부산대학교 도서관

While ordered bicontinuous double diamond (OBDD) in blockcopolymershas always been considered as an unstable structure relative to orderedbicontinuous double gyroid (OBDG), here we report the existence ofa thermodynamically stable OBDD structure in a diblock copolymer composedof a stereoregular block. A slightly asymmetric syndiotactic polypropylene-block-polystyrene (sPP-b-PS) as cast fromxylene was found to display the OBDD morphology. When the OBDD-formingdiblock was heated, this structure transformed to the OBDG phase atca. 155 °C. Interestingly, OBDD was recovered upon cooling evenin the temperature range above melting point of sPP, indicating thatOBDD was a thermodynamically stable structure for sPP-b-PS melt, which was in contradiction to the conventional view. Wepropose that the larger free energy cost encountered in OBDD due tothe larger packing frustration may be compensated sufficiently bythe release of free energy due to local packing of the conformationallyordered segments of sPP blocks, which stabilizes the OBDD structureat the lower temperatures. [ABSTRACT FROM AUTHOR]