We found that cellulosic liquid-crystalline films displayed not only a wide-ranging colour change but also inversion of circular dichroism upon a mechanical stimulus.

The surface chemistry of polymer films and coatings is relevant to a wide range of applications, and recent work has shown that bottlebrush polymers can be used as additives to modify film interfaces and surfaces. In blends with linear polymers of a sufficient molecular weight, bottlebrush polymers will enrich interfaces driven, in part, by entropic effects. However, prior work has only studied a limited set of systems with either neutral or repulsive interactions between the bottlebrush and linear polymers. Herein, we investigated surface segregation in blends of bottlebrush and linear polymers with attractive intermolecular interactions. Specifically, we studied blends of bottlebrush poly(cyclohexyl methacrylate) (BBPCHMA) and linear polystyrene (PS) over a range of BBPCHMA backbone and linear PS lengths. Time-of-flight secondary ion mass spectroscopy measurements of the blends showed that bottlebrush additives strongly segregated to the film surface when the bottlebrush side chain was shorter than matrix linear PS, and the surface remained enriched with bottlebrush after 2 days of thermal annealing. In comparison to studies with bottlebrushes having neutral or repulsive interactions with linear PS, the surface segregation of BBPCHMA was weaker in the as-cast films but more significant after thermal annealing. This comparison suggests that architectural effects can drive segregation during casting and the interaction of the polymers with the air interface is more significant during thermal annealing. Finally, we demonstrated that these bottlebrush additives could self-heal a damaged surface by diffusing to a damaged region during thermal annealing. This work provides new insight into the segregation behavior of bottlebrush polymer additives and factors that drive segregation during casting and thermal annealing.

Wide use of bio-based polymers could play a key role in facilitating a more sustainable society because such polymers are renewable and ecofriendly. Cellulose is a representative bio-based polymer and has been used in various materials. To further expand the application of cellulose, it is crucial to develop functional materials utilizing cellulosic physicochemical properties that are acknowledged but insufficiently applied. Cellulose derivatives and cellulose nanocrystals exhibit a cholesteric liquid crystal (ChLC) property based on rigidity and chirality, and this property is promising for constructing next-generation functional materials. The form of such materials is an important factor because material form is closely related with function. To date, researchers have reported cellulosic ChLC materials with a wide range of material forms—such as films, gels, mesoporous materials, and emulsions—for diverse functions. We first briefly review the fundamental aspects of cellulosic ChLCs. Then we comprehensively review research on cellulosic ChLC functional materials in terms of their material forms. Thus, this review provides insights into the creation of novel cellulosic ChLC functional materials based on material form designed toward the expanded application of cellulosics.