Isoprene-based polymer cyclized product, alicyclic polymer, and optical resin

[0104]Under a nitrogen atmosphere, a glass reaction vessel in which a magnetic stirrer was placed was charged with 20 ml of a chlorobenzene solution of 0.10 mmol of the yttrium benzamidinate complex expressed by the following formula (10) and 5.11 g (75 mmol) of isoprene and was cooled to −10° C. Note that the yttrium benzamidinate complex expressed by the following formula (10) was synthesized by the method described in Japanese Patent Publication (A) No. 2007-238857.

[0105]Next, 10 ml of a chlorobenzene solution containing, as a polymerization activation agent, 0.10 mol of [Ph3C] [B(C6F5)4] was added. The mixture was stirred and polymerized at −10° C. for 20 minutes. After this, a small amount of methanol was added to the reaction system to stop the polymerization, then the reaction solution was poured into a large excess of methanol containing a small amount of hydrochloric acid and 2,6-di-t-butyl-p-cresol (BHT). Further, the precipitated polymer was recovered, was washed by metha...

[0107]Except for using, instead of a yttrium benzamidinate complex, a scandium benzamidinate complex expressed by the following formula (11), the same procedure was followed as in Synthesis Example 1 to obtain 5.1 g of polyisoprene (B). The scandium benzamidinate complex expressed by the following formula (11) was synthesized in accordance with the method described in Japanese Patent Publication (A) No. 2007-238857.

[0108]The obtained polyisoprene (B) had an Mn=204,600 and Mw / Mn=2.21, had a ratio of content of 3,4-bond units (structural units expressed by the above general formula (1)) of 99.5 mol % or more, and had an isotacticity of the structural units expressed by the above general formula (1) expressed by triads of 100% mm and expressed by pentads of 99% mmmm.

[0109]Except for using toluene instead of chlorobenzene and changing the polymerization temperature from −10° C. to 25° C., the same procedure was followed as in Synthesis Example 2 to obtain 5.0 g of polyisoprene (C). The obtained polyisoprene (C) had an Mn=132,500 and Mw / Mn=3.82, and had a ratio of content of 3,4-bond units (structural units expressed by the above general formula (1)) of 80 mol %. No regularity was observed in the tacticity of the 3,4-bond units.