Controlling Polymeric Supramolecular Microstructures through Host-Guest Interactions Assisted with Ultrasound Oscillation

Fabrication of geometric structures through self-assembly of block copolymers normally requires complicated synthesis steps. Herein, we introduce a simple approach to prepare polymeric supramolecular microstructures through non-covalent self-assembly induced by host-guest co-crystallization assisted with ultrasound oscillation. Inclusion compounds formed between poly(epsilon-caprolactone)s (PCLs) and urea molecules in the ultrasound field were confirmed by FTIR, DSC, and X-ray diffraction. Homogeneous microscale particles and platelets with significant geometric structures were observed by SEM. Interestingly, instead of sophisticated techniques, the morphologies of inclusion compounds can be converted from particles to platelets by simply changing the guest polymer molecular weights due to their distinct crystal growth habits. Other parameters including guest polymer concentrations, ultrasound temperatures, powers, and mixing methods, which affect the size, shape, and uniformity of inclusion compound particles, were also studied. Considering the abundance of possible inclusion compounds formed between polymer guests and small molecule hosts, we believe that the understanding gleaned in this work will open a novel avenue for the design and the construction of polymeric supramolecular complexes.