Synthesis and mesomorphic properties of 1,1-difluoroalkyl-substituted biphenylthienyl and terphenyl liquid crystals. A comparative study of mesomorphic behavior relative to alkyl, alkoxy and alkanoyl analogsElectronic supplementary information (ESI) available: experimental details for compounds 4, 9, 10, 12, 15–19, 25–39, 45 and 49. See http://www.rsc.org/suppdata/jm/b1/b102059p/