Chains oligomers

Depending on the final polymerization conditions, an equilibrium concentration of monomers (ca 8%) and short-chain oligomers (ca 2%) remains (72). Prior to fiber spinning, most of the residual monomer is removed. In the conventional process, the molten polymer is extmded as a strand, solidified, cut into chip, washed to remove residual monomer, and dried. In some newer continuous processes, the excess monomer is removed from the molten polymer by vacuum stripping. 

In this synthesis, the cationic resin Amberlite IR 122 was used as catalyst. The product was isolated by high vacuum distillation at 175°, a temperature which may have also depolymerized some of the open-chained oligomers present. ... 

In a further extension to this approach, longer chain oligomers (83)-(86) have been prepared via two different methodologies, either a Cadiot-Chod-... 

The solid state conformations of macromolecular phosphazene chains can be successfully modeled using short chain oligomers. 

For short-chain oligomers the absorption maxima also depend on molecular weight, reaching a limiting value in silicon chains about 40-50 atoms in length. See ref. 17. 

V. Carlier, J. Devaux, R. Legras and D.J. Blundell, Extrapolation of short chain oligomers melting temperatures at infinite molecular weight, ]. Poly. Sci., Part B Poly. Pkys., 36 (1998) 2563-2571. 

Low molecular weight polymer (71) short chain oligomer (72)... 

PET contains about 2-3 % of short chain oligomers, which cause problems in the processing of the polymer. Oligomers can occur as linear or cyclic molecules and can be extracted by suitable solvents. Different compounds have been identified depending on the solvent and the analysis technique used [49-52], After their extraction from the polymer, oligomers will reform by thermal treatment of the extracted sample [49], and a dynamic equilibrium between polymer and oligomers has been proposed. 

Lower reactivity of short chain oligomers had already been found by Challa [41], who determined that the reaction rate for the transesterification of BHET was half that for longer molecules. Challa assumed that the reactivities of the dimer and the trimer may also be lower but was not able to verify this hypothesis. 

This equation is not intended to imply a mechanism for peptide synthesis. The equilibrium position for this reaction in an aqueous solution favors the free amino acids rather than the peptide. Therefore, both biological and laboratory syntheses of peptides usually do not involve a simple splitting out of water. Since the dipeptide of Eq. 2-11 still contains reactive carboxyl and amino groups, other amino acid units can be joined by additional peptide linkages to form polypeptides. These range from short-chain oligomers to polymers of from 50 to several thousand amino acid units, the proteins.75-77... 

The products resulting from reactions 1 and 2 are short-chain oligomers mixed with... 

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