## 4 In-Situ Technique Combinations
The Couette cylinders were constructed of titanium with thin mylar windows, allowing access to the neutron beam as well as for impedance measurements between the inner and outer cylinders (See Figure 15 for a schematic layout of the experiments). Crucial for this type of experiment is the synchronization of the different techniques, which can be readily achieved using 'event-mode' data collection [146]. Data were successfully obtained on the self-assembly of conjugated polymer melts and shear sensitive ionic liquids. In order to investigate how high a molecular weight of polyethylene glycol dimethyl ether (PEG DME) can be incorporated in the crystalline region of syndiotactic polystyrene, one requires both the structural information provided by neutron scattering and vibrational spectroscopy. This was done by combining Fourier Transform Infrared Spectroscopy (FTIR) with SANS [147; 148]. Here one encounters the issue that the optimum sample thickness required by both techniques is not the same. This can be partially overcome by using an FTIR sample cell and Attenuated Total Reflection, where the infrared beam makes multiple passes through the sample material [149]. However, a better solution is to place the IR and neutron beams co-parallel to ensure that one is studying the same part of the sample. This can be achieved by coupling the IR beam with an elaborate system of KBr crystals that act  
Figure 15: Schematic of a Couette rheology cell that allows for the simultaneous collection of rheological, dielectric spectroscopy, and neutron scattering data. The electrical impedance is measured between the Ti cylinders. Temperature control is achieved by using a forced convection oven that surrounds the cell (reproduced with permission from [145], AIP Publishing, 2017). as mirrors for the IR beam but are relatively transparent to neutrons. As a compromise, the sample thickness was chosen to be 50 \(\upmu\)m, just sufficiently thick for neutron scattering but thin enough for infra-red measurements. The combined data sets showed a distinct difference between the PEGDME conformation in the amorphous and crystalline regions of the polystyrene. In experiments where the materials exhibit (partial) orientation and are transparent to visible light, birefringence is widely used to determine orientational effects. Neutron and X-ray scattering are also sensitive to orientational order, albeit on different length scales than birefringence. Scattering is mainly sensitive to the alignment of molecules, whilst birefringence is sensitive to bulk material properties [150]. Although such a capability seems to be very useful, it is somewhat surprising that this has not been applied more often [62; 150; 151]. Even though it is understood that having combined neutron and X-ray scattering data is highly beneficial in understanding a system, these techniques are not combined as often as they should [152; 153; 154]. In an ideal world, one would be able to use parallel beams of X-rays and neutrons, but an orthogonal combination is technically easier to realize. The achievable time-resolution, i.e., the length per time frame in which useable data can be collected, for the two experiments should be of the same order of magnitude. Until recently, such a combination was not feasible, but developments in X-ray generation and detector technology have allowed the first steps in allowing such a combined scattering instrument to be developed. Specifically, the two probe beams were placed at right angles to one another, making the system less useful for samples that are anisotropic, but it can serve as a proof of principle [155]. The complication that one faces with the development of such an instrument is that one invariably tries to mount an X-ray system on an existing neutron scattering beamline. Hence, one encounters space and shielding issues that make things more complicated (but not impossible).