2-氨基吡啶镍配合物/MAO高活性催化β-蒎烯聚合研究

合成了一系列2-氨基吡啶镍配合物(2-PyCH2NAr)NiBr,Ar=2,6-二甲基苯基(a),2,6-二异丙基苯基(b),2,6-二氟苯基(c).在助催剂甲基铝氧烷(MAO)存在下,该系列配合物能高活性催化β-蒎烯聚合,得到的聚β-蒎烯分子量明显比传统正离子聚合所得到的聚合物高.对配合物配体结构以及聚合条件对该聚合的催化活性以及聚合物分子量的影响进行了研究.所得聚合物经1H-NMR和13C-NMR分析表明,β-蒎烯聚合是通过正离子方式进行的,聚合中产生开环异构化,得到由环己烯和异丁烷结构单元交替组成的聚β-蒎烯.

HIGH EFFICIENT POLYMERIZATION OF β-PINENE CATALYZED BY 2-AMINOPYRIDINE NICKEL(Ⅱ) COMPLEXES/MAO

A series of 2-aminopyridine Ni(II) complexes bearing different substituent groups {(2-PyCH_2NAr)NiBr,Ar=2,6-dimethylphenyl(a),Ar=2,6-diisopropylphenyl(b),Ar=2,6-difluorophenyl(c)} have been synthesized.In the presence of methylaluminoxane(MAO),these Ni complexes could be highly efficient to catalyze β-pinene polymerization and afforded(poly(β-pinene)s) with higher molecular weight than those prepared by traditional cation polymerizations.Among these complexes,complex c with ortho-electroattracting-substitution exhibited the highest catalytic activity up to 1.48×10~7g/(molNi·h),while complex b with bulky ortho-isopropyl-substitution gave the highest molecular weight of the polymer.The effects of polymerization conditions on the catalytic activity and the molecular weight of poly(β-pinene)s were also studied.With an increase in temperature,the catalytic activity increased and reached a maximum value at 40～50℃,and the molecular weight of the obtained polymer decreased.Increasing in monomer concentration,molar ratio of MAO to the Ni complexes or decreasing in Ni complex concentration would increase the catalytic activity for β-pinene polymerization.The~1H-NMR and~(13)C-NMR analyses of the obtained polymers revealed that the polymers consisted of alternating sequences of isobutylene and cyclohexene units,indicating the propagation proceeded in a manner typical for conventional carbocationic polymerization process.