New approach for SANS measurement of micelle chain mixing during size and morphology transitions† Taylor Larison, a Sai Venkatesh Pingali b and Morgan Stefik *a Abstract Chain exchange in amphiphilic block polymer micelles is measurable with time-resolved small-angle neutron scattering (TR-SANS) where contrast-matched conditions reveal chain mixing as reduced intensity. However, analyzing chain mixing on short time scales e.g. during micelle transformations remains challenging.