{ We analyse the Schlieren textures formed by the nematic director in a thermotropic main-chain liquid crystalline polymer. After an initial coarsening, the textures reach a stable time-independent state which appears to be an equilibrium function of temperature and material parameters, with a characteristic length scale of order 2 m. In particular, we study the evolution of this domain size when the temperature approaches the nematic-isotropic transition Tni. The texture size increases towards Tni, but decreases reversibly when the temperature decreases back into the nematic phase. We discuss possible theoretical models that may explain such an equilibrium polydomain state of nematic director and the dependence of its size on the nematic order parameter.

Abstract. We report a dynamical-mechanical study of stress relaxation at small deformation in a natural (polyisoprene) rubber well above its glass transition temperature Tg. We find that an almost complete relaxation of stress takes place over very long relaxation periods, even though the elastic network is retained. The relaxation rate and the long-time equilibrium modulus are sensitive functions of temperature which do not follow time-temperature superposition. Many characteristic features of non-ergodic ageing response are apparent at both short and very long times. We interpret the observed behaviour in terms of the nature of rubber crosslinks, capable of isomerisation under stress, and relate the results to recent models of slow glassy rheology.

In a polydisperse thermotropic main-chain liquid crystalline polymer, we observe the process of thermally induced nematic−nematic phase separation between short and long polymer chains. We study the dynamical features of this system, in particular the evolution of Schlieren textures formed by disclinations surrounding areas of relatively uniform director. We analyze the dependence of domain size ξ on temperature and the nematic order parameter, and the evolution of textures with the waiting time at a temperature well below the nematic transition T ni. We find that before phase separation the coarsening proceeds toward the uniform state, with characteristic size of the texture increasing as ξ ∼ t 1/4. When the system is phase-separated, the texture in the regions with long chains is frozen at an equilibrium value ξ, a reversible function of temperature, while in the short-chain regions the coarsening accelerates. This behavior is interpreted in terms of a miscibility gap that is proportional to the degree of nematic order, which is different for the different lengths of the nematic polymers.

This chapter presents a non-conventional formative initiative which considers the e-assessment and feedback of project management competences in higher education. The proposed model is built upon a virtual learning environment (VLE) that offers opportunities for students to experience situations that are similar to what they will encounter in the working world. More specifically, the simulation environment is used to recreate the reality of an organization dedicated to direct, manage, and organize projects. The designed VLE enables the e-assessment and feedback of individual project management competences by considering a set of performance indicators for each participant in the simulation. That is, the performance and contribution of each student is measured through different pieces of evidence that are pertinent to each assessed competence. Additionally, the analysis and process of the information gathered from the VLE allows to deliver varied and detailed information to the learners with the intention of modifying their thinking or behavior and improving their learning process.