A phenyl ether phenyl phosphate polymer, specifically poly(biphenyl ether triphenyl phosphate), was modified to increase its tractability and to improve its toughness. The first goal was achieved by increasing its solubility by sulfonation of the chain, and the second, by the in situ generation of a rubbery phase. This phase was generated by a modification of the usual sol-gel reaction (which usually generates a hard silicalike material by the hydrolysis of a tetrafunctional organosilicate). In this case, a difunctional silicate was included, thus introducing some softening organic groups into the dispersed phase. A bonding agent, N,N-diethylaminopropyltrimethoxysilane, was also included to improve the bonding between the two phases in this organic-inorganic composite. As expected, the glass transition temperatures generally increased slightly upon sulfonation, but decreased significantly upon introduction of the rubbery phase. Most important, the toughness of the polymer was successfully increased with, for example, only 8 wt % of the rubbery phase, quadrupling extensibility to 20 % and markedly increasing the toughness.