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Synthesis of PSt-b-PtBA Diblock Copolymer by Activator Generated by Electron Transfer Atom Transfer Radical Polymerization

Author: LiYuanYuan
Tutor: ZhangLiWu
School: Chongqing University
Course: Polymer Chemistry and Physics
Keywords: Atom transfer radical polymeriation block copolymer styrene tert-Butyl acrylate bulk polymerization
CLC: O631.3
Type: Master's thesis
Year: 2011
Downloads: 181
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Abstract


In this paper, The block copolymers were synthesized by a two-step method. The macroinitiator（PSt-Cl） was first prepared by using styrene as monomer, benzyl bromide as initiator, and [FeCl3.6H2O] / [PPh3] as catalyst via Activator generated by electron transfer for atom transfer radical polymerization（AGET-ATRP）. Then, atom transfer radical polymerization（ATRP） of block copolymers PSt-b-PtBA were carried out using PSt-Cl as initiator, CuCl as catalyst, bipyridine （bpy） as ligand. the products is Characterized by gel permeation chromatography（GPC）, IR and 1H-NMR. The following research on processing of the block copolymer polymerization had also been discussed.The synthesis of macroinitiator by bulk polymerization was superior to solution polymerization, because the macroinitiator was synthesized by bulk polymerization had a higher conversion and a faster polymerization rate, and the appropriate reaction time is 36h.The ln （[M]0/[M]） value versus the reaction time shows authentic linear realtionship when the reaction temperature rising from 95 to 120 centigrade degree, and the linear fitting constant R2 appears to 0.9948 at 110℃that corresponds with the first order reaction characteristic of livingradical polymerization including ATRP. Meanwhile, the apparent growing rate (kpapp) is 8.92×10-6s-1, which indicates that the temperature of polymerization is easier to control. A higher monomer conversion rate and a lower polydispersities （PDI） polymer was obtained when selecting BzBr as the initiator. The iron-based catalyst was used in this study, for its non-toxicand easy removal. Increasing the amount of reducing agent increased the polymerization rate （Rp）, and the PDI is kept narrow. Mn,GPC values increased linearly with conversion, and were close to the corresponding theoretical values, indicating that the iron（Ⅲ）-mediated AGET-ATRP of St was a controlled/’’living’’radical polymerization. However, excessive dosage of reductant will reduce the controllability of polymerization.The reaction time of synthesizing block copolymer is between the 28-36h via ATRP, and the temperature is 95℃. Increasing the amount of monomerof tert-butyl acrylate increased the molecular weights and conversion. Utilizing the principle of halide exchange, we used mixed halogen initiator-catalyst system in experiments, the monomer conversion is higher, and the polymerization is better controlled.GPC, IR and 1H-NMR analyses show that the synthesized PSt-Cl macromtiator and block copolymers have the desired structure with low polydispersities, and the PDI is 1.36 and 1.44. Finally, PSt-b-PtBA were hydrolyzed to obtain the amphiphilic block copolymer PSt-b-PAA. The IR and 1H-NMR characterization show that the block copolymer were hydrolyzed successfully.

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CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Polymer physics and physical chemistry of polymers > The chemical nature of polymers
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