New, chiral and achiral benzoxazine monomers (S)-alpha-3-methylbenzyl-3,4-dihydro-6, 8-di-tert-butyl-2H-1,3-benzoxazine and rac-alpha-3-methylbenzyl-3,4-dihydro-6,8-di-tert-butyl-2H-1,3-benzoxazin e were prepared by Mannich condensation from enantiomerically pure (S-alpha) and racemic (rac) methylbenzylamine H2NCH(CH3)C6H5, formaldehyde and 2,4-di-tert-butylphenol. Their DSC exhibit exotherms at 291 and 263 degrees C which correspond to oxazine thermal polymerization. The resulted polymers show very low T-g values of 31 and 19 degrees C for poly-S-1 and poly-rac-1, respectively. Higher value for the polymer obtained from enantiomerically pure monomer results from the monomer derived stereoregularity of the polymer. A comparison of thermal stabilities of both polymers showed significantly lower heat resistance for the polymer obtained from racemic monomer. The resulted data are compared with those obtained for similar rac-alpha-3-methylbenzyl-3,4-dihydro-8-(1,1,3,3-tetra-methylbutyl)-2H-1, 3-benzoxazine with a free ortho position at the phenyl.