An irreversible structural phase transformation is observed in tetrakis(4,4'-(2,2-diphenyl-vinyl)-1,1'-biphenyl)methane, C(DPVBi)(4), upon increasing the temperature. The PI phase of the as-synthesized material is crystalline with tiny (typically 10-20nm) crystallites. The PI phase has hexagonal symmetry (space group P6) with the following lattice parameters a = 2.068 nm and c = 2.194 nm. When PI is annealed above its melting point (T. = 260 C), the structure transforms irreversibly into a different hexagonal phase, PIT, (space group P6/m) with lattice parameters a = 2.102 nm, c = 3.370 nm. The PII phase melts at around T-m = 278 degreesC. When heated above 278 degreesC, C(DPVBi)(4) becomes amorphous with random molecular packing. ne amorphous phase has a glass transition temperature, T-g, around 138 degreesC. The PI phase transforms directly into the amorphous phase if the sample is continuously heated above the melting point (T = 278 degreesC) of PIT. (C) 2002 Elsevier Science B.V. All rights reserved.