A photocurable reaction mixture comprising a vinyl-functional polydiorganosiloxane having functional groups, wherein the functional groups consist of vinyl groups, and the vinyl-functional polydiorganosiloxane is represented by the following formula (Formula I): R 2 2 SiO( 2 SiO) x Si 2 R 2 wherein: each R independently represents methyl or phenyl; each R 2 independently represents vinyl groups; x = 1 or more; and a thiol-functional polydiorganosiloxane having functional groups, wherein the functional groups consist of thiol groups, wherein the thiol-functional polydiorganosiloxane has an average thiol equivalent weight of 1200 Daltons or more, as determined by the NMR-spectroscopy method described in the present specification, and wherein the thiol-functional polydiorganosiloxane is represented by the following formula (Formula II): R 5 (R 3)SiO((R 3)SiO) w (R 3 R 4 SiO) z Si(R 3) 2 R 5 wherein: each R 3 independently represents methyl or phenyl; each R 4 independently represents a mercaptoalkyl group having from 2 to 12 carbon atoms; each R 5 independently represents methyl, phenyl, or a mercaptoalkyl group having from 2 to 12 carbons; w = 1 or more; and z > 0; the w repeat units ((R 3)SiO) and z repeat units (R 3 R 4 SiO) are in random and/or block arrangements; a phosphine oxide photoinitiator; and at least 35 wt-% thermally conductive filler, based on the total weight of the photocurable reaction mixture, wherein the filler has at least a bi-modal particle size distribution. wherein: each R independently represents methyl or phenyl; each R 2 independently represents vinyl groups; x = 1 or more; and a thiol-functional polydiorganosiloxane having functional groups, wherein the functional groups consist of thiol groups, wherein the thiol-functional polydiorganosiloxane has an average thiol equivalent weight of 1200 Daltons or more, as determined by the NMR-spectroscopy method described in the present specification, and wherein the thiol-functional polydiorganosiloxane is represented by the following formula (Formula II): R 5 (R 3)SiO((R 3)SiO) w (R 3 R 4 SiO) z Si(R 3) 2 R 5 each R independently represents methyl or phenyl; each R 2 independently represents vinyl groups; x = 1 or more; and a thiol-functional polydiorganosiloxane having functional groups, wherein the functional groups consist of thiol groups, wherein the thiol-functional polydiorganosiloxane has an average thiol equivalent weight of 1200 Daltons or more, as determined by the NMR-spectroscopy method described in the present specification, and wherein the thiol-functional polydiorganosiloxane is represented by the following formula (Formula II): R 5 (R 3)SiO((R 3)SiO) w (R 3 R 4 SiO) z Si(R 3) 2 R 5 wherein: each R 3 independently represents methyl or phenyl; each R 4 independently represents a mercaptoalkyl group having from 2 to 12 carbon atoms; each R 5 independently represents methyl, phenyl, or a mercaptoalkyl group having from 2 to 12 carbons; w = 1 or more; and z > 0; the w repeat units ((R 3)SiO) and z repeat units (R 3 R 4 SiO) are in random and/or block arrangements; a phosphine oxide photoinitiator; and at least 35 wt-% thermally conductive filler, based on the total weight of the photocurable reaction mixture, wherein the filler has at least a bi-modal particle size distribution. each R 3 independently represents methyl or phenyl; each R 4 independently represents a mercaptoalkyl group having from 2 to 12 carbon atoms; each R 5 independently represents methyl, phenyl, or a mercaptoalkyl group having from 2 to 12 carbons; w = 1 or more; and z > 0; the w repeat units ((R 3)SiO) and z repeat units (R 3 R 4 SiO) are in random and/or block arrangements; a phosphine oxide photoinitiator; and at least 35 wt-% thermally conductive filler, based on the total weight of the photocurable reaction mixture, wherein the filler has at least a bi-modal particle size distribution.