Golf balls having a foam inner core with thermal barrier

A golf ball, comprising a core assembly and a cover, the core assembly comprising:

• i) an inner core comprising a foam composition having a geometric center, outer surface, and thermal barrier layer, wherein the inner core layer has a diameter in the range of about 0.100 to about 1.100 inches and an outer surface hardness (Hinner core surface) and a center hardness (Hinner core center), the Hinner core surface being the same as or less than the Hinner core center to provide a zero or negative hardness gradient in the inner core;
• and
• ii) an outer core comprising a non-foamed thermoset or thermoplastic composition, the outer core layer being disposed about the inner core layer and having a thickness in the range of about 0.100 to about 0.750 inches, and an outer surface hardness (Houter surface of OC), wherein the (Houter surface of OC is greater) than the (Hinner core center) to provide a positive hardness gradient across the core assembly.