The structure and thermal properties of novel DOPO-containing 1,3-benzoxazines
Three DOPO (9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide)-containing benzoxazin (3a–3c) were successfully prepared from 2-hydroxybenzaldehyde, p-substituted aniline, and DOPO by a three-step procedure. Since the phosphorus and the adjacent aliphatic carbon are both chiral centers, two pairs of enantiomers exist in 3a, 3b, or 3c. Compound 3a′, which is a pair of enantiomers existing in 3a, was isolated using recrystallization in ethyl acetate solvent. All the structures were confirmed by FT-IR, NMR, and MS spectra. The X-ray analysis indicated that the 3a′ is the RR/SS enantiomers and belongs to the monoclinic crystal system, its space group being P21/c. The thermal properties were investigated by DSC and TG. It has been found that the peak temperature of thermally induced ring-opening reaction was around 260–270 °C. Compounds (3a–3c, 3a′, and 3c′) had two similar thermal processes from 50 to 600 °C in TG, whereas the compound 3b′ had three thermal processes. The char yields of 3a–3c were 18.10, 16.84, and 16.34 %, respectively, while those of 3a′–3c′ were 26.00, 31.80, and 19.21 %, respectively. The results indicated that compounds 3a′–3c′ had better char properties than 3a–3c.
KeywordsDOPO-containing benzoxazine Synthesis Enantiomers XRD Char property
The authors acknowledge the financial support for this study from the Education Department of Sichuan Province, Xihua University, open laboratory of State Key Laboratory of Polymer Materials and Engineering(Sichuan University).
- 2.Schreiber H, Gurrit E, Betamide patents. 1973; DE 2255504; DE 2323936.Google Scholar
- 3.Peng CR. Study on synthesis of novel benzoxazine based on polyamine and application in PCB. Master’s thesis. Sichuan University, Chengdu, 2006.Google Scholar
- 4.Gu Y, Xie ML, Liu XH. Progress in the study of phenolic resin using ring-opening polymerization of benzoxazines. Chem Ind Eng Prog. 1998;2:43–7.Google Scholar
- 5.He YL, Li L, Dong FY. Advance in the research of benzoxazines of high property. Insul Mater. 2009;39(4):5–8.Google Scholar
- 7.Ishida H. US Patent 5543516, 1996.Google Scholar
- 11.Men WW, Lu ZJ. High performance polybenzoxazines. Prog Chem. 2007;19(5):779–86.Google Scholar
- 12.Wolfgang M. Method for producing organic compounds containing poly-DOPO and the use of the same. P US20060247344A1. 2006;11:2.Google Scholar
- 13.Wang Y, Luo Y, Zhang Z. Study on epoxy resin modified with flame retardant DOPO-MA. Insul Mater. 2010;43(3):20–3.Google Scholar
- 14.Satio T, Shi K. Cyclic organophosphorus compounds and process for making same. US Patent 3702878. 1972-11-24.Google Scholar
- 17.Qian LJ, Ye Lj, Xu GZ, Guo JQ. Preparation and characterization of hexa-(DOPO-hydroxymethyl phenoxy)-cyclotriphosphazene. New Chem Mater. 2010;38(8):48–50.Google Scholar