One of the most exciting developments in the areas of catalysis, organometallic chemistry, and polymer science in recent years has been the intense exploration and commercialization of new polymerization technologies based on single-site and metallocene coordination olefin polymerization catalysts.1 The vast number of specifically designed/synthesized transition metal complexes (catalyst precursors) and main-group organometallic compounds (cocatalysts) allows unprecedented control over polymer microstructure, the generation of new polymer architectures, and the development of new polymerization reactions. Commercialization of new generations of single-site and metallocene catalyst-based technologies has provided the multibillion pound per year polyolefins industry with the ability to deliver a wide range of new and innovative olefin-based polymers having improved properties.2-4 The intense industrial activity in the field and the challenges to our basic understanding that have come to light have in turn 1391 Chem. Rev. 2000, 100, 1391−1434

/pdf/cocatalysts-for-metal-catalyzed-olefin-polymerization-37a9jvjiei.pdf

Cocatalysts for Metal-Catalyzed Olefin Polymerization: Activators, Activation Processes, and Structure−Activity Relationships

The advent of well-defined catalysts for olefin metathesis which combine high activity, durability, and excellent tolerance towards polar functional groups has revolutionized the field. The past decade has seen the rapid embrace of these reagents as tools for advanced organic and polymer chemistry and the success of this development is witnessed by a plethora of elegant applications to the synthesis of natural and nonnatural products. This review article provides an overview of these developments and intends to familiarize the reader with some very recent advances which hold the promise to expand the scope of the reaction even further. Moreover, the positive impact of metathesis on the fundamental logic of retrosynthetic planning is demonstrated by means of typical examples. Finally, it will be shown that metathesis is by no means restricted to alkenes as substrates, and some comments on metathesis reactions following unconventional mechanistic pathways will also be presented.

Olefin Metathesis and Beyond

Selectivity in propene polymerization with metallocene catalysts.

Supramolecular nanotube architectures based on amphiphilic molecules.

2.2.1. Polyisocyanates 6117 2.2.2. Polysilanes 6118 2.2.3. Polyacetylenes 6120 2.3. Foldamer-Based Helical Polymers 6124 2.3.1. Click Polymerization 6126 2.3.2. Ring-Closing Reaction 6126 2.4. Other Types of Helical Polymers 6127 2.4.1. π-Conjugated Helical Polymers 6127 2.4.2. Metallosupramolecular Helical Polymers 6128 2.5. Induced Helical Polymers 6130 2.5.1. Induced Helical Polyacetylenes 6130 2.5.2. Other Induced Helical Polymers and Oligomers 6132

Helical polymers: synthesis, structures, and functions

Publisher Summary This chapter discusses crystalline high polymers of α-olefins. The linear crystalline polymers of α-olefins are synthesized and the chapter also discusses the properties of crystalline polypropylene, poly-α-butylene, and polystyrene. Depending on the structure of the catalyst, different amounts, ranging from 0 to 100%, of the polymerization products are crystallizable and can be separated easily from the much more soluble noncrystalline polymers by solvent extraction. The new crystalline poly hydrocarbons have higher melting point, higher density, and lower solubility in organic solvents than the corresponding amorphous polyhydrocarbons having intrinsic viscosity of the same order of magnitude. The infrared spectra of crystalline polypropylene, of melted samples of the same polymer and of the amorphous polypropylene, show between 2 and 7.5 μ, the high adsorption regions characteristic of hydrocarbons.

CRYSTALLINE HIGH POLYMERS OF α-OLEFINS

The crystal structure of isotactic polypropylene and its chemical-physical properties are described here. The polymer crystallizes in the Cc space group with the following constants of the unit cell: a = 6.65 ± 0.05 A ; b = 20.96 ± 0.15 A ; c = 6.50 ± 0.05 A β = 99 ° 20 ′ ± 1 ° .

Structure and properties of isotactic polypropylene

Crystal Structure of Isotactic Poly-alpha-Butene.

Systematic x-ray and electron diffraction studies of polymers of 1,3-butadiene prepared by different anionic catalysts have made it possible for us to identify two types of highly crystalline materials. One of us (G. N.) has already reported that our synthesis was carried out with the aid of different highly selective catalysts. The description of the preparation of these catalysts, which have made it possible for the first time to prepare these new polymers, will be separately published by one of us (G. N.) with L. Porri. Infrared analysis carried out by E. Mantica and D. Morero in our Institute has established that one type of these crystalline polymers obtained with heterogeneous catalysts represents a continuous l,4-trans arrangement of the monomer units. X-ray diffraction has shown that this material is dimorphous, having one crystalline modification that is stable at room temperature and another stable above 60° C. The x-ray melting point of a polymer having a molecular weight of the order ...

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pol.1956.120209503

The structure of crystalline 1,2‐polybutadiene and of other “syndyotactic polymers”

Results of new research work in the field of polymers with an ordered steric structure, obtained by stereospecific polymerization, are reported. Some of the results concern the relationship between steric structure and crystallinity; these show that a regular steric structure is a necessary, but not a sufficient condition for the crystallizability of the polymers.

In the isotactic polymers of CH2 = CHR type monomers, the shape and size of the R group not only determine the different conformations of isotactic helices (with a number of monomeric units per pitch varying from 3 to 4) but in some particular cases are responsible for the lack of crystallinity.

It is possible, through chemical processes which modify the shape and size of the R substituent, to obtain crystalline polymers from isotactic, amorphous, not crystallizable polymers.

The crystalline structure of syndiotactic polypropylene is described for the first time and is compared with the structure of other syndiotactic polymers.

Furthermore the structure of crystalline polymers of “di-isotactic type”, obtained by polymerizing RCH = CHR1 type monomers is discussed, and a nomenclature for the different possible stereoisomers is suggested.

Cases of polymorphism, isomorphism and di-isomorphism in the macromolecular field are examined and a new type of isomorphism among different monomeric units is discussed. Crystalline copolymers of isomorphous monomeric units have a melting point which is intermediate between the melting points of the corresponding pure homopolymers.

The effects which influence the steric purity of polymers having an ordered structure are discussed and the influence of steric purity on the physical properties and mainly on the mechanical properties of the polymers (especially in the case of polybutadiene obtained at the Polytechnic of Milan with a content of cis–1,4: units higher than 99 per cent) is pointed out.

Giulio Natta

Papers

CRYSTALLINE HIGH POLYMERS OF α-OLEFINS

Structure and properties of isotactic polypropylene

Crystal Structure of Isotactic Poly-alpha-Butene.

The structure of crystalline 1,2‐polybutadiene and of other “syndyotactic polymers”

Progress in stereospecific polymerization