Soft Matter plays an essential role in everyone’s life. Soft materials are for example biological tissues, polymers or liquid crystals (thermotropic or lyotropic). Their properties depend on the materials nano- and microstructure. In order to design new, improved materials it is crucial to know the parameters of structure formation and the structure-property relationships. Crystals with long-range positional and often orientational order can be analysed by single crystal analysis in detail (see lecture M2). In general, soft materials do not afford X-Ray diffraction data of sufficient quality to assign atomic positions. Thus other techniques are applied to obtain structural models of materials, which can eventually be correlated with their mechanical, electrical or optical properties.

This lecture will focus on the structure elucidation of liquid crystals by means of two techniques 1) Polarised optical microscopy (POM) and 2) X-Ray powder diffraction of oriented samples and their analysis combined with data from dilatometry and solid state NMR spectroscopy. POM textures provide information on phase structure and orientation. X-Ray on aligned samples afford data on the dimension of the self-assembly and their 1D, 2D or 3D order. The analysis is based on the assumption that nano-segregation of chemically or physically different building blocks and dense packing are the principal driving forces towards the molecular self-assembly into soft materials. Dilatometry affords the temperature-dependent molecular volume, which is necessary to develop a structural model. Solid state NMR techniques and AFM (see lecture E5) provide additional information for structure confirmation.

The class will introduce the different techniques and will present the development of structural models based on some selected examples.