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在四氢呋喃(THF)与环己烷的混合溶剂中,以正丁基锂(n-BuLi)为引发剂,选取P配合物(Pcomplex)为调节剂,实现了异戊二烯(Ip)的负离子可控聚合,得到了高3,4结构率的聚异戊二烯(PI)(78.76%).采用1H-NMR对聚合物的结构进行了表征和分析.证实了由n-BuLi引发的负离子聚合,单体插入离子对之间参与聚合的速率及聚合结构取决于正负离子对之间的尺度,该尺度与单体插入所需求的尺度相当时,插入聚合速率最快,最容易.对Ip而言,单体插入离子对之间聚合形成3,4-PI时需求的尺度最小.Pcomplex由于其同时含有与Li+同源的锂原子以及空间位阻较大的苯、萘、蒽等基团,可通过改变活性种正负离子对之间的通道尺度,有效地促进3,4聚合反应,抑制1,2和1,4聚合反应,因而有效提高了PI 3,4结构率,使得Ip的聚合变得可控.相反,升高温度可以增加正负离子对之间的尺度,使得3,4聚合结构含量减少,1,4聚合结构含量增加,但温度越高,反式含量越多.
In the mixed solvent of tetrahydrofuran and cyclohexane, n-BuLi was used as initiator, and Pcomplex was selected as the regulator to achieve the isoprene (Ip) negative ions Polymerization of polyisoprene (PI) with high 3,4 structure ratio (78.76%) was obtained by controlled polymerization. The structure of the polymer was characterized and analyzed by 1H-NMR. It was confirmed that n-BuLi-induced negative ions Polymerization, monomer insertion ion pairs involved in the polymerization rate and polymerization structure depends on the scale between the positive and negative ions, the scale required for the insertion of monomer equivalent scale, the fastest insertion rate, the easiest for the Ip , The minimum size required for the polymerization of the monomer-inserted ion pairs to form 3,4-PI is minimal.Pcomplex, due to its simultaneous presence of lithium atoms that are homologous to Li + and sterically hindered benzene, naphthalene, anthracene and other groups , By changing the channel between positive and negative ion pairs of active species, effectively promote the 3,4 polymerization, inhibition of 1,2 and 1,4 polymerization, thus effectively increasing the PI 3,4 structure, making the polymerization of Ip Become controllable.Conversely, increasing the temperature can increase the scale between the positive and negative ion pairs, reducing the content of 3,4 polymerization structure, 1,4 poly Structure content increased, but the higher the temperature, the more trans content.