Mechanism of chain propagation in “living” polypropylene synthesis. ¹H and ¹³C NMR analyses of chain‐end structures

Abstract

The mechanism of chain propagation in the living coordination polymerization of propene initiated by the soluble V(acac),/Al(qH,hCl catalyst was studied by lH and 13C NMR analyses of iodine-terminated polypropylenes of low molecular weights (M, = 630 to 3 200). A vanadium-carbon bond in the living polypropylene end reacts quantitatively with the iodine molecule to yield a new iodine-polymer bond. The lH and 13C NMR analyses of iodine-bonded polypropylene provide direct evidence on the stereochemistry of the first and last inserted propylene units and the structure of the living polypropylene end.

Syndiospecific Polymerization of Propene Promoted by Bis(salicylaldiminato)titanium Catalysts: Regiochemistry of Monomer Insertion and Polymerization Mechanism

“…In summary, 1,2 insertion is favored only in the initiation step, while syndiospecific propagation proceeds via 2,1 monomer insertion, and chain termination occurs mainly via β-hydrogen elimination, while chain transfer with MAO is infrequent, at least under the above conditions. A similar picture was previously observed for the classical V-based catalysts, although the latter are stereospecific only at subambient temperature, mainly due to thermal instability of the active species, at which temperature chain termination is disfavored (“living” polymerization) …”

Catalyzed chain growth (CCG) on a main group metal: an efficient tool to functionalize polyethylene

“…We showed that the addition of iodine after polyethylene catalyzed chain growth led to highly functionalized endhalogenated PE (PE-I). 17 This successful iodide introduction was confirmed by 1 H NMR analyses which show a triplet at 3.00 ppm corresponding to the methylene adjacent to the iodine atom. Functionalization rates up to 97% determined by 1 H NMR demonstrated the efficiency of the end functionalization (Fig.…”

Polypropylene Plastic Waste Conversion to Lubricants over Ru/TiO2 Catalysts

“…Liquid samples produced over Ru/TiO 2 with a polymer/catalyst ratio of 20 were selected for a detailed structural study. NMR spectroscopy has been employed for characterizing the polypropylene microstructure, some of its oligomers, − and the lubricant oil Figure S3).…”