Molecular chains trimerization

PFSA membrane is better connected than that in Nafion. This signature of better coimectivity of aqueous domains in SSC at intermediate hydration level shown for the small molecular weight chains (trimers), is also observed for the simulations of the chains composed of 15 repeat units as depicted in Fig. 10. In Fig. 9(c), the high value of Ro (4.5 A) has shifted all the curves to larger cluster sizes. Still, where there is a difference between the two polymer electrolytes, SSC PFSA membrane shows a more connected aqueous domain. 

Figure 4.16. Simplified molecular orbital diagram for a chain trimer.

The minor products are generally 1-3% of the total yield and arose from (a) side-chain fragmentation producing hydrogen and low-molecular-weight hydrocarbons (b) addition of these fragments to the free olefin (c) dimerization and trimerization of the free olefin (d) fragmentation of the alkyl radical and cation intermediates. 

When catalyzed by acids, low molecular weight aldehydes add to each other to give cyclic acetals, the most common product being the trimer. The cyclic trimer of formaldehyde is called trioxane, and that of acetaldehyde is known as paraldehyde. Under certain conditions, it is possible to get tetramers or dimers. Aldehydes can also polymerize to linear polymers, but here a small amount of water is required to form hemiacetal groups at the ends of the chains. The linear polymer formed from formaldehyde is called paraformaldehyde. Since trimers and polymers of aldehydes are acetals, they are stable to bases but can be hydrolyzed by acids. Because formaldehyde and acetaldehyde have low boiling points, it is often convenient to use them in the form of their trimers or polymers. 

Techniques were developed for the dilute solution characterization of polydlchlorophosphazene. The purity of the trimer has a significant effect on oligomer formation, polymerization time and polymer MW and MWD. The polymers prepared in this study have high molecular weights and broad molecular weight distributions and probably have similar, if not identical, chain structures. 

The size of the polymer molecules increases at a relatively slow rate in step polymerization compared to chain polymerization due to the lower rate constants in the former since k is of the order of 10 3-10 liter/mole-sec. One proceeds slowly from monomer to dimer, trimer, tetramer, pentamer, and so on until eventually large polymer molecules have been formed. Any two molecular species containing respectively the two different functional groups can react with each other throughout the polymerization. The average size of the molecules increases slowly with time and high molecular weight polymer is not obtained until near the very end of the reaction (i.e., above 95% conversion). ... 

The usual alkali employed is lime. The raw material for gelatine is tropocollagen, which is present in the original hides or bones. This protein consists of three polypeptide chains arranged in a triple helix. In contrast, gelatine consists of several free or interassociated chains, ranging in molecular weight from around ten thousand to several hundred thousand. On extraction, monomers (a-chains MW 100 000), dimers (P-chains) and trimers ( -chains) and some lower order peptides are released. 

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