A boron-containing styrenic monomer, 5-benzyl-2-phenyl-5-(4-vinylbenzyl)[1,3,2)-dioxaborinane, was synthesized to study the influence of boron on the properties of the homopolymer and copolymer with styrene. A similar monomer without boron was also prepared and polymerized so that the properties of its polymer could be compared with the aforementioned boron-containing polymers. These monomers were characterized by elemental analysis, mass spectrometry, Fourier transform infrared, and H-1 and C-13 NMR. The thermal degradation of boron-containing styrenic polymers was studied by means of Fourier transform infrared, which showed the presence of boric acid as char. The flame-retardant effect was assessed by the measurement of the limiting oxygen indices and char yields during heating in nitrogen and air. The boron-containing polymers had higher limiting oxygen indices and gave greater yields of char than those without boron. (c) 2005 Wiley Periodicals, Inc.