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Papers by Sreenivasulu Puchalapalli

Research paper thumbnail of Molecular Imprinting in Hydrogen Bonding Networks of Polyamide Nylon for Recongnition of Amino Acids

Chemistry Letters, 1999

Abstract;Molecularly imprinted Nylon-6 was prepared from the polymer solution of formic acid havi... more Abstract;Molecularly imprinted Nylon-6 was prepared from the polymer solution of formic acid having L-glutamine template. The recognition of amino acids by L-glutamine imprinted-polymer was evaluated by binding experiments for L-glutamine and its analogues. It was revealed ...

Research paper thumbnail of Aromatic polyamide–imides as materials for membranes. I. Synthesis and characterization

Journal of Applied Polymer Science, 1995

Diamine amic acids were synthesized by reacting aromatic diamines with pyromellitic dianhydride i... more Diamine amic acids were synthesized by reacting aromatic diamines with pyromellitic dianhydride in dimethylacetamide/dioxane. High molecular weight polyamide-amic acids were prepared by low-temperature solution polymerization of diamine amic acids with isophthaloyl chloride in dimethylacetamide. The cyclodehydration of polyamide-amic acids to the corresponding polyamide–imides was accomplished by heating the cast films at 175°C for 3 h. The polyamide–imides were soluble in polar aprotic solvents like dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone and could be cast into tough and flexible films. They were characterized by elemental analyses, inherent viscosities, IR, and 1H-NMR spectra. The glass transition temperatures of polyamide–imides were determined by differential scanning calorimetry. The thermal stabilities of the polymers were measured by thermogravimetric analyses in air. © 1995 John Wiley & Sons, Inc.

Research paper thumbnail of Synthesis and characterization of novel aromatic poly(amide–imide)s with alternate (amide–amide) and (imide–imide) sequences

European Polymer Journal, 1998

Diamine amic acids were synthesized by reacting aromatic diamines with 3,3′,4,4′-benzophenonetetr... more Diamine amic acids were synthesized by reacting aromatic diamines with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride in dimethylacetamide and were characterized by melting points, elemental analyses, IR, 1H-NMR and HPLC. Poly(amide–amic acid)s were prepared by low temperature solution polycondensation of diamine amic acids with isophthaloyl chloride in dimethylacetamide. Poly(amide–imide)s with alternate (amide–amide) and (imide–imide) sequences were obtained by cycloimidization of poly(amide–amic acid)s with Et3N–Ac2O mixture in dimethylacetamide solution. They were characterized by solubilities, inherent viscosities, IR and 1H-NMR. Thermal properties of the polymers were measured by differential scanning calorimetry and thermogravimetric analyses.

Research paper thumbnail of Molecular imprinting of caffeine and its recognition assay by quartz-crystal microbalance

Analytica Chimica Acta, 2001

Phase inversion precipitation method was applied to prepare molecularly imprinted polyacrilonitri... more Phase inversion precipitation method was applied to prepare molecularly imprinted polyacrilonitrile (PAN) copolymers. Three types of PAN copolymers with pyridine and styrene moieties were used for caffeine (CAF) imprinting. For encoding shape of the template molecules into the ...

Research paper thumbnail of Recognition characteristics of dibenzofuran by molecularly imprinted polymers made of common polymers

European Polymer Journal, 2002

Dibenzofuran (DBF) recognition was studied by a molecularly imprinted polymer (MIP) made of comme... more Dibenzofuran (DBF) recognition was studied by a molecularly imprinted polymer (MIP) made of commercially available polymers: polyvinyl chloride (PVC), polysulfone, polystyrene, and polyacrylonitrile. Preparation of MIPs was carried out by phase inversion of the polymer. ...

Research paper thumbnail of Molecularly Imprinted Polysulfone Membranes Having Acceptor Sites for Donor Dibenzofuran as Novel Membrane Adsorbents: Charge Transfer Interaction as Recognition Origin

Chemistry of Materials, 2002

Novel molecularly imprinted membranes having dibenzofuran (DBF) recognition were developed and bi... more Novel molecularly imprinted membranes having dibenzofuran (DBF) recognition were developed and binding properties of DBF were studied using the polysulfone membrane prepared by phase inversion imprinting. Polysulfone (PSf) having a phenyl-sulfone group and DBF template was solublized in dimethyl acetamide (DMAc) and the polymer solution was coagulated in water to prepare porous membranes. After template molecules were extracted from the membranes by washing with methanol, recognition experiments with DBF-imprinted membranes were carried out in methanol solution, water/methanol solution, and water solution for DBF and DBF analogues, dibenzodioxin (DBD), diphenyl ether (DPE), and benzodioxin (BDO). In water, high binding amounts of DBF and DBD were observed in the range of 28-39 µmol/g capacity, but the recognition was very low. Methanol/water media showed high recognition of the imprinted membrane with a low binding capacity of DBF (4.5 µmol/g). These results indicated that nonselective binding occurred in the water media due to a hydrophobic effect. Evidence revealed that membrane recognition in methanol and methanol/water was effective for DBF because of charge transfer (CT) complexation between the donor DBF and acceptor phenyl-sulfone group of PSf. This kind of interaction was very useful for high retention and recognition of DBF as an efficient membrane adsorbent via donor-aceptor CT interaction.

Research paper thumbnail of Molecular Imprinting in Hydrogen Bonding Networks of Polyamide Nylon for Recongnition of Amino Acids

Chemistry Letters, 1999

Abstract;Molecularly imprinted Nylon-6 was prepared from the polymer solution of formic acid havi... more Abstract;Molecularly imprinted Nylon-6 was prepared from the polymer solution of formic acid having L-glutamine template. The recognition of amino acids by L-glutamine imprinted-polymer was evaluated by binding experiments for L-glutamine and its analogues. It was revealed ...

Research paper thumbnail of Aromatic polyamide–imides as materials for membranes. I. Synthesis and characterization

Journal of Applied Polymer Science, 1995

Diamine amic acids were synthesized by reacting aromatic diamines with pyromellitic dianhydride i... more Diamine amic acids were synthesized by reacting aromatic diamines with pyromellitic dianhydride in dimethylacetamide/dioxane. High molecular weight polyamide-amic acids were prepared by low-temperature solution polymerization of diamine amic acids with isophthaloyl chloride in dimethylacetamide. The cyclodehydration of polyamide-amic acids to the corresponding polyamide–imides was accomplished by heating the cast films at 175°C for 3 h. The polyamide–imides were soluble in polar aprotic solvents like dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone and could be cast into tough and flexible films. They were characterized by elemental analyses, inherent viscosities, IR, and 1H-NMR spectra. The glass transition temperatures of polyamide–imides were determined by differential scanning calorimetry. The thermal stabilities of the polymers were measured by thermogravimetric analyses in air. © 1995 John Wiley & Sons, Inc.

Research paper thumbnail of Synthesis and characterization of novel aromatic poly(amide–imide)s with alternate (amide–amide) and (imide–imide) sequences

European Polymer Journal, 1998

Diamine amic acids were synthesized by reacting aromatic diamines with 3,3′,4,4′-benzophenonetetr... more Diamine amic acids were synthesized by reacting aromatic diamines with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride in dimethylacetamide and were characterized by melting points, elemental analyses, IR, 1H-NMR and HPLC. Poly(amide–amic acid)s were prepared by low temperature solution polycondensation of diamine amic acids with isophthaloyl chloride in dimethylacetamide. Poly(amide–imide)s with alternate (amide–amide) and (imide–imide) sequences were obtained by cycloimidization of poly(amide–amic acid)s with Et3N–Ac2O mixture in dimethylacetamide solution. They were characterized by solubilities, inherent viscosities, IR and 1H-NMR. Thermal properties of the polymers were measured by differential scanning calorimetry and thermogravimetric analyses.

Research paper thumbnail of Molecular imprinting of caffeine and its recognition assay by quartz-crystal microbalance

Analytica Chimica Acta, 2001

Phase inversion precipitation method was applied to prepare molecularly imprinted polyacrilonitri... more Phase inversion precipitation method was applied to prepare molecularly imprinted polyacrilonitrile (PAN) copolymers. Three types of PAN copolymers with pyridine and styrene moieties were used for caffeine (CAF) imprinting. For encoding shape of the template molecules into the ...

Research paper thumbnail of Recognition characteristics of dibenzofuran by molecularly imprinted polymers made of common polymers

European Polymer Journal, 2002

Dibenzofuran (DBF) recognition was studied by a molecularly imprinted polymer (MIP) made of comme... more Dibenzofuran (DBF) recognition was studied by a molecularly imprinted polymer (MIP) made of commercially available polymers: polyvinyl chloride (PVC), polysulfone, polystyrene, and polyacrylonitrile. Preparation of MIPs was carried out by phase inversion of the polymer. ...

Research paper thumbnail of Molecularly Imprinted Polysulfone Membranes Having Acceptor Sites for Donor Dibenzofuran as Novel Membrane Adsorbents: Charge Transfer Interaction as Recognition Origin

Chemistry of Materials, 2002

Novel molecularly imprinted membranes having dibenzofuran (DBF) recognition were developed and bi... more Novel molecularly imprinted membranes having dibenzofuran (DBF) recognition were developed and binding properties of DBF were studied using the polysulfone membrane prepared by phase inversion imprinting. Polysulfone (PSf) having a phenyl-sulfone group and DBF template was solublized in dimethyl acetamide (DMAc) and the polymer solution was coagulated in water to prepare porous membranes. After template molecules were extracted from the membranes by washing with methanol, recognition experiments with DBF-imprinted membranes were carried out in methanol solution, water/methanol solution, and water solution for DBF and DBF analogues, dibenzodioxin (DBD), diphenyl ether (DPE), and benzodioxin (BDO). In water, high binding amounts of DBF and DBD were observed in the range of 28-39 µmol/g capacity, but the recognition was very low. Methanol/water media showed high recognition of the imprinted membrane with a low binding capacity of DBF (4.5 µmol/g). These results indicated that nonselective binding occurred in the water media due to a hydrophobic effect. Evidence revealed that membrane recognition in methanol and methanol/water was effective for DBF because of charge transfer (CT) complexation between the donor DBF and acceptor phenyl-sulfone group of PSf. This kind of interaction was very useful for high retention and recognition of DBF as an efficient membrane adsorbent via donor-aceptor CT interaction.