Polyisoprene (PI) with high 3

4-structure content (78.76%) was synthesized by anionic polymerization using n-BuLi as the initiator and tetrahydrofuran/cyclohexane as the mixed solvent.P-complex was also introduced into the system to improve the controllability of the polymerization.The molecular structure was characterized by 1H-NMR.Results indicated that when n-BuLi was used as the initiator

the polymerization rate and molecular structure of the products were determined by the channel space between the ion pairs.When the channel space was compatible with the requirement for inserting of the monomers

the polymerization rate would be maximum.The channel space required for 3

4 polymerization of isoprene is the smallest.P-complex with same lithium atom as initiator and large steric hindrance can adjust the channel space between the cation-anion pairs.P-complex can partially block the channel space.Therefore

the introduction of a small dosage of P-complex could not only accelerate 3

4 polymerization

inhibit 1

2 and 1

4 polymerization effectively

but also increase the content of 3

4-PI.On the contrary

with the increase of the temperature

the channel space expanded

resulting in the decrease of 3

4-PI content and the increase of 1

4-PI content.The higher the temperature was

the more content of trans-1

4-PI would be.