Filamentous Viruses Grafted with Thermoresponsive Block Polymers: Liquid Crystal Behaviors of a Rodlike Colloidal Model with “True” Attractive Interactions

Understanding how attractive interactions among rigid polymers or rodlike particles influence their liquid crystal (LC) phase behavior is of fundamental and practical importance. This question has not been fully answered yet, mainly due to the shortage of model systems with “true” pairwise attractions on a single particle level while with excellent colloidal stability. Herein, we report on a well-defined rodlike system that fulfills such criteria, through covalently grafting the free end of the thermoresponsive PNIPAM block of poly(ethylene glycol)-block-poly(N-isopropylacrylamide) (PEG-b-PNIPAM) onto the classic rodlike model system—the fd or M13 virus—which is the hallmark in understanding the LC behaviors of rigid polymer or rodlike particles. Increasing temperature induces dehydration and collapse of the PNIPAM chains onto the virus surface and therefore introduces attractions among the viruses, while the outer hydrophilic PEG block offers steric stabilization to prevent interparticle aggregation, gel...