est having 6 to 20 carbon atoms, M is a mesogenic group of the general formula ???A???Z, ???A???Y1???B???Z, ???A???Y1???B???Y2???C???Z, or a steroidal moiety, preferably selected of the group of cholesteryl compounds, wherein each A, B and C independently is a substituted or unsubstituted aromatic moiety having 6 to 24 carbon atoms, a substituted or unsubstituted heteroaromatic moiety having 2 to