Selectivity in Propene Polymerization with Metallocene Catalysts

Boosting TiO2-anatase antimicrobial activity: Polymer-oxide thin films

“…The important industrial success of isotactic polypropylene (iPP) and the wide range of its applications are basically due to the combination of outstanding physical properties, as the low density, the high tensile strength, stiffness, hardness, thermal and good environmental resistance, ease of processability and recycling at a moderate cost [3]. The discovery of single-site metallocene catalysts has determined great improvements and advantages in polymerization and copolymerization of olefins [4,5]. Taking into account their good transparency, their aesthetic and mechanical properties, metallocene-catalyzed polypropylene resins provide a replacement for glass in some critical uses, as packaging of species keeping their organoleptic qualities, and for other plastics, as polyvinyl chloride in medical devices.…”

Design of stereoselective Ziegler–Natta propene polymerization catalysts

“…Although neither isotactic nor syndiotactic polypropylene are chiral molecules ( Fig. 2) (5), each individual monomer insertion implies a chiral recognition, the catalytic species selecting one of the two enantiofaces of propene in the favored regiochemistry with an enantiomeric excess that, in several reported cases (6,7), is Ն99.8% (an unrivaled performance for a substrate with no functional groups other than an olefinic double bond).…”

“…On the other hand, the hundreds of metallocene (7,13) and nonmetallocene (14) catalyst structures that have been disclosed and tested in the last two decades, and the thorough theoretical studies on realistic models thereof (6,7), highlighted a number of basic principles relating catalyst structure and performance. These can now be used successfully, if not (yet) for attempts of de novo design, certainly for catalyst fine-tuning.…”

“…3) and give rise to appreciable free energy differences between the competing diastereomeric transition states. This element can be the configuration of the growing polypropylene chain (and in particular of the asymmetric C in the last-inserted monomeric unit) and͞or the possible chirotopicity of the active site(s) (6,7).…”

Transition metal-based polymer chemistry: a critical micro-review

“…It would certainly exceed by far the scope of this article if one attempted to give a comprehensive review on group IV-based polyole n chemistry. Fortunately, some excellent reviews on this topic, including carbocationic alkene polymerization [28], have been published quite recently and will serve as a reference for comprehensive reading [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. Nevertheless, a few aspects of this chemistry that certainly deserve to be discussed will be mentioned.…”