Nitroxide-mediated controlled radical polymerization is used to synthesize gradient and block copolymers of styrene ( S) and 4-acetoxystyrene ( AS), and conventional free radical polymerization is used to synthesize S/AS random copolymers. The S/AS copolymers are hydrolyzed to yield S/4-hydroxystyrene (HS) copolymers. Gel permeation chromatography and H-1 NMR of aliquots taken during polymerization yield proof of the controlled nature of the gradient copolymer structures. The glass transition temperature (T-g) responses are compared using the derivative of differential scanning calorimetry heat curves, with the temperature range over which the derivative exceeds a base level being equated to the T-g breadth. A single, narrow T-g is obtained in each random copolymer, consistent with a single phase of limited compositional nanoheterogeneity. Two narrow T(g)s are evident in each block copolymer, consistent with well-developed nanophases containing nearly pure S or nearly pure AS or HS units with a very narrow interphase yielding no indication of an intermediate Tg. In contrast, T-g breadths of similar to 65-80 degrees C are observed in many S/HS gradient copolymers, consistent with ordered nanostructures in which the unit cell composition varies sinusoidally. The possibility of capitalizing on the broad T-g of gradient copolymers in damping applications is discussed.