Colloidal Magnetic Polymers in Nematic Liquid Crystals

Polymers embedded in liquid crystal solutions represent an interesting class of composite soft materials, but experiments are often difficult due to chemical incompatibility between the two types of molecule. Paramagnetic colloidal materials are of practical interest for their ability to manipulate structures at the micron scale. Standard paramagnetic spheres will form linear chains due to dipolar alignment in the presence of an external magnetic field, but these chains eventually dissociate at room temperature due to thermal fluctuations. It is possible, however, to link these chains 'permanently' using a polymer such as polyethylene-glycol mediated by a non-covalent bond. We study the behavior of these linked paramagnetic chains in the presence of a nematic liquid crystal (LC) director. We aim to quantify the competition between applied magnetic field and the local orientation of the LC to control the conformation of the linked polymer chain using video microscopy.