Chain-making

Hydrophobic fibers are difficult to dye with ionic (hydrophilic) dyes. The dyes prefer to remain in the dyebath where they have a lower chemical potential. Therefore nonionic, hydrophobic dyes are used for these fibers. The exceptions to the rule are polyamide and modified polyacrylonitriles and modified polyester where the presence of a limited number of ionic groups in the polymer, or at the end of polymer chains, makes these fibers capable of being dyed by water-soluble dyes. 

Figure 9.10 Schematic diagrams illustrating the complex between DNA (orange) and one monomer of the homeodomain. The recognition helix (red) binds in the major groove of DNA and provides the sequence-specific interactions with bases in the DNA. The N-terminus (green) binds in the minor groove on the opposite side of the DNA molecule and arginine side chains make nonspecific interactions with the phosphate groups of the DNA. (Adapted from C.R. Kissinger et al Cell 63 579-590, 1990.)...

DNA is made up ot two intertwined strands. A sugar-phosphate chain makes up the backbone of each, and the two strands are joined by way of hydrogen bonds betwen parrs of nucleotide bases, adenine, thymine, guanine and cytosine. Adenine may only pair with thymine and guanine with cytosine. The molecule adopts a helical structure (actually, a double helical stnrcture or double helix ). 

There are more than a million known carbon compounds, of which thousands are vital to life processes. The carbon atom s unique and characteristic ability to form long stable chains makes carbon-based life possible. Elemental carbon is found free in nature in three allotropic forms amorphous carbon, graphite, and diamond. Graphite is a very soft material, whereas diamond is well known for its hardness. Curiosities in nature, the amounts of elemental carbon on Earth are insignificant in a treatment of the... 

Figure 2. Diagram of chains making up a lamella of thickness I.

Characterization of Limited Chain Extensibility. The molecular origin of the unusual properties of bimodal PDMS networks having been elucidated at least to some extent, it is now possible to utilize these materials in a variety of applications. The first involves the interpretation of limited chain extensibility in terms of the configurational characteristics of the PDMS chains making up the network structure (5,12,13). 

Two electrons flowing down the chain make 3 ATP/NADH 2 ATP/FADH2... 

Fig. 54. An asparagine side chain making a hydrogen-bond to the main chain NH of residue n + 2, an arrangement which helps stabilize the central peptide of a tight turn. Residues 91-93 from chymotrypsin.

Alkenes are like alkanes less two hydrogens, giving them a double bond somewhere in the chain, making them an olefin. They have the formula, CnH2n. such as butene (more often called butylene), isobutene (isobutylene), and propene (usually called propylene). 

So what does all of this have to do with polymers Natural, unheated rubber is a polymer, so it has long chains of molecules with some cross-links. When rubber is heated and sulfur is added to it, the sulfur forms many more cross-links between the chains, making it very strong. Rubber is elastic—it bounces back—because the chains are coiled into loops that can stretch out as the rubber bends or stretches, then coil back up when they re released. 

Earlier we found that the addition of alkyl-modified poly(propylene imine) dendrimers to polypropylene leads to fibers which can be dyed in conventional acid or disperse dyeing processes [3]. The alkyl chains make the additive compatible with the polypropylene matrix, while the polar core of the dendrimer can act as a receptor for the dye molecules. This host-guest behavior is analogous to the principle of the dendritic box as described by Meijer et al. [30] and elaborated by Baars et al. for dye extraction processes [31]. 

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