Metal-Free Atom Transfer Radical Polymerization In Mesoporous Confinement And Air

Recently,the emerging metal-free atom transfer radical polymerization(ATRP)is widely used in the fields of preparation of organic/inorganic hybrid materials and various polymers with different structures,because it overcomes the shortcomings of traditional ATRP,such as high reaction temperature,complicated operation steps,and difficult to remove metal ions residues.Currently,the metal-free ATRP system is very sensitive to oxygen,and requires inserting inertia gas or to remove the oxygen.These methods are complicated and time-consuming,and it is more difficult for non-polymer researchers,limiting its application.In view of above problems,this thesis focuses on metal-free ATRP,in which the metal-free ATRP in the confined space of mesoporous material SBA-15 was carried out,and the effects of modified SBA-15 on the properties of polymers were studied,and the effects of reaction conditions on metal-free ATRP was investigated.Based on this,a metal-free ATRP that can be carried out in air was developed and its polymerization kinetics was studied.The specific research contents and conclusions are as follows:(1)Metal-free ATRP of methyl methacrylate(MMA)was carried out in the SBA-15 which were modified with different silane coupling agents(KH-550,KH-560,KH-570)under the irradiation of blue light.The results showed that the mesoporous channels of SBA-15 could be used as "nanoreactors" for successful metal-free ATRP polymerization of MMA.The polymer obtained in the confined channel exhibited higher molecular weight and thermal stability.After modified by the silane coupling agent,the channel of the SBA-15 afforded load more polymers,and the molecular weight and thermal stability of the polymer increased.However,the molecular weight distribution did not change much.(2)The suface-initiated(SI)metal-free ATRP solution polymerization of MMA was carried out with the 2-Bromoisobutyryl bromide(BiBB)anchored on the surface of self-synthesized rod-like mesoporous material SBA-15 as the initiator on the basis of the reductive quenching mechanism.The results demonstrated that the ordered mesoporous structure of SBA-15 was not disrupted after the polymerization.With an increase in illumination time,the grafting amount and the number average molecular weight of poly(methyl methacrylate)(PMMA)on the surface of SBA-15 linearly increased,and the molecular weight distribution(?)widened.The chain extension confirmed the chain end functionality of PMMA grafted on SBA-15.(3)Mesoporous silica nanoparticles/polymer hybrid materials were prepared via SI metal-free ATRP.The effects of the ligand/photocatalyst(L/Cat)ratio,solvent volume,and monomer/initiator molar ratio(M/I)on the grafting density,molecular weight,and molecular weight distribution were investigated.The results show that a higher L/Cat ratio leads to a higher reaction rate and better controllability of the polymerization but also to a lower grafting density.With increasing M/I molar ratio,the grafting rate,molecular weight,and grafting density exhibited increasing trends.These properties were also affected by the solvent.When the solvent volume was monomer/solvent =1/4,v/v,the polymerization was controlled best.(4)By adjusting the ligand/photocatalyst(L/Cat)ratio,a metal-free ATRP of MMA was successfully performed in the present of air.It maintained the typical characteristics of controlled/ "living" free-radical polymerization.Controllable polymer preparation could be further optimized by mediating reaction conditions such as ligand/catalyst ratio,ligand type,and concentration of photocatalyst.