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For the first time, dielectric and calorimetric investigations of an homologous series of Janus polynorbornenes with rigid main backbones and flexible -Si(OR)3 side groups, of differing length alkyl chains (R = Propyl, Butyl, Hexyl, Octyl, Decyl) is reported. Generally, this class of polymers has some potential for applications in the field of gas separation membranes. Two dielectrically active processes are observed at low temperatures, denoted as β- and α- relaxation. The former can be assigned to localized fluctuations, whilst the latter is related to the glassy dynamics of the flexible -Si(OR)3 side groups, creating a nanophase separation in both the alkyl chain rich and backbone rich domains. This is confirmed through temperature modulated DSC measurements and X-ray scattering experiments. The glass transition temperatures of the backbone rich domains, which are beyond or near to their degradation temperatures in terms of conventional DSC, are determined for the first time using Fast Scanning Calorimetry employing both fast heating and cooling rates. This is complimented with scattering experiments that show how the size of the alkyl chain rich domains increases with chain length. Alongside these results, a significant conductivity contribution was observed for all poly(tricyclononenes) with -Si(OR)3 side groups, which is interpreted in terms of a percolation model.
In the course of miniaturizing modern technology down to the molecular scale, understanding the materials behavior has to be investigated and deviations from the bulk that might arises from confinement effects has to be understood. Here, a combination of nano-sized relaxation spectroscopies (Broadband dielectric spectroscopy (BDS) and Specific heat spectroscopy (SHS); employing AC nanochip calorimetry) were utilized to investigate the glassy dynamics of ultra-thin films of blends of Poly (vinyl methyl ether) (PVME) / Polystyrene (PS) 50:50 wt-%, which are miscible bulk (thicknesses: 8nm - 200nm, film thickness was controlled by ellipsometry, film topography by AFM). Both methods are sensitive to different probes; where SHS senses entropy fluctuations while BDS measures dipole fluctuations. For BDS measurements, a recently developed nano-structured electrode sample arrangement is employed; where ultra-thin films are spin-coated on an ultra-flat highly conductive silicon wafer, sandwiched between a wafer with nanostructured SiO2 nano-spacers with heights between 35 nm and 70 nm. The method was applied for film thicknesses up to 50 nm. For thicker films, the samples were prepared between crossed electrodes. It was proven that, for 50 nm films, both contact methods will lead to identical results. By measuring the dynamic Tg in dependence of the film thickness, SHS showed that the Tg of the whole film was strongly influenced by a nanometer-thick surface layer at the polymer/air interface due to a self-assembling process [1]. The dynamic Tg obtained from the SHS measurements decrease with decreasing film thickness, evidencing the importance of a mobile surface layer at the polymer/air interface for the glass transition of the whole film. Compared to the SHS results, the BDS measurements show a completely different behavior. At high temperatures, the temperature dependence of the relaxation times of the films follows that of bulk-like PS/PVME; obeying the VFT-law. With decreasing temperature, the temperature dependence deviates from the VFT to an Arrhenius law; where the apparent activation energy decreases with decreasing film thickness. This is the first example where confinement induced changes were observed by BDS for ultra-thin films. All results were analyzed in details in a comprehensive discussion.