Preparation And Properties Of Fluorinated Poly(aryl Ether)s Containing Double-decker Silsesquioxane In The Main Chains

Fluoropolymers are very attractive for a broad range of advanced applications,because of their excellent optical and electronic properties,high thermal and chemical stabilities and low surface tension.However,fully fluorinated polymers such as polytetrafluoroethylene usually have high crystallinity which results in the poor processability.Therefore,many partially fluorinated polymers with improved processability have been studied.Among them,poly(arylene ether)s containing perfluoro-monomers have shown relatively high fluorine content as well as easy processability which have been applied in low dielectric constant materials,optical waveguide devices and fluoride sensors.POSS is a class of nanoscale molecule with an inorganic silicon and oxygen framework covered by organic substituents.Incorporating POSS into a polymer materials can dramatically improve its mechanical properties as well as thermal stability,nonflammability,oxidative resistance etc.A lot of POSS-containing materials have been synthesized for porous materials,magnetic materials,optical materials,superhydrophobic materials,catalyst supports and biomedical applications,such as scaffolds for drug delivery,imaging reagents,and combinatorial drug development.With POSS incorporated,poly(arylene ether)s are expected to possess desirable properties of organic and inorganic compounds.In this paper,a diphenol POSS with good nucleophilicity is used to copolymerize perfluoro-monomers with different polarities via a two-step nucleophilic substitution procedure to prepare high molecular weight poly(arylene ether)s free of any crosslinked structure.To suppress the side reaction,in this approach,the diphenol is first converted to phenoxide at a high temperature and then further reacted with perfluoro-monomers at a low temperature.The effects of reaction temperature and time were investigated and the kinetic equation and activation energy were evaluated to study the effect of the monomer polarities on the reaction and summarize the optimal condition of the polymerization.All polymers exhibit not only low dielectric constants in the range of 1.85-2.37 at 1MHz at room temperature but also low dielectric losses,hydrophobic properties,low water uptake and good thermal properties.In particular,the DDSQ-DFPK film showed the ultra-low dielectric constant of 1.83 at 1 MHz.With increasing polarity of the perfluoro-aromatics,the water contact angles decrease from 108 o to 102 o.The kinetic behaviors of the polymerizations were studied.All the reactants show high reactivity even at a low temperature 30 oC in DMAc.Results show that the polymerization rate increases with the increasing of polarity of the perfluoro-monomers and the polymerization of 2OH-DDSQ with decafluorodiphenyl sulfone exhibits the highest rate constant at low temperatures of 30 oC,40oC and 45 oC.Moreover,to prepare the fluorinated poly(arylene ether)s containing POSS in the main chains with better thermal stabilities,cross-linkable groups were included into the end of the molecular chain.Furthermore,the dielectric properties of the fluorinated poly(arylene ether)s containing POSS in the main chains were also investigated.Additionally,water sorption,crystallinities,thermal properties and surface properties of the polymers were evaluated and the synergistic effects of fluorine and POSS on these properties were also discussed.All polymers with cross-linkable groups are self-crosslinkable which can be crosslinked at a temperature of 270 oC.Tgs of the polymers were improved to 187oC-193 oC after curing and the solvent resistance have been greatly improved.However,the water contact angles decreased to 96o-103 o and the dielectric constants were increased to 2.17-2.58(1 MHz).All in all,fluorinated poly(ary ether)s containing double-decker silsesquioxane in the main chains with cross-linkable groups have a wider foreground of applications.