Abstract: Phosphorus- and bromine-containing polymers having the formula ##STR1## WHEREIN R.sub.1 is an alkylene group having 2-3 carbon atoms; ##STR2## WHEREIN M IS AN INTEGER OF 1-4 AND B is an alkylene or alkylidene group having 1-6 carbon atoms or sulfone group; Z is --R.sub.2 or --OR.sub.2, provided that R.sub.2 is an alkyl or aryl group; Y is sulfur or oxygen; l is 0 or 1; p and q are integers of at least 1 and a sum of p and q is an integer of not more than 4; and n is an integer of 3-40 are colorless and have an excellent thermal property. The polymers are excellent as a flame retardant for inflammable organic high polymers, and flame resistant compositions having excellent washing resistance, light resistance and whiteness can be obtained by compounding the phosphorus- and bromine-containing polymer with the inflammable organic high polymer.

Abstract: Phosphorus and bromine-containing polymers having the formula ##STR1## WHEREIN R.sub.1 is an alkylene group having 2-3 carbon atoms; ##STR2## WHEREIN M IS AN INTEGER OF 1-4 AND B is an alkylene or alkylidene group having 1-6 carbon atoms or sulfone group; Z is --R.sub.2 or --OR.sub.2, provided that R.sub.2 is an alkyl or aryl group; Y is sulfur or oxygen; l is 0 or 1; p and q are integers of at least 1 and a sum of p and q is an integer of not more than 4; and n is an integer of 3-40 are colorless and have an excellent thermal property. The polymers are excellent as a flame retardant for inflammable organic high polymers, and flame resistant compositions having excellent washing resistance, light resistance and whiteness can be obtained by compounding the phosphorus- and bromine-containing polymer with the inflammable organic high polymer.