Carboxylic acids highly branched structures

As noted in Section 6.5.2, the hydrolysis resistance of latex films from emulsion polymers prepared from the vinyl acetate (VA) monomer is marginal for ontdoor use. In Europe and recently in the United States, vinyl versatate (II) (Ri = —CH2CH2CH2CH2CH2CH2CH3 and R2 = R3 = —CH3) has been introduced for use along with vinyl acetate for improved outdoor performance of latex coatings. Vinyl versatate is the vinyl ester of versatic acid, a 10-carbon carboxylic acid of the highly branched structure sometimes called neo ... 

Another highly effect chain extender is trimellitic anhydride (TMA) which gives rise to branching of the PET structure. Note that the multifunctional epoxies (see Table 14.2) react quickly with the terminal carboxylic acid groups of PET but can also react with the film former and the silane coupling agent on glass fibre reinforcements. 

One of the first hyperbranched polymers described in the literature was polyphenylenes, which were presented by Kim et al. [30-32] who also coined the term hyperbranched . The polyphenylenes were prepared via Pd(0) or Ni(II) catalyzed coupling reactions of various dihalophenyl derivatives such as di-bromophenylboronic acid. The polymers were highly branched polyphenylenes with terminal bromine groups which could be further transformed into a variety of structures such as methylol, lithiate, or carboxylate (Fig. 5). 

Lactones are normally stable compounds, which have found ample application as synthetic intermediates, and, quite recently, have been detected as the central structural unit in physiologically active natural products like obaflorin (123) and lipstatin (124). Characteristic applications of 3-lactones in synthesis are the stereospecific CO2 elimination to form di- and tri-substituted alkenes (e.g. from 125 equation 40) or Grignard addition to the carbonyl group e.g. equation 41). Particularly useful is the formation of 3-lactone enolates (126), which react with a variety of electrophiles (EX) wiA high stereocontrol (equation 42). Organocuprates may be used in chain elongations to form 3-branched carboxylic acids (equation 43). ... 

Fulvic acids. Marine sedimentary humic substances soluble in base and acid (fulvic acids) have previously been examined by and NMR (12). The dominant structural components were postulated to be polysaccharide - like substances, probably polyuronic acids. Solid-state NMR spectra of fulvic acids isolated from a number of marine and estuarine sediments are shown in Figure 1. Major peaks at 72 and 106 ppm betray the overwhelming presence of polysaccharide -like substances, and, as shown by Hatcher and others (12.), the moderate peak for carboxyl or amide carbon at 175 ppm suggests that these polysaccharides are more like polyuronides. Aromatic carbons (110 to 160 ppm) are decidedly minor components. Aliphatic carbons (0-50 ppm) are also minor components. H NMR spectra shown by Hatcher and others (12) indicate that these aliphatic structures are highly branched. 

Humic acids of marine and estuarine sediments are characterized by major amounts of paraffinic structures that previous studies have shown to be highly branched and to contain significant quantities of carboxyl/amide and alcohol/ether carbon. Some humic acids, namely those from well preserved sapropelic marine sediments show significant quantities of carbohydrate-like structures incorporated. This, no doubt, is a reflection of the solubility characteristics of polysaccharides which may have some carboxyl functionalities (uronic acid groups). 

Yakubchik and his co-workers (1956, 1959 and 1962) have preferred to separate the acid derivatives by means of partition chromatography and compared the results with those obtained from an artificial mixture of those acids expected to be present. In the case of Ziegler-Natta catalyzed polybutadienes with less than 1% 1,2- units the presence of 1,4-1,2-1,4 sequences was indicated by the identification of some 1,2,4-butane tricarboxylic acid. Examination of their chromatograms suggests, at most, just a trace of any hexane tetra-carboxylic acid so that only a very small amount, if any, of 1,4-1,2-1,2-1,4 structures were present. Furthermore, no trace of any 1,2,3-propane tricarboxylic acid was found so there was no positive sign of any branching at the a-methylene position. On the other hand in the case of rubidium-catalyzed poly butadienes, which, like other polybutadienes prepared by the use of alkali metal catalyst systems, have a high 1,2- content, both hexane tetracarboxylic acid and 1,2,3-propane tricarboxylic acid were present in the ultimate products of ozonolysis. 

Star polymers may be considered to be highly branched polymers that have linear chains radiating out from a central area. This area may be one atom, a small molecule, or a "core". The "core" is a quasi-spherical structure as opposed to a linear structure that would be present in a conventional comb or branched polymer. An early example of stars made from small molecules is the star polymer of Schaefgren and Flory (1) who polymerized E-caprolactam in the presence of a tetrafunctional or octafunctional carboxylic acid to produce polymers that have 4 or 8 arms radiating out from a central molecule. Other examples use the coupling of "living" anionically polymerized polystyrene with silicone tetrachloride (2) or chloromethyl-benzene (3). Recent work in this area includes that of Fetters (4) who has made 12 and 18 arm stars with this general technique. 

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