Papers of the American Chemical Society, 2007

Research paper thumbnail of Photocrosslinking of poly(ethylene terephthalate) copolymers containing photoreactive comonomers

Polymer, 2005

Poly(ethylene terephthalate) (PET) copolymers containing 4,4′-, 3,5-, and 2,4-benzophenone dicarb... more Poly(ethylene terephthalate) (PET) copolymers containing 4,4′-, 3,5-, and 2,4-benzophenone dicarboxylate chromophores have been synthesized by transesterification of PET with benzophenone 4,4′-dicarboxylic acid (4,4′-BDA), dimethyl benzophenone 4,4′-dicarboxylate (4,4′-BDE), dimethyl benzophenone 3,5-dicarboxylate (3,5-BDE) and dimethyl benzophenone 2,4-dicarboxylate (2,4-BDE). The benzophenone segments in the backbone induce photocrosslinking upon UV irradiation in the solid state most probably by a hydrogen atom abstraction mechanism. The crosslinking rate depends upon the concentration and the structure of chromophores as evidenced by gel content measurements. The photocrosslinking efficiency of 4,4′-benzophenone dicarboxylate containing polymers is higher than for 2,4- or 3,5-benzophenone dicarboxylate containing polymers. Photocrosslinked PET copolymers show increased glass transition temperatures and broadening of melting transitions.

Research paper thumbnail of A novel photoinimer for the polymerization of acrylates and methacrylates

Journal of Polymer Science Part A: Polymer Chemistry, 2005

A new class of multifunctional photoinitiating system based on 3-(acryloyloxy)-2-hydroxypropyl me... more A new class of multifunctional photoinitiating system based on 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM), N,N,N 0-trimethylethylenediamine (TMED) and 3-benzoylbenzoyl chloride present in the same molecule has been synthesized and characterized by 1 H and 13 C NMR spectroscopy. This self-contained photoinitiator-monomer (photoinimer) was used to efficiently initiate polymerization of acrylates and methacrylates. Both rate of polymerization and percentage conversion increased with increase in initiator concentration. An increment in rate of polymerization observed when the benzophenone moiety was directly attached to the parent molecule (obtained from the Michael addition reaction between AHM and TMED) appears to be due to proximity effect: chemical bonding provides a high local concentration of both components of the photo-activated system involving benzophenone and a hydrogen atom source from an electron-rich tertiary amine. For the three initiating systems investigated, lowering the initiator concentration plays an important role; i.e., the polymerization rate for the chemically linked system was about two times faster than the mixed initiating system.

Research paper thumbnail of Development of graft copolymer flocculating agents based on hydroxypropyl guar gum and acrylamide

Journal of Applied Polymer Science, 2001

Graft copolymers of hydroxypropyl guar gum (HPG) with polyacrylamide (PAM) have been synthesized ... more Graft copolymers of hydroxypropyl guar gum (HPG) with polyacrylamide (PAM) have been synthesized using a ceric ion-induced solution polymerization technique at 28°C. Six graft copolymers have been synthesized with variation in the number and length of grafted PAM chains. The graft copolymers were characterized by viscometry, infrared (IR) spectroscopy, and thermal analysis studies. Flocculation jar tests were carried out in 0.25 wt % kaolin, iron ore, and silica suspensions. Among the series of graft copolymers, the one with fewest but longest PAM chains shows the better performance. The flocculation characteristics of this best performing graft copolymer are compared with various commercially available flocculants in the three suspensions.

Research paper thumbnail of Synthesis and characterization of grafted hydroxypropyl guar gum by ceric ion induced initiation

European Polymer Journal, 2001

A study was made of the ceric-ammonium-nitrate-initiated graft copolymerization of polyacrylamide... more A study was made of the ceric-ammonium-nitrate-initiated graft copolymerization of polyacrylamide onto hydroxypropyl guar gum by solution polymerization technique. Six grades of graft copolymers have been synthesized by varying catalyst and monomer concentrations. The synthesized products were then characterized by various instrumental techniques like viscometry, elemental analysis, IR, thermal, XRD and SEM studies. The percentage of grafting increases with increasing catalyst concentration and decreases with monomer concentration taking other parameters constant.

Research paper thumbnail of Multifunctional photo-initiator for acrylate and methacrylate polymerization

Abstracts of Papers of the American Chemical Society, 2005

Research paper thumbnail of Highly exfoliated poly (ϵ‐caprolactone)/organomontmorillonite nanocomposites prepared by in situ polymerization

Poly(e-caprolactone)/organomodified montmorillonite nanocomposites were prepared by in situ polym... more Poly(e-caprolactone)/organomodified montmorillonite nanocomposites were prepared by in situ polymerization with dibutyltin dimethoxide as an initiator/ catalyst. The montmorillonite was first modified with 1-decyl-2-methyl-3-(11-hydroxyundecyl)imidazolium cation. The hydroxyl functionality was used not only for initiating polymer chains from the surface of the clay platelets but also for grafting polymer chains to the surface by acting as a reversible chain-transfer agent. The molecular weights of the polymer chains were controlled by the ratio of monomer to hydroxyl content. X-ray diffraction and transmission electron microscopy studies confirmed that highly exfoliated nanostructures were formed. The amount of inorganic component did not affect the thermal behavior of the polymer matrix as shown by differential scanning calorimetry or thermogravimetric analysis. The highly exfoliated clay sheets acted as nucleating agents and increased the degree of crystallinity from 51 to 69% at 5 wt %. Dynamic mechanical analysis revealed an enhancement of the storage modulus with increasing clay content above the glass-transition temperature.