AB-Type

For monomers of the AB type, reactions (5.CC) and (5.DD) become AB -> and 2AB AbaB, respectively. If kj. and k are the respective rate constants for these reactions, derive an expression which gives the ring to linear ratio in the product as a function of AB concentration and the two rate constants. Criticize or defend the following proposition To obtain a test of Eq. (5.47) without the complications of intramolecular condensations, a series of otherwise identical polymeriztion reactions could be carried out on monomer mixtures at different concentrations. By... 

Synthesis and Properties. Polyquinolines are formed by the step-growth polymerization of o-aminophenyl (aryl) ketone monomers and ketone monomers with alpha hydrogens (mosdy acetophenone derivatives). Both AA—BB and AB-type polyquinolines are known as well as a number of copolymers. Polyquinolines have often been prepared by the Friedlander reaction (88), which involves either an acid- or a base-catalyzed condensation of an (9-amino aromatic aldehyde or ketone with a ketomethylene compound, producing quinoline. Surveys of monomers and their syntheses and properties have beenpubhshed (89—91). 

Fig. 1. Effect of amide frequency on the melting points of AB-type (x ) and AABB-type ( ) polyamides. The numbers on the curves indicate the specific...

Property Polystyrene (PS) Poly(styrene-i) (j-acrjio-nitrile ) (SAN) Glass-fil led PS High impact PS HIPS Acrylonitrile— butadiene—styrene terpolymer (ABS) Type 1 Type 2 Standard ABS Super ABS... 

The common synthetic route to bismaleimides or maleimide functionalized oligomers is the condensation of diamines or amino-terminated oligomers with maleic anhydride. Another possibiUty is the use of an AB-type monomer of the following general formula to build the polymaleimide, where X represents a functional group that can be employed in condensation reactions. 

Figure 16.13. Variation in impact strength against concentration of rubber in ABS Type 1 blends"...

There has also been a demand in recent years for an ABS-type material with an enhanced heat distortion temperature. In ABS polymers this is largely controlled by the Tg of the resin or glassy component. Consequently three approaches to raising the distortion temperature have been developed. They... 

The first approach has been important commercially. The monomer most commonly used is a-methylstyrene (see Section 16.11), whose polymer has a Tg of about 120°C. The heat distortion temperature of the resultant-ABS type polymer will depend on the level of replacement of styrene by the a-methyl-styrene. (It may be noted in passing that a-methylstyrene-acrylonitrile binary copolymers have been available as alternatives to styrene-acrylonitrile materials but have not achieved commercial significance.)... 

Blending of ABS with other polymers is not restricted to the aim of raising the distortion temperature. Blends with PVC are made for various purposes. For example, 80 20 ABS/PVC blends are used to produce fire-retarding ABS-type materials, as already mentioned, while 10 90 blends are considered as impact-modified forms of unplasticised PVC. ABS materials have also been blended with plasticised PVC to give a crashpad sheet material. 

Blending of ABS with an acrylic material such as poly(methyl methacrylate) can in some cases allow a matching of the refractive indices of the rubbery and glassy phases and providing that there is a low level of contaminating material such as soap and an absence of insoluble additives a reasonable transparent ABS-type polymer may be obtained. More sophisticated are the complex terpolymers and blends of the MBS type considered below. Seldom used on their own, they are primarily of use as impact modifiers for unplasticised PVC. 

As previously described, all microspheres discussed in this chapter were synthesized from AB type diblock copolymers. Precursor block copolymers, poly(styrene-b-4-vinyl pyridine) (P[S-b-4VP]) diblock copolymers, were synthesized using the additional anionic polymerization technique [13]. The basic properties of the block copolymers were determined elsewhere [24,25] and are listed... 

In three dimensions, Ohta and Kurokawa [32] reported that a BCC arrangement was only slightly more favored than the FCC arrangement. In fact, many BCC structures have been reported for AB type block copolymers and the blends of homopolymer-block copolymer systems [27,33-35]. However, the lattice structure of the core-shell type polymer microspheres was FCC. This FCC formation resulted in the lower viscosity of... 

The chain arrangement of this morphology was schematically proposed as in Fig. 10. The cell of the microsphere has a hexagonal surface, and the AB diblock copolymers form a bilayer between the microspheres. From this schematic arrangement, the optimal blend ratio of the AB block copolymer in this system was calculated as 0.46. This value was very close to the blend ratio of the AB type block copolymer 0.5 at which the blend showed the hexagonal packed honeycomb-like structure. 

The morphology obtained from the blend of the core-shell type microspheres and AB type block copolymers with spherical morphology is shown next [37]. Figure 12 shows the typical morphologies of the blend ob-... 

Vinyl polymerization initiated by macroinitiator yield AB, ABA, or (AB) types block copolymers. Macroinitiators such as macrobis peroxides, polyazoesters, and... 

Attempts to determine the equilibrium constant for Equation (60), applying the method proposed by Fialkov [313] for an AB2 = A+2B type interaction, provided values that defy physical logic. This means that the equilibrium in Equation (60) shifts almost completely to the left, and that it is also disturbed by A + B = AB type interactions [313], which, in this case, correspond to the interaction F" + TaFs = TaF6". Due to the improbability of the presence of TaF5 in the melts, it makes more sense to attribute the TaFg ions to the equilibrium described in Equation (61), which provides an analogical effect on the additive values of the property. 

Polyester block copolymers can be defined as (AB) -type alternating multiblock copolymers composed of flexible aliphatic polyester or polyether blocks (A-type blocks) and rigid high-melting aromatic-aliphatic polyester blocks IB-type blocks) (Formula 2.2). 

PAs can be divided into polymers synthesized from diamines and diacids, called AA-BB-type polymers as in (3.1) and polymers based on amino acids, called AB-type polymers as in (3.2) ... 

The AB polyamides are made from either >-amino acids or cyclic lactams, derivatives of the oj-amino acids (Table 3.1). In these polymers, the amino and acid groups are inherently balanced and the polymer also contains one amino and one acid endgroup. There are a number of different routes available for polymerizing these AB-type polyamides ... 

The most important AB-type PA is PA-6, having six carbon atoms in the repeat unit and therefore five methylene groups. In addition to PA 6, PA-11 and PA-12 are also commercially available. The synthesis of many AB-type PAs, PA-1 to PA-22, have been studied,5,6,12,28 but the quality of the resultant polymers is highly dependent on the purity of the starting materials. 

Scheme 6.5 Friedel-Crafts sulfonylation of AA-BB and AB types of polycondensations.

AB-type polycondensations, 330 AB-type polymers, 135 Accelerated weathering tests, 245 Acceptor-catalytic polyesterification, 75 4-Acetoxy benzoic acid, poly esterification of, 74... 

Alcohols, reaction of isocyanates with, 224-225 Alcoholysis, 69 Alicyclic dianhydrides, 297 Alignment coating, for liquid crystal devices, 269-270 Aliphatic AA-BB-type polyamides, synthesis of, 164-173 Aliphatic AB-type polyamides, 173-180 Aliphatic acids, 60... 

The Wittig-Horner procedure, starting from bisphosphonate or aromatic bisphosphine oxide monomers, allows for AA/BB-coupling of the PO-activated bismethylene monomers, not only with aromatic dialdehydes but also with aromatic diketones to the corresponding PPV derivatives (76), and for the selfcondensation of AB-type aromatic starting compounds containing both alde-hyde/keto and PO-activated methylene functions [101]. 

The synthesis of a PPV derivative, 94, with donor (di-n-hexylamino) and acceptor (nitro) substituents attached regioselectively to the PPV backbone, was published by Yu et al. following the Heck-type cross coupling approach [118] starting from an AB-type monomer (95). The red-orange polymer (94), which is soluble in THE, chloroform and 1,2-dichloroethane, displays a number-average molecular weight M of about 12,000. 

Two intact units of acetate were incorporated into neosaxitoxin as evidenced by the appearance of two sets of AB type signals in the C-NMR spectrum. The orientation of the incorporated acetate units was determined by feeding [2- Cjacetate as shown in Scheme 2. This result clearly excludes the original pathway in which C-5 should come from C-1 of arginine. 

As early as 1952, Flory [5, 6] pointed out that the polycondensation of AB -type monomers will result in soluble highly branched polymers and he calculated the molecular weight distribution (MWD) and its averages using a statistical derivation. Ill-defined branched polycondensates were reported even earlier [7,8]. In 1972, Baker et al. reported the polycondensation of polyhydrox-ymonocarboxylic acids, (OH)nR-COOH, where n is an integer from two to six [ 9]. In 1982, Kricheldorf et al. [ 10] pubhshed the cocondensation of AB and AB2 monomers to form branched polyesters. However, only after Kim and Webster published the synthesis of pure hyperbranched polyarylenes from an AB2 monomer in 1988 [11-13], this class of polymers became a topic of intensive research by many groups. A multitude of hyperbranched polymers synthesized via polycondensation of AB2 monomers have been reported, and many reviews have been published [1,2,14-16]. 

Figure 5. Acetylated RG-I helices generated from the low-energy conformations of the disaccharides (see Figures 2 and 3). Left the AA type with n = -3 and h = 6.75 A right the AB type with n = 2 and h = 7.48 A.

Analytes from class AB can self-associate through the hydrogen bonds and, hence, under mild chromatographic conditions, they can participate in the self-associative lateral interactions of the AB. .. AB type. Moreover, they can participate in the mixed lateral interactions of three different types (AB. .. A, AB. .. B, and AB,. ..AB2). 

Self-associative lateral interactions can only occur with the AB-type analytes, chromatographed in sufficiently mild chromatographic conditions. In planar chromatography, this type of lateral interaction was first demonstrated on monocarboxylic fatty acids and a,co-dicarboxylic acids, chromatographed on microcrystalhne cellulose with aid of decalin and 1,4-dioxane as monocomponent eluents, respectively [8,20,23]. 

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