Study On Macromonomer Synthesis And Graft Modification Of Silica Using Anionic Polymerization

Carbanionic and oxanionic polymerization were powerful tools for macromolecule-design and the grafting modification of inorganic particles.This dissertation was focused on the synthesis of polystyrene (PS) and polyepoxides macromonomers and the grafting of poly(ethylene oxide)(PEO) on silica surface.The detailed information is as follows:1.Synthesis of polystyrene macromonomer based on p-styrenesulfonyl chloride by carbanionic polymerization.Polystyrene macromonomers were synthesized from living polymer chains via three different methods.In the first method,living polystyryl anions were terminated directly by p-styrenesulfonyl chloride(SSC). However,no double bonds were detected in the final products.In the second method,living polystyryl anions were end-capped firstly by 1,1-diphenylethene(DPE),and then reacted with SSC.There were still no polystyrene macromonomers obtained.In the third method,living polystyryl anions were end-capped firstly by ethylene oxide(EO),and then reacted with SSC.The expected polystyrene macromonomers were obtained successfully with only small amount of polystyrene dimmer.By optimizating experimental conditions,macromonomers were obtained with narrow molecular weight distribution,double bond functional group content up to 91%,and dimmer content only 0.9%.Polystyrene macromonomers were also synthesized by esterization method in two steps,which further confirmed the high reactivity of SSC. In the first step,hydroxyethylated PS(PS-OH) was synthesized by killing EO end-capped polystyryl anion with acidic methanol.In the second step, esterization reaction of PS-OH with SSC was employed to synthesize the macromonomers.¹H NMR and FT-IR show the products had the same structure as those obtained above and had higher functionality up to 97%. Further more,no dimmers were detected in this method.2.Synthesis of poly(ethylene oxide) and poly(ethylene oxide)-b-Poly (propylene oxide) macromonomers by oxanionic ring-opening polymerization2-Methacryloxyl poly(ethylene oxide)(PEO-MA) macromonomers were synthesized using initiator method and terminator method respectively.In the initiator method,2-hydroxyethyl methacrylate(HEMA) and 4-Hydroxycyclohexyl methacrylate(HCMA) were transferred into alkoxide by potassium naphthalene,and then initiated the anionic ring-opening polymerization of EO.However,no double bonds were detected in the products,the possible reason for which is the strong hydrolyzations of ester group.In the terminator method,the anionic ring-opening polymerization of EO was carried out with methanol as initiator,and the macromonomers were synthesized by quenching the living polymer chains with methacryloyl chloride(MAC).Well-defined Poly(ethylene oxide) macromonomers were obtained with functionality up to 73%and narrow molecular weight distribution.The influence of triisobutylaluminum(Al(i-Bu)₃) on the anionic ring-opening polymerization was discussed.2-Methacryloxyl poly(ethylene oxide)-b-poly(propylene oxide) macromonomers(PEO-PPO-MA) were also prepared by the terminator method.In this method,macromonomers were synthesized by the addition of EO and PO sequently,and then terminated with MAC.¹H NMR spectrca showed that the diblock macromonomers had well-defined structure with functionality up to 73%.And the molecular weight distribution was very narrow.Finally,styrene emulsion polymerization was carried out using PEO-PPO-MA as polymerizable surfactants.3.Grafting of poly(ethylene oxide) from toluene diisocyanate modified silica particles.Firstly,isocyanate groups were introduced onto the silica surface by the reaction of silanols on the surface with excess toluene diisocyanate (TDI).Secondly,silica particles with hydroxyl groups(SiO₂-TDI-EG) or epoxyl groups(SiO₂-TDI-PO) were prepared by the reaction of isocyanate groups on the silica surface with hydroxyl groups of ethylene glycol or glycidol resepectively.Finally,grafting of PEO from silica surface was carried out by three methods as follows.(1) EO was anionic ring-opening polymerized from alkoxides on the silica surface,which was modified from SiO₂-TDI-EG by potassium naphthalene.(2) EO was co-polymerized with SiO₂-TDI-PO by anionic ring-opening polymerization with methyl alkoxide as initiator.(3) Living PEO anions were prepared by the anionic ring-opening polymerization with methyl alkoxides as initiators,and then reacted with SiO₂-TDI-PO.Functional groups and grafted PEO on the modified particles were characterized by FT-IR and ¹³C CPMAS NMR.The grafting amount of PEO was calculated by thermo gravimetric analysis.4.Grafting of poly(ethylene oxide) from silica particles by direct anionic ring-opening polymerization.Grafting of PEO from non-modified silica was performed by the ring-opening polymerization of EO with potassium silanolate as initiator, which was transferred from silianol on the silica surface.Herein, Al(i-Bu)₃ was used as an activator of the monomer,and formed initiating complex with potassium silanolate.FT-IR,¹³C and ²⁹Si CPMAS NMR were used to characterize the resulting products,and thermo gravimetric analysis and elemental analyses were used to calculate the grafted amount of PEO.Influences of solvents,monomer and Al(i-Bu)₃ amount on the grafting percent of PEO were investigated.