Spontaneous Creation of Anisotropic Polymer Crystals with Orientation-Sensitive Birefringence in Liquid Drops

Crystallization-dictated assembly of block copolymers and nanoparticles under three-dimensional confinement

Crystallization-dictated self-assembly of crystalline block copolymers (BCPs) in solution has been utilized to produce many impressive nanostructures. However, when the assembly of crystalline BCPs happens in a three-dimensional (3D) confined space, predicting the self-assembly structure of BCPs becomes challenging due to the competition between crystallization and microphase separation. In this feature article, we summarize the recent progress in the self-assembly of crystalline BCPs under confinement, emphasizing the impact of crystallization behavior on the assembly structure. Furthermore, we highlight the crystallization-directed assembly of inorganic nanoparticles (NPs), either by pre-assembling crystalline polymers as templates or using crystalline polymer chain segments as ligands. By exploring the impact of crystallization behavior on the assembled structure of BCPs and NPs, it is helpful to predict and manipulate the properties of polymer/nanoparticle composites, thereby enabling the precise design of polymer metamaterials.

Dual-Effect Coupling for Superior Dielectric and Thermal Conductivity of Polyimide Composite Films Featuring "Crystal-Like Phase" Structure

To match the increasing miniaturization and integration of electronic devices, higher requirements are put on the dielectric and thermal properties of the dielectrics to overcome the problems of delayed signal transmission and heat accumulation. Here, a 3D  porous thermal conductivity network is successfully constructed inside the polyimide (PI) matrix by the combination of ionic liquids (IL) and calcium fluoride (CaF2 ) nanofillers, motivated by the bubble-hole forming orientation force. Benefiting from the 3D thermal network formed by IL as a porogenic template and "crystal-like phase" structures induced by CaF2 - polyamide acid charge transfer, IL-10 vol% CaF2 /PI porous film exhibits a low permittivity of 2.14 and a thermal conductivity of 7.22 W m-1 K-1 . This design strategy breaks the bottleneck that low permittivity and high thermal conductivity in microelectronic systems are difficult to be jointly controlled, and provides a feasible solution for the development of intelligent microelectronics.

Liquid-liquid phase separation of immiscible polymers at double emulsion interfaces for configurable microcapsules

Liquid-liquid phase separation at complex interfaces is a common phenomenon in biological systems and is also a fundamental basis to create synthetic materials in multicomponent mixtures. Understanding the liquid-liquid phase separation in well-defined macromolecular systems is anticipated to shed light on similar behaviors in cross-disciplinary areas. Here we study a series of immiscible polymers and reveal a generic phase diagram of liquid-liquid phase separation at double emulsion interfaces, which depicts the equilibrium structures by interfacial tension and polymer fraction. We further reveal that the interfacial tensions in various systems fall on a linear relationship with spreading coefficients. Based on this theoretical guideline, the liquid-liquid phase separation can be modulated by a low fraction of amphiphilic block copolymers, leading the double emulsion droplets configurable between compartments and anisotropic shapes. The solidified anisotropic microcapsules could provide unique orientation-sensitive optical properties and thermomechanical responses. The theoretical analysis and experimental protocol in this study yield a generalizable strategy to prepare multiphase double emulsions with controlled structures and desired properties.

Milk Protein-Based Nanohydrogels: Current Status and Applications

Milk proteins are excellent biomaterials for the modification and formulation of food structures as they have good nutritional value; are biodegradable and biocompatible; are regarded as safe for human consumption; possess valuable physical, chemical, and biological functionalities. Hydrogels are three-dimensional, cross-linked networks of polymers capable of absorbing large amounts of water and biological fluids without dissolving and have attained great attraction from researchers due to their small size and high efficiency. Gelation is the primary technique used to synthesize milk protein nanohydrogels, whereas the denaturation, aggregation, and gelation of proteins are of specific significance toward assembling novel nanostructures such as nanohydrogels with various possible applications. These are synthesized by either chemical cross-linking achieved through covalent bonds or physical cross-linking via noncovalent bonds. Milk-protein-based gelling systems can play a variety of functions such as in food nutrition and health, food engineering and processing, and food safety. Therefore, this review highlights the method to prepare milk protein nanohydrogel and its diverse applications in the food industry.

Simple One-Step and Rapid Patterning of PDMS Microfluidic Device Wettability for PDMS Shell Production

Double emulsion (DE) droplets with controlled size and internal structure are a promising platform for biological analysis, chemical synthesis, and drug delivery systems. However, to further “democratize” their application, new methods that enable simple and precise spatial patterning of the surface wettability of droplet-generating microfluidic devices are still needed. Here, by leveraging the increase in hydrophilicity of polydimethylsiloxane (PDMS) due to the plasma-treatment used to permanently bond to glass, we developed a one-step method to selectively pattern the wettability of PDMS microfluidic devices for DE generation. Our results show that both Aquapel-treated and 1H,1H,2H,2H-Perfluorodecyltriethoxysilan (PFDTES)-treated devices are functionally showing the generality of our method. With the resulting microfluidic devices, both water-in-oil-in-water (w/o/w) and oil-in-water-in-oil (o/w/o) DE droplets can be produced. Using a PDMS mixture containing cross-linking agents, we formed PDMS microcapsules by solidifying the shell layer of water-in-PDMS-in-water DE droplets. We also characterize the morphological properties of the generated droplets/microcapsules. We anticipate the method developed in this work could be used in a broad range of applications of DE droplets.