1,721,143 research outputs found
Physiochemical characterization and coating of polyurethane with a new heparin adsorbing material
No full textThe coating of polyurethane devices was obtained by using a solution of a new heparin-adsorbing material. PUPA. The structure of the coated material was investigated at different depths by FTIR techniques. The bond with heparin is electrostatic, as revealed by subtracting the spectrum of the native PUPA from that of the heparinized sample
Thermodynamics of protonation and Cu(II) complex formation with polymers containing different basic groups.
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Protonation thermodynamics of multiple-stimuli responsive polymers in drug delivery technology
No full textA series of polyelectrolytes having an additional carboxyl group in the side chain was investigated. The four polymers: poly(N-acryloyl-L-valine) (PAV), poly(N-methacryloyl-L-valine) (PMAV), poly(N-acryloyl-L-leucine) (PAL) and poly(N-methacryloyl-L-leucine) (PMAL) were synthesized by radical polymerization of the corresponding monomers. The protonation of the carboxylate group in the polymer and copolymer showed polyelectrolyte behavior with compact conformation in water due to hydrophobic forces between isopropyl groups
Thermodynamic behavior of polyelectrolytes with the lower critical solution temperature (LCST) phenomenon
No full textA series of vinyl polymers with L-valine and L-leucine residues, and related copolymers with N-isopropylacrylamide, were studied in aqueous solution at different temperatures (25, 30 and 35 degrees C) and at two ionic strengths (0.01 M and 0.1 M NaCl). The protonation behavior revealed great differences between the polymers that were attributed to the size of the hydrophobic lateral group. macromolecular shrinkage, occurring above a critical degree of protonation beta, was related to hydrophobic forces outweighing the electrostatic repulsions between COO-groups. Low salt concentrations increased the electrostatic potential while high temperatures increased the hydrophobic interaction at lower beta. The release of fewer water molecules structured around the polymer chain, responsible for the lower critical solution temperature phenomenon, revealed lower entropy changes at higher temperatures. The reversible configuration of graft polymer chains instantly responded to changes in pH and temperature, modifying the water filtration rates through the pores of cellulose membranes
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