研究目的
The aim of this work is to study the impact of ring-substitution pattern in azobenzenes incorporated to PMMA matrix (guest-host) and covalently attached to the polymer (side-chain) on their thermophysical properties.
研究成果
Thermophysical parameters of azobenzene-containing polymer thin films with different substituents in the side-chain, and guest-host systems were investigated. The combination of PTR and SThM with AFM imaging provides complementary information about the heat transport properties of azobenzene polymer thin films. The results showed the influence of peripheral substituents as well as that of the polymer system on the thermophysical properties of studied azo polymers.
研究不足
Organic polymers are challenging materials because of their temperature sensitive structure. Accordingly, thermophysical measurements should be carried out at the lowest temperature possible, while keeping a high signal to noise ratio. This can be especially problematic when the size of sample is reduced to sub-microns, resulting in a subtle thermal signal.
1：Experimental Design and Method Selection
Photothermal radiometry (PTR) and scanning thermal microscopy (SThM) were used for determination of thermophysical properties of polymer samples. The topography of studied compounds was examined by atomic force microscopy (AFM).
2：Sample Selection and Data Sources
The methacrylic polymer films containing azobenzenes with different peripheral substituents in the form of side-chain (P) and guest-host (A) systems were thermally investigated. The azo polymers with thicknesses below 1 μm were deposited on glass substrates using spin coating method.
3：List of Experimental Equipment and Materials
Spin-coater (Chemat Technology, SCS G3P-8, Inc USA), sputter coater (Bal-Tec SCD 050, USA), profilometer (KLA Tencor, Alpha-Step IQ, USA), microscope (Park Systems XE-70, Korea), lock-in amplifier (Stanford Research Systems, SR865, USA), laser (Dream Lasers Technol. Co., SDL-532-300T, China).
4：Experimental Procedures and Operational Workflow
The polymer thin films were deposited on cleaned BK7 glass substrates using a spin-coater. After deposition, the thin films were baked at 70°C for 60 min to remove any remaining solvent. Half of the surface of each polymer sample was coated with gold/palladium (80/20). The Au/Pd films were deposited by sputter coater.
5：Data Analysis Methods
A one-dimensional (1D) model of heat propagation in a multilayered system was applied for the analysis of amplitude and phase spectra of the investigated samples. The quadrupole method including radiation absorption in the first layer (Au/Pd film) was used to fit the experimental data.
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