Cationic bottlebrush homopolymers are polymerized using a grafting‐through approach by ring‐opening metathesis polymerization (ROMP) to afford well‐defined polymers. Quaternary ammonium macromonomers (MMs) are prepared by quaternizing tertiary amine MMs synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization. The quaternary ammonium MMs undergo ROMP to target molecular weights (Mn = 30 000–100 000 g mol−1) and a low dispersity (Đ = 1.10–1.30). Halide‐ligand exchange between the third generation Grubbs catalyst (G3) and halide counter ions (bromide and iodide ions) of MMs changes the catalyst activity throughout ROMP, causing it to deviate from pseudo‐first order kinetic behavior; however, the polymerization still follows controlled behavior without significant catalyst termination. Increasing steric bulk of the MMs decreases the polymerization rate as well. Amphiphilic block copolymers are synthesized by sequential polymerization of quaternary ammonium MMs and polystyrene (PS) MMs. Using a PS macroinitiator affords block copolymers with lower Đ values as compared to the less active cationic macroinitiator.

A simple strategy was developed to synthesize polyimine-coated cellulose nanofibrils (CNF) for effective CNF drying and composite reinforcement. The polyimine was synthesized in an aqueous medium using a selective hydrophilic and hydrophobic component that forces the polyimine to precipitate, which prevents the reverse imine reaction. The polyimine coating allowed the CNF to be easily oven-dried while maintaining a fibrillar morphology to provide mechanical reinforcement in poly­(ethylene terephthalate glycol) (PETG) composites. In comparison, poor mechanical performance and a heterogeneous fracture surface were observed when the coated CNF were incorporated into poly­(l-lactide) (PLA) composites. It is hypothesized that intermolecular aromatic–aromatic interactions are formed at the interface between fibers and the polymer matrix in the PETG system, while no such phenomena occur in the PLA system. Overall, this facile strategy to produce modified, easily dried CNF can be adapted to produce polyimine-coated CNF with unique functionalities that are useful in a range of applications.

Well-defined and densely grafted amphiphilic cationic bottlebrush block copolymers (BBCPs) containing polystyrene (PS) and quaternary ammonium polymer (PDMH) side chains, PS-b-PDMH, were successfully generated from grafting-through ring-opening metathesis polymerization. The amphiphilic BBCP thin films, analyzed by atomic force microscopy (AFM), could self-assemble into distinct nanometer-scale domains of which the morphologies were manipulated by the volume fraction of the cationic block (f PDMH ), degree of polymerization, and asymmetric block side-chain lengths. The morphological stability of the BBCP thin films upon water exposure was investigated. The AFM images of casted BBCP films demonstrated surface roughening and morphology changes upon submersion as compared to precursor dry films, which was attributed to the swelling of the cationic domains and the rearrangement of the alkyl chain pendant groups under water. Thermally annealed films of PS-b-PDMH with an f PDMH of 0.5 exhibited water-stable surfaces after water submersion, indicating that the BBCP structure can prevent some surface rearrangement. Such coatings could be used as potential antimicrobial and antifouling surfaces in future studies.