Donor acceptor copolymers

Table 7.4 lists the Q and e values for an assortment of common monomers. The extremes in the column of e values in Table 7.4—which are listed in order-quantify the range of donor-acceptor properties which is used as the basis for ranking in Fig. 7.2. The Q values perform a similar ranking with respect to resonance effects. The eight different Q-e combinations in Table 7.4 allow the estimation of ri and values for 28 different copolymers. Of course, in these systems Q and e values were assigned to give the best fit to r values which had already been measured. As an illustration of the predictive values of the Q-e scheme, consider the following example ... 

The radical-catalyzed polymerization of furan and maleic anhydride has been reported to yield a 1 1 furan-maleic anhydride copolymer (89,91). The stmcture of the equimolar product, as shown by nmr analyses, is that of an unsaturated alternating copolymer (18) arising through homopolymerization of the intermediate excited donor—acceptor complex (91,92). 

Alternating copolymers of chloroprene have been prepared from a number of donor acceptor complexes in the presence of metal haUdes. 

Numerous reports of comparable levels of success in correlating adhesion performance with the Scatchard-Hildebrand solubility parameters can be found in the literature [116,120-127], but failures of this approach have also been documented [128-132J. Particularly revealing are cases in which failure was attributed to the inability of the Scatchard-Hildebrand solubility parameter to adequately account for donor-acceptor (acid-base) interactions [130,132]. Useful reviews of the use of solubility parameters for choosing block copolymer compatibilizers have been prepared by Ohm [133] and by Gaylord [134]. General reviews of the use of solubility parameters in polymer science have been given by Barton [135], Van Krevelen [114], and Hansen [136]. 

Free radical alternating 1 1 copolymerization of donor-acceptor monomer systems has been known for quite some time. Linear copolymers from donor-acceptor systems... 

Copolymerization, on the other hand, is very easy with maleic anhydride. It copolymerizes by a free-radical reaction with a wide variety of monomers and many of the copolymers are perfectly alternating. This tendency of MA to form alternating copolymers derives from the participation of a donor-acceptor complex formed by the two reacting monomers. The term is used to describe... 

Like the vinyl ethers, isopropenyl acetate does not readily form homopolymers by free radical initiation. It does participate in the donor-acceptor mode of polymerization with maleic anhydride and the copolymer was made by free radical polymerization (see Table III). When attempts were made to measure molecular weight by GPC using THF as a solvent on STYRAGEL columns, the polymer did not elute. Therefore, viscosity in acetone at 30"C was used as a measure of molecular size changes on irradiation. The changes on exposure... 

The second type of nonideal models takes into account the possible formation of donor-acceptor complexes between monomers. Essentially, along with individual entry of these latter into a polymer chain, the possibility arises for their addition to this chain as a binary complex. A theoretical analysis of copolymerization in the framework of this model revealed (Korolev and Kuchanov, 1982) that the statistics of the succession of units in macromolecules is not Markovian even at fixed monomer mixture composition in a reactor. Nevertheless, an approach based on the "labeling-erasing" procedure has been developed (Kuchanov et al., 1984), enabling the calculation of any statistical characteristics of such non-Markovian copolymers. 

It was further indicated that copolymerization of two monomers which were close together in the donor-acceptor series gave a random copolymer, while monomers which were well separated in the series had a marked tendency to give an alternating copolymer. 

The diradical nature of the intermediate in the copolymerization of monomers through a charge transfer intermediate has been suggested by Zutty et al. (88) as a result of studies on the copolymerization and terpolymerization of monomer systems containing bicycloheptene and sulfur dioxide. The third monomer apparently enters the copolymer chain as a block segment, while the donor-acceptor monomer pair enter the chain in a 1 1 molar ratio, irrespective of the ratio present in the monomer mixture. 

In the recent miscibility studies with a-methyl styrene/acrylonitrile copolymer and a a-methyl styrene/methyl methacrylate/acrylonitrile terpolymer (8), it was found that almost all miscible second components contain amides, imides, nitriles, or esters, each of which contains lone-pair electrons capable of donor-acceptor complexation—a state which... 

Schneider HA, Cantow HJ, Percec V. (1982) Donor-acceptor complexation in macromolecu-lar systems. 1. Viscoelastic properties of polydonor-polyacceptor blends and of corresponding copolymers. Polym. Bull. (Berlin, Germany) 6 617-621. 

Alkylaluminium chlorides form complexes with methyl acrylate which can react with styrene yielding alternating copolymers [164], The donor-acceptor complex of acrylonitrile (donor) and potassium persulphate (acceptor) makes possible the homopolymerization of acrylonitrile in polar media (in water, dimethylformamide, dimethylsuphoxide, dioxan) at low temperatures [165]. The initiating radicals are formed according to the scheme... 

When a monomeric donor of suitable structure is encountered by a monomeric acceptor, a donor-acceptor (DA) complex is formed. It is characterized by a reorganized electron structure accompanied by charge shift. Therefore such formation are also designated as charge-transfer (CT) complexes. Until recently, the tendency to the formation of alternating copolymers has been ascribed to a special kind of monomer reactivity and of the resulting... 

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