Gao Lujie, Ren Hegang, Hou Yanhui, Ye Linlin, Meng Hao, Liu Binyuan, Yang Min
Hebei Key Laboratory of Functional Polymers, Institute of Polymer Science and Engineering, Hebei University of Technology, Tianjin 300401, China.
School of Material Science and Engineering, Guangdong University of Petrochemical Technology, Maoming 525000, China.
Polymers (Basel). 2024 Aug 22;16(16):2376. doi: 10.3390/polym16162376.
The α-diimine late transition metal catalyst represents a new strategy for the synthesis of atactic polypropylene elastomer. Taking into account the properties of the material, enhancing the molecular weight of polypropylene at an elevated temperature through modifying the catalyst structure, and further increasing the activity of α-diimine catalyst for propylene polymerization, are urgent problems to be solved. In this work, two α-diimine nickel(II) catalysts with multiple hydroxymethyl phenyl substituents were synthesized and used for propylene homopolymerization. The maximum catalytic activity was 5.40 × 10 gPP/molNi·h, and the activity was still maintained above 10 gPP/molNi·h at 50 °C. The large steric hindrance of catalysts inhibited the chain-walking and chain-transfer reactions, resulting in polypropylene with high molecular weights (4071101 kg/mol) and low 1,3-enchainment content (3.5716.96%) in toluene. The low tensile strength (0.31.0 MPa), high elongation at break (218403%) and strain recovery properties (S.R. ~50%, 10 tension cycles) of the resulting polypropylenes, as well as the visible light transmittance of approximately 90%, indicate the characteristics of the transparent elastomer.
α-二亚胺后过渡金属催化剂代表了一种合成无规立构聚丙烯弹性体的新策略。考虑到材料的性能，通过修饰催化剂结构在高温下提高聚丙烯的分子量，以及进一步提高α-二亚胺催化剂用于丙烯聚合的活性，是亟待解决的问题。在这项工作中，合成了两种带有多个羟甲基苯基取代基的α-二亚胺镍（II）催化剂，并将其用于丙烯均聚。最大催化活性为5.40×10 gPP/molNi·h，在50℃时活性仍保持在10 gPP/molNi·h以上。催化剂的大空间位阻抑制了链行走和链转移反应，在甲苯中得到了高分子量（4071101 kg/mol）和低1,3-插入含量（3.5716.96%）的聚丙烯。所得聚丙烯的低拉伸强度（0.31.0 MPa）、高断裂伸长率（218403%）和应变回复性能（S.R. ~50%，10次拉伸循环），以及约90%的可见光透过率，表明了其透明弹性体的特性。
