| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Tuesday Sessions |
| Session TF-TuM |
| Session: | Nanostructured Surfaces & Thin Films II |
| Presenter: | Cathy McNamee, Shinshu University, Japan |
| Authors: | C. McNamee, Shinshu University, Japan S. Fujii, Osaka Institute of Technology, Japan S. Yusa, University of Hyogo, Japan M. Kappl, MPIP, Germany |
| Correspondent: | Click to Email |
The use of Langmuir monolayers of polymer particles stabilized at air/liquid surfaces in medical and industrial applications are affected by their physical properties, e.g., stiffness (deformability), their resistance against breakage upon impact of other materials, and their adhesion to other surfaces. We previously studied the physical properties of a Langmuir monolayer of polystyrene particles loaded with poly(N,N-dimethylaminoethyl methacrylate) (particle abbreviation: “PDMA_PS”) at air/aqueous interfaces by using the Monolayer Particle Interaction Apparatus [1]. A particle was attached to an Atomic Force Microscope cantilever (probe), which acted as the colliding material. The probe was brought from the bulk water to the monolayer of PDMA_PS particles at the air/water interface and then returned back into the bulk water, during which time the forces between the probe and the monolayer were measured. A monolayer of PDMA_PS particles at the air/water interface was seen from the force-distance curves to give a low stiffness, a result explained by the induced movement of the particles in the monolayer at the air/water interface by the probe, when the probe was brought into contact with the monolayer from the bulk water.
In this study, we aimed to create a Langmuir monolayer of polymer particles at an air/water interface that showed a high stiffness, even after the collision of a probe or another material. This was achieved by adding a poly(2-hydroxyethyl methacrylate) (“PHEMA”) polymer to a Langmuir monolayer of PDMA_PS particles at an air/water interface. The mixed PHEMA- PDMA_PS monolayer gave a polymer-like monolayer at low surface pressures and a particle-like monolayer at high surface pressures. The PDMA_PS particles formed small aggregates that were dispersed throughout the PHEMA monolayer at low surface pressures, a result suggesting that the particles were trapped in the PHEMA network. The stiffness of the mixed monolayer was independent of the surface pressure, but increased as the ratio of PHEMA in the mixed monolayer increased. The stiffness increase was explained by the PDMA_PS particles being embedded in the PHEMA polymer network, which inhibited the movement of the PDMA_PS particles by the probe. A PHEMA polymer monolayer containing a small amount of PDMA_PS particles gave a stiffer film than a pure PHEMA polymer monolayer. It was therefore concluded that the stiffness of a particle monolayer could be changed by adding a polymer to a Langmuir monolayer of particles.
[1] McNamee, C.E.; Fujii, S.; Yusa, S.; Azakami, Y.; Butt, H.-J.; Kappl, M. Colloid Surf. B-Biointerfaces, 2015, 470, 322-332.