Polymer oligomers

Reactions involving alkoxy- or aryloxyphosphines with amines might also be expected to yield phosphazane oligomers/polymers. However, PhP(0Ph)2 with 1,2-(NH2)2c6Hit produced only the Arbuzov type rearrangement product CgHi, (NH) 2P(0)Ph. 

Species present during polymerization Monomer, polymer and propagating chains (at very low concentration) Monomer, dimer, trimer, oligomer, polymer... 

U. Scherf and K. Mullen, Design and synthesis of extended TT-systems monomer, oligomers, polymers, Synthesis. 23-38, 1992. 

Brunelle, D. J. and Serth-Guzzo, J. Titanate-catalyzed ring-opening polymerization of cyclic phthalate ester oligomers, Polym. Prep., 40(1), 566 (1999). 

Despite the vast quantity of data on electropolymerization, relatively little is known about the processes involved in the deposition of oligomers (polymers) on the electrode, that is, the heterogeneous phase transition. Research - voltammetric, potential, and current step experiments - has concentrated largely on the induction stage of film formation of PPy [6, 51], PTh [21, 52], and PANI [53]. In all these studies, it has been overlooked that electropolymerization is not comparable with the electrocrystallization of inorganic metallic phases and oxide films [54]. Thus, two-or three-dimensional growth mechanisms have been postulated on the basis that the initial deposition steps involve one- or two-electron transfers of a soluted species and the subsequent formation of ad-molecules at the electrode surface, which may form clusters and nuclei through surface diffusion. These phenomena are still unresolved. 

Recent work on the synthesis, structure and some properties of macromolecules bearing furan rings is discussed. Two basic sources of monomers are considered, viz. furfural for monomers apt to undergo chain polymerization and hydroxymethylfurfural for monomers suitable for step polymerization.Within the first context, free radical, catiomc and anionic systems are reviewed and the peculiarities arising from the presence of furan moieties in the monomer and/or the polymer examined in detail. As for the second context, the polymers considered are polyesters, polyethers, polyamides and polyurethanes. Finally, the chemical modification of aU these oligomers, polymers and copolymers is envisaged on the basis of the unique reactivity of the furan heterocycle. 

A mechanism for explaining how oligomeric and polymeric forms of a protein or polypeptide can arise by three-dimensional swapping of internal domains in monomers. The basic idea is that a protein s ternary structure is stabilized by the contacts between its domains, and under certain circumstances, the domains of several polypeptide chains may bind in a way that gives rise to nonphysiologic oligomers, polymers, and aggregates. 

When bidentate solvents are present, the clusters may crystallize forming linear polymers by linking clusters together, as in complexes 292-295. This further diminishes solubility and reactivity of the alkyllithium compound, making the unassociated RLi species the most probable reactive form in synthetic processes. MeLi dissolved in diethoxymethane shows at room temperature a single Li NMR peak, that resolves into four distinct peaks at —80°C, pointing to temperature-dependent monomer/oligomer/polymer equilibria . 

Lee CW, Do Chung J (2009) Synthesis and biodegradation behavior of poly(ethylene terephthalate) oligomers. Polymer (Korea) 33 198-202... 

For instance, it has been shown for PEO (oligomer) — PMA (polymer) interaction that the reaction heat calculated per monomer unit does not depend on the DP of the oligomer26). Then the probability of oligomer-polymer association is... 

Controlled single-stage carboalumination of 1-alkenes by using a zirconocene catalyst can be achieved selectively and in high yields without the production of unwanted oligomers, polymers, and hydrometallation products in significant yields. 

Depurination, or hydrolysis of the N-glycosidic bond, occurs for both RNA and DNA strands (oligomers/polymers) or analogs (monomers). RNA is much less prone to depurination than DNA as a result of the inductive effect of the 2 -OH group (180). Acid-catalyzed depurination is illustrated in Figure 129. 

K. I. Kanno and K. Hatanaka, Synthesis of l,6-anhydro-4-0-benzyl-2-deoxy-3-0-p-methoxybenzoyl-2-phthalimido-/ -D-glucopyranose and its oligomer, Polym. J. (Tokyo), 30 (1998) 678-680. 

---