Oligomers chemical structures

Figure 10.7 shows the photopolymerization profiles of VE functionalized urethane and silicone oligomers, in comparison with that of the divinyl ether of triethyleneglycol (DVE-3) often used as reactive diluent. The UV-cured polymers thus obtained have a low elastic modulus and can he designed for adhesive applications hy a proper choice of the oligomer chemical structure (aliphatic groups) and of its molecular weight (M < 1000 g). 

This article, while not being intended to provide a full account of poly(arylene)s, emphasises the synthetic aspects. The synthesis of conjugated oligomers and polymers is, however, always part of an interdisciplinaiy approach with their active physical function being a key concern. In that sense the research being reviewed above concentrates on physical properties rather than playing with exotic chemical structures. 

In a complementary study of the interaction between polyanilinc and ITO, oligomeric polyaniline model compounds, namely phenyl-capped amino (PC2) and imino (PC20X) dimers [113, 114] have been used. The chemical structures of the polyaniline oligomers are displayed in Figure 5-20. Both substances are soluble in... 

Glycolysis of PETP leads to oligomers that are polycondensed with eaprolaetone. The obtained diols are extended with hexamethylene diisoeyanate. In eertain conditions the polyurethanes are totally miseible with PVC, leading to acceptable meehanieal eharaeteristies for the blend. A relation between the strueture of the polyurethane and miscibility with PVC is described. The mechanical characteristics of the blend depends on the polyurethane chemical structure. 34 refs. 

Figure 6.9 Chemical structures of Chimassorb 944 oligomers. After Lattimer [37]. Reprinted from Journal of Analytical and Applied Pyrolysis, 26, R. P. Lattimer, 65-92, Copyright (1993), with permission from Elsevier...

It should be clear by the definition given so far that the carbene-analogous state is limited to molecular species. The oligomer of EX2 (EX2)n is, of course, much more stable than EX2 in every respect. It should nevertheless be noted that also the oxidation number does not change in going from the monomer to the polymer the chemical, structural, and electronic properties of these species are completely different. 

There are two different oligomer series present in all spectra. The oligomer series can be identified by calculating the masses of the end groups and assigning them to specific chemical structures (Pasch and Schrepp, 2003 Weidner et al., 2004). In the present example, the two species are the propionic amide-acid (R-am-ac) and the propionic amide-propionic amide polyamides (R-am-am-R). The use of MALDI-TOF MS as a structure-sensitive detector allows the resolution to be indirectly enhanced since several species coelute, as shown in Fig. 17.21. The polarity of the... 

Fig. 37 a Schematic diagram that illustrates the equilibrium shifting driven by folding and ligand binding. The sequences are color coded, b Chemical structure of oligomers used in the metathesis reaction... 

This study also suggests that molecular size and structure play a role in this interaction. The binding behaviors of dextrin oligomers for four different pharmaceuticals (ibuprofen, ketoprofen, furosemide, and warfarin) were observed under the same experimental conditions. Ibuprofen and ketoprofen, two compounds that are similar in chemical structure and pharmaceutical use, showed obvious differences in interaction patterns (Fig. 13A and B). Ketoprofen, having an extra aromatic ring, required an octa-saccharide (DP = 8) for binding, whereas ibuprofen required a heptasac-... 

Fig. 12. Chemical structure of maleimide-terminated imide oligomer...

The idea of synthesizing imide oligomers which carry acetylenic terminations appeared attractive because homopolymerization through acetylenic endgroups occurs without any volatile evolution and provides materials with good properties. Landis et. al (8,9) published the synthesis of such acetylene terminated imide oligomers from benzophenone tetracarboxylic anhydride, aromatic diamine and 3-ethynylaniline via the classical route. As usual, the amide acid is formed as an intermediate which, after chemical cyclodehydration, provides the polymide. Since ethynyl-terminated polyimide is used as a matrix resin for fiber composites, processing is possible via the amide acid, which is soluble in acetone, or via the fully imidized prepolymer, which is soluble in NMP. The chemical structure of the fully imidized ethynyl-terminated polyimide is provided in Fig. 44. 

The key to acetylene terminated polyimides is the availability of the end-capper which carries the acetylene group. Hergenrother (130) published a series of ATI resins based on 4-ethynylphthalic anhydride as endcapping agent. This approach first requires the synthesis of an amine-terminated amide acid prepolymer, by reacting 1 mole of tetracarboxylic dianhydride with 2 moles of diamine, which subsequently is endcapped with 4-ethynylphthalic anhydride. The imide oligomer is finally obtained via chemical cyclodehydration. The properties of the ATI resin prepared via this route are not too different from those prepared from 3-ethynylaniline as an endcapper. When l,3-bis(3-aminophenox)benzene was used as diamine, the prepolymer is completely soluble in DMAc or NMP at room temperature, whereas 4,4 -methylene dianiline and 4,4 -oxydianiline based ATIs were only partially soluble. The chemical structure of ATIs based on 4-ethynylphthalic anhydride endcapper is shown in Fig. 45. 

According to Table 1, the greater part of experimental work was devoted to particular cases of selectivity of interpolymer interactions with regard to chemical structure (reactions of substitution). From the viewpoint of a theoretical description of such reactions, two cases should be distinguished polymer—two oligomers systems and oligomer—two polymers systems. 

Resin solidification (curing) occurs by a free radical addition mechanism at the double bonds. That is why no by-products are formed. Curing compositions based on polyester resins contain a large number of different components (resins, initiators, accelerators, monomers, oligomers, fillers, etc), which may have various chemical structures, and may be used in various proportions. 

One of the principal features of the compounds discussed above is their ability to be transformed into final products and/or articles from mixtures of almost any composition, even those whose components have little compatibility. The use of oligomers and monomers of various chemical structures expands the assortment of materials and articles that can be produced by combining different components. The interest in so-called hybrid binders, interpenetrating networks, polymer-oligomer systems, and other possible reactive components has increased during recent years. 

The chemical structure of UP oligomers is more complex than might be expected from the chemistry of the reactions, Eqs. (2.13) and (2.14). The addition of hydroxyl groups to the activated double bonds is one of the most important side reactions - Eqs. (2.16) and (2.17) (Table 2.4) - called Ordelt reactions. It leads to the formation of side chains and to a modification of the COOH/OH stoichiometry due to diol consumption. 

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