Study On Photoinitiated Controlled Polymerization Of MMA With Porphyrin MOFs

The preparation of polymers with controllable molecular weight and regular structure is one of the research hotspots in the field of polymer synthesis.As a controllable polymerization method,atom transfer radical polymerization(ATRP)shows characteristics including a wide range of applicable monomers and good controllability.In order to overcome the problems of large amount of metal catalyst and environmental pollution in traditional ATRP reaction.In recent years,the photoinduced ATRP has received widespread attention.Through photoinitiation,polymerization can be carried out under mild reaction conditions,and the amount of metal catalyst is greatly reduced.In the process of photo initiated ATRP,the core problem is how to construct photoreducting agent with wide band light absorption and good photoactivity for achieving efficient and controllable polymerization.In this thesis,the aim is to prepare polymers with controllable molecular weight and uniform molecular weight distribution by photoinitiation.Using porphyrin carboxylic acids as organic ligands,titanium and zirconium as inorganic units,visible light responsive MOFs has been prepared by solvothermal method.With MOFs as photoreducting agent,visible light responsive MOFs based ATRP system was constructed to realize the controllable polymerization of methacrylate monomers.The specific research content is as follows:1.Two metal-organic framework compounds with csq topology were prepared by coordination of tetracarboxyphenylporphyrin and zinc tetracarboxyphenylporphyrin with zirconium based metal salt.The two porphyrin MOFs named MOF-545(H2)and MOF-545(Zn).Tests have shown that the series of porphyrin MOFs have a wide light absorption range and good photo-generated charge separation.We use two porphyrin MOFs compounds as photoreducing agents to reduce Cu(Ⅱ)complexes by visible light to form Cu(Ⅰ)complexes,achieving the controlled polymerization of acrylates monomers.The polymerization product has the characteristics of controllable molecular weight,narrow molecular weight distribution(PDI≤1.4)and chain terminal activity.Compared with traditional atom transfer radical polymerization,MOFs-regulated atom transfer radical polymerization system uses a non-toxic divalent copper catalyst,and amount of the catalyst is greatly reduced(the concentration of catalyst is 4 mmol/L).At the same time,the heterogeneous characteristics of MOFs make it easy to separate from polymerization products.2.In view of the variable valence state and good photophysical activity of titanium based metals,we prepared a porphyrin titanium based MOF(DGIST-1)by two-step method.By using DGIST-1 as photoreducting agent,visible-light-initiated atom transfer radical polymerization of methacrylate monomers was successfully realized.The obtained polymers have the characteristics of controllable molecular weight,narrow molecular weight distribution and chain terminal activity.The kinetic study shows that the reaction rate of porphyrin titanium MOFs is faster than the porphyrin zirconium MOF.Therefore the molecular weight distribution of the polymer is relatively narrow(PDI≤1.3).The polymerization system also shows the convenience of being controlled at any time by light source.The results of this paper provide a new way for the preparation of polymer with controllable molecular weight and regular structure.It provides a reference for the construction of new photoinduced atom transfer radical polymerization system.