Synthesis and characterization of fluorinated polyurethane with fluorine-containing pendent groups

A novel fluorinated polyurethane （FPU） with fluorine-containing pendent groups was prepared by using fluorinated polyether glycol （PTMG-g-HFP） as a soft segment, 1,6-hexamethylene diisocyanate （HDI） or toluene diisocyanate （TD1） as a hard segment and 1,4-butanodiol （BDO） as a chain extender. FTIR, ^1H NMR, ^13C NMR and GPC were used to characterize the structure of the fluorinated polyurethane. Thermal stabilities of the fluorinated polyurethane and the corresponding hydrogenated polyurethane were studied by TGA. XPS analysis at two different sampling depths for the fluorinated polyurethane was used to investigate the surface compositions of FPU. The results showed the fluorine enrichment on the surface of FPU.

SURFACE STRUCTURE AND BULK PROPERTIES OF FLUORINATED POLY(ETHER URETHANE)S AND POLY(ETHER URETHANE) BLENDS

It has been well known that fluorinated polyurethanes exhibit uniquely low surface energy, biocompatibility and biostability, thermal and oxidative stability and nonsticking behavior. Consequently, these polymers have attracted considerable interest. However, the mechanical properties of fluorinated polyurethanes usually decline with increasing fluorine contents. The blending of fluorinated polyurethanes with normal polyurethane was carried out to achieve balanced mechanical and surface properties. It was found that polyurethane with good mechanical properties and low surface energy can be obtained by adding a small amount of fluorinated polyurethane. The fluorinated side chains can easily migrate to uppermost surfaces of the blends untill the fluorine level at the surface becomes almost saturated. It has been shown from contact angle, XPS and AFM measurements that only as little as 0.34 wt% of fluorine level is enough to produce a surface saturated with fluorine, and the fluorine level at the uppermost surface is one hundred times higher than that in the blend bulk. The final outer surface structures of the polyurethane blend were independent of the content of the fluorinated polyurethane in the blends due to the surfaces saturated by fluorine.

Synthesis and Characterization of Novel UV-curable Fluorinated Polyurethane-acrylate Copolymer

A series of UV-curable fluorinated polyurethane-acrylate（PUA） has been developed by incorporating octafluoropentyl alcohol into the segment of UV-curable polyurethane-acrylate to improve the thermal property and surface property of the copolymer material. The structures of the synthesized polymers were characterized by Fourier transform infrared（FTIR） spectrometry. In order to find out the effect of incorporated fluorine on the UV-cured films, the properties of the UV-cured films were tested through contact angle, water absorption, and thermogravimetric analysis （TGA）. The fractured-surface morphologies of the UV-cured coatings were investigated by scanning electron microscopy（SEM）. With increasing the content of fluorine segments, the contact angle of the UV-cured films increased and the water absorption decreased, suggesting the fluorine segments migrated and formed a fluorine-covered surface to avoid water penetration. The observation of the fractured-surface morphology through SEM test showed that the fluori- nated UV-cured films gained rough fractured-surface compared with the pure UV-cured polyacrylate film, demonstrating the migrating of the fluorine segments. The TGA curves show that the fluorinated UV-cured films gained higher thermal degradation temperature than the virgin UV-cured polyacrylate film. And as increasing the fluorine content, the thermal degradation temperature increased. These phenomena could be reasonably explained by the enrichment of fluorinecontained segment on the surface of the film and the high thermal property due to fluorine atom.

Synthesis and Characterization of Fluorinated Polyurethane Containing Carborane in the Main Chain: Thermal, Mechanical and Chemical Resistance Properties

In this study, two fluorinated polyurethanes（FPU） containing carborane groups in the main chains were firstly designed and synthesized via the reaction of hexamethylene diisocyanate trimer（HDI trimer） with fluorinated polyesters（CFPETs） having hydroxyl-terminated carborane groups at room temperature. The structures of carborane fluorinated polyesters（CFPETs） and polyurethanes（CFPUs） were characterized by gel permeation chromatography（GPC）, Fourier transform infrared（FTIR） spectroscopy and nuclear magnetic resonance（NMR） measurements. The thermal stability, mechanical properties, Shore A hardness, solvent resistance and acid-alkali resistance of the carborane fluorinated polyurethane films were also studied. Thermogravimetric analysis（TGA） tests manifested that the introduction of carborane groups into the main chain of fluorinated polyurethane endowed the obtained fluorinated polyurethane with excellent thermal stability. The thermal decomposition temperature of carborane fluorinated polyurethane（CFPU） increased by 190 °C compared with that of the carborane-free fluorinated polyurethane（FPU）. Even at 800 °C, CFPU showed the char yield of 66.5%, which was higher than that of FPU（34.3%）. The carborane-containing fluorinated polyurethanes also showed excellent chemical resistance and prominent mechanical property even after the cured films being immersed into Jet aircraft oil or 37% HCl for 168 h or at high temperature（700 °C）. It is found that the structural characteristics of carborane group and the compacted structure of CFPU effectively improve the thermal stability, mechanical property, solvent resistance and acid-alkali resistance of the carborane-free fluorinated polyurethane. These excellent properties make CFPU as the useful raw materials to prepare the high temperature resistant coatings or adhesives for automotive engines, engine or fuel tank of aircraft and other equipment working in high-temperature or high concentrations of acid-alkali environments.

A fluorine-rich phenolic polyurethane elastomer with excellent selfhealability and reprocessability and its applications for wearable electronics

Polyurethane elastomers with covalent adaptable networks(PU-CANs)based on the dynamic urethane bond have attracted remarkable attention owing to their reprocessability,adaptability,and self-healability.However,it is still a formidable challenge to achieve excellent dynamics at low temperatures since the urethane bond energy is usually high.Herein,a fluorinated phenolic polyurethane(FPPU)elastomer with CANs based on phenol±carbamate bonds was successfully designed and prepared.Subsequently,the effects of fluorine atoms on the mechanical properties,thermal stability,reprocessability,and self-healability,surface free energy,and hydrophobicity of the prepared elastomers were systematically investigated.The FPPU elastomer showed notch-insensitivity,remarkable self-healable efficiency(98%),low dynamic dissociation temperature(60℃),excellent reprocessability,and low surface energy(62 MJ m^(-2))compared with non-fluorinated counterpart phenolic polyurethane elastomer(APPU).Based on the above-mentioned features,FPPU was selected as an elastic substrate to assemble into a triboelectric nanogenerator(TENG)to harvest energy from natural motion.This TENG exhibited an excellent electrical output performance with a peak open-circuit voltage of 103 V,a peak short-circuit current of 4.7μA and a peak short-circuit charge of 43 nC.In addition,the TENG possessed high selfcleaning and reprocessing efficiency.Furthermore,a stretchable and self-healing composite conductor based on FPPU was fabricated for flexible electronic devices.