Tristan Tsai Yuan Tan

Superhydrophobic fluorinated POSS–PVDF-HFP nanocomposite coating on glass by electrospinning

Fluorinated polyhedral oligomeric silsesquioxanes–poly(vinylidene fluoride-co-hexafluoro propylene) (fluoroPOSS–PVDF-HFP) nanocomposite mixtures are prepared by individually mixing two fluorinated POSS materials (FP8 and FPSi8) with PVDF-HFP solution and transparent superhydrophobic coatings on a glass substrate are produced by electrospinning. The fabricated superhydrophobic surface exhibits continuous, uniform and non-beaded nanofibers with a high water contact angle (157.3°) and a low sliding angle (SA < 5°). The superhydrophobic properties including surface energy, water contact angle, and contact angle hysteresis as well as the optical properties are studied by altering the wt% of fluoroPOSS in PVDF-HFP solution. It is observed that due to the increase in the viscosity of the solution, the diameter of the nanofibers increases with increase in the concentration of fluoroPOSS. It is also observed that as the concentration of fluoroPOSS in PVDF solution increases, the amount of fluorine content increases thereby the surface energy of the coating decreases (to around 10 mN m−1) leading to a superhydrophobic surface with low contact angle hysteresis (<5°). The optical properties of the coatings produced using FPSi8 fluoroPOSS–PVDF-HFP mixture are compared with those of FP8 fluoroPOSS, and the former is found to be more transparent due to its relatively high solubility in PVDF-HFP.

Photoresponsive Liquid Marbles and Dry Water

Stimuli-responsive liquid marbles for controlled release typically rely on organic moieties that require lengthy syntheses. We report herein a facile, one-step synthesis of hydrophobic and oleophobic TiO2 nanoparticles that display photoresponsive wettability. Water liquid marbles stabilized by these photoresponsive TiO2 particles were found to be stable when shielded from ultraviolet (UV) radiation; however, they quickly collapsed after being irradiated with 302 nm UV light. Oil- and organic-solvent-based liquid marbles could also be fabricated using oleophobic TiO2 nanoparticles and show similar UV-induced collapse. Finally, we demonstrated the formation of the micronized form of water liquid marbles, also known as dry water, by homogenization of the TiO2 nanoparticles with water. The TiO2 dry water displayed a similar photoresponse, whereby the micronized liquid marbles collapsed after irradiation and the dry water turned from a free-flowing powder to a paste. Hence, by exploiting the photoresponsive wettability of TiO2, we fabricated liquid marbles and dry water that display photoresponse and studied the conditions required for their collapse.

Synthesis of Complexes with Abnormal “Protic” N-Heterocyclic Carbenes

Neutral 4-iodo-N-ethylimidazole 3 oxidatively adds to [Pt(PPh3)4] to give, in the presence of different tetraalkylammonium salts, complexes trans-[4], trans-[5], and trans-[6] containing an anionic C4-bound heterocycle with an unsubstituted ring-nitrogen atom. Complex trans-[4] reacts with the proton source NH4 I under protonation of the ring-nitrogen atom to produce complex trans-[7]I which bears an NH,NR-substituted aNHC ligand. The reaction of trans-[4] with CH3I yields the complex trans-[8]I which has a classical aNHC ligand with two alkylated ring-nitrogen atoms.

High-Fidelity, Narcissistic Self-Sorting in the Synthesis of Organometallic Assemblies from Poly-NHC Ligands

Highly selective, narcissistic self-sorting has been observed in the one-pot synthesis of three organometallic molecular cylinders of type [M3 {L-(NHC)3 }2 ](PF6 )3 (M=Ag+ , Au+ ; L=1,3,5-benzene, triphenylamine, or 1,3,5-triphenylbenzene) from L-(NHC)3 and silver(I) or gold(I) ions. The molecular cylinders contain only one type of tris-NHC ligand with no crossover products detectable. Transmetalation of the tris-NHC ligands from Ag+ to Au+ in a one-pot reaction with retention of the supramolecular structures is also demonstrated. High-fidelity self-sorting was also observed in the one-pot reaction of benzene-bridged tris-NHC and tetrakis-NHC ligands with Ag2 O. This study for the first time extends narcissistic self-sorting in metal-ligand interactions from Werner-type complexes to organometallic derivatives.

Template Synthesis of Three‐Dimensional Hexakisimidazolium Cages

A procedure for the synthesis of three-dimensional hexakisimidazolium cage compounds has been developed. The reaction of the trigonal trisimidazolium salts H3 L(PF6 )3 , decorated with three N-olefinic pendants, and silver oxide yielded trinuclear trisilver(I) hexacarbene molecular cylinders of the type [Ag3 L2 ]3+ with the olefinic pendants from the two different tricarbene ligands arranged in three pairs. Subsequent UV irradiation gave three cyclobutane links between the two tris-NHC ligands in three [2+2] cycloaddition reactions, thereby generating a three-dimensional hexakis-NHC ligand. Removal of the metal ions resulted in the formation of three-dimensional hexakisimidazolium cages with a large internal cavity.