Macroscopic Regulation of Hierarchical Nanostructures in Liquid-crystalline Block Copolymers towards Functional Materials

Liquid Crystalline Nanoparticles via Polymerization-Induced Self-Assembly: Morphology Evolution and Function Regulation

Liquid crystalline nanoparticles (LC NPs) are a kind of polymer NPs with LC mesogens, which can form special anisotropic morphologies due to the influence of LC ordering. Owing to the stimuli-responsiveness of the LC blocks, LC NPs show abundant morphology evolution behaviors in response to external regulation. LC NPs have great application potential in nano-devices, drug delivery, special fibers and other fields. Polymerization-induced self-assembly (PISA) method can synthesize LC NPs at high solid content, reducing the harsh demand for reaction solvent of the LC polymers, being a better choice for large-scale production. In this review, we introduced recent research progress of PISA-LC NPs by dividing them into several parts according to the LC mesogen, and discussed the improvement of experimental conditions and the potential application of these polymers.

Self-recovery of chiral microphase separation in an achiral diblock copolymer system

Macroscopic regulation of chiral supramolecular nanostructures in liquid-crystalline block copolymers is of great significance in photonics and nanotechnology. Although fabricating helical phase structures via chiral doping and microphase separation has been widely reported, the chiral memory and self-recovery capacity of asymmetric phase structures are the major challenge and still deeply rely on the presence of chiral additives. Herein, we demonstrate the first controllable chiral microphase separation in an achiral amphiphilic block copolymer consisting of poly(ethylene oxide) and azobenzene (Azo) groups. Chirality can be transferred to the fabricated helical nanostructures by doping with chiral additives (tartaric acid, TA). After the removal of the chiral additives and then performing cross-linking, the formed helical nanostructures will completely dispense with the chiral source. The supramolecular chirality and the micron-scale phase structure can be maintained under UV irradiation and heating-cooling treatment, enabling a reversible "on-off" chiroptical switch feature. This work is expected to avoid the tedious synthesis and expensive raw materials and shows a great application prospect in chiral separation and so on.

ABC-Type, Bola-Form Giant Surfactants: Synthesis and Self-Assembly

Due to the fast phase separation kinetics and small feature size, the self-assembly of giant molecules has attracted lots of attention. However, there is not much study on multicomponent giant surfactants. In this work, through a modular synthetic strategy, different polyhedral oligomeric silsesquioxane (POSS)-based molecular nanoparticles are installed with diverse functionalities (hydrophobic octavinyl POSS (VPOSS), hydrophilic dihydroxyl-functionalized POSS (DPOSS), and omniphobic perfluoroalkyl-chain-functionalized POSS (FPOSS)) on the ends of one polystyrene (PS) chain to build up a series of triblock bola-form giant surfactants denoted as XPOSS-PS_n -FPOSS (X represents V or D). The target molecules are prepared by a combination of atom transfer radical polymerization (ATRP), esterification, as well as Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) and thiol-ene "click" reactions. These macromolecules are thoroughly characterized by combined technologies including nuclear magnetic resonance (NMR), size exclusion chromatography (SEC), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analyses. It is revealed by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) that VPOSS-PS_n -FPOSS adopts a two-phase separation scenario where VPOSS and POSS are segregated in one phase. DPOSS-PS_n -FPOSS with a third hydrophilic DPOSS shows a three-phase separation scenario, where highly ordered phase structures are difficult to develop owing to the competition of mutual phase separation processes and may be trapped in kinetically metastable states.