Bromoacetyl bromide, sodium azide, copper(I) bromide, copper(I) iodide, Bromotris(triphenylphosphine)copper(I), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), N,N-diisopropylethylamine (DIPEA), N,N,N',N",N"-pentamethyldiethylenetriamine (PMDTA), propargyl alcohol, 1,4-butanediol, 1,6-hexanediol
, sebacoyl chloride, adipoyl chloride, succinyl chloride, lithium bromide, acetone, ethanol, acetonitrile, hexane, ethyl acetate, dichloromethane (DCM), 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), trifluoroethanol (TFE), 1,3-dimethyl-2-imidazolidinone (DMI), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), and Tween 20 were purchased from Sigma-Aldrich, MO, USA, and used without further purification.
One of the polyols was polytetramethylene glycol (PTMEG) with molecular weight 1000 Da and it was chosen to obtain polyether diol-based polyurethanes (the typical formulation in the current internal coating for pipeline), and the other polyol was a copolymer of polycarbonate of 1,6-hexanediol
and 1,5-pentanediol of molecular weight 500 Da--PCD--(Eternacoll[R] PH50, UBE Chemical Europe S.A., Castellon, Spain).
Rohn, "Structure, thermal stability and mechanical properties of polyurethanes based on glycolysate from polyurethane foam waste, prepared with use of 1,6-hexanediol
as a glycol," Polimery/Polymers, vol.
The formation mechanism can be attributed to reduction and Ostwald ripening: [Fe.sub.2][O.sub.3] submicrospheres are firstly synthesized; hematite is then reduced to magnetite and an incomplete layer consisted of [Fe.sub.3][O.sub.4] nuclei is formed on the solid [Fe.sub.2][O.sub.3] surfaces; a [Fe.sub.2][O.sub.3]-[Fe.sub.3][O.sub.4] core-cell structure is formed in the presence of 1,6-hexanediol
; finally, [Fe.sub.3][O.sub.4] hollow submicrospheres are obtained through Ostwald ripening process.