Self-healable and reprocessable networks of Poly (propylene oxide) with POSS crosslinked with disulfide bonds
Abstract
The organic-inorganic networks involving poly(propylene oxide) (PPO) and POSS were synthesized via the in situ crosslinking with disulfide bonds. First, a tri-armed PPO star with amino termini was reacted with 4-(phenoxymethyl)-1,3-dithiolane-2-thione, a cyclic five-membered thiocarbonate to obtain the tri-armed PPO star with mercapto thiourethane termini. In the meantime, 4-aminobutylhepta(3,3,3-trifloroproply) POSS was also reacted with 4-(phenoxymethyl)-1,3-dithiolane-2-thione to obtain a mercapto thiourethane -functionalized POSS macromer. Thereafter, both PPO star and POSS macromer which contained mercapto thiourethane moieties were co-crosslinked via the radical coupling reaction, in which the thiol groups were coupled into disulfide bonds. The POSS-containing PPO networks were microphase-separated. It was found that the POSS cages grafted onto PPO networks were self-organized into the spherical nanodomains. Compared to the control network, the nanocomposites displayed the improved thermomechanical properties and surface hydrophobicity. More importantly, the organic-inorganic networks were self-healable and can be repeatedly processed without sacrificing the mechanical strengths. The exchange reaction of dynamic disulfide bonds is attributable to the self-healing or/and reprocessing properties. In addition, the break and reform of the POSS microdomains are also contributable to the reprocessing behavior at elevated temperature.
