The Study Of Iodide-Mediated Radical Polymerization

This research was focused on the study of iodide-mediated radical polymerization, including the preparation of amphiphilic block copolymer and star polymer, the polymerization details in presence of Cu and its halides and the halogen exchange in the polymerization process. The detailed information is as followes:1．Amphiphilic polystyrene-b-poly(acrylic acid) (PS-b-PAA) diblock copolymers were prepared by iodide-mediated radical polymerization. Firstly, free radical polymerization of styrene was carried out with AIBN as initiater and iodoform as chain-transfer agent, giving iodine atom-ended polystyrene with controlled molecular weights. Secondly, tert-butyl acrylate (tBA) was polymerization using above obtained polystyrenes as macro-chain-transfer agents and PS-b-PtBA diblock copolymers with controlled molecular weights were obtained. Finally, amphiphilic PS-b-PAA diblock copolymers were prepared by hydrolysis of PS-b-PtBA under the acid condition. The formation of PS-b-PtBA and PS-b-PAA diblock copolymers was confirmed by the use of gel permeation chromatography and ¹H NMR Spectroscopy.2．Amphiphilic star-block copolymers composed of polystyrene and poly(acrylic acid) were synthesized by iodide-mediated radical polymerization. Firstly, free radicalpolymerization of styrene was carried out with AIBN as initiator and 1,1,1-tri(methyl iodoisobutyl) propane as chain transfer agent, giving iodine atom ended star-shaped polystyrene with three arm chains, R(polystyrene). Secondly, tert-butyl acrylate was polymerization using polystyrene obtained as macro-chain transfer agent, and star-block copolymer, R(polystyrene-b-poly(tert-butyl acrylate))₃ with controlled molecular weight was obtained. Finally, amphiphilic star-block copolymer, R(polystyrene-b-poly(acrylic acid))₃ was obtained by hydrolysis of R(polysryrene-b-poly(tert-butyl acrylate))₃ under acidic condition.3．The end structure of polystyrene obtained from iodide-mediated radical polymerization with Ethyl 2-iodo-2-methyl-propionoate as initiator (IMP) and CuBr/2,2'-bipyridine as catalyst was analyzed by 1H NMR. The results confirmed that the ratio of IMP/CuBr was one of the major factors for that controlled the C-X terminal (X=1 or Br) of PS. The terminal of PS was the mixture of C-I and C-Br when the ratio of IMP/CuBr varied from 2 to 1 and was converted into C-Br completely when the ratio of IMP/CuBr was reduced to 0．5．Based on this result, the initiating efficiency of IMP/ CuBr / 2,2'-bipyridine in the polymerization of MMA was investigated. The block polymerization of MMA was also attempted in presence of macromolecule initiator PS-I and catalyst CuBr.4．The Ethyl 2-iodo-2-methyl-propionoate (IMP) was synthesized by ethyl 2-bromoisobutyrate and NaI in dry acetone. The free radical solution polymerization of styrene was followed carried out with IMP as initiator and Cu/bipy as catalyst. The effect of catalyst on the polymerization process was investigated by varied the catalyst dosage. Furthermore, the initiating efficiency of IMP/CuBr/2,2'-bipyridine in the polymerization of MMA and EA was also studied.5．Amphiphilic polystyrene-b-poly(acrylic acid) (PS-b-PAA) diblock copolymers were prepared by radical polymerization of acrylic acid (AA) with the iodineatom-ended polystyrene (PS-I) as macro-chain-transfer agents and AIBN as initiator. The formation of amphiphilic PS-b-PAA diblock copolymers was confirmed by FTIR spectra. This kind of amphiphilic block polymers was detected carrying self assembled behavior in presence of NaOH in methanol. Transmission electron microscopy and dynamic light scattering were performed to measure the self assembled structure of the amphiphilic polymer.