Thermoplastic resin polymer compositions having a block of random polysiloxane co- or terpolymer structure, such as substituted phenyl-terminated polysiloxane co- or terpolymers having the general structure: provide improved flame resistance, optical clarity, and better low-temperature impact strength compared to conventional blends, additives, and copolymers. The substituted phenyl terminated polysiloxanes may be used to make various polysiloxane-thermoplastic resin polymer and polymer blends, as well as articles including such polysiloxane-thermoplastic resin polymer and blends.