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

Living ring-opening metathesis polymerization

Synthetic helical polymers: conformation and function.

Precise control of polyolefin stereochemistry using single-site metal catalysts.

Palladium-Catalyzed Alternating Copolymerization of Alkenes and Carbon Monoxide.

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

Results of viscometric and osmotic measurements as well as solubility experiments with isotactic and atactic polystyrene fractions are reported. The fractionation of isotactic polystyrene, in spite of its crystallizability, can be carried out by the usual techniques of fractional precipitation at ordinary temperatures. This is possible because of its state of metastability in solution and its low kinetic tendency toward crystallization. The relation between [η] and M in benzene and in toluene was found to be the same for the two types of polymer. On the other hand, the second virial coefficients ? (in toluene) are appreciably different. Calculated values of the “limiting interaction affinity” QE in toluene and the results of solubility experiments in MEK and in toluene-methanol mixtures show that atactic polystyrene is always more soluble than isotactic polystyrene, regardless of whether the latter is in the crystalline or in the amorphous (metastable) state. MEK is shown to be a selective solvent in the separation of the two types of polystyrene. The value of B or φE is suggested as a possible measure of the isotacticity.

Some solution properties of isotactic and atactic polystyrenes

Publisher Summary Considerable interest is displayed today in the comparison between the behavior in solution of isotactic and atactic polymers of the same monomer. It clarifies the influence of the variation of steric structure on the macromolecular configuration and, consequently, on all related properties. Conversely, it enables the determination of whether the properties in solution may reveal differences in the steric composition of stereoisomeric polymers. With the accuracy of the methods employed, the relation between intrinsic viscosity and osmotic molecular weight for fractions of the two types of polystyrene does not practically depend on the variation of steric structure. In the case of the polypropylene, there must be no considerable difference in the viscometric behavior of isotactic and atactic polymers in solution. This chapter illustrates the relationship between intrinsic viscosity and molecular weight for polypropylene in decalin.

Giovanni Moraglio

Papers

CRYSTALLINE HIGH POLYMERS OF α-OLEFINS

Some solution properties of isotactic and atactic polystyrenes

On the behavior of isotactic and atactic polypropylene in solution

CRYSTALLINE HIGH POLYMERS OF α-OLEFINS

Second order transition temperatures of polyethylenes