Nanoparticle containing compositions

A flame retardant composition, comprising:

• (i) 55 to 92% by weight of at least one phosphonate oligomer or polymer, comprising units of formula (I):
• wherein:
• each Ar is independently the same or different aromatic or aromatic containing group;
• each R is independently the same or different group selected from C1-20 alkyl, C2-20 alkene, C2-20 alkene, C5-20 cycloalkyl, or C6-20 aryl;
• and
• n is from 3 to 200;
• (ii) 1% to 44.5% by weight of nanoparticles based on the weight of flame retardant composition, nanoparticles have a length in at least one dimension of 1 nm to 1000 nm which are selected from the group consisting of attapulgite, bentonite, montmorillonite, boehmite, illite, hydroxyapatite, smectite, kaolinite, dickite, nitrite, sepiolite, hectorite, halloysite and talcum particles, or any combination thereof;
• and
• (iii) 0.5% to 10% by weight of dispersing agent(s) based on the weight of the flame retardant composition.