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Titolo:
Low frequency dielectric investigations into the relaxation behavior of frozen polyvinylpyrrolidone-water systems
Autore:
Barker, SA; He, R; Craig, DQM;
Indirizzi:
Queens Univ Belfast, Sch Pharm, Belfast BT9 7BL, Antrim, North Ireland Queens Univ Belfast Belfast Antrim North Ireland BT9 7BL m, North Ireland
Titolo Testata:
JOURNAL OF PHARMACEUTICAL SCIENCES
fascicolo: 2, volume: 90, anno: 2001,
pagine: 157 - 164
SICI:
0022-3549(200102)90:2<157:LFDIIT>2.0.ZU;2-H
Fonte:
ISI
Lingua:
ENG
Soggetto:
DIFFERENTIAL SCANNING CALORIMETRY; AMORPHOUS PHARMACEUTICAL SOLIDS; GLASS-TRANSITION TEMPERATURES; MOLECULAR MOBILITY; POLYMER-SOLUTION; POLY(VINYLPYRROLIDONE); FORMULATIONS; SUCROSE; STATE;
Keywords:
amorphous; dielectric; freeze drying; glass; modulated temperature differential scanning calorimetry (MTDSC); polyvinylpyrrolidone (PVP); relaxation;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
34
Recensione:
Indirizzi per estratti:
Indirizzo: Craig, DQM Queens Univ Belfast, Sch Pharm, 97 Lisburn Rd, Belfast BT9 7BL,Antrim, North Ireland Queens Univ Belfast 97 Lisburn Rd Belfast Antrim North Ireland BT9 7BL
Citazione:
S.A. Barker et al., "Low frequency dielectric investigations into the relaxation behavior of frozen polyvinylpyrrolidone-water systems", J PHARM SCI, 90(2), 2001, pp. 157-164

Abstract

The low frequency dielectric response of aqueous solutions containing 0, 1, 5, and 10% w/v polyvinylpyrrolidone (PVP) was studied to characterize thelow temperature relaxation behavior of these systems. Complementary modulated temperature differential scanning calorimetry (MTDSC) studies allowed measurement of the glass transition temperature for these materials, corresponding to the behavior of the nonfrozen phase. Dielectric investigations inthe frequency range of 10(6) to 10(-2) Hz were performed on the systems inthe liquid state, with a Maxwell-Wagner response noted for both the PVP solutions and water. The solid-phase responses were studied over a range of temperatures down to -70 degreesC, with a relaxation peak observed for the PVP systems in the kilohertz region. The spectra were modeled using the Havriliak-Negami equation and the corresponding relaxation times were calculated, with a satisfactory fit to the Arrhenius equation noted. The calculated activation energies were similar to literature values for the dielectric relaxation of water. It is suggested that the dielectric response is primarily a reflection of the relaxation behavior of the water molecules in the nonfrozen fraction, thereby indicating that the dielectric technique may yieldinsights into specific components of frozen aqueous systems. (C) 2001 Wiley-Liss, Inc.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 02/07/20 alle ore 21:03:45