Lianglin Zhang,Shuwei Lin,Yi Li,Baozong Li,Yonggang Yang
Four Ala–Ala dipeptides with a semi-perfluoroalkyl chain were synthesized. The intermolecular hydrogen bonding among amide groups and carboxyl groups as well as the hydrophobic association of semi-perfluoroalkyl chains drove the self-assembly of dipeptides. Homochiral dipeptides were able to self-assemble into coiled nanoribbons in a mixed solvent of DMSO/H2O (5/5, v/v), while entangled twisted nanofibers formed for heterochiral ones in a mixed solvent of DMSO/H2O (4/6, v/v). The handedness of self-assemblies and the stacking chirality of phenylene groups were controlled by the chirality of the alanine residue at the C-terminal. The vibration circular dichroism investigation indicated that the helicity of the semi-perfluoroalkyl chain was controlled by the handedness of dipeptide self-assemblies. The X-ray diffraction study showed that homochiral and heterochiral dipeptides underwent distinct molecular packing during the self-assembly. Our results clearly demonstrated that, through supramolecular self-assembly, the chirality transferred from the amino acid building block to the self-assemblies and eventually to the semi-perfluoroalkyl chain.
Tetrafluoro-λ 6 -sulfanyl (–SF 4 –) was synthesized via oxidative fluorination and used as a bridging group to bond perfluoroalkyl to phenylene. As a result, perfluoroalkylphenyltrichlorosilane was prepared by hydrosilylation using perfluoroalkylstyrene as a raw material under platinum catalytic conditions. And the corresponding monolayers produced a coating on silicon surfaces by spontaneous self-assembly from solution. Due to the introduction of –SF 4 –, it can increase the shielding effect of the fluoroalkyl group and reduce the surface energy of the material on the basis of extending the length of the perfluoroalkyl chain. At the same time, the sulfur–carbon bond formed by the bridge group is more likely to decrease under ultraviolet light. Once the bridge bond is broken, the perfluoroalkyl-terminated carbon chain perfluoroalkyl group is decomposed and detached. Therefore, the fluorine-containing material has good ultraviolet light degradation property, and the obtained fluorine-containing material is environmentally friendly. The self-assembled film containing a perfluoroalkylsilane can effectively reduce the friction properties and adhesion of the substrate, and the substrate modified with the self-assembled film containing a perfluoroalkylsilane has good stability.
Jialong Zhu,Yuanchuan Ma,Jiao Wei,Yang Hu,Haolan Gou,Hailong Wang,Wenyu Fang,Hong Fan,Jintao Wan
Developing hard yet flexible organic-inorganic hybrid coating with enhanced substrate adhesion and self-cleaning ability is of the great interest to many application scenarios such as foldable display devices. To this end, herein polysilsesquioxanes (PGSQ-F) with perfluorinated alkyl and epoxy moieties are synthesized and then coated on the amine-modified substrates (glass and PET) to create strong interfaces by the epoxy-amine reaction. After UV curing in the presence of a photoinitiator, the epoxy group of PGSQ-F undergoes a ring-opening polymerization to form a highly cross-linked network. The adhesion of PGSQ-F coating to the treated glass and PET substrates is as high as 3.9 ± 0.4 MPa and 1.5 ± 0.3 MPa, respectively. The high adhesive strength enhances the coating's resistance to various solvents. Moreover, the obtained coatings display the high pencil hardness (9H pencil hardness), excellent flexibility (1 mm bending diameter) and high transmittance (89.5 % 550 nm). In addition, the perfluorinated alkyl chains from PGSQ-F spontaneously aggregate onto the coating surface, endowing the coating with omniphobic feature, with water and n-hexane contact angle of 115.1 ± 0.7° and 70.2 ± 0.5°, respectively, which account for their outstanding antismudge and self-cleaning properties.
Developing suitable alternatives to long fluoroalkyl chain surfactants has drawn considerable attention on account of the concerns over the environmental safety and human health. However, low surface activity, poor water solubility and complex preparation process of most currently reported alternatives restrict their widespread applications. Herein, a series of nonionic urethane fluorinated surfactants (F m EG n F m ) were synthesized by one-pot method using poly (ethylene glycol) (PEG), isophorone diisocyanate (IPDI) and short chain fluorinated alcohol as raw materials. The surfactant molecule is composed of two short fluoroalkyl chains connected to a PEG molecule via two IPDI spacers. Benefit from the special molecular structure design, these fluorinated surfactants displayed high surface activities, which could reduce the surface tensions of 17.8–28.7 mN/m and had low critical micelle concentrations of 0.17–0.98 mmol/L. These fluorinated surfactants showed good salt and pH resistance. Furthermore, contact angle and emulsifying experiments demonstrated that these fluorinated surfactants possessed excellent wetting and emulsifying properties at an extremely low concentration of 0.1 wt%. More importantly, the cytotoxicity experiment verified that these fluorinated surfactants had no obvious cytotoxicity. The ideal properties coupled with a simple and green preparation process make this strategy a new avenue to fabricate sustainable alternatives to long fluoroalkyl chain surfactants.
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