TY - JOUR
T1 - Monolayer behavior of silica particles at air/water interface
T2 - A comparison between chemical and physical modifications of surface
AU - Lee, Yuh Lang
AU - Du, Zhung Ching
AU - Lin, Wei Xin
AU - Yang, Yu Min
N1 - Funding Information:
This research is partially supported by the National Science Council of the Taiwan through Grant No. NSC 92-2214-E-006-024. Professors Chien-Hsiang Chang, Hsien-Hung Wei and Bing-Hung Chen are gratefully acknowledged for their helpful discussion.
PY - 2006/4/1
Y1 - 2006/4/1
N2 - Silica particles are hydrophobized either by chemical graft of alkyl chains or by physical adsorption of cationic surfactants, alkyltrimethylammonium bromide. The effects of the two modification methods on the monolayer behavior of silica particles at the air/water interface are studied, as well as the packing structure of the particulate films. The results show that the hydrophobicity of particles chemically modified by octanol (SiO 2-C8) and dodecanol (SiO2-C12) are similar and higher than that modified by butanol (SiO2-C 4). The monolayer composed of particles with higher hydrophobicity shows a large lift-off area, higher compressibility, and significant hysteresis due to the higher particle-particle interaction. As a result, the particulate films exhibit 2-dimensional (2D) aggregative domains of closely-packed structure, but with particle free regions presenting among the domains. The monolayer prepared by SiO2-C4 shows a contrary behavior resulted from the higher particle-water interaction. The particles modified by adsorption of cationic surfactants have an amphiphilic property at the air/water interface. Such monolayer exhibits lower compressibility and hysteresis, higher re-spreading characteristic, and a lower collapse pressure compared with those of the chemically modified particles. A particulate film with high uniformity and closely-packed structure can be obtained by using the octyltrimethylammonium bromide (OTAB) modified particles. When the alkyl chain of surfactant increases, the packing of the particles becomes looser. Such phenomenon is probably caused from the higher probability for the long-chain surfactants to stay at the air/water interface which obstructs the intimate contact of particles.
AB - Silica particles are hydrophobized either by chemical graft of alkyl chains or by physical adsorption of cationic surfactants, alkyltrimethylammonium bromide. The effects of the two modification methods on the monolayer behavior of silica particles at the air/water interface are studied, as well as the packing structure of the particulate films. The results show that the hydrophobicity of particles chemically modified by octanol (SiO 2-C8) and dodecanol (SiO2-C12) are similar and higher than that modified by butanol (SiO2-C 4). The monolayer composed of particles with higher hydrophobicity shows a large lift-off area, higher compressibility, and significant hysteresis due to the higher particle-particle interaction. As a result, the particulate films exhibit 2-dimensional (2D) aggregative domains of closely-packed structure, but with particle free regions presenting among the domains. The monolayer prepared by SiO2-C4 shows a contrary behavior resulted from the higher particle-water interaction. The particles modified by adsorption of cationic surfactants have an amphiphilic property at the air/water interface. Such monolayer exhibits lower compressibility and hysteresis, higher re-spreading characteristic, and a lower collapse pressure compared with those of the chemically modified particles. A particulate film with high uniformity and closely-packed structure can be obtained by using the octyltrimethylammonium bromide (OTAB) modified particles. When the alkyl chain of surfactant increases, the packing of the particles becomes looser. Such phenomenon is probably caused from the higher probability for the long-chain surfactants to stay at the air/water interface which obstructs the intimate contact of particles.
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U2 - 10.1016/j.jcis.2005.08.070
DO - 10.1016/j.jcis.2005.08.070
M3 - Article
C2 - 16183071
AN - SCOPUS:33644607606
SN - 0021-9797
VL - 296
SP - 233
EP - 241
JO - Journal of Colloid And Interface Science
JF - Journal of Colloid And Interface Science
IS - 1
ER -