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Titolo:
Poly(ethylenimine) as a subphase stabilizer of stearic acid monolayers at the air water interface: Surface pressure-area isotherm and infrared spectroscopy study
Autore:
Hwang, MJ; Kim, K;
Indirizzi:
Seoul Natl Univ, Dept Chem, Seoul 151742, South Korea Seoul Natl Univ Seoul South Korea 151742 Chem, Seoul 151742, South Korea Seoul Natl Univ, Ctr Mol Catalysis, Seoul 151742, South Korea Seoul Natl Univ Seoul South Korea 151742 ysis, Seoul 151742, South Korea
Titolo Testata:
LANGMUIR
fascicolo: 10, volume: 15, anno: 1999,
pagine: 3563 - 3569
SICI:
0743-7463(19990511)15:10<3563:PAASSO>2.0.ZU;2-E
Fonte:
ISI
Lingua:
ENG
Soggetto:
LANGMUIR-BLODGETT-FILMS; REFLECTION-ABSORPTION SPECTROMETRY; NORMAL-ALKYL CHAINS; H STRETCHING MODES; STRUCTURAL CHARACTERIZATION; VIBRATIONAL SPECTROSCOPY; AGGREGATION STRUCTURE; AIR/WATER INTERFACE; OCTADECANOIC ACID; PHASE-TRANSITIONS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
36
Recensione:
Indirizzi per estratti:
Indirizzo: Kim, K Seoul Natl Univ, Dept Chem, Seoul 151742, South Korea Seoul Natl Univ Seoul South Korea 151742 eoul 151742, South Korea
Citazione:
M.J. Hwang e K. Kim, "Poly(ethylenimine) as a subphase stabilizer of stearic acid monolayers at the air water interface: Surface pressure-area isotherm and infrared spectroscopy study", LANGMUIR, 15(10), 1999, pp. 3563-3569

Abstract

The effect of poly(ethylenimine) (PEI) dissolved in water on the surface pressure-area (pi-A) isotherm of stearic acid (STA) at the air/water interface was investigated. When the concentration of PEI was quite low, for example, 2.2 x 10(-4) g/L (5.1 x 10(-6) M in monomeric unit concentration), the isotherm of the STA monolayer was little affected by PEI. On a concentratedPEI solution, for example, at 2.2 x 10(-2) g/L, the isotherm of the STA monolayer exhibited a noticeable variation as a function of subphase pH; particularly in basic conditions. The isotherm of STA could be obtained very reproducibly even at pH 10.4. At basic pHs, PEI induced the occurrence of a wide plateau region in an isotherm that could be attributed to the coexistence of liquid-condensed (LC) and liquid-expanded (LE) phases of STA on a water subphase. In addition, the collapse pressure of the STA monolayer was raised to 68 mN/m, indicating that the stability of the monolayer could be increased dramatically by virtue of an acid-base-type interaction between theamine group of PEI and the carboxyl group of STA. In situ reflection-absorption infrared (RAIR) spectroscopy revealed that at acidic pi-Is STA molecules should form two-dimensional crystalline domains even at high "per molecular" area. In contrast, at basic pHs RAIR spectral data dictated that STA molecules were strongly disordered at high per molecular area, and a near-crystalline structure seemed to form only when the per molecular area was lowered to a value corresponding to a pure LC phase in the pi-A isotherm of STA on the PEI-containing subphase.

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Documento generato il 03/04/20 alle ore 04:03:56