Properties of Poly a-olefin s

Many poly(ot-olefin)s reported in the literature are not used commercially for various reasons. Table 6.6 lists some of the olefins polymerized by the Ziegler-Natta catalysts [72, 83]. 

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Being acquainted with the structure of poly(a-olefin)s, one may reasonably explain some of the differences in their physicochemical properties. For example, isotactic polypropylene, the chains of which in the helical conformation can be closely packed, has rather a high density (0.92-0.94 g/cm3) and melting point (175°C) and is insoluble in low-boiling aliphatic hydrocarbons at boiling point. Syndiotactic polypropylene, consisting of chains in the form of binary helices, which cannot be packed so closely as in the previous case, has a density of 0.89-0.91 g/cm3 and a melting point of 135°C, which is 40 k lower from that of isotactic polypropylene syndiotactic polypropylene is also moderately soluble in... 

As with poly(a-olefin)s, the properties of polymers derived from polar monomers may be highly dependent on the stereoregularity of the polymer backbone. Moreover, copolymers of polar monomers with olefins may exhibit some... 

Abstract Many similarities between the chemistry of carbon and phosphorus in low coordination numbers (i.e.,CN=l or 2) have been established. In particular, the parallel between the molecular chemistry of the P=C bond in phosphaalkenes and the C=C bond in olefins has attracted considerable attention. An emerging area in this field involves expanding the analogy between P=C and C=C bonds to polymer science. This review provides a background to this new area by describing the relevant synthetic methods for P=C bond formation and known phosphorus-carbon analogies in molecular chemistry. Recent advances in the addition polymerization of phosphaalkenes and the synthesis and properties of Tx-con-jugated poly(p-phenylenephosphaalkene)s will be described. 

The disadvantages of all biochemical routes is the lack of variable tacticity in the polymer and, even more important, the need for time-consuming purification. PHB materials of feasible properties are only achieved with high production costs. In the 1990s, ICl sold a copolymer of 3-HB and 3-HV (BIOPOL) for about 10-20 /kg whereas the price of PP was less than 2 /kg. Therefore, a fermentative synthesis is feasible for smaller applications but not cannot compete with packaging materials such as poly(olefin)s [43 5] (Fig. 10). 

During the years 1992-1998, numerous publications emerged from Prof. Graessley s laboratory. The model PEs with different stmctures (see Fig. 18.10) were commercial (e.g., HDPE or PP) or from laboratory (e.g., hydrogenation/deuteration of diolefins, anionic reaction for PIB, Z-N catalysis using a V-based catalyst in Cg for poly (ethylene-co-a-olefin) or later a metallocene catalyst. The thermodynamic properties of numerous PO blends were extracted from the pressuie-volume-temperature (PVT) data (Walsh et al. 1992 Krishnamoorti et al. 1996) or from SANS results (Krishnamoorti et al. 1994, 1995 Graessley et al. 1994, 1995 Reichart et al. 1997 Alamo et al. 1997). 

Acid scavengers are also addressed as acid absorbers, antacids, or still less precisely as costabilizers. The addition of acid scavengers is necessary because catalyst residues from processing and manufacture may contribute to imdesired properties. This does not necessarily cause a diminished stability of the polymeric base material. Instead, residues from Ziegler-Natta catalysts in poly(olefine)s may contain traces of halogen that could cause corrosion reactions to metals that are in contact with the polymer. 

Yadav JS, Abraham S, Reddy BVS, Sabitha G (2001) Addition of pyrroles to electron deficient olefins employing InCL. Tetrahedron Lett42 8063-8065. doi 10.1016/S0040-4039(01)01697-5 Yamamoto T, Morita A, Miyazaki Y, Mamyama T, Wakayama H, Zhou ZH, Nakamura Y, Kanbara T, Sasaki S, Kubota K (1992) Preparation of Jt-conjugated poly(thiophene-2,5-diyl), poly(p-phenylene), and related polymers using zerovalent nickel complexes. Linear structure and properties of the ii-conjugated polymers. Macromolecules 25 1214-1223. doi 10.1021/ ma00030a003... 

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