Short-side-chain polymers

Figure 10b. Effect of conversion from precursor to sulfonic acid and sodium sulfonate on the dynamic mechanical behavior of the short-side chain polymer with equivalent weight of 800. Continued on next page.

The short side-chain polymer PVII-Cl produced over a 9 fold increase in the rate due primarily to the electrostatic interaction. By far the most efficient catalyst studied is the long side-chain polymer, PVII-C16, which combines both electrostatic and hydrophobic interactions to yield over a 45 fold increase in the reaction rate. 

The short side chain branching frequency is inversely proportional to polymer crystallinity. Short branches occur at frequencies of 2—50 per 1000 carbons in chain length their corresponding crystallinity varies from 35 to 75%. Directiy proportional to the polymer density, crystallinity can be calculated by the following formula,... 

The more recently developed so-called linear low-density polyethylenes are virtually free of long chain branches but do contain short side chains as a result of copolymerising ethylene with a smaller amount of a higher alkene such as oct-1-ene. Such branching interferes with the ability of the polymer to crystallise as with the older low-density polymers and like them have low densities. The word linear in this case is used to imply the absence of long chain branches. 

Short alkoxy side-chain polymers are water sensitive, but polymers with long alkyl chains are stable in water, presumably due to the ability of the long alkyl chains to wrap around the core and protect the sensitive Si-O functionality.188 189 These polymers also showed UV absorption maxima red-shifted about 22 nm relative to their... 

Strictly speaking, the term polyester ought to refer to a chemical compound containing many ester groups in each molecule. In practice, however, it usually refers to polymeric materials containing ester groups as major structural components of the main chains of the macromolecules of which the polymer is composed, and this is the sense in which it is used here. The term is not now usually applied to polymers that contain ester groups attached to the main chain either directly, as in cellulose triacetate, poly(vinyl acetate) or poly(methyl acrylate), or within short side-chains. 

For instance, the Dow experimental membrane and the recently introduced Hyflon Ion E83 membrane by Solvay-Solexis are "short side chain" (SSC) fluoropolymers, which exhibit increased water uptake, significantly enhanced proton conductivity, and better stability at T > 100°C due to higher glass transition temperatures in comparison to Nafion. The membrane morphology and the basic mechanisms of proton transport are, however, similar for all PFSA ionomers mentioned. The base polymer of Nation, depicted schematically in Figure 6.3, consists of a copolymer of tetrafluoro-ethylene, forming the backbone, and randomly attached pendant side chains of perfluorinated vinyl ethers, terminated by sulfonic acid head groups. °... 

The use of rubber for sports balls and for waterproofing fabric had been noted by Christopher Columbus in his voyages to America, but the results had not been satisfactory (Asimov 1989). Natural rubber is a polymer of the isoprene molecule (CsHs) with molecular weight in the order of 200,000, and consists of thousands of chains with short side chains. 

With these three different examples it has been demonstrated that the systematics observed for the polymorphism of m-l.c. s is also valid for the side chain polymers, provided that a flexible spacer connects the rigid mesogenic moieties to the polymer main chain. Deviations from this behavior are observed, when the mesogenic moieties are directly linked to the backbone. Under these conditions, normally no liquid crystalline behavior is to be expected, according to the model considerations mentioned in Chap. 2.1. Some examples, however, proved l.c. properties for such systems, which are characterized by two striking properties Very high glass transition temperatures and only smectic structures even in case of short substituents... 

Through the addition of small amounts of propene, 1-butene, 1-hexene or 1-octene to ethylene, short side chains can be added to the main polymer chain. The word linear should be interpreted to mean the absence of chain branches. With these short side chains LLDPE has a density range from 0.900 g/cm3 for VLDPE (very LDPE) to 0.935 g/cm3 for octene-ethylene copolymer. In this field metallocene catalysts become more and more important. 

Solution Properties. Typically, if a polymer is soluble in a solvent, it is soluble in all proportions. As solvent evaporates from the solution, no phase separation or precipitation occurs. Tire solution viscosity increases continually until a coherent film is formed. Tire film is held together by molecular entanglements and secondary bonding forces. The solubility of the acrylate polymers is affected by the nature of the side group. Polymers that contain short side chains are relatively polar and are soluble in polar solvents such as ketones, esters, or ether alcohols. As the side chain increases in length the polymers are less polar and dissolve in relatively nonpolar solvents, such as aromatic or aliphatic hydrocarbons. 

When the polymer backbone contains a large number of substituents, or long side chains, it is clear that its valence band photoelectron spectrum will contain a lot of peaks each side group will bring its own fingerprint in the XPS spectrum, and the interpretation of the data will be very difficult. An example of this limitation has been found in the study of polydiacetylenes, which until now were not synthesized with sufficiently short side chains to reduce the number of bands (molecular orbitals) appearing in the valence spectrum (, 25). 

Nafion, a perfluorinated sulfonic acid (PFSA) polymer electrolyte developed and produced by the E. I. Dupont Company, has been extensively studied as a fuel cell membrane. Despite its age, it remains the industry standard membrane because of its relatively high proton conductivity, toughness and quick start capabilities. Attempts to build upon the strengths of Nafion have resulted in a class of PFSA polymer electrolytes, including the short-side-chain (SSC) PFSA polymer electrolyte, originally synthesized by Dow and now produced by Solvay Solexis. Stracturally, PFSA polymer... 

The order of decreasing viscosity is as follows C q > C12 > C14 > precursor. This order is contrary to that of fully substituted PMAS polymers (7). The decrease in viscosity in this order probably results from the decrease in side-chain miscibility with poly(dimethylsiloxane). Longer side chains, such as Ci4 side chains, are expected to phase-separate and form a more-ordered polymer compared with short side chains (Cio)- However, C12 and Ci4 side chains are not long enough to crystallize above room temperature. 

The chiral side chain polymers derived from asymmetric esters of terephthalic acid and hydroquinone can form (in a broad temperature range, including ambient temperature) an unusual mesophase (the isotropic smectic phase, IsoSm ) characterized by high transparency and optical isotropy within the visible wavelength range, combined with a hidden layered smectic ordering and some elements of helical superstructure at shorter dimensions of 10 to 250 nm. The short-pitch TGB A model seems to be the most adequate for the mesophase structure. 

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