کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5184074 1381038 2010 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Chain walking copolymerization of ethylene with cyclopentene - Effect of ring incorporation on polymer chain topology
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آلی
پیش نمایش صفحه اول مقاله
Chain walking copolymerization of ethylene with cyclopentene - Effect of ring incorporation on polymer chain topology
چکیده انگلیسی

Chain walking ethylene copolymerizations with cyclopentene (CPE) as the ring-forming comonomer were carried out in this study to investigate the tuning of polyethylene chain topology via the unique strategy of ring incorporation. Four sets of polymers containing five-membered rings on the polymer backbone at various low contents (in the range of 0-7.5 mol%) were synthesized by controlling CPE feed concentration at four different ethylene pressure/temperature combinations (1 atm/15 °C, 1 atm/25 °C, 1 atm/35 °C, and 6 atm/25 °C, respectively) using a Pd-diimine catalyst, [(ArNC(Me)-(Me)CNAr)Pd(CH3)(NCMe)]+SbF6− (Ar = 2,6-(iPr)2C6H3). The polymers were characterized extensively using 13C nuclear magnetic resonance (NMR) spectroscopy, triple-detection gel permeation chromatography (GPC), and rheometry to elucidate the chain microstructures and study the effect of ring incorporation on polymer chain topology. It was found that CPE was incorporated in the copolymers primarily in the form of isolated cis-1,3 ring units, along with a small fraction in the form of isolated cis-1,2 ring units. Significant linearization of polymer chain topology was achieved with ring incorporation in each of the three sets of polymers synthesized at 1 atm on the basis of the incrementally raised intrinsic viscosity curves in the Mark-Houwink plot and the significantly enhanced zero-shear viscosity of the polymer melts with the increase of ring content despite the decreasing polymer molecular weight. For the set of polymers synthesized at 6 atm/25 °C, the effect of ring incorporation on polymer chain topology was negligible or weaker due to their linear chain topology resulting at this polymerization condition. The results obtained in this study support the proposed blocking effect of backbone-incorporated rings on catalyst chain walking, and demonstrate that effective tuning of polyethylene chain topology from hyperbranched to linear can be conveniently achieved via CPE incorporation while without changing ethylene pressure or polymerization temperature.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Polymer - Volume 51, Issue 3, 5 February 2010, Pages 597-605
نویسندگان
, , , , ,