We report a new strategy toward polymer–protein conjugates using a grafting-from method that employs photoinduced electron/energy transfer–reversible addition–fragmentation chain transfer (PET–RAFT) polymerization. Initial screening of reaction conditions showed rapid polymerization of acrylamides under high dilution in water using eosin Y as a photocatalyst in the presence of a tertiary amine. A lysozyme-modified chain transfer agent allowed the same conditions to be utilized for grafting-from polymerizations, and we further demonstrated the broad scope of this technique by polymerizing acrylic and styrenic monomers. Finally, retention of the RAFT end group was suggested by successful chain extension with N-isopropylacrylamide from the polymer–protein conjugates to form block copolymer–protein conjugates. This strategy should expand the capabilities of grafting-from proteins with RAFT polymerization under mild conditions to afford diverse functional materials.

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Methylcellulose (MC) is a water-soluble cellulose derivative with a wide range of commercial applications. Upon heating, MC solutions reversibly form ∼15–20 nm diameter fibrils, which percolate into a fibrillar network, resulting in macroscopic gelation. Using mid-angle X-ray scattering (MAXS) and wide-angle X-ray scattering (WAXS), we have analyzed MC chain organization within fibrils aligned in dried films that have been stretched by over 300%. MAXS and WAXS show distinct anisotropic scattering features, which we interpret as reflecting crystalline domains within the fibrils. The scattering peaks are consistent with a body-centered monoclinic unit cell, with similar dimensions as other cellulosic crystals, a = 11.4 Å, b = 8.9 Å, and c = 10.2 Å, and γ in the range of 90–100°, with MC chains oriented along the long axis of the fibril. Phase-plate cryogenic transmission electron microscopy images of MC fibrils contribute to a more comprehensive picture. Along the long axis of MC fibrils, there is evidence of dense twisted domains, which are interpreted as regions containing semicrystalline MC, interspersed with looser, less organized amorphous domains. Together, these two techniques provide the most complete interpretation of MC subfibril structure currently available.

Block copolymers (BCPs) self-assembled into 3D network phases are promising for designing useful materials with multiple properties that rely on domain continuity. However, access to potential applications has been limited because network formation with linear BCPs tends to occur only over narrow compositional windows. Another constraint is slow self-assembly kinetics at higher molecular weights, which limits the network unit cell dimensions and the resulting material properties. Architecturally asymmetric, linear-bottlebrush BCPs have previously been demonstrated to promote self-assembly into complex micellar phases. The architectural asymmetry has been demonstrated to induce favorable curvature toward the linear block. However, linear-bottlebrush copolymer phase behavior and self-assembly into network phases have not been systematically studied. Here, we map the phase behavior of eight sets of diblock polymers with a linear-bottlebrush architecture in the expected vicinity of the double-gyroid phase. We demonstrate the effects of architectural asymmetry and the linear block cohesive energy density on self-assembly into double-gyroid, lamellar, and hexagonal phases. Through a combination of molecular and structural characterization techniques, we demonstrate that the shape of the polymer and the identity of the linear block provide significant control over the molecular factors that dictate network formation.

Interactions of nonionic poly(ethylene oxide)-b-poly(propylene oxide) (PEO-PPO) block copolymers, known as Pluronics or poloxamers, with cell membranes have been widely studied for a host of biomedical applications. Herein, we report how cholesterol within phosphatidylcholine (POPC) lipid bilayer liposomes and bilayer curvature affects the binding of several PPO-PEO-PPO triblocks with varying PPO content and a tPPO-PEO diblock, where t refers to a tert-butyl end group. Pulsed-field-gradient NMR was employed to quantify the extent of copolymer associated with liposomes prepared with cholesterol concentrations ranging from 0 to 30 mol % relative to the total content of POPC and cholesterol and vesicle extrusion radii of 25, 50, or 100 nm. The fraction of polymer bound to the liposomes was extracted from NMR data on the basis of the very different mobilities of the bound and free polymers in aqueous solution. Cholesterol concentration was manipulated by varying the molar percentage of this sterol in the POPC bilayer preparation. The membrane curvature was varied by adjusting the liposome size through a conventional pore extrusion technique. Although the PPO content significantly influences the overall amount of block copolymer adsorbed to the liposome, we found that polymer binding decreases with increasing cholesterol concentration in a universal fashion, with the fraction of bound polymer dropping 10-fold between 0 and 30 mol % cholesterol relative to the total content