Some variations provide a curable resin formulation for a water-decomposable thermoset material, comprising: first molecules containing a boron-oxygen-silicon group and a first functional group that is reactive for free-radical, cationic, and/or hydrosilylation polymerization; optionally second molecules containing at least one second functional group that is reactive with the first molecules; and a polymerization initiator. Other variations provide a curable resin formulation comprising: first molecules containing a polyester group and a first functional group that is reactive for free-radical, cationic, and/or hydrosilylation polymerization; optionally second molecules containing at least one second functional group that is reactive with the first molecules; and a polymerization initiator. Other variations provide a cured, water-decomposable thermoset solid material comprising boron-oxygen-silicon groups and/or polyester groups, wherein the material is characterized by at least 50 wt % decomposition in water with a pH of 7, for 60 minutes, at a temperature of 100° C.