With expanding applications of hydrogels in diverse fields ranging from biomaterials to sensors, actuators, and soft robotics, there is an urgent need to endow one single gel with multiple physicochemical properties, such as stimuli-responsiveness, injectability, self-healing, and tunable internal structures. However, it is challenging to simultaneously incorporate these highly sought-after properties into one single gel. Herein, a conceptual hydrogel system with all of these properties is presented via combining bioconjugate chemistry, filamentous viruses, and dynamic covalent bonds. Nanofilamentous bioconjugates with diol affinity were prepared by coupling a tailor-synthesized low-pK a phenylboronic acid (PBA) derivative to a well-defined green nanofiber the M13 virus with a high aspect ratio (PBA-M13). Dynamic hydrogels with tunable mechanical strength were prepared by using multiple diol-containing agents such as poly­(vinyl alcohol) to cross-link such PBA-M13 via the classic boronic–diol dynamic bonds. The as-prepared hydrogels exhibit excellent injectability and self-healing behaviors as well as easy chemical accessibility of the PBA moieties on the virus backbone inside the gel matrix. Ordered internal structures were imparted into virus-based hydrogels by simple shear-induced alignment of the virus nanofibers. Furthermore, unique hydrogels with chiral internal structures were fabricated through in situ gelation induced by diffusion of diol-containing molecules to fix the chiral liquid crystal phase of the PBA-M13 virus. Sugar responsiveness of this gel leads to a glucose-regulated release behavior of payloads such as insulin. All of these properties have been implemented at physiological pH, which will facilitate future applications of these hydrogels as biomaterials.

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, gelation, or other dynamically arrested states. The influence of the temperature, and consequently of the attraction strength between rodlike particles, on the LC phase behaviors of hard rodlike particles was thoroughly investigated via a forced phase separation assisted by a low-speed centrifuge, leading to an apparent phase diagram in the space of attractive strength and isotropic−nematic coexisting LC phases. At T ≪ LCST, the block polymers are in the fully hydrophilic state and the rodlike system behaves as hard rods. Its LC behaviors can be quantitatively described by the flexibility-corrected Onsager's hard rod theory. Although the forced phase separation is not truly in phase equilibrium, increasing temperature to induce the collapse of the PNIPAM blocks does lead to theoretically predicted widening of the isotropic−nematic coexisting concentrations with increasing temperature. Fitting our experimental data with advanced theories reveals several physical parameters that probably characterize the LC phase of rigid polymers or rod systems with attractive interactions in general.