聚(酰胺-胺)树状大分子负载钛催化乙烯聚合

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

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.

The first-generation poly（amidoamine）（PAMAM） dendrimer was modified by the salicylaldehyde via a Schiff-base condensation reaction, and reacted with TICl4·2THF 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 AI/Ti = 1000） in comparison with the corresponding phenoxy-imine complexes. The melting point temperature （Tm） of the polyethylene as determined by DSC was 138℃, and the crystallization temperature （ To ） was 116℃ .The apparent molecular weight of the polyethylene（ Mv ） 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.