Molecular weight and melting points

An unusual method for the preparation of syndiotactic polybutadiene was reported by The Goodyear Tire Rubber Co. (43) a preformed cobalt-type catalyst prepared under anhydrous conditions was found to polymerize 1,3-butadiene in an emulsion-type recipe to give syndiotactic polybutadienes of various melting points (120—190°C). These polymers were characterized by infrared spectroscopy and nuclear magnetic resonance (44—46). Both the Ube Industries catalyst mentioned previously and the Goodyear catalyst were further modified to control the molecular weight and melting point of syndio-polybutadiene by the addition of various modifiers such as alcohols, nitriles, aldehydes, ketones, ethers, and cyano compounds. 

Austin, J. 1930. A Relation Between the Molecular Weights and Melting Points of Organic Compounds. J. Am. Chem. Soc. 52, 1049. 

Mackay (2000) recommends two methods, one of which uses the value of log Kow to derive solubility. The SRC program WSKOWWIN also predicts solubility from the value of log Kow (Meylan et al. 1996). Molecular weight and melting point (if known, for solids) are also inputs to WSKOWWIN. 

This part contains 64 indexes of analytical data, tabulated in numerical order, and includes all the data for chromatography, spectrophotometry, and mass spectrometry, together with indexes of molecular weight and melting point. 

The physico-chemical properties of amino acids are summarized in Table 1. This includes a wide array of measiues, from refractivity and melting point to the pKa at the amino group. Some of the parameters span a narrow range of values (e.g., the molecular weights and melting points). Other parameters differ by a factor of 100-fold or more, which include the pKas at the amino group and solubility. The AAindex database compiled by Kawashima et al. (21) is an excellent soiuce of additional information that concerns the physico-chemical properties of amino acids. 

Table 12. Typical molecular weights and melting points of Poly(FAD-SA) ...

The table gives the molecular weight and melting point of the acid and the melting and boiling points of the methyl ester of the acid when available. A superscript on the boiling point indicates the pressure in mmHg (torr) if there is no superscript, the value refers... 

The effectiveness of stearic acid in activating vulcanization is a function of its solubility in the elastomer, molecular weight, and melting point. 

In addition, the anionic polymerization of l,l-dimethyl-2,3-benzo-l-silacyclo butene with the use of K-mirror in THF (or n-BuLi in a hydrocarbon solvent) was performed in [82]. As a result, powderlike polymers with lower molecular weight and melting point than those in the case of TROP were isolated. 

Polymers obtained from PEL monomers of different optical purity were characterized as follows (1) for crystalline properties by differential scanning calorimetry (DSC) and wide-angle x-ray diffraction (2) for relative molecular weights by solution viscosity (3) for structure by IR and NMR spectroscopy and (4) for chiroptical properties in solution by optical rotatory dispersion (ORD) and circular dichroism (CO). Molecular weight and melting point data for both the racemic and optically-active PEL polymers are collected in Table I. 

As the demand for new polymers increased, catalysts with two active sites per molecule were developed. It was found that tris-pentafluoropheityl-aluminium, (C6F5)3A1, could be used to replace the borate derivatives, and when used in conjunction with the typical transition metallocene catalyst precursors, a series of di-cationic derivatives of titanium and zirconium could be produced. Work in Dow showed that these di-cationic catalysts were up to 30 times more reactive than boron activated catalysts, while still producing polymers with the same molecular weight and melting point. ... 

---