Fabrication Of Swellable Organic-Inorganic Hybrid Polymer For CO₂-Assisted Hydration Of Propylene Epoxide

Swelling was a commonly natural phenomenon.Many studies on the swelling of organic materials had been reported.However,welling behaviors of inorganic substances had rarely been reported.To promote a highly swelling and dispersion of inorganic materials,hybridization with swellable organic materials was undoubtedly a promising approach.In this thesis,we aimed to design and synthesize a new type of swellable organic-inorganic hybrid polymer by using swellable poly（ionic liquid）and calcined hydrotalcite as the raw materials.The hybridization could help calcined hydrotalcite particles（CHT）achieve swelling and dispersion,and this unique swellable ability could help the organic-inorganic hybrid polymer efficiently catalyze the CO₂-assisted hydration of propylene oxide（PO）.The main research elements and results of this dissertation were as follows.（1）A new type of swellable organic-inorganic hybrid polymer（PIL@CHT）was successfully prepared through free radical copolymerization of vinyl-functionalized calcined hydrotalcite（CHT-Si V）,brominated quaternary phosphonium ionic liquid monomer and the cross-linker（divinylbenzene,DVB）.The successful realization of the hybridization was demonstrated by various characterization methods including NMR,FT-IR and TGA.The molar swelling ratios（Q_M）of PIL@CHT in thirteen commonly used solvents were measured and the relationship between the Q_M and various solvent parameters were investigated.A significant correlation was found between Q_M and the Hansen solubility parameters of the solvents.In particular,a linear positive correlation was obtained between Q_M and Hansen solubility parameters when the Hansen solubility parameters were greater than 24.4 MPa^1/2,and the largest Q_M（305.3 mmol/g）was exhibited in the water with the largest Hansen solubility parameter.It was observed by cryo-SEM that PIL@CHT exhibited an obvious porous network structure after swelling in water,and the CHT particles,which were closely connected to the poly（ionic liquid）（PIL）,were uniformly dispersed on the surface of the channels formed by swelling,achieving a high dispersion of calcined hydrotalcite particles successfully.（2）A new pathway for CO₂-assisted hydration of propylene oxide（PO）was explored.The involvement of CO₂ was found to alter the traditional pathway of direct hydration of PO,in which the cycloaddition reaction of PO with CO₂ and the subsequent hydrolysis reaction of propylene carbonate（PC）occurred,achieving a one-pot two-step reaction.Furthermore,the catalytic performance of PIL@CHT in this one-pot two-step reaction was explored.It was found that PIL@CHT combined the catalytic active cites of the PIL and CHT,exhibiting an excellent synergistic catalytic effect with high yield（93.0%）and selectivity（98.2%）of 1,2-Propylene glycol（1,2-MPG）at a low hydration ratio（1.5:1）.Moreover,PIL@CHT was used as catalyst with good recyclability and substrate generality.