Studies of structural arrest transition inL64/D2O micellar solutions

Abstract

We summarize the results of analyses of a series of small angle neutron scattering (SANS)experiments on dense L64 copolymer micellar solutions in heavy water. The system ismodelled as a suspension of micellar particles that interact among themselves with a hardcore plus a short range square well attractive interaction. The observed phasebehaviour in the plane of temperature and polymer concentration is described.Characteristic features such as the existence of the glass-to-liquid-to-glass re-entrancetransition and the line of glass-to-glass transition with its associated end point(A3 singularity) are found which are quantitatively consistent with the recent mode couplingtheory calculations using the same model potential. Supplementary to SANS experiments,photon correlation spectroscopy experiments on the same system have been performed.They show that although the Debye–Waller factors (the long time limits of the coherentintermediate scattering functions) of the two glasses do indeed become identical at theA3 point as predicted, the intermediate scattering functions exhibit distinctlydifferent intermediate time relaxations. Furthermore, we show thatthe Debye–Waller factors obtained from volume fractions beyond theA3 point have the same magnitude as for the repulsive glass obtained before theA3 point. In addition, the effect of applied pressure on the kinetic glass transition(KGT) is explored for the first time. We observe that, for the KGT inL64/D2O micellar system, increasing applied pressure at constant temperature has a similar effect toreducing temperature at constant pressure. The preliminary observation of the ageing effecton quenching into the attractive glass state with the SANS technique is reported as well.