聚(酰胺-胺)树状大分子负载钛催化乙烯聚合

用水杨醛对第一代聚(酰胺-胺)(PAMAM)树状大分子通过Schiff碱缩合反应进行修饰,然后再与TiCl4.2THF反应,得到了树状大分子负载的钛配合物,并用1H-NMR、电感耦合等离子体发射光谱法(ICP-AES)和电喷雾电离质谱法(ESI-MS)对其结构进行了表征.用甲基铝氧烷(MAO)活化,将其用作乙烯聚合的催化剂前体.当Al/Ti比为1000时,可得良好的活性.聚乙烯的粘弹性能表明材料为超高分子量的聚乙烯.

ETHYLENE POLYMERIZATION CATALYZED BY POLY(AMIDOAMINE)-SUPPORTED TITANIUM DENDRITIC CATALYSTS

The first-generation poly(amidoamine)(PAMAM) dendrimer was modified by the salicylaldehyde via a Schiff-base condensation reaction,and reacted with TiCl_4·2THF to give rise to a novel dendrimer-supported titanium complex.Its architecture was determined by~1H-NMR,ICP-AES and ESI-MS.The application as a catalyst precursor,activated by methylaluminoxane(MAO),for ethylene polymerization was also carried out.The results revealed that the metallodendrimer catalyst for the polymerization of ethylene had a higher activity(56.56 kg PE/(mol Ti·h),at a ratio of Al/Ti=1000) in comparison with the corresponding phenoxy-imine complexes.The melting point temperature(T_m) of the polyethylene as determined by DSC was 138℃,and the crystallization temperature(T_c) was 116℃.The apparent molecular weight of the polyethylene(M_v) was 1.28×10~6 by viscometry.The results implied that these polymers were linear low-density polyethylene.The viscoelastic properties of the polyethylene also indicated that the polyethylene was of ultra high molecular weight.