Polycarbonate containing spiro dilactam segment

A polycarbonate polymer having a first repeating segment of the formula ##STR7## and up to twice the molar quantity of the first segment of a second repeating segment ##STR8## wherein R is aromatic of up to 15 carbon atoms and up to two aromatic rings, inclusive, R' is R or aliphatic of up to 10 carbon atoms, inclusive, r is 0 or 1, X is a direct valence bond or X represents alkylene of up to 8 carbon atoms, inclusive, OXY, thio, sulfonyl, carbonyl, dioxyphenylene, 2,2-di(oxyphenyl)propane, di(oxyphenyl) sulfone or dioxydiphenylene, Z independently is >C(Z').sub.2 in which Z' independently is hydrogen, lower alkyl, fluoro, chloro or phenyl, or Z is such that two adjacent Z groups taken together form a ring system Z" of from 5 to 7 ring atoms up to two of which are heteroatoms selected from nitrogen, oxygen or sulfur with the remainder of the ring atoms being carbon atoms, two of which form a bridge between the carbon atoms connected by the adjacent Z groups, and G is hydrogen, lower alkyl, chloro or bromo.