A process for preparing a polydiorganosiloxane-polycarbonate block copolymer, the process comprising: (a) providing a composition comprising hydroxyaryl end-capped polydiorganosiloxane monomers having the following formula (Ia): wherein: each R is independently a C 1 -C 13 monovalent organic group; each X is independently a C 2 -C 4 alkylenyl group; each R' is independently selected from the group consisting of halo, cyano, nitro, C 1 -C 8 alkyl, C 1 -C 8 alkoxy, C 1 -C 8 thioalkoxy, C 2 -C 8 alkenyl, C 2 -C 8 alkenyloxy, C 3 -C 8 cycloalkyl, C 3 -C 8 cycloalkyloxy, C 6 -C 10 aryl, C 6 -C 10 aryloxy, C 7 -C 12 arylalkyl, and C 7 -C 12 arylalkoxy; each m is independently 0, 1, 2, 3 or 4; and n is 30 to 200; preferably 30 to 100; wherein the composition has a polydispersity index (Mw/Mn) of less than 2.2, as measured by size exclusion chromatography with ultraviolet and refractive index detection; and wherein the composition has a % low molecular weight fraction of less than 15% as determined using an SEC-UV-RI method, wherein % low molecular weight fraction is as defined in the description; and (b) reacting the composition with a carbonate precursor and a dihydroxy monomer of formula (ia): HO-R 1 -OH (ia) wherein R 1 comprises an aliphatic, alicyclic, or aromatic group, or any combination thereof; to form the polydiorganosiloxane-polycarbonate block copolymer; preferably wherein the polydiorganosiloxane is present in the polydiorganosiloxane-polycarbonate block copolymer in an amount of 2 wt% to 25 wt% based on the total weight of the polydiorganosiloxane-polycarbonate block copolymer. (a) providing a composition comprising hydroxyaryl end-capped polydiorganosiloxane monomers having the following formula (Ia): wherein: each R is independently a C 1 -C 13 monovalent organic group; each X is independently a C 2 -C 4 alkylenyl group; each R' is independently selected from the group consisting of halo, cyano, nitro, C 1 -C 8 alkyl, C 1 -C 8 alkoxy, C 1 -C 8 thioalkoxy, C 2 -C 8 alkenyl, C 2 -C 8 alkenyloxy, C 3 -C 8 cycloalkyl, C 3 -C 8 cycloalkyloxy, C 6 -C 10 aryl, C 6 -C 10 aryloxy, C 7 -C 12 arylalkyl, and C 7 -C 12 arylalkoxy; each m is independently 0, 1, 2, 3 or 4; and n is 30 to 200; preferably 30 to 100; wherein the composition has a polydispersity index (Mw/Mn) of less than 2.2, as measured by size exclusion chromatography with ultraviolet and refractive index detection; and wherein the composition has a % low molecular weight fraction of less than 15% as determined using an SEC-UV-RI method, wherein % low molecular weight fraction is as defined in the description; and each R is independently a C 1 -C 13 monovalent organic group; each X is independently a C 2 -C 4 alkylenyl group; each R' is independently selected from the group consisting of halo, cyano, nitro, C 1 -C 8 alkyl, C 1 -C 8 alkoxy, C 1 -C 8 thioalkoxy, C 2 -C 8 alkenyl, C 2 -C 8 alkenyloxy, C 3 -C 8 cycloalkyl, C 3 -C 8 cycloalkyloxy, C 6 -C 10 aryl, C 6 -C 10 aryloxy, C 7 -C 12 arylalkyl, and C 7 -C 12 arylalkoxy; each m is independently 0, 1, 2, 3 or 4; and n is 30 to 200; preferably 30 to 100; wherein the composition has a polydispersity index (Mw/Mn) of less than 2.2, as measured by size exclusion chromatography with ultraviolet and refractive index detection; and wherein the composition has a % low molecular weight fraction of less than 15% as determined using an SEC-UV-RI method, wherein % low molecular weight fraction is as defined in the description; and (b) reacting the composition with a carbonate precursor and a dihydroxy monomer of formula (ia): HO-R 1 -OH (ia) wherein R 1 comprises an aliphatic, alicyclic, or aromatic group, or any combination thereof; to form the polydiorganosiloxane-polycarbonate block copolymer; preferably wherein the polydiorganosiloxane is present in the polydiorganosiloxane-polycarbonate block copolymer in an amount of 2 wt% to 25 wt% based on the total weight of the polydiorganosiloxane-polycarbonate block copolymer.