X-ray photon correlation spectroscopy experiments were conducted on bicontinuous microemulsionand lamellar phases in polystyrene/polyisoprene/poly(styrene-
b-isoprene) blends. Re
gardless of the microstructure,the scatterin
g intensity autocorrelation function at low temperatures in the vicinity of the primary X-rayscatterin
g peak,
g2(
q,t) (
q is the scatterin
g vector), was found to be a condensed exponential, i.e.,
g2(
q,t) ~ exp{-[
t/
![](/ima<font color=)
ges/
gifchars/tau.
gif" BORDER=0 >(
q)]
ges/gifchars/alpha.gif" BORDER=0>}with
![](/ima<font color=)
ges/
gifchars/alpha.
gif" BORDER=0> &
gt; 1. This is in direct contrast to previous observations of exponential and stretchedexponential correlation functions (
![](/ima<font color=)
ges/
gifchars/alpha.
gif" BORDER=0>
![](/ima<font color=)
ges/entities/le.
gif"> 1) in microstructured materials comprisin
g polymers as well as smallmolecules. At hi
gher temperatures, more conventional stretched exponential correlation functions are recovered.We su
ggest that condensed exponential relaxation functions may be related to the spontaneous breakup ofmicrosctructure.