Poly a-olefins

A value of 4 = 292 was found for poly [(S)-4-methyl hexene-1], whereas the value for the hydrogenated monomer chosen as model compound is only 9.9 (in each case, expressed in units of 10 deg dm cm mol ). The increased value for the polymer undoubtedly results from the contribution of the helical structure. 

The dependence of the molar optical rotation of poly(a-olefins) on the wavelength of the polarized light used can be well represented by the one-term Drude equation. The constant Xo is of approximately the same magnitude for polymers and their hydrogenated monomers (Table 4-11). For polymers. 

The molar optical rotation of poly(a-olefins) decreases with increasing temperature. This is interpreted as the melting of relatively long, left- 

The molar optical rotation of configurational copolymers of (S) and (R) isomers of the same monomer is generally, in the case of poly(a-olefins), a hyperbolic and not a linear function of the optical purity of the monomers. Thus, the molar optical rotation of the copolymers is always greater than that obtained by additivity rules. Whether this is caused by tactic blocks in the polymers or by mixtures of (S) and (R) unipolymers has not been established yet. 

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The melting points of a series of poly(a-olefin) crystals were studied. All of the polymers were isotactic and had chain substituents of different bulkinesses. Table 4.2 lists some results. Use Eq. (4.5) as the basis for interpreting the trends in these data. 

Table 4.2 Values of T j, for Poly(a-olefin) Crystals in Which the Polymer has the Indicated Substituent (Results are Discussed in Example 4.1)...

Synthetic oils have been classified by ASTM into synthetic hydrocarbons, organic esters, others, and blends. Synthetic oils may contain the following compounds diaLkylben2enes, poly(a-olefins) polyisobutylene, cycloaUphatics, dibasic acid esters, polyol esters, phosphate esters, siUcate esters, polyglycols, polyphenyl ethers, siUcones, chlorofluorocarbon polymers, and perfluoroalkyl polyethers. 

Alkylated aromatic lubricants, phosphate esters, polyglycols, chlorotrifluoroethylene, siUcones, and siUcates are among other synthetics that came into production during much that same period (28,29). Polyphenyl ethers and perfluoroalkyl polyethers have followed as fluids with distinctive high temperature stabiUty. Although a range of these synthetic fluids find appHcations which employ their unique individual characteristics, total production of synthetics represent only on the order of 2% of the lubricant market. Poly(a-olefin)s, esters, polyglycols, and polybutenes represent the types of primary commercial interest. 

Although synthetic lubrication oil production amounts to only about 2% of the total market, volume has been increasing rapidly (67). Growth rates of the order of 20% per year for poly( a-olefin)s, 10% for polybutenes, and 8% for esters (28) reflect increasing automotive use and these increases would accelerate if synthetics were adopted for factory fill of engines by automotive manufacturers. The estimated production of poly( a-olefin)s for lubricants appears to be approximately 100,000 m /yr, esters 75,000, poly(alkylene glycol)s 42,000, polybutenes 38,000, phosphates 20,000, and dialkyl benzene 18,000 (28,67). The higher costs reflected in Table 18 (18,28) have restricted the volume of siUcones, chlorotrifluoroethylene, perfluoroalkylpolyethers, and polyphenyl ethers. 

In the early 1950s, Ziegler observed that certain heterogeneous catalysts based on transition metals polymerized ethylene to a linear, high density material at modest pressures and temperatures. Natta showed that these catalysts also could produce highly stereospecific poly-a-olefins, notably isotactic polypropylene, and polydienes. They shared the 1963 Nobel Prize in chemistry for their work. 

Miscellaneous Commercial Applications. Dimer acids are components of "downweU" corrosion inhibitors for oil-drilling equipment (see Petroleum Corrosion and corrosion inhibitors). This may account for 10% of current dimer acid use (71). The acids, alkyl esters, and polyoxyalkylene dimer esters are used commercially as components of metal-working lubricants (see Lubrication). Dimer esters have achieved some use in specialty lubricant appHcations such as gear oils and compressor lubricants. The dimer esters, compared to dibasic acid esters, polyol esters and poly(a-olefin)s, are higher in cost and of higher viscosity. The higher viscosity, however, is an advantage in some specialties, and the dimer esters are very stable thermally and can be made quite oxidatively stable by choice of proper additives. 

A large number of organic acrylic ester polymer have been prepared in the laboratory. Poly (methyl acrylate) is tough, leathery and flexible. With increase in chain length there is a drop in the brittle point but this reaches a minimum with poly-(n-octyl acrylate) (see Figure 15.12.). The increase in brittle point with the higher acrylates, which is similar to that observed with the poly-a-olefins and the poly(alkyl methacrylate)s, is due to side-chain crystallisation. 

In amorphous poly-a-olefins (APAO), the main monomer is propylene. Compared to EVA, it provides better heat resistance. APAO shows good adhesion properties to nonpolar surfaces, good flexibility and high resistance to temperature and moisture. 

Poly-a-olefins (PAOs) are biodegradable and nontoxic to marine organisms they also meet viscosity and pour point specifications for formulation into oil-based muds [78]. 

By coating poly-a-olefins with a fatty acid wax as a partitioning agent and dispersing it in a long-chain alcohol, a nonagglomerating, nonaqueous suspension can be obtained [918]. 

Polymers that incorporate steric centers into their backbones can display various types of tacticity. The three principal types of tacticity are isotactic, syndiotactic, and atactic, as illustrated in Fig. 1.8 for polypropylene. Other polymers that display tacticity include polystyrene and poly a-olefins,... 

Another significant cooperativity effect in preferential helical screw sense optically active copolymers is the majority rule phenomenon.18bl8q In this case, the screw sense of a helical main chain with unequal proportions of opposite chirality enantiopure chiral side groups is controlled by the enantiomeric excess only. Since this phenomenon was first reported from poly-a-olefins made of vinyl co-monomers bearing nonenantiopure chiral moieties by Green et al.8b and Pino et al.,16b this majority rule has been established in... 

Figure 9. Proposed allowed equilibrium conformational states for poly (a-olefin sulfones) in solution. Note that the sulfone dipoles cancel and that during the transitions ttt g tg g tg there is no net reorientation of these dipoles (dielectrically inactive motions), but there is a reorientation of backbone C-H vectors (C-13 NMR active motions).

Fig. 2. Chains of stereoisomeric poly-a-olefins supposing the main chain stretched on a plane, I. Isotactic. II. Syndiotactic. III. Atactic.

Base fluids (BFs) represent the major ingredient of nonaqueous drilling mud systems. They act as the continuous phase in OBMs and SBMs. Oil-based fluids (OBFs) such as diesel and mineral oils have been replaced with synthetic-based fluids (SBFs) because of the deleterious environmental hazards of OBMs. The SBFs contain fatty adds which are usually derived from vegetable oil (e.g., palm oil) or fish oil. SBFs usually constitute about 50-90% by volume of the fluid portion of the SBM [27] and about 20-40 % of the mass of the mud [35]. Ethers, esters, acetals, polymerized olefins (poly-a-olefins, linear a-oleftns, and internal olefins), enhanced mineral oils, and paraffins are used most frequently as SBFs (Table 11.2) in mud formulations [8, 36, 37]. 

Polymerized olefins include poly-a-olefins (PAOs), linear a-olefins (LAOs), and internal olefins (IOs) [24]. Hydrocarbon chain length and branching are selected to optimize the drilling properties and minimize the environmental toxicity [20]. 

A very important field of polymerization, stereospecific polymerization, was opened in 1955. In this year, Natta and his coworkers (1—3) polymerized a-olefins to crystalline isotactic poly-a-olefins with the Ziegler catalyst, and Pruitt and Baggett (4,5) polymerized dl-propylene oxide to crystalline polypropylene oxide, which was later identified as an isotactic polymer by Price and his coworkers (6,7). Since then, a large number of compounds including both unsaturated and cyclic compounds were polymerized stereospecifically and asymmetrically. Development of the stereospecific polymerization stimulated... 

The second method is the most widely used to prepare optically active vinyl polymers (poly-a-olefins, poly-vinyl-ethers, polyacrylic esters and amides etc.. ... 

The third method (106), which has been so far adopted only to produce optically active polymers from poly-a-olefins obtained from racemic monomers, is of great interest, owing to its simplicity and to the relatively high optical purity attained in one step. 

Some optically active poly-a-olefins of the series XXI (n = 0, 1, 2) were prepared in 1959 by Natta, Pino and Lorenzi 87) successively, Raine and co-workers 121)... 

These experimental findings suggest that the poly-a-olefins obtained in the presence of the conventional stereospecific catalysts should have the same optical purity as the monomers. Therefore, in the polymer of a (S) monomer having high optical purity, the remarkable differences in optical activity observed in the fractions having different stereoregularity cannot be attributed to the presence of different amounts of (R) asymmetric carbon atoms in the lateral chain, formed by racemization of the monomer during the polymerization. 

Preliminary data on the crystalline structure of some poly-a-olefins obtained from optically active and racemic monomers were obtained by G. Natta, P. Corradini, I. W. Bassi (80) and are reported in Table 6. 

The data obtained by different authors for the rotatory power of the optically active poly-a-olefins are in general1 in excellent agreement. 

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