Molecular dynamics polymer films

A capacitive sensor with a molecularly imprinted polymer film as a sensitive layer has been reported. The layer was prepared by electropolymerization of phenol on a gold electrode with the template molecule, phenylalanine. The sensor capacitance was decreased by the addition of phenylalanine, but there was almost no change with glycine, tryptophan and phenol. The response time was 15 min (time for a half of the stationary value, 60 min), and the dynamic range was given as 0.5 to... 

While thin polymer films may be very smooth and homogeneous, the chain conformation may be largely distorted due to the influence of the interfaces. Since the size of the polymer molecules is comparable to the film thickness those effects may play a significant role with ultra-thin polymer films. Several recent theoretical treatments are available [136-144,127,128] based on Monte Carlo [137-141,127, 128], molecular dynamics [142], variable density [143], cooperative motion [144], and bond fluctuation [136] model calculations. The distortion of the chain conformation near the interface, the segment orientation distribution, end distribution etc. are calculated as a function of film thickness and distance from the surface. In the limit of two-dimensional systems chains segregate and specific power laws are predicted [136, 137]. In 2D-blends of polymers a particular microdomain morphology may be expected [139]. Experiments on polymers in this area are presently, however, not available on a molecular level. Indications of order on an... 

Polymer films were produced by surface catalysis on clean Ni(100) and Ni(lll) single crystals in a standard UHV vacuum system H2.131. The surfaces were atomically clean as determined from low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). Monomer was adsorbed on the nickel surfaces circa 150 K and reaction was induced by raising the temperature. Surface species were characterized by temperature programmed reaction (TPR), reflection infrared spectroscopy, and AES. Molecular orientations were inferred from the surface dipole selection rule of reflection infrared spectroscopy. The selection rule indicates that only molecular vibrations with a dynamic dipole normal to the surface will be infrared active [14.], thus for aromatic molecules the absence of a C=C stretch or a ring vibration mode indicates the ring must be parallel the surface. 

Photophysical Studies of Molecular Mobility in Polymer Films and Bulk Polymers. 3. Dynamic Excimer Formation of Pyrene in Bulk PDMS, Macromolecules 23, 2217-2222. 

Chapter 11 Molecular Dynamics In Thin Polymer Films 595... 

This aspect facilitates a deeper insight into the mechanism of the Tg reductions observed in thin polymer films [36-42], Faster dynamics, by definition an increase of the average relaxation rate, can be achieved in two ways Either the polymer segments (at the molecular level), are relaxing faster... 

---