Using Small-Angle Scattering and Contrast Matching to Understand Molecular Packing in Low Molecular Weight Gels

Small molecules can self-assemble into one-dimensional structures to give self-supporting gels. Such gels have a wide range of uses, including tissue engineering and drug delivery catalysis. It is difficult to understand how the molecules are packed in these structures, but this is hugely important if we are going to be able to learn from and design such materials. Here, we use a combination of small-angle X-ray and small-angle neutron scattering with selectively deuterated molecules to understand the packing in the pre-gelled aggregates and in the gel state. We also use kinetic measurements to understand the transition between these aggregates. Our data show that there is a lack of order in the gel state, correlating with the limited predictive design rules in this field and with the importance of kinetics in forming the gel state. This approach allows us to understand our specific systems but represents a general approach that could be taken with different classes of gelator.