Carbon trifluoromethylation reactions of hydrocarbon derivatives and heteroarenes.

Hyperbranched polymers (HPs) are highly branched three-dimensional (3D) macromolecules. Their globular and dendritic architectures endow them with unique structures and properties such as abundant functional groups, intramolecular cavities, low viscosity, and high solubility. HPs can be facilely synthesized via a one-pot polymerization of traditional small molecular monomers or emerging macromonomers. The great development in synthetic strategies, from click polymerization (i.e., copper-catalyzed azide–alkyne cycloaddition, metal-free azide–alkyne cycloaddition, strain-promoted azide–alkyne cycloaddition, thiol–ene/yne addition, Diels–Alder cycloaddition, Menschutkin reaction, and aza-Michael addition) to recently reported multicomponent reactions, gives rise to diverse HPs with desirable functional/hetero-functional groups and topologies such as segmented or sequential ones. Benefiting from tailorable structures and correspondingly special properties, the achieved HPs have been widely applied in various fields such as light-emitting materials, nanoscience and technology, supramolecular chemistry, biomaterials, hybrid materials and composites, coatings, adhesives, and modifiers. In this review, we mainly focus on the progress in the structural control, synthesis, functionalization, and potential applications of both conventional and segmented HPs reported over the last decade.

Hyperbranched polymers: advances from synthesis to applications

Fluorinated high-performance polymers: Poly(arylene ether)s and aromatic polyimides containing trifluoromethyl groups

Silicone containing copolymers: Synthesis, properties and applications

The change in shape inducible in some photo-reversible molecules using light can effect powerful changes to a variety of properties of a host material. This class of reversible light-switchable molecules includes molecules that photo-dimerize, such as coumarins and anthracenes; those that allow intra-molecular photo-induced bond formation, such as fulgides, spiro-pyrans, and diarylethenes; and those that exhibit photo-isomerization, such as stilbenes, crowded alkenes, and azobenzenes. The most ubiquitous natural molecule for reversible shape change, however, and perhaps the inspiration for all artificial bio-mimics, is the rhodopsin/retinal protein system that enables vision, and this is the quintessential reversible photo-switch for performance and robustness. Here, the small retinal molecule embedded in a cage of rhodopsin helices isomerizes from a cis geometry to a trans geometry around a C=C double bond with the absorption of just a single photon. The modest shape change of just a few angstroms is quickly amplified and sets off a cascade of larger shape and chemical changes, eventually culminating in an electrical signal to the brain of a vision event, the energy of the input photon amplified many thousands of times in the process. Complicated biochemical pathways then revert the trans isomer back to cis, and set the system back up for another cascade upon subsequent absorption. The reversibility is complete, and many subsequent cycles are possible. The reversion mechanism back to the initial cis state is complex and enzymatic, hence direct application of the retinal/rhodopsin photo-switch to engineering systems is difficult. Perhaps the best artificial mimic of this strong photo-switching effect however in terms of reversibility, speed, and simplicity of incorporation, is azobenzene. Trans and cis states can be switched in microseconds with low-power light, reversibility of 105 and 106 cycles is routine before chemical fatigue, and a wide variety of molecular architectures is available to the synthetic materials chemist, permitting facile anchoring and compatibility, as well as chemical and physical amplification of the simple geometric change. This review article focuses on photo-mechanical effect taking place in various material systems incorporating azobenzene. The photo-mechanical effect can be defined as reversible change in shape by absorption of light, which results in a significant macroscopic mechanical deformation, and reversible mechanical actuation, of the host material. Thus, we exclude simple thermal expansion effects, reversible but non-mechanical photo-switching or photo-chemistry, as well as the wide range of optical and electro-optical switching effects for which good reviews exist elsewhere. Azobenzene-based material systems are also of great interest for light energy harvesting applications across much of the solar spectrum, yet this emerging field is still in an early enough stage of research output as to not yet warrant review, but we hope that some of the ideas put forward here toward promising future directions of research, will help guide the field.

Azobenzene photomechanics: prospects and potential applications

Decreasing the dielectric constant and water uptake by introducing hydrophobic cross-linked networks into co-polyimide films

Synthesis and properties of soluble fluorinated poly(ether imide)s with different pendant groups

Polyimide schiff base as a high-performance anode material for lithium-ion batteries

Pendant-group cross-linked highly sulfonated co-polyimides for proton exchange membranes

A novel fluorinated hyperbranched polyimide (HBPI) is synthesized by using a new triamine monomer, l,3,5 -tris(2-trifluoromethyl-4-aminophenoxy)benzene (TFAPOB) (A 3 ), as a 'core' molecule, 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) as a B 2 monomer, and 3,5-ditrifuoromethylphenyl as an endcapping reagent. The polymer shows a glass transition temperature of 232 C and a temperature of 10% weight loss at 535 °C. The HBPI presents a birefringence as low as 0.002 at 650 nm. Near-IR results indicate that HBPI exhibits desirable properties for low loss optical waveguide applications.

Fluorinated Hyperbranched Polyimide for Optical Waveguides

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