Oligomers, polyether

Other backbone stmctures that have generated a great interest are the polyether ketones. An attempt was made to synthesize amino-terminated arylene ether ketones, which were subsequendy converted into the corresponding maleinhde-terrninated oligomers (26). The aim of this approach was to obtain tough, solvent-resistant, high temperature thermosets. 

Liquid organic rubbers with reactive functionality can be prepared by several methods. End-functional oligomers are preferred. Chains attached to the network at only one end do not contribute as much strength to the network as those attached at both ends [34], Urethane chemistry is a handy route to such molecules. A hydroxy-terminated oligomer (commonly a polyester or a polyether) can be reacted with excess diisocyanate, and then with a hydroxy methacrylate to form a reactive toughener [35]. The methacrylate ends undergo copolymerization with the rest of the acrylic monomers. The resulting adhesive is especially effective on poIy(vinyl chloride) shown in Scheme 2. 

In the absence of any added salts, the distribution of adducts formed was found to be variable by ESI—MS. In general, however, the lower molecular weight surfactant oligomers showed a preference for the Na+ adduct, whilst the higher oligomers showed an increase in preference for the K+ adduct. This is consistent with the metal-ion complexing abilities described for polyether derivatives [39,40], Simplification of the spectra was achieved with the addition of salt solutions to the mobile phase, as shown for NH4C1 in Fig. 2.8.4 [29], With the addition of salt... 

The most successful class of thermally reactive oligomers consists of the functional polymers containing either pendant or terminal triple bonds, especially ethynyl groups. This area of research was recently reviewed (2), and the more recent developments in the field of a,w-bis(ethynylpheny1) aromatic polyether sulfones were summarized in two recent papers (5,6). 

An example for the synthesis of poly(2,6-dimethyl-l,4-phenylene oxide) - aromatic poly(ether-sulfone) - poly(2,6-dimethyl-1,4-pheny-lene oxide) ABA triblock copolymer is presented in Scheme 6. Quantitative etherification of the two polymer chain ends has been accomplished under mild reaction conditions detailed elsewhere(11). Figure 4 presents the 200 MHz Ir-NMR spectra of the co-(2,6-dimethyl-phenol) poly(2,6-dimethyl-l,4-phenylene oxide), of the 01, w-di(chloroally) aromatic polyether sulfone and of the obtained ABA triblock copolymers as convincing evidence for the quantitative reaction of the parent pol3rmers chain ends. Additional evidence for the very clean synthetic procedure comes from the gel permeation chromatograms of the two starting oligomers and of the obtained ABA triblock copolymer presented in Figure 5. 

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. 

Formation of Cyclic Oligomers. Chain transfer reactions occur by intermolecular attack of oxygen from another polyether chain on the a-methylene carbons of the oxonium ion. In an intramolecular attack a distant oxygen of the growing polymer chain itself attacks the a-methylene position of its oxonium center. 

Copolymers of methacrylic add and ethylene termed as ethylene ionomers have been used as the base polymer for binding alkali, alkaline earth and transition metal ions. Organic amines such as n-hexylamine, hexamethylene tetraamine, 2,2,6,6-tetramethyM-hydroxy piperazine, ethylene diamine and polymeric diamines such as silicone diamine, polyether diamine and polymeric diamines such as silicone diamine, polyether diamine and polyamide oligomers considerably enhance the complex formation characteristics of Zn(II) ethylene ionomers thereby enhancing the physico-chemical properties [13]. 

The application of perfluorous polyethers in biphasic catalysis was first described by Vogt (133), who also synthesized ligands based on hexafluor-opropene oxide oligomers to create metal complexes that are soluble in the perfluorous polyethers. The solvophobic properties of the fluorous solvent were successfully incorporated in the metal complexes catalytic oligomerization and polymerization reactions with nickel and cobalt complexes were demonstrated. 

Reaction of 91 with methacrylic acid gives rise to double unsaturated side-chain compounds (93) these were subjected to polymerization.185 Subjecting isosorbide to etherification with a, m-dihaloalkanes, mono- and dialkyl derivatives were obtained. These could not be transformed into polyethers. The use of tram-1,4-dichlorobutene lead to oligomers up to the... 

The reactive oligomer can be any low-molar-mass polymer containing at least a couple of double bonds. It can be based on a polyester, polyether, or polyurethane backbone. One mole of a, oo-OH-terminated polyester or polyether is prereacted with two moles of acrylic acid to obtain an a, oo-diacrylate oligomer. For polyurethanes, 1 mole of a, m-diisocyanate oligomer is prereacted with 2 moles of hydroxyethylacrylate (Sec. 2.2.3c). 

As a second example, there is a wide variety of breakdown products and oligomeric products that may be formed from the reactive monomers that are the building blocks of plastics. For plastics, the general assumption has been that any side-reaction products and breakdown products are likely to be significantly less toxic than the monomers, and so restricting the migration of the monomer was accepted as an indirect way to limit any hazard from the oligomers also. Whilst this approach is probably acceptable for addition polymers, such as those made from the unsaturated monomers vinyl chloride, butadiene and acrylonitrile where the unsaturated monomer is far more noxious than their products, the validity of this means of indirect control is questionable for condensation polymers such as polyesters and for polyethers formed from epoxide monomers. 

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