End groups, polar

HU2 Huber, S., Hutter, N., and Jordan, R., Effect of end group polarity upon the lower critical solution temperature of poly(2-isopropyl-2-oxazoline). Colloid Polym. Sci., 286, 1653,2008.1... 

For example, the end-group polarity of 6-hydroxy-2-naphthoic acid (C—1=250°) is certainly greater than that of 6-methoxy-2-naphthoic acid (C—N=206° N—1=219°). In this case, hydrogen bonding is thought to be responsible for the nonmesogenic property of the hydroxy acid. 

Polybutenes enjoy extensive use as adhesives, caulks, sealants, and glaring compounds. They are used as plasticizers in mbber formulations with butyl mbber, SBR, and natural mbber. In linear low density polyethylene (LLDPE) blends they induce cling to stretch-wrap films. Polybutenes when modified at their unsaturated end groups with polar fiinctionahty are widely employed in lubricants as dispersants. Blends of polybutene with polyolefins produce semisoHd gels that can be used as potting and electrical cable filling materials. 

Fluorocarbons with a hydrophilic functional group are very active surfactants [23]. Less than 1% of ionic or nonionic surfactants with perfluoroalkyl groups can reduce the surface tension of water from 72 to 15-20 dyne/cm, compared with 25-35dyne/cm for typical hydrocarbon surfactants [24] Perfluoroether surfactants are about as active as their perfluoroalkyl counterparts of similar chain length [25, 26], but fluorosurfactants with more polar alkyl end groups are considerably less active than their perfluoroalkyl analogues (Table 7)... 

The presence of a large number of chain-ends in the fully synthesized dendrimer molecules makes them highly soluble and also readily miscible, for example with other dendrimer solutions. The solubility is controlled by the nature of the end-groups, so that dendrimers with hydrophilic groups, such as hydroxyl or carboxylic acid, at the ends of the branches are soluble in polar solvents, whereas dendrimers with hydrophobic end-groups are soluble in non-polar solvents. The density of the end-groups at the surface of the dendrimer molecule means that they have proportionately more influence on the solubility than in linear polymers. Hence a dendritic polyester has been shown to be more soluble in tetrahydrofuran than an equivalent linear polyester. 

There are two different oligomer series present in all spectra. The oligomer series can be identified by calculating the masses of the end groups and assigning them to specific chemical structures (Pasch and Schrepp, 2003 Weidner et al., 2004). In the present example, the two species are the propionic amide-acid (R-am-ac) and the propionic amide-propionic amide polyamides (R-am-am-R). The use of MALDI-TOF MS as a structure-sensitive detector allows the resolution to be indirectly enhanced since several species coelute, as shown in Fig. 17.21. The polarity of the... 

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