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Author: LiYang
Tutor: YangJinZong;GuMingChu;HongDingYi
School: Dalian University of Technology
Course: Fine Chemicals
Keywords: Dilithium Initiator Butadiene lsoprene Styrene Homo-polymer Stereo-block-polymer Block Copolymer Terpolymer
CLC: O632
Type: PhD thesis
Year: 2000
Downloads: 316
Quote: 8
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During the last few years, the focus on development of alkyllithium initiator gradually shafted from monolithium to dilithium or multilithium or mixed-lithium initiators. Among them, the dilithium initiator was developed very fast and increasingly attracted extensive attentions since the dissolution problem of the dilithium initiator in non-polar solvent had been overcome. Dilithium initiator possessed the incomparable advantages over monolithium in preparing lithium-initiated polymers, among them, the most important characteristic was that the symmetrical polymer could be synthesized when the initiation, propagation and termination of the chain occurred at two ends at the same time. Combined with the features of anionic active polymerization, the dilithium initiator already created a new growth point in technology of lithium-initiated polymer through its application in the ternary copolymerization field of butadiene-isoprene-styrene. At present, the dilithium initiator manufactured by Dow Company, USA, was known as the best commercialized product in comprehensive properties, however, there still existed problems which remain to be resolved, such as non-single solvent system, slow initiation speed, inferior solubility and long preparation time, Under the precondition of ensuring the advantages such as good solubility, uniform functionality, fast initiation speed, single solvent system, simplified preparation technology, short synthesis time and low cost, the present thesis developed two kinds of dilithium initiators. One was the dilithium oligomer prepared via addition reaction of diene, named as diene addition type dilithium; the novel initiator reached the current international level in the technical indexes and formed proprietary technology. The other was dilithium oligomer prepared through substitution reaction of dihalogenated alkane, named as dihalogenated alkane substitution type dilithium. Thanks to the breakthrough in the understanding against the traditional concept of dilithium, the development of the dihalogenated alkane substitution type dilithium was injected with the fresh vigor proceeding from facilitating the practical application on industrial scale, making the initiator meet the requirements in application and realizing the localization of the initiators. Based on the philosophy of macromolecular design throughout the thesis, the author fully utilized the monomers of butadiene, isoprene and styrene produced in bulk to synthesize a series of novel copolymers with the dilithium as initiator, cyclohexane as solvent and diethylene glycol dimethyl ether / tetramethyl ethylenediamine as polar additive. Following were the typical block copolymers as prepared, including the polybutadiene, polyisoprene, 1,2-1,4-1 ,2-stereo-triblock polybutadiene, 3,4-1 ,4-3,4-stereo-triblock polyisoprene, symmetrical two-end tapered block copolymer of butadiene/styrene, symmetrical two-end tapered block copolymer of isoprene/styrene and symmetrical two-end tapered block terpolymer of butadiene/isoprene/styrene. Furthermore, this thesis also studied systematically the kinetic behaviour and heat effect in the polymerization process. The microstructure, sequential arrangement and morphology as well as the mechanical properties of the polymers mentioned above were also investigated in detail. From the summary of the full thesis, it came to the conclusions that: 1. The dihalogenated alkane substitution type dilithium was one kind of initiator that possessed pret

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CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Carbon - chain polymers
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