One-pot Synthesis Of Sliding-ring Gel By Thiol-ene Click Reaction

Slide-ring(SR) gel has topological characteristics, its figure-of-eight cross-links which could slide along the polymer chains freely make the gel exhibits more excellent mechanical strength, swellability compared to the traditional polymer gels.The synthesis of SR gels is demanding, requiring three steps:(1) formation of the pseudo-polyrotaxane: many cyclic molecules are threaded on a single polymer chain;(2) formation of the polyrotaxane: the pseudo-polyrotaxane are trapped by capping the chain with bulky end groups to prevent the cyclic molecules slipping from the polymer chain;(3) The polyrotaxane is cross-linked via catalyst in the appropriate solvent.This procedure has multistep and low yield. To solve this problem, in this paper, we attempt to simplify this process. The SR gels were fabricated through a convenient one-pot approach using thiol-ene click reaction. The entire one-pot preparation of the SR gel were in the same solution, without isolation. The thiol-ene click reaction are simple, quick, almost has no byproducts. Through the thiol-ene click reaction, we can prepare the SR gel faster, more accurate.The one-pot fabrication conclude two stages, first many cyclic molecules are threaded on a single polymer chain;Second, the double bond of the polymer chain with the hydrosulfide group in cyclic molecule occurs click reaction via catalyst(the reaction between the polymer chains). Endcapping with cross-linking occur simultaneously.This paper’s main research work and results are as follows:1. The modification of the polymer chain. The PEO-PPO-PEO(Pluronic F127) triblock polymer terminal hydroxyl group is modified by acryloyl chloride, finally we synthesis Pluronic F127 Diacrylate(DA Pluronic F127), bring the double bond into the polymer chain.2. The modification of the cyclic molecule. Mono-6-thio-β-cyclodextrins and Per-6-thio-β-cyclodextrins were synthesized by the modification of the cyclodextrins.This step we introduced the hydrosulfide group to β-cyclodextrins.3. One-pot systhesized slide-ring gel. Firstly, we tried to use Mono-6-thio-β-cyclodextr-ins and DA Pluronic F127 to systhesize slide-ring gel, but without success. We surmise the reason for the failure is that mono-6-thio-β-cyclodextrins has by-products, and its terminal functional groups is too small. Then we attempts to use Per-6- thio-β-cyclodextrins and DA Pluronic F127 prepared sliding-ring gel, according the above-mentioned procedure, at last we get the gel. After testing, we find when the gel mass fraction of 15%, the molar ratio between DA Pluronic F127 and Per-6- thio-β-cyclodextrins is 3:1, the gel exhibits the best mechanical properties, the maximum elongation at break of 500%, the maximum stress of 300 KPa. But it has a wide gap compared to the slide-ring gel that reported before. We surmise the reason is that Per-6- thio-β-cyclodextrins is too large due to steric hindrance, and the influence of the DMSO, Per-6-thio-β-cyclodextrins can’t thread into the polymer,directly cross-linked with DA Pluronic F127 to form a gel.