Glass transition temperature experimental demonstration

Analysis of the experimental data shows that the glass transition temperature decreases when the film thickness is less than 400nm (compare these data with results for bulk PS film (1pm thick) in Rg. 7.13). Note that the x axis is not continuous in this figure. For the thinnest film presented in this plot, the glass transition temperature decreases by 20 C from its bulk value. These results follow general trends observed for ultrathin polymeric films deposited on solid substrates with weak film-substrate interactions (Tsukruk et al. 2003). These data demonstrate the sensitivity of the present micro/nano-TA design to probe nanometer-thick polymer films. 

Polymer blends are used for a variety of reasons. The principal motivation is to enhance the properties of the individual homopolymers in the blend. However, the polymers must be compatible, which means that they must form stable mixtures at the molecular level. The behavior of polymer blends depends, in general, on the degree of mixing of the components and their mutual interaction, as well as on the individual properties of the components. Most pairs of polymers are not miscible on a molecular level, and, in the majority of cases, the mixing of two polymers results in phase separation. Such phase-separated systems exhibit poor mechanical properties. The presence of one polymer in the other polymer phase is commonly demonstrated by experimental observations of the glass transition temperature, Tg, of the coexisting phases. The Tg of one component will be displaced in the direction of the Tg of the second component. For amorphous polymer blends, only a single Tg is observed. 

---