The Synthesis of Liquid Crystalline Polymer on Gold Nanoparticles

Abstract

ABSTRACTGold nanoparticles with thiol stabilizing layers were prepared with various fractions of end-functional thiols. Alcohol end-groups were further elaborated to norbornyl moieties so that a ruthenium alkylidene initiator could be tethered to the nanoparticle surfaces. In two different nanoparticle formulations the functional thiols possessed hydrocarbon chains that held the metal centers either near to or far from the surface of the thiol stabilizing layer. The tethered organometallic complexes were used to initiate polymerization from the nanoparticle surfaces. Liquid crystalline polymer was grown from nanoparticles where the metal center was tethered far from the surface but polymerization could not be initiated when the metal centers were held close to the surface. We hypothesize that steric hindrance is controlled by the length of the tethering thiol. Polarized optical microscopy showed that the polymer coated gold nanoparticles could still form a nematic mesophase at elevated temperature although the orientation of mesogens is restricted by crowding at the nanoparticle surface. Samples of unbound polymer were also prepared and exhibited similar transition behavior.