Study Of Iodoform-Mediated Chloroprene Free Radical Emulsion Polymerization And Synthesis Of Its Block Copolymers

To the best of our knowledge, the study on living free radical polymerization of chloroprene and the synthesis of its block copolymers has never been reported. In this dissertation, the controlled radical polymerization characteristics of chloroprene emulsion polymerization was mainly researched with iodoform as chain transfer agent; the methods of degenerative transfer radical solution and emulsion polymerization (DTRP) was further studied to attempt at preparing polychloroprene and polychloroprene-b-polystyrene block copolymers (PCP-b-PS), also the reaction activity difference of using various iodide polymers as macro-chain transfer agents was investigated to synthesize diblock copolymers via solution polymeriation; the comprehensive properties of three new kinds of chloroprene rubbers (CR) prepared with iodoform as molecular weight regulator instead of traditional regulator D (isopropyl xanthogen disulfide) was preliminarily discussed and meanwhile made comparison with those of the traditional regulator D mediated CR-244, CR-232 as well as compound regulator mediated CR-322 (regulator D plus sulfur). The detailed work is as follows:1. Employing iodoform as chain transfer agent to replace the traditional regulator D, the chloroprene low-temperature emulsion polymerization was smoothly carried out in lab based on the domestic traditional industrial large-scale production formula and reaction conditions of adhesive type CR-244. Through analyses of monomer conversions, Gel Permeation Chromatography (GPC) determined relative number-average molecular weights, molecular weight distributions, as well as Nuclear Magnetic Resonance ('HNMR) spectra, etc., the chloroprene emulsion polymerization was found to have the characteristics of living free radical polymerization, similar to those of styrene solution polymerization system, giving the structure of iodine atom-ended polychloroprene (PCP-I).2. Adopting iodoform as chain-transfer agent, the iodine atom-ended polychloroprene was prepared first in accordance with the aforementioned method. Then styrene solution polymerization was conducted in toluene with AIBN as initiator and the above obtained polychloroprenes as macro-chain transfer agents. The polymerization process showed living free radical features, however styrene conversion could only reach up to 30%. PCP-b-PS diblock copolymers were acquired successfully and further confirmed by GPC and'HNMR Spectroscopy. In addition, the preparation of PCP-b-PS diblock copolymers was attempted as well using reverse route. Firstly, styrene radical solution polymerization was proceeded based on AIBN as initiator and iodoform as chain-transfer agent, giving iodine atom-ended polystyrene (PS-I) with controlled molecular weights. Secondly, chloroperene was polymerized in toluene with the synthesized PS-I as macro-chain transfer agents, to attempt for the preparation of PCP-b-PS diblock copolymers. However due to lower initiation efficiency of PS-I to chloroprene monomer comparing with that of PCP-I to styrene monomer, the PCP-b-PS diblock copolymer attempt was not as successful as when PCP-I macro-chain transfer agents were used.3. Taking iodide as chain-transfer agent, PCP-b-PS diblock copolymers were prepared through seed emulsion polymerization. In the first place, based on the domestic traditional industrial large-scale production formula and reaction conditions of adhesive type CR-244, the chloroprene free radical emulsion polymerization was performed by iodoform as the degenerative chain transfer agent to obtain the iodine atom-ended polychloroprene seed latex. After the unpolymerized chloroprene was devolatilized under vacuum, styrene was then added and the emulsion polymerization of styrene using above obtained polychloroprenes as macro-chain transfer agents was proceeded. The seed emulsion polymerization indicates more obvious living free radical characteristics and better reaction activity than the result of before-mentioned solution polymerization method in terms of the blocking reaction with styrene. Therefore, more narrowly distributed PCP-b-PS diblock copolymers at much higher styrene conversion were successfully prepared and further confirmed by GPC and 1HNMR Spectroscopy.4. Applying iodoform as molecular weight regulator to substitute traditional regulator D, three new kinds of CR were synthesized through chloroprene emulsion polymerization according to the domestic traditional industrial large-scale production formulas and reaction conditions of adhesive type CR-244 and general purpose types of CR-232, CR-322 (compound regulation type), and the relative contrasts were made with regard to CR comprehensive properties between iodofrm and regulator D respectively mediated CR-244, CR-232 as well as CR-322 (iodofrom or regulator D plus sulfur).