Phase behaviour of the discotic mesogen 5,10,15,20-tetrakis(4-N-dodecylphenyl) porphyrin under hydrostatic pressure

The phase behaviour of the discotic mesogen 5,10,15,20-tetrakis(4-n-dodecyl phenyl) porphyrin(C12TPP) was investigated under hydrostatic pressures up t o 350 MPa by high-pressure DTA and wide-angle X-ray diffraction measurement s. Seven crystal polymorphs are found, depending upon the temperature and p ressure. The discotic lamellar(D-L) phase is observed enantiotropically und er pressures up to ca. 240 MPa, while the monotropic D-L phase appears on c ooling under pressures between 240 and 310 MPa. Further increasing pressure above 310 MPa disappears completely the D-L phase, showing the crystal-iso tropic transition.