Interactions between a polystyrene particle and hydrophilic and hydrophobic surfaces in aqueous solutions
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Interactions between a polystyrene particle and hydrophilic and hydrophobic surfaces in aqueous solutions. / Thormann, Esben; Simonsen, Adam C.; Hansen, Per L.; Mouritsen, Ole G.
In: Langmuir, Vol. 24, No. 14, 15.07.2008, p. 7278-7284.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Interactions between a polystyrene particle and hydrophilic and hydrophobic surfaces in aqueous solutions
AU - Thormann, Esben
AU - Simonsen, Adam C.
AU - Hansen, Per L.
AU - Mouritsen, Ole G.
PY - 2008/7/15
Y1 - 2008/7/15
N2 - The interaction between a colloidal polystyrene particle mounted on an AFM cantilever and a hydrophilic and a hydrophobic surface in aqueous solution is investigated. Despite the apparent simplicity of these two types of systems a variety of different types of interactions are observed. The system containing the polystyrene particle and a hydrophilic surface shows DLVO-like interactions characteristic of forces between charged surfaces. However, when the surface is hydrophobized the interaction changes dramatically and shows evidence of a bridging air bubble being formed between the particle and the surface. For both sets of systems, plateaus of constant force in the force curves are obtained when the particle is retracted from the surface after being in contact. These events are interpreted as a number of individual polystyrene molecules that are bridging the polystyrene particle and the surface. The plateaus of constant force are expected for pulling a hydrophobic polymer in a bad (hydrophilic) solvent. The plateau heights are found to be of uniform spacing and independent of the type of surface, which suggests a model by which collapsed polymers are extended into the aqueous medium. This model is supported by a full stretching curve showing also the backbone elasticity and a stretching curve obtained in pentanol, where the plateau changes to a nonlinear force response, which is typical for a polymer in a good or neutral solvent. We suggest that these polymer bridges are important in particular for the interaction between polystyrene and the hydrophilic surface, where they to some extent counteract the long-range electrostatic repulsion.
AB - The interaction between a colloidal polystyrene particle mounted on an AFM cantilever and a hydrophilic and a hydrophobic surface in aqueous solution is investigated. Despite the apparent simplicity of these two types of systems a variety of different types of interactions are observed. The system containing the polystyrene particle and a hydrophilic surface shows DLVO-like interactions characteristic of forces between charged surfaces. However, when the surface is hydrophobized the interaction changes dramatically and shows evidence of a bridging air bubble being formed between the particle and the surface. For both sets of systems, plateaus of constant force in the force curves are obtained when the particle is retracted from the surface after being in contact. These events are interpreted as a number of individual polystyrene molecules that are bridging the polystyrene particle and the surface. The plateaus of constant force are expected for pulling a hydrophobic polymer in a bad (hydrophilic) solvent. The plateau heights are found to be of uniform spacing and independent of the type of surface, which suggests a model by which collapsed polymers are extended into the aqueous medium. This model is supported by a full stretching curve showing also the backbone elasticity and a stretching curve obtained in pentanol, where the plateau changes to a nonlinear force response, which is typical for a polymer in a good or neutral solvent. We suggest that these polymer bridges are important in particular for the interaction between polystyrene and the hydrophilic surface, where they to some extent counteract the long-range electrostatic repulsion.
UR - http://www.scopus.com/inward/record.url?scp=47949105303&partnerID=8YFLogxK
U2 - 10.1021/la8005162
DO - 10.1021/la8005162
M3 - Journal article
C2 - 18553951
AN - SCOPUS:47949105303
VL - 24
SP - 7278
EP - 7284
JO - Langmuir
JF - Langmuir
SN - 0743-7463
IS - 14
ER -
ID: 230977307