A method of preparing a thermoplastic composition comprising a poly(arylene ether); and a poly(arylene ether)- polysiloxane block copolymer comprising a poly(arylene ether) block, and a polysiloxane block comprising, on average, 35 to 80 siloxane repeating units; wherein the method comprises: oxidatively copolymerizing a monohydric phenol and a hydroxyaryl-terminated polysiloxane to form a thermoplastic composition; wherein the oxidative copolymerization is initiated in the presence of at least 50 weight percent of the hydroxyaryl-terminated polysiloxane and less than or equal to 50 weight percent of the monohydric phenol; wherein the oxidative copolymerization is conducted with a reaction time greater than or equal to 110 minutes; wherein the hydroxyaryl-terminated polysiloxane comprises, on average, 35 to 80 siloxane repeating units; wherein the hydroxyaryl-terminated polysiloxane constitutes 1 to 8 weight percent of the combined weight of the monohydric phenol and the hydroxyaryl-terminated polysiloxane; wherein the poly(arylene ether) block comprises arylene ether repeating units having the structure wherein for each repeating unit, each Z 1 is independently halogen, unsubstituted or substituted C 1 -C 12 hydrocarbyl provided that the hydrocarbyl group is not tertiary hydrocarbyl, C 1 -C 12 hydrocarbylthio, C 1 -C 12 hydrocarbyloxy, or C 2 -C 12 halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and oxygen atoms; and each Z 2 is independently hydrogen, halogen, unsubstituted or substituted C 1 -C 12 hydrocarbyl provided that the hydrocarbyl group is not tertiary hydrocarbyl, C 1 -C 12 hydrocarbylthio, C 1 -C 12 hydrocarbyloxy, or C 2 -C 12 halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and oxygen atom; wherein the polysiloxane block comprises repeating units having the structure wherein each occurrence of R 1 and R 2 is independently hydrogen, C 1 -C 12 hydrocarbyl or C 1 -C 12 halohydrocarbyl; and wherein the polysiloxane block further comprises a terminal unit having the structure wherein Y is hydrogen, C 1 -C 12 hydrocarbyl, C 1 -C 12 hydrocarbyloxy, or halogen, and wherein each occurrence of R 3 and R 4 is independently hydrogen, C 1 -C 12 hydrocarbyl or C 1 -C 12 halohydrocarbyl; and wherein the thermoplastic composition incorporates at least 80 weight percent of the hydroxyaryl-terminated polysiloxane into the poly(arylene ether)-polysiloxane block copolymer; and wherein the poly(arylene ether) is the product of polymerizing the monohydric phenol alone and is a by-product of the block copolymer synthesis. oxidatively copolymerizing a monohydric phenol and a hydroxyaryl-terminated polysiloxane to form a thermoplastic composition; wherein the oxidative copolymerization is initiated in the presence of at least 50 weight percent of the hydroxyaryl-terminated polysiloxane and less than or equal to 50 weight percent of the monohydric phenol; wherein the oxidative copolymerization is conducted with a reaction time greater than or equal to 110 minutes; wherein the hydroxyaryl-terminated polysiloxane comprises, on average, 35 to 80 siloxane repeating units; wherein the hydroxyaryl-terminated polysiloxane constitutes 1 to 8 weight percent of the combined weight of the monohydric phenol and the hydroxyaryl-terminated polysiloxane; wherein the poly(arylene ether) block comprises arylene ether repeating units having the structure wherein for each repeating unit, each Z 1 is independently halogen, unsubstituted or substituted C 1 -C 12 hydrocarbyl provided that the hydrocarbyl group is not tertiary hydrocarbyl, C 1 -C 12 hydrocarbylthio, C 1 -C 12 hydrocarbyloxy, or C 2 -C 12 halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and oxygen atoms; and each Z 2 is independently hydrogen, halogen, unsubstituted or substituted C 1 -C 12 hydrocarbyl provided that the hydrocarbyl group is not tertiary hydrocarbyl, C 1 -C 12 hydrocarbylthio, C 1 -C 12 hydrocarbyloxy, or C 2 -C 12 halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and oxygen atom; wherein the polysiloxane block comprises repeating units having the structure wherein each occurrence of R 1 and R 2 is independently hydrogen, C 1 -C 12 hydrocarbyl or C 1 -C 12 halohydrocarbyl; and wherein the polysiloxane block further comprises a terminal unit having the structure wherein Y is hydrogen, C 1 -C 12 hydrocarbyl, C 1 -C 12 hydrocarbyloxy, or halogen, and wherein each occurrence of R 3 and R 4 is independently hydrogen, C 1 -C 12 hydrocarbyl or C 1 -C 12 halohydrocarbyl; and wherein the thermoplastic composition incorporates at least 80 weight percent of the hydroxyaryl-terminated polysiloxane into the poly(arylene ether)-polysiloxane block copolymer; and wherein the poly(arylene ether) is the product of polymerizing the monohydric phenol alone and is a by-product of the block copolymer synthesis.