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Zhang Q.,Institute of Polymerization and Polymer Engineering | Yu G.,Institute of Polymerization and Polymer Engineering | Wang W.-J.,Institute of Polymerization and Polymer Engineering | Yuan H.,Zhejiang University | And 2 more authors.
Langmuir | Year: 2012

This work reports the development of a reversibly coagulatable and redispersible polystyrene latex system that can be triggered by N 2/CO 2. The coagulatability and redispersibility of the latexes were achieved by employing 0.9-5.6 wt % (N-amidino)dodecyl acrylamide (DAm), a reactive switchable surfactant, in an emulsion polymerization of styrene under CO 2 atmosphere. The resulted latex particles were readily coagulated by N 2 bubbling at 60 °C and redispersed by CO 2 bubbling and ultrasonication, which switched amidine moieties between neutral and ionic states. The coagulation/redispersion processes were repeatable. The prepared latexes showed good stabilities against electrolytes, especially with higher charges. © 2012 American Chemical Society.


Chen Z.-H.,Institute of Polymerization and Polymer Engineering | Yao Z.,Institute of Polymerization and Polymer Engineering | Zhu F.-J.,Institute of Polymerization and Polymer Engineering | Cao K.,Institute of Polymerization and Polymer Engineering | And 3 more authors.
Journal of Chemical and Engineering Data | Year: 2010

Gas-liquid critical properties of ethylene + hydrogen and propylene + hydrogen are measured in the olefin-enriched region by using a high-pressure view cell with direct visual observation. The critical temperature of the two systems decreases with increasing concentration of hydrogen, whereas the critical pressure increases. The Soave-Redlich-Kwong (PSRK) and group contribution equations of state are used to predict the critical points, and the results agree well with the experimental data. © 2010 American Chemical Society.


Morgan S.,Laurentian University | Ye Z.,Laurentian University | Subramanian R.,Laurentian University | Wang W.-J.,Institute of Polymerization and Polymer Engineering | Ulibarri G.,Laurentian University
Polymer | Year: 2010

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, [(ArN{double bond, long}C(Me)-(Me)C{double bond, long}NAr)Pd(CH3)(N{triple bond, long}CMe)]+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. © 2009 Elsevier Ltd. All rights reserved.

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