TY - JOUR
T1 - Continuous thermal control of hydrophilicity/hydrophobicity changes of hybrid films and of their directionality
T2 - Kinetics and substrate effects
AU - Ralbag, Noam
AU - Ruiz-Cabello, Francisco Javier Montes
AU - Rodríguez Valverde, Miguel Ángel
AU - Gutkin, Vitaly
AU - Sfez, Ruthy
AU - Avnir, David
N1 - Publisher Copyright:
© 2017 Elsevier Inc.
PY - 2017/11/1
Y1 - 2017/11/1
N2 - A successful methodology for obtaining hybrid films which allow thermal triggering and continuous, irreversible, control of their hydrophilicity/hydrophobicity nature was developed. Two types of poly(dimethylsiloxane)-silica (PDMS@SiO2) films were prepared for that purpose: A hydrophilic film in which the thermal treatment causes an irreversible gradual increase of hydrophobicity; and a hydrophobic film that turns more hydrophilic upon thermal treatment. The opposite directionality of the change is dictated by the film substrate, on which the same hybrid is deposited. In both cases the thermal treatment induced a phase separation which caused the change in hydrophobicity. The magnitude of change in hydrophilicity/hydrophobicity is continuously controllable in both types of films by either the temperature or heating time. The films were characterized before and after heating by a variety of methods, including contact angle (CA) measurements with the sessile drop and the tilting plate methods, and by X-ray photoelectron spectroscopy (XPS) analysis. A thorough kinetic study was carried out, following the progress of the changes in the wettability property of the surfaces. The kinetics analyses proved that the changes in the wettability in all cases are due to phase separation processes, the directionality of which is determined by the treatment of the substrate on which the films are deposited. By monitoring the change of wettability (ΔCA) at various temperatures, an Arrhenius plot was obtained from which the activation energy and Arrhenius pre-exponential factor for the phase separation were derived, corroborating the proposed mechanism. To the best of our knowledge, this is the first use of phase separation behavior of a hybrid film in order to apply irreversible, thermally controllable change of surface wettability, tailored to proceed in opposite directions, and the first kinetic study of such a process.
AB - A successful methodology for obtaining hybrid films which allow thermal triggering and continuous, irreversible, control of their hydrophilicity/hydrophobicity nature was developed. Two types of poly(dimethylsiloxane)-silica (PDMS@SiO2) films were prepared for that purpose: A hydrophilic film in which the thermal treatment causes an irreversible gradual increase of hydrophobicity; and a hydrophobic film that turns more hydrophilic upon thermal treatment. The opposite directionality of the change is dictated by the film substrate, on which the same hybrid is deposited. In both cases the thermal treatment induced a phase separation which caused the change in hydrophobicity. The magnitude of change in hydrophilicity/hydrophobicity is continuously controllable in both types of films by either the temperature or heating time. The films were characterized before and after heating by a variety of methods, including contact angle (CA) measurements with the sessile drop and the tilting plate methods, and by X-ray photoelectron spectroscopy (XPS) analysis. A thorough kinetic study was carried out, following the progress of the changes in the wettability property of the surfaces. The kinetics analyses proved that the changes in the wettability in all cases are due to phase separation processes, the directionality of which is determined by the treatment of the substrate on which the films are deposited. By monitoring the change of wettability (ΔCA) at various temperatures, an Arrhenius plot was obtained from which the activation energy and Arrhenius pre-exponential factor for the phase separation were derived, corroborating the proposed mechanism. To the best of our knowledge, this is the first use of phase separation behavior of a hybrid film in order to apply irreversible, thermally controllable change of surface wettability, tailored to proceed in opposite directions, and the first kinetic study of such a process.
KW - Hybrid-films
KW - Hydrophilic film
KW - Hydrophobic film
KW - Kinetics analysis
KW - PDMS
KW - Phase separation
KW - Silica
KW - Sol-gel
KW - Thermal trigger
UR - http://www.scopus.com/inward/record.url?scp=85021132915&partnerID=8YFLogxK
U2 - 10.1016/j.jcis.2017.06.036
DO - 10.1016/j.jcis.2017.06.036
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C2 - 28658655
AN - SCOPUS:85021132915
SN - 0021-9797
VL - 505
SP - 692
EP - 702
JO - Journal of Colloid and Interface Science
JF - Journal of Colloid and Interface Science
ER -