Preparation And Applications Of AMS-Containing Copolymers

α-Methylstyrene(AMS) is a commercially available and toxicity-free monomer.Nevertheless,it undergoes with much difficulty the radical homopolymerization under usual conditions due to the high steric hindrance and low ceiling temperature.On the other hand,AMS easily proceeds free radical copolymerizations with other monomers. During the copolymerizations,AMS-based free radicals and depropagation reactions can hinder the polymerization,by which the copolymerization rate is controllable.The primary advantage associated with this rate control is that low molecular weight polymers can be produced without the requirement for chain transfer agents or initiators.Based on the thermal decomposition of the copolymers derived fromα-methylstyrene(AMS),a novel approach has been developed in this dissertation for preparing block copolymers and core-shell particles without extra initiator.The AMS copolymers were also applied to the functionalization of carbon nanotubes.This method has been proved both scientifically significant and industrially important.The major contents are as follows:1.AMS-containing copolymers with different compositions and molecular weights were prepared via radical solution copolymerization in THF with AIBN as initiator.The thermal degradation mechanism of the obtained AMS copolymers was studied.According to the results of structure analysis by GPC,ESR and NMR spectroscopy,when the temperature is above 80℃,the AMS-GMA(head-head) and AMS-AMS (head-head) weak bonds are first scissored into two macroradicals.The weak bonds are found to be produced by the coupling terminations during the preparation of AMS-containing copolymers.Once the macroradicals were generated,β-scission and hydrogen abstraction followed,giving birth to monomers.The generation of monomers was identified by ~1H NMR,photoionization mass spectroscopy(PIMS) and FT-IR techniques. The weak bonds of AMS copolymers opened new routes for the synthesis of block copolymers.2.AMS copolymers prepared by radical solution copolymerization were heated together with some specific monomers.When the temperature was raised above 80℃,chain radicals were formed by the thermal decomposition of AMS copolymers.Such kind of chain radicals subsequently initiated the polymerization of the monomers,forming block copolymers.Based on this concept,a series of block copolymers including PAG-b-PMMA(M_n=63100 g/mol,M_w/M_n=1.77) and PAG-b-PSt-b-PAG(M_n=44700 g/mol,M_w/M_n=1.63),were prepared by simply heating poly(AMS-co-GMA)(PAG) and the monomers.The influence of the amount of AMS copolymers,polymerization temperature and time were studied.This simple method is expected to be applicable to kinds of monomers,and it might be succifient even for industrial applications.3.Copolymers consisting of AMS and a second monomer,e.g. glycidyl methacrylate(GMA),or styrene(St),were synthesized and then utilized to modify CNTs.The copolymers were heated in the presence of CNTs in solution,and decomposition of the AMS copolymers occurred, providing macroradicals,which further reacted with the double bonds and flaws on the CNT surfaces.Grafting of the copolymer chains onto the surface of the CNTs was thus achieved,as demonstrated by FTIR,XPS and Raman measurements.The resulting poly(AMS-co-GMA)-g-MWNTs could be uniformly dispersed in N,N-dimethylformamide(DMF) and acetone;this is also true for poly(AMS-co-St)-g-MWNTs in DMF.The influence of solvent,the amount of AMS copolymers and reaction temperature were investigated in detail.4.Copolymers containing AMS segments,such as poly(AMS-co-BA-co-AA) and poly(AMS-co-MMA-co-AA) were synthesized through soap-free emulsion polymerization,in which ammonium persulfate(APS) was used as initator and acrylic acid(AA) as fuctional monomer.The monomer conversion was measured by gravimetry,and the products were characterized by transmission electron microscopy(TEM),differential scanning calorimeter(DSC),IR spectroscopy,quasielastic light scattering(QLS),contact angle and XPS. The effects of the amount of AMS,APS and AA,polymerization temperature,were studied.Without any extra initiator and emulsifier,the AMS copolymers obtained above,including poly(AMS-co-BA-co-AA) and poly(AMS-co-MMA-co-AA) were heated with St monomer, providing monodisperse core-shell particles.The AMS copolymers acted as the initiator,and the polymerization of St occurred inside the AMS copolymer parities.