New stable states of liquid crystal 8CB could be induced by nonlinear shear conditions and observed by a newly developed rheology/X-ray scattering setup using synchrotron X-ray radiation. Nonlinear oscillatory shear created a distorted sixth order orientational structure. Even when oscillatory shear is switched off, the induced structure remains stable and can be removed only by heating the system into the isotropic state. We assume the structure to be stabilized by defects that pin the new 6-fold phase.

In-situ flow alignment kinetics of a selfassembled lamellar phase polystyrene-block-polyisoprene (PSb-PI, M w = 26 500 g/mol, f PS = 51%) diblock copolymer melt has been investigated in detail under mechanical large amplitude oscillatory shear (LAOS) utilizing a unique Rheo−SAXS combination developed in cooperation with the German Electron Synchrotron (DESY) in Hamburg. This marks the first time that the strain and time dependence of the shear-induced macroscopic perpendicular orientation of the lamellar microstructure could be monitored with a time resolution of 10 s per frame. Two mechanical parameters were used to compare the structural evolution and dynamics with the mechanical response of the sample. The mechanical loss modulus G″, which was directly obtained from the in situ Rheo−SAXS experiments performed with a stress controlled rheometer, and the nonlinear parameter I 3/1 , which was calculated by Fourier-transform-rheology (FT-rheology) from the raw stress data obtained from a strain controlled rheometer. Significant correlations between the mechanical response and the structural changes of the sample were detected. For example, the orientation times τ calculated from both the X-ray and the mechanical measurements showed a power law dependence with τ ∼ γ 0 −1.6 (in situ SAXS) and ∼ γ 0 −2 (FT-rheology). Furthermore, the quality of the macroscopic orientation at large shear amplitudes (γ 0 = 2 and γ 0 = 3) was found to be a function of the mechanical excitation time. A better macroscopic orientation for shorter mechanical excitation times was achieved, while longer experimental times caused an unexpected reduction in the degree of orientation. In these situations, ex-situ SAXS and TEM studies indicated that a stable biaxial distribution of the lamellar microstructure that was preferentially orientated both parallel and perpendicular was formed, causing a drastic change in the response of both the mechanical quantities G″(t) and I 3/1 (t).

A highly sensitive rheodielectric experimental setup was used to investigate the macroscopic alignment of symmetric poly(styrene-b-1,4-isoprene) (SI) diblock copolymers under large-amplitude oscillatory shear (LAOS). The dielectric normal-mode of the 1,4-cis-polyisoprene chains in the diblock copolymer was chosen to probe in situ the macroscopic orientation process. It was shown that the development of the overall orientation of the lamellar microstructure can be followed in situ using the time progression of the dielectric loss modulus ε″(t). The dielectric loss ε″(t) correlates directly with the nonlinear mechanical response I 3/1(t) of the sample as determined via Fourier transform rheology (FT-rheology). In addition to these two dynamic methods, small-angle X-ray scattering was used to ascertain the degree and type of the macroscopic orientation as a function of the applied shear conditions. Evidence presented here showed that a decrease in ε″(t) relative to the initial value of ε″(t = 0 s) for a macroscopically isotropic sample melt was indicative of a macroscopic parallel orientation while an increase in ε″(t) corresponded to an overall perpendicular alignment. These phenomena are explained on a molecular level by the anisotropic diffusion of the confined polymer chains, resulting in a higher mobility of the dielectrically active end-to-end vector parallel to the interface, which can be detected via dielectric spectroscopy.

The reaction of [Ni2(iPr2Im)4(COD)] (1) {iPr2Im = 1,3‐bis(isopropyl)imidazolin‐2‐ylidene} with hexafluorobenzene and decafluorobiphenyl results at room temperature in the formation of the products of a C–F bond activation reaction, i.e. [Ni(iPr2Im)2(F)(C6F5)] (2) and [Ni(iPr2Im)2(F)(C12F9)] (4). The reactions of 2 and 4 with 1 or the reactions of hexafluorobenzene and decafluorobiphenyl with 1 equiv. or excess of dinuclear 1 (stoichiometric ratio nickel/substrate > 2:1) at higher temperatures afford the complexes of a consecutive C–F bond‐activation reaction, [1,4‐{Ni(iPr2Im)2(F)}2(C6F4)] (3) and [4,4′‐{Ni(iPr2Im)2(F)}2(C12F8)] (5). Complexes 3 and 5 cleanly react in THF at room temperature with chlorotrimethylsilane and (isopropyl)(trimethylsilyl)selenane under elimination of fluorotrimethylsilane to yield the corresponding chloro and selenolato complexes [1,4‐{Ni(iPr2Im)2(X)}2(C6F4)] [X = Cl (6), iPrSe (7)] and [4,4′‐{Ni(iPr2Im)2(X)}2(C12F8)] [X = Cl (8), iPrSe (9)].

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