The preparation and characterization of 6,6'-bis(3,4-dihydro-3-methyl-2H- 1,3-benzoxazinyl)isopropane (1) and 6,6'bis(3,4-dihydro-3-methyl-2H-1,3-benzoxazinyl)sulphone (2) using FTIR, H-1 and C-13 NMR spectroscopy and elemental analysis, is reported. Molecular simulation using both molecular mechanics and molecular dynamics techniques are reported for poly(bis-benzoxazine)s of both materials and the data compare well with literature values for the polymer of (1). The same methodology is extended to predict a T, for the polymer of the newly-prepared, novel monomer (2), for which no published data currently exist. Preliminary measurements of the thermal behaviour, particularly the T, values, of the monomers and polymers are made using differential scanning calorimetry (DSC). The latter show very good agreement for 6,6'- bis(3,4-dihydro-3-methyl-2H -1,3-benzoxazinyl) isopropane (an accepted literature value of T, for this polymer is 180 degrees C, the onset of T-g from our empirical DSC measurement is ca. 177 degrees C, and the extrapolated value of T, from simulation is 180 degrees C. In the case of the new monomer, 6,6'- bis(3,4-dihydro- 3 -methyl-2 H - 1, 3 -benzoxazinyl)sulphone, the predicted T, from simulation lies in the range 120-150 degrees C (with an extrapolated value at 130 degrees C and the empirical DSC measurement yields an onset value of ca. 117 degrees C. (c) 2005 Elsevier B.V. All rights reserved.