Polarity hydrocarbon polymers

Recent studies of blends of polyisoprene (PIP) with polybutadiene (PBD) have revealed a number of remarkable features [1-5]. Non-polar hydrocarbon polymers such as PIP and PBD are not expected to exhibit miscibility given the absence of specific interactions. When the polybutadiene is high in 1,2 microstructure, however, it has a remarkable degree of miscibility with PIP. This miscibility is the consequence of a close similarity in both the polarizability and the expansivity of the two polymers [3,4]. Their mixtures represent a very unusual instance of miscibility between chemically distinct, non-reacting homopolymers. As its 1,4- content increases, both the polarizability and the thermal expansivity of the PBD diverge from that of PIP, resulting in a reduced degree of miscibility. This effect of PBD microstructure on miscibility with PIP can be seen in the data in Table I [3]. ... 

Because both aliphatic polyesters likely adopt nearly fully extended all-trans conformations when included in their a-CD-lCs/ the dipole moments in neighboring repeat units point in approximately opposite directions. This might cause partial cancellation of the net PLLA dipole moment in each a-CD, because two PLLA repeat units occupy each host a-CD, while only a single PCL ester group is included. Aside from this potential caveat, and because purely non-polar hydrocarbon polymers may be included in CDs, it is likely that dipolar electrostatic interactions do not play a major role in the nano-threading and subsequent formation of polymer-CD-lCs. 

Oil resistance demands polar (non-hydrocarbon) polymers, particularly in the hard phase. If the soft phase is non-polar but the haid phase polar, then swelling but not dissolution will occur (rather akin to that occurring with vulcanised natural rubber or SBR). If, however, the hard phase is not resistant to a particular solvent or oil, then the useful physical properties of a thermoplastic elastomer will be lost. As with all plastics and rubbers, the chemical resistant will depend on the chemical groups present, as discussed in Section 5.4. 

Most heterochained polymers, including condensation polymers, are susceptible to aqueous-associated acid or base degradation. This susceptibility is due to a combination of the chemical reactivity of heteroatom sites and the materials being at least wetted by the aqueous solution allowing contact between the proton and hydroxide ion. Both these factors are related to the difference in the electronegatives of the two different atoms resulting in the formation of a dipole that acts as a site for nucleophilic or electrophilic chemical attack and that allows polar materials to come in contact with it. Such polymers can be partially protected by application of a thin film of hydrocarbon polymer that acts to repel the aqueous solutions. 

DNPH-steroids can be separated by HPLC with several partition systems [31,32] including 1 % /3,/3 -oxydipropionitrile (BOP) on Zipax with eluting solvents containing 0-20% tetrahydrofuran in heptane or 2-methylheptane, or 1% ethylene glycol on Zipax with 3% chloroform in heptane as the mobile phase. Reversed-phase chromatography with 1.0% hydrocarbon polymer (HCP) or 1% cyanoethyl silicone (ANH) on Zipax and methanol-water as the mobile phase can be useful for the separation of several polar steroids. Gradient elution (water to methanol) on octadecylsilane (ODS), Permaphase (chemically bonded on Zipax), also provides a separation of polar DNPH-steroids. The separation of five DNPH-steroids on 1.5% BOP coated on Zipax is shown in Fig.4.13. 

The second article by Kawahara and his coworkers focuses on polyolefin (PO)-based hybrid materials (POH), in view of their synthesis, structures, and properties. POs are currently the most widely and conveniently used polymeric materials as recognized by the production amount of over one hundred million tons annually in the world, due to the cheap price yet good properties. They are basically hydrocarbon polymers, and hence hydrophobic and less polar. These basic properties are to be modified by introducing a polar function for a wider use in practical applications. Preparation of POHs is one of the best ways to... 

Application of Eq. (11.14) to these polymers (as a first orientation) yields values for the mean dipole moment of the structural units varying from 0 debye units for hydrocarbon polymers to about 1 debye unit for polyamides. The measured values are low compared with the dipole moments of the polar groups in liquids. 

High solubility of stabilizers is an essential requirement for a good physical retention of a stabilizer in a polymer [27]. Molecules of most stabilizers have relatively high polarity and their solubility in unpolar hydrocarbon polymers is, therefore, only low. Microscopic domains consisting of aggregated polar stabilizers and surface exudates can be formed and are one of reasons for the uneven distribution of a stabilizer in the host polymer as well as for the physical loss of a stabili r. 

Generally, the compatibility of antioxidants in polymers is improved when the antioxidant and the host polymer have similar characteristics. Compatibility of antioxidants in nonpolar hydrocarbon polymers, therefore, decreases with increasing antioxidant polarity and increases with the number, length, and branching of the inert alkyl substituents attached to the antioxidant function.Many commercial antioxidants with higher molecular masses (e.g.. Table 1, compare AO 5 with AO 1) have been developed and many have inert long (8 to 18 C-atoms) alkyl chains (e.g.. Table 1, AO 4). 

Figure 6.5 shows various functional groups which may be detected on silica, talc, and clay surfaces. The surface character of carbon black differs in that it is mostly nonpolar whereas the surface of silica is polar. Thus carbon black is more compatible with hydrocarbon polymers which are also nonpolar. Silica and other similar fillers (talc, clay) have more affinity to each other than to nonpolar polymers. This is a major factor in the inferior performance in rubber applications where interfacial adhesion is reduced. 

In dishwashing, one must consider soil and surfactant adsorption to both polar and nonpolar surfaces. Metals (aluminum, stainless steel, carbon steel, cast iron, silver, and tin), siliceous surfaces (china, glass, and pottery), and organics (polyethylene, polypropylene, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), and wood) present a wide variety of surface characteristics. They span the range of high interfacial free energy (metals and many ceramics) to low interfacial free energy (hydrocarbon polymers) surfaces [27,28],... 

The temperature and frequency dependences of depend drastically upon whether a polymer is polar or nonpolar, i.e., whether it contains permanent dipoles or does not contain them. Nonpolar polymers (such as the hydrocarbon polymers which by definition contain only... 

Note, from inspection of Table 9.3, that the largest differences between n(exp) and l(fit) occur for the nonpolar hydrocarbon polymers which have very small or zero dipole moments. Any errors in measured and/or fitted and n values are amplified when the very small difference (Pll - Rll) ks calculated for such polymers. The agreement between n(exp) and ja(fit) is far better for polymers containing polar groups, whose (Pll - Rll) ls larger. For example, if the 11 hydrocarbon polymers are excluded from the comparison between fl(exp) and p(fit), then for the 29 remaining polymers, all of which contain heteroatoms, the standard deviation is only 0.0790 debyes, and the correlation coefficient is 0.9684. The standard deviation is only 11.4% of the average fl(exp) value of 0.6903 debyes for these polymers, which really should manifest polarity and have nonzero dipole moments. 

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