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Differential scanning calorimetry (DSC) of triple blends of high molecular weight poly(N‐vinyl pyrrolidone) (PVP) with oligomeric poly(ethylene glycol) (PEG) of molecular weight 400 g/mol and copolymer of methacrylic acid with ethylacrylate (PMAA‐co‐EA) demonstrates partial miscibility of polymer components, which is due to formation of interpolymer hydrogen bonds (reversible crosslinking). Because both PVP and PMAA‐co‐EA are amorphous polymers and PEG exhibits crystalline phase, the DSC examination is informative on the phase state of PEG in the triple blends and reveals a strong competition between PEG and PMAA‐co‐EA for interaction with PVP. The hydrogen bonding in the triple PVP–PEG–PMAA‐co‐EA blends has been established with FTIR Spectroscopy. To evaluate the relative strengths of hydrogen bonded complexes in PVP–PEG–PMAA‐co‐EA blends, quantum‐chemical calculations were performed. According to this analysis, the energy of H‐bonding has been found to diminish in the order: PVP–PMAA‐co‐EA–PEG(OH) > PVP–(OH)PEG(OH)–PVP > PVP–H2O > PVP–PEG(OH) > PMAA‐co‐EA–PEG(O) > PVP–PMAA‐co‐EA > PMAA‐co‐EA–PEG(OH). Thus, most stable complexes are the triple PVP–PMAA‐co‐EA–PEG(OH) complex and the complex wherein comparatively short PEG chains form simultaneously two hydrogen bonds to PVP carbonyl groups through both terminal OH‐groups, acting as H‐bonding crosslinks between longer PVP backbones. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Mechanisms of molecular interaction in the blends of a polybase, a copolymer of N,N-dimethylaminoethylmethacrylate with methylmethacrylate and butylmethacrylate (PDMAEMA-MMA/BMA), with a polyacid, a copolymer of methacrylic acid with ethylacrylate (PMAA-co-EA), and plasticizer, triethylcitrate (TEC), have been investigated with FTIR Spectroscopy and potentiometry. To evaluate the strengths of hydrogen and ionic bonds in the polyelectrolyte complexes, quantum-chemical calculations were performed. According to this analysis, the energy of ionic and hydrogen bonding diminishes in the order: multi-component complexes involving protonated aminogroup of DMAEMA (ammonium cation) in the presence of chlorine counterion with ionized or unchanged carboxyl groups and water molecules (690-520 kJ/mol) > ternary H-bonded acid-base complexes associated with molecule of water (520-420 kJ/mol) > binary ionic complex of carboxylate anion and ammonium cation (404 kJ/ mol) > H-bonded complex of carboxylate and ammonium ions (257 kJ/mol) > binary H-bonded complex of uncharged carboxyl group with ammonium cation (114 kJ/mol) > ternary H-bonded complex of uncharged carboxyl group, aminogroup and water molecule (43 kJ/mol) > binary H-bonded complex between nonionized carboxyl and amino groups (26 kJ/mol). Proton-donating capability of functional groups in the studied polyelectrolyte blends diminishes in the order: HN þ (CH 3 ) 2 À > HOOCA > HOA. The proton-donating capacity can be significantly improved in the presence of Cl À ions, the effect of which may be appreciably inhibited if Na þ cations are available in the blend or solution. Proton-accepting capability weakens in the order: uncharged aminogroup > carboxylate anion > uncharged carboxyl group > hydroxyl group. The results of quantum chemical calculations facilitate interpretation of FTIR spectra.

Transdermal delivery of fentanyl from various adhesive matrix formulations to achieve a steady-state skin flux was investigated. For this purpose, various pressure-sensitive adhesives selected from the three chemical classes of polymers (polyisobutylene (PIB), acrylate, and silicone adhesives) were characterized with respect to fentanyl's solubility, diffusion coefficient, and permeability coefficient. The solubility of fentanyl in various pressure-sensitive adhesives at 32 degrees C was determined by the drug absorption-desorption method. The solubilities of fentanyl in these adhesives were in the following order: acrylate > silicones > PIB. The permeability coefficient and diffusion coefficient of fentanyl in these adhesives were determined by the membrane diffusion method. The diffusion coefficient rank order was silicone-2920 > silicone-2675 > or = acrylate > PIB. The release profiles of fentanyl in the aqueous buffer from these adhesives with 2-4% drug loading was evaluated. The release rate of fentanyl from the acrylate polymer was significantly higher than those of silicone and PIB adhesives. The in vitro flux of fentanyl through cadaver skin from various adhesives with 2% drug loading was determined at 32 degrees C using modified Franz diffusion cells. The skin fluxes of fentanyl from silicone-2920 and PIB adhesives were 6.3 +/- 0.7 and 3.1 +/- 0.3 micrograms/cm2/h, respectively. On the other hand, the skin fluxes of fentanyl from acrylate and silicone-2675 adhesive matrices were about 1 microgram/cm2/h. The effect of drug loading on skin flux was investigated using PIB as a model adhesive. The drug released in the phosphate buffer (pH = 6.0) increased linearly as the drug loading in the PIB was increased from 1% to 4%; and as the drug loading exceeded 4%, an initial burst effect followed by a zero-order release was observed. The skin flux of fentanyl increased proportionally as the drug loading in the PIB adhesive was increased from 1 to 4%, and a plateau was reached beyond 4% drug loading. These results suggest that fentanyl concentration in the PIB adhesive might have reached saturation above 4% drug loading and that the optimum skin flux was accomplished from such a system because of attainment of maximum thermodynamic activity.