Frequency Response of
Polymer Films Made from a Precursor
Colloidal Monolayer on a Nanomechanical Cantilever
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Abstract
Nanomechanical cantilevers (NMC) were used for the characterization
of the film formation process and the mechanical properties of colloidal
monolayers made from polystyrene (PS). Closely packed hexagonal monolayers
of colloids with diameters ranging from 400 to 800 nm were prepared
at the air–water interface and then transferred in a controlled
way on the surface of NMC. The film formation process upon annealing
of the monolayer was investigated by measuring the resonance frequency
of the NMC (≈12 kHz). Upon heating of non-cross-linked PS colloids,
we could identify two transition temperatures. The first transition
resulted from the merging of polymer colloids into a film. This transition
temperature at 147 ± 3 °C as measured at ≈12 kHz
remained constant for subsequent heating cycles. We attributed this
transition temperature to the glass transition temperature <i>T</i><sub>g</sub> of PS which was confirmed by dynamic mechanical
thermal analysis (DMTA) and using the time temperature superposition
principle. The second transition temperature (175 ± 3 °C)
was associated with the end of the film formation process and was
measured only for the first heating cycle. Furthermore, the transition
of the colloidal monolayer into a homogeneous film preserved the mass
loading on the NMC which allowed determination of the Young’s
modulus of PS (≈3 GPa) elegantly