Study On The Polymerization Of Methacrylates Catalyzed By Salen-Ni Catalyst

Salen metal complexes can be applied in many fields such as catalytic polymerization,biomedicine,etc.One of the advantages of Salen late transition metal complexes is that they can effectively catalyze the polymerization of polar monomers,but it is rarely reported about catalyzing the polymerization of long chain high-grade acrylics with Salen late transition metal complexes.In this paper,Salen metal complexes are used as catalysts for the homopolymerization and copolymerization of dodecyl methacrylate and octadecyl methacrylate,and the synthesized homopolymers and copolymers are used as the pour point depressant of diesel,lubricating oil and crude oil.Firstly,Salen-Ni-salicylaldehyde complexes were synthesized through the condensation reaction of o-phenylenediamine and 3,5-di-tert-butyl salicylaldehyde.Secondly,the catalytic system of Salen-Ni-salicylaldehyde and azobisisobutyrate were used to catalyze the homopolymerization and copolymerization of dodecyl methacrylate and octadecyl methacrylate.The effect of the ratio of co-catalyst to catalyst,reaction time,reaction temperature,and the ratio of monomer to catalyst on the activity of the catalyst and the relative molecular mass of the polymer was investigated.The polymer was characterized by means of infrared spectroscopy,nuclear magnetic resonance and thermogravimetric analysis.When the monomer is dodecyl methacrylate,the maximum catalytic activity is 40874.534g·mol^-1·h^-1.The optimum polymerization conditions are:the ratio of cocatalyst to catalyst is3:1,and the reaction temperature is 110°C,reaction time 8h,monomer and catalyst ratio2400:1;When the monomer is octadecyl methacrylate,the maximum catalytic activity is83781.716 g·mol^-1·h^-1.Currently,the preferred polymerization conditions are:the ratio of cocatalyst to catalyst is 4:1,and the reaction temperature is 90°C,reaction time 10h,monomer to catalyst ratio 3200:1;When dodecyl methacrylate is copolymerized with octadecyl methacrylate,the catalytic activity is at most 110350.746 g·mol^-1·h^-1,and the molar ratio of octadecyl methacrylate and dodecyl methacrylate is 5:1,the molar ratio of AIBN to L₂-Ni-salicylaldehyde is 6:1,the reaction temperature is 90°C,the optimal reaction time is 10h,and the optimum monomer and catalyst ratio is 3600:1.Finally,typical poly dodecyl methacrylates,poly octadecyl methacrylates and the copolymers of dodecyl methacrylates and octadecyl methacrylates is used as pour point depressants for diesel,lubricating oil and crude oil.Different oils have different effects of pour point depressant.By comparison of the results,it can be concluded that the depigmentation effect of octadecyl methacrylate homopolymer is better than that of dodecyl methacrylate homopolymer in the diesel fuel ca.5 to 8°C.For lubricating oils,the degrading pour point effect of homopolymers of octadecyl methacrylate is 2°C better than that of dodecyl methacrylate,and2-3°C is better for crude oil.The pour point depressing effect of the copolymer is better than that of the homopolymer.