Encounter between Gyroid and Lamellae in Janus Colloidal Particles Self-Assembled by a Rod-Coil Block Copolymer

Controlling the internal structure of block copolymer (BCP) particles has a significant influence on its functionalities. Here, a structure-controlling method is proposed to regulate the internal structure of BCP Janus colloidal particles using different surfactants. Different microphase separation processes take place in two connected halves of the Janus particles. An order-order transition between gyroid and lamellar phases is observed in polymeric colloids. The epitaxial growth during the structural transformation from gyroid to lamellar phase undergoes a two-layered rearrangement to accommodate the interdomain spacing mismatch between these two phases. This self-assembly behavior can be ascribed to the preferential wetting of BCP chains at the interface, which can change the chain conformation of different blocks. The Janus colloidal particles can further experience a reversible phase transition by restructuring the polymer particles under solvent vapor. It is anticipated that the new phase behavior found in Janus particles can not only enrich the self-assembly study of BCPs but also provide opportunities for various applications based on Janus particles with ordered structures.

Recent Progress in Polymer Cubosomes and Hexosomes

Polymer cubosomes and hexosomes are polymer colloids with inverted lyotropic liquid crystal phases as internal structures. They are composed of regular networks of water-filled channels surrounded by a bilayer membrane made from amphiphilic block copolymers. Due to the uniform, tunable, and highly ordered porous structure, polymer cubosomes and hexosomes present numerous advantages over polymer micelles and vesicles, such as the high loading volumes for both hydrophilic and hydrophobic substances, large specific surface areas, and good mechanical and chemical stabilities. The polymer chemistry also enables unlimited molecular design to endow these polymer colloids with a lot of adjustable physical and chemical properties. Therefore, polymer cubosomes and hexosomes have attracted increasing attention for their potential applications in materials science and nanotechnology. This review outlines the recent progress in this field with an emphasis on the polymer architectures, the self-assembly conditions and mechanisms, and some application examples which are special for these inverted polymer colloids. It is hoped to provide some practical guidance for researchers interested in polymer cubosomes and hexosomes.

Triggered Degradable Colloidal Particles with Ordered Inverse Bicontinuous Cubic and Hexagonal Mesophases

We herein report a facile strategy to prepare triggered degradable block copolymer nano/macro-objects, ranging from typical micelles, worms, jellyfish, and vesicles to rarely achieved spongosomes, cubosomes, and hexosomes via RAFT-mediated polymerization-induced self-assembly (PISA). The morphological transitions from a simple spherical micelle to a spongosome, ordered Im3¯m cubosome, and p6mm hexosome were captured and demonstrated by TEM, SEM, and synchrotron SAXS. In addition, morphological phase diagrams including important factors, such as solid contents, degree of polymerization (DP), and stabilizer block chain length, were constructed to unveil the formation mechanism and guide the scalable preparation of complex morphologies with packing parameter (P) > 1. This study not only represents an example that achieved inverse mesophases via acrylate-based monomers with high conversion but also reports a triggered degradable system in the most extended morphological range via PISA. The facile synthesis and stimuli-responsiveness of our system should greatly expand the utility of polymer inverse mesophases for triggered releasing, templating, and many other applications.

Efficient Access to 3D Mesoscopic Prisms in Polymeric Soft Materials

The preparation of 3D functional isolated mesoscopic assemblies remains a challenge in the self-assembly of polymers. Here, well-defined 3D hexagonal and hexagram prisms with uniform dimensions are acquired by the crystallization of the inclusion complex composed of a crystalline molecule tris-o-phenylenedioxycyclotriphosphazene (TPP) and a block copolymer. The crystalline TPP plays an important role in the self-assembling process. The faceted morphologies of the hexagonal and hexagram prisms are infrequent in the self-assembly field of soft materials. The formation of the prisms experiences a 3D growth mechanism. The epitaxial growth, accompanied by the heterogeneous nucleation in the edges, yields the growth of inclusion crystals. This study provides a path to construct well-defined polymeric soft materials with broad utility based on numerous supramolecular complexes.

Tailored Polymer Particles with Ordered Network Structures in Emulsion Droplets

The structural control of block copolymer (BCP) particles, which determines their properties and utilities, is quite important. Understanding the structural relationship between solution-cast samples and polymer particles in a confined space is necessary to precisely regulate the internal structure of polymer particles. Therefore, a facile method by choosing an appropriate selective solvent is reported to prepare spherical polymer particles with ordered network structures. The rod-coil BCP, poly(dimethylsiloxane)-b-poly{2,5-bis[(4-methoxyphenyl)-oxycarbonyl]styrene} (PDMS-b-PMPCS), was chosen as a model polymer because of its strong phase segregation ability. First, the structures of the BCP with a thermodynamically stable lamellar structure cast from different selective solvents were systematically studied. Then, a polymer particle with the same internal structure as that of the solution-cast sample can be easily prepared by self-assembling in an emulsion confined space. The relatively large particle size is of importance in this process because the large value of the particle size to periodicity ratio can provide a weak confined environment. This method helps us understand the inherent self-assembling mechanism of polymer particles in an emulsion confined space and accurately control the internal structure of the polymer particle obtained.