Polymeric hydrogen acceptor reactions

Because almost any diacid can be leaddy converted to the acid chloride, this reaction is quite versatile and several variations have been developed. In the interfacial polymerization method the reaction occurs at the boundary of two phases one contains a solution of the acid chloride in a water-immiscible solvent and the other is a solution of the diamine in water with an inorganic base and a surfactant (48). In the solution method, only one phase is present, which contains a solution of the diamine and diacid chloride. An organic base is added as an acceptor for the hydrogen chloride produced in the reaction (49). Following any of these methods of preparation, the polymer is exposed to water and the acid chloride end is converted to a carboxyhc acid end. However, it is very difficult to remove all traces of chloride from the polymer, even with repeated washings with a strong base. 

Association Complexes. The unshared electron pairs of the ether oxygens, which give the polymer strong hydrogen bonding affinity, can also take part in association reactions with a variety of monomeric and polymeric electron acceptors (40,41). These include poly(acryhc acid), poly(methacryhc acid), copolymers of maleic and acryflc acids, tannic acid, naphthoHc and phenoHc compounds, as well as urea and thiourea (42—47). 

Although alcohols can be fluorinated directly with selenium tetrafluoride, yields can be disappointing because of rearrangement/polymerization due to the presence of hydrogen fluoride produced during the reaction. Higher yields have been obtained when the reaction is performed in the presence of 1 equivalent of pyridine, which forms a 1 1 donor-acceptor complex with selenium tetrafluoride. The reaction proceeds in two distinct steps first is the reaction of the alcohol with the complex to form an alkoxyselenium trifluoride, the second is the thermal decomposition to the alkyl fluoride. 

The proton transfer reaction, in which no C —C bond but instead a C-H bond is formed, is known to be an important follow-up reaction of the exciplex when the donor or the acceptor possesses active hydrogen atoms. It proceeds in the intimate radical ion pairs or between the radical ions. The first charge-transfer, followed by proton transfer, produces two free radicals, which may initiate polymerizations or lead to addition products. Lewis [84] has recently reviewed this reaction. 

A typical interfacial system employs an aqueous solution of one reactant, such as a diamine, and an organic solution of the other reactant, such as a bifunctional acid chloride. In this case the aqueous phase would also include an acid acceptor. In most such polymerizations the polymer is formed on the organic side of the interface, of course. The interface may function primarily in controlling the diffusion of the diamine into the immediate polymerization zone. The aqueous phase is a carrier for the diamine and a stronger base to neutralize the evolved hydrogen chloride, and aids in removing hydrogen chloride from the reaction zone. The acid chloride will normally have little solubility in the aqueous phase, while the... 

Polycarbonates from bisphenols (Equation 2) have reached commercial importance. They may be made by several methods, including both low- and high-temperature procedures (16). A recently constructed plant for the preparation of the polycarbonate from Bisphenol A [2,2-bis(4-hydroxyphenyl) propane] is reported to use phosgene in a low-temperature process (2). The reaction is carried out in a single solvent for the reactants and polymeric product. Pyridine is used as the acceptor for by-product hydrogen chloride. 

Reactive impurities are substances that can react with the monomers, the growing chain-ends, or the acid acceptor to terminate the polymerization prematurely. They can be introduced with the solvent or with the intermediates. The acid chloride may contain impurities originating in its synthesis or storage such as hydrogen chloride, thionyl chloride, phosphorus halides, or monoacid halides. The diamine may contain monoamines, water, or carbonates. It may degrade oxidatively in air or absorb moisture and carbon dioxide. The degree of interference caused by these impurities depends on both the quantity of the impurities as well the relative reaction rates of the desired polymerization vs. those of the impurities. 

Combinations of donor/acceptor systems, comprised of at least one multifunctional monomer, are actually capable of sustaining rapid fi ee-radical polymerization without external photoinitiators. Donor monomers can be vinyl ethers, N-vinylformamides, and N-vinylalkylamides. The acceptor monomers are maleic anhydride, N-arylmaleimides, N-alkylmaleimides, dialkyl maleates, and dialkyl fumarates. N-alkylmaleimides can participate in excited state hydrogen abstraction fi om diacrylates. The reaction proceeds either in the presence or in the absence of oxygen. ... 

In general, biosensors contain a biological (usually polymeric) entity in the recognition environment of the sensor [166, 167]. Enzymes are the most frequently used biomodifiers, in particular, such ones that catalyze oxidation or reduction reactions (oxidoreductases), that is, oxidases and dehydrogenases, when the former ones exploit oxygen as the electron acceptor with consequent reduction to hydrogen peroxide or water. 

Butadiene and other olefinic compounds polymerize in anhydrous liquid hydrogen fluoride or undergo rearrangement reactions. While aliphatic saturated hydrocarbons are usually insoluble, aromatic hydrocarbons are soluble and capable of accepting a proton23-25 Acetic acid and even trifluoroacetic acid act as proton acceptors in liquid hydrogen fluoride ... 

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