We have used anionic polymerization to synthesize polymers of linear and bottlebrush architecture each with a polydimethylsiloxane backbone. The blending of polymer architectures has the effect of changing material properties, e.g., the viscoelasticity, which are connected to the chain conformation. Thus, we explore the conformation of bottlebrush polymers in a linear host melt both as a function of the concentration and for various molecular weights of the linear host matrices. Our bottlebrush polymers are seen as shell-only particles with a negligible core size. We find a substantial influence of the molecular weight of the linear matrices on the structure of the bottlebrushes and their interactions. In samples with a low molecular weight matrix that have the same degree of polymerization as the side chains, the bottlebrush behavior is consistent with an effective theta solvent condition for all concentrations. With increasing molecular weight of the host matrix, this condition is only reached at the highest concentration of the bottlebrush polymers. The increase of the molecular weight of the host matrix leads to a shrinkage of the bottlebrushes and subsequently to a formation of clusters at higher volume fractions. None of the scattering patterns show a pronounced correlation peak; however, decreased forward scattering associated with a structure factor effect is observed.
Within the framework of the R&D studies for the International Thermonuclear Experimental Reactor (ITER) project, the first full size NbTi conductor sample was fabricated industrially and tested in the SULTAN facility (Villigen, Switzerland). This sample (PF-FSJS), which is relevant to the poloidal field coils of ITER, is composed of two parallel straight bars of conductor, connected at the bottom through a joint designed according to the CEA twin-box concept. The two conductor legs are identical except for the use of different strands: a nickel plated NbTi strand with a pure copper matrix in one leg, and a bare NbTi strand with a copper matrix and internal CuNi barrier in the other leg. The two conductors and the joint were extensively tested as regards DC and AC properties. This paper reports on the test results and analysis, stressing the differences between the two conductor legs and discussing the impact of the test results on the ITER design criteria for the conductor and joint. While joint DC resistance, conductors and joint AC losses fulfilled the ITER requirements, neither conductor could reach its current sharing temperature at relevant ITER currents, due to instabilities. Although the drop in temperature is slight for the CuNi strand cable, it is more significant for the Ni plated strand cable.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.