title: Relaxation processes in a lower disorder order transition diblock copolymer.
abstract: The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition TODT, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system.
authors: Instituto de Estructura de la Materia, IEM-CSIC. C/ Serrano 121, Madrid 28006, Spain.
authors: Alejandro
authors: A
authors: Sanz
authors: Instituto de Estructura de la Materia, IEM-CSIC. C/ Serrano 121, Madrid 28006, Spain.
authors: Tiberio A
authors: TA
authors: Ezquerra
authors: Instituto de Ciencia y Tecnología de Polímeros, ICTP-CSIC. C/ Juan de la Cierva 3, Madrid 28006, Spain.
authors: Rebeca
authors: R
authors: Hernández
authors: Petra III at DESY, Notkestr. 85, 22607 Hamburg, Germany.
authors: Michael
authors: M
authors: Sprung
authors: Instituto de Estructura de la Materia, IEM-CSIC. C/ Serrano 121, Madrid 28006, Spain.
authors: Aurora
authors: A
authors: Nogales