Diversity of Synthetic Approaches to Functionalized Perfluoropolyalkylether Polymers

Rational Design of Highly Comprehensive Liquid-Like Coatings with Enhanced Transparency, Concerted Multi-Function, and Excellent Durability: A Ternary Cooperative Strategy

Durable repellent surfaces of high transparency find key applications in daily life and industry. Nevertheless, developing anti-reflective coatings with omni-repellency, concerted multi-function, and desirable durability remains a daunting challenge. Here, a highly comprehensive coating is designed based on the combination of structural design and molecular design. The resulting silica hybrid coating not only manifests enhanced transparency and exceptional omniphobicity, but also achieves integration of multi-function (e.g., anti-smudge, anti-icing, and anti-corrosion). The unprecedented durability of the coating is evidenced by maintaining slipperiness after rigorous treatments, such as 2.5 × 105-cycle mechanical abrasion with a high loading pressure of 100 kPa, 1000-cycle adhesion/peeling and soaking in extreme pH solutions, etc. This work provides a design blueprint for manufacturing versatile and durable coatings for wide-ranging applications.

One-step flow synthesis of size-controlled polymer nanogels in a fluorocarbon microfluidic chip

Synthetic polymer nanoparticles (NPs) with biomimetic properties are ideally suited for different biomedical applications such as drug delivery and direct therapy. However, bulk synthetic approaches can suffer from poor reproducibility and scalability when precise size control or multi-step procedures are required. Herein, we report an integrated microfluidic chip for the synthesis of polymer NPs. The chip could sequentially perform homopolymer synthesis and subsequent crosslinking into NPs without intermediate purification. This was made possible by fabrication of the chip with a fluorinated elastomer and incorporation of two microfluidic mixers. The first was a long channel with passive mixing features for the aqueous RAFT synthesis of stimuli-responsive polymers in ambient conditions. The polymers were then directly fed into a hydrodynamic flow focusing (HFF) junction that rapidly mixed them with a crosslinker solution to produce NPs. Compared to microfluidic systems made of PDMS or glass, our chip had better compatibility and facile fabrication. The polymers were synthesized with high monomer conversion and the NP size was found to be influenced by the flow rate ratio between the crosslinker solution and polymer solution. This allowed for the size to be predictably controlled by careful adjustment of the fluid flow rates. The size of the NPs and their stimuli-responses were studied using DLS and SEM imaging. This microfluidic chip design can potentially streamline and provide some automation for the bottom-up synthesis of polymer NPs while offering on-demand size control.

Nanoenergetic Composites with Fluoropolymers: Transition from Powders to Structures

Over the years, nanoenergetic materials have attracted enormous research interest due to their overall better combustion characteristics compared to their micron-sized counterparts. Aluminum, boron, and their respective alloys are the most extensively studied nanoenergetic materials. The majority of the research work related to this topic is confined to the respective powders. However, for practical applications, the powders need to be consolidated into reactive structures. Processing the nanoenergetic materials with polymeric binders to prepare structured composites is a possible route for the conversion of powders to structures. Most of the binders, including the energetic ones, when mixed with nanoenergetic materials even in small quantities, adversely affects the ignitability and combustion performance of the corresponding composites. The passivating effect induced by the polymeric binder is considered unfavorable for ignitability. Fluoropolymers, with their ability to induce pre-ignition reactions with the nascent oxide shell around aluminum and boron, are recognized to sustain the ignitability of the composites. Initial research efforts have been focused on surface functionalizing approaches using fluoropolymers to activate them further for energy release, and to improve the safety and storage properties. With the combined advent of more advanced chemistry and manufacturing techniques, fluoropolymers are recently being investigated as binders to process nanoenergetic materials to reactive structures. This review focuses on the major research developments in this area that have significantly assisted in the transitioning of nanoenergetic powders to structures using fluoropolymers as binders.

Free-Radical Photopolymerization for Curing Products for Refinish Coatings Market

Even though there are many photocurable compositions that are cured by cationic photopolymerization mechanisms, UV curing generally consists of the formation of cross-linking covalent bonds between a resin and monomers via a photoinitiated free radical polymerization reaction, obtaining a three-dimensional polymer network. One of its many applications is in the refinish coatings market, where putties, primers and clear coats can be cured faster and more efficiently than with traditional curing. All these products contain the same essential components, which are resin, monomers and photoinitiators, the latter being the source of free radicals. They may also include additives used to achieve a certain consistency, but always taking into account the avoidance of damage to the UV curing—for example, by removing light from the innermost layers. Surface curing also has its challenges since it can be easily inhibited by oxygen, although this can be solved by adding scavengers such as amines or thiols, able to react with the otherwise inactive peroxy radicals and continue the propagation of the polymerization reaction. In this review article, we cover a broad analysis from the organic point of view to the industrial applications of this line of research, with a wide current and future range of uses.

Nanotechnology as a Versatile Tool for 19F-MRI Agent's Formulation: A Glimpse into the Use of Perfluorinated and Fluorinated Compounds in Nanoparticles

Simultaneously being a non-radiative and non-invasive technique makes magnetic resonance imaging (MRI) one of the highly sought imaging techniques for the early diagnosis and treatment of diseases. Despite more than four decades of research on finding a suitable imaging agent from fluorine for clinical applications, it still lingers as a challenge to get the regulatory approval compared to its hydrogen counterpart. The pertinent hurdle is the simultaneous intrinsic hydrophobicity and lipophobicity of fluorine and its derivatives that make them insoluble in any liquids, strongly limiting their application in areas such as targeted delivery. A blossoming technique to circumvent the unfavorable physicochemical characteristics of perfluorocarbon compounds (PFCs) and guarantee a high local concentration of fluorine in the desired body part is to encapsulate them in nanosystems. In this review, we will be emphasizing different types of nanocarrier systems studied to encapsulate various PFCs and fluorinated compounds, headway to be applied as a contrast agent (CA) in fluorine-19 MRI (19F MRI). We would also scrutinize, especially from studies over the last decade, the different types of PFCs and their specific applications and limitations concerning the nanoparticle (NP) system used to encapsulate them. A critical evaluation for future opportunities would be speculated.

Cyclic Perfluoropolyether: Distinct Film Formability and Thermostabilization Upon Recyclable Cyclic-Linear Topological Transformation

Perfluoropolyether (PFPE) is an industrially important fluoropolymer and has great industrial importance due to its flexible, noncombustible, and chemically robust properties. However, exploration and application of chemically modified homogeneous PFPEs are hampered by their immiscibility against nonfluorine-containing molecules. Here, the synthesis is reported of cyclic PFPE with hexaarylbiimidazoles (HABIs) in chains from linear PFPE having 2,4,5-triphenylimidazole (lophine) end groups. While phase separation between the end groups and main chains took place for linear PFPE, HABIs and main chains in cyclic PFPE are miscible to form transparent glass films. The design of cyclic PFPE also enables cyclic to linear topological transformation based on conversion of HABIs into lophines upon mild heating in the glass film state. Sequential linear-to-cyclic and cyclic-to-linear topological transformations enable fabrication of thermostabilized transparent films derived from PFPE.

Robust Scalable-Manufactured Smart Fabric Surfaces Based on Azobenzene-Containing Maleimide Copolymers for Rewritable Information Storage and Hydrogen Fluoride Visual Sensor

Functionalized materials with reversible color switching are highly attractive in many application fields, especially as rewritable media for information storage. It is critical yet challenging to develop a cost-effective strategy for the fabrication of stimulus-responsive chromogenic systems. Herein, we present a versatile dip-coating approach to fabricate robust smart textile with acid/base-driven chromotropic capability. Owing to the introduction of novel maleimide-based copolymers bearing azobenzene derivative moieties, smart textiles possess rapid color switching between yellow and orange-red, which is triggered by acid-base stimulations with the resulting reversible protonation/deprotonation of maleimide moieties. As a proof of concept of the application of the smart textile for high-performance rewritable media, various rewritable elaborate patterns can be fast trifluoroacetic acid-printed/triethylamine-erased (within 20 s) with excellent cycling stability and long legible duration (>30 days). Meanwhile, the smart textile can be employed as a visual sensor for the detection of hydrogen fluoride gas leakage. It is highlighted that the as-prepared robust smart textiles with superhydrophobic surfaces have excellent antifouling properties and chemical/mechanical stabilities, which can tolerate harsh environmental conditions and repetitive mechanical deformation. The robust smart textiles with simple low-cost large-scale production may find more advanced potential applications besides information storage and sensors demonstrated.

An Ultra-Low-Temperature Elastomer with Excellent Mechanical Performance and Solvent Resistance

Elastomers presenting good elasticity, ductility, and chemical resistance at low temperatures can serve as superior performers for explorations in extremely cold environments. However, no commercially available elastomer to date can comprehensively fulfill those demands. Here, a perfluoropolyether (PFPE)-based network crosslinked by dynamic urethane chemistry is demonstrated, which may satisfy the demands of application in ultracold environments. As the crucial constitute in such a crosslinked network, PFPE provides the elastomer with excellent elasticity at a temperature down to -110 °C and outstanding ductility within the cryogenic temperature range. Importantly, the high proportion of fluorocarbon segment also provides wonderful compatibility to most organic solvents, accounting for the low-swelling characteristics of the elastomer in sealing applications. Furthermore, the dynamic crosslinking feature allows the cured elastomer to be reprocessed like thermoplastic polymers, which affords great promise to recycle and reuse the elastomer after its disposal. Inherently, this elastomer would inspire a worldwide interest in the design of elastic devices that are adaptable to extremely low temperature.