Effect chain

In mbber production, the thiol acts as a chain transfer agent, in which it functions as a hydrogen atom donor to one mbber chain, effectively finishing chain growth for that polymer chain. The sulfur-based radical then either terminates with another radical species or initiates another chain. The thiol is used up in this process. The length of the mbber polymer chain is a function of the thiol concentration. The higher the concentration, the shorter the mbber chain and the softer the mbber. An array of thiols have subsequendy been utilized in the production of many different polymers. Some of these apphcations are as foUow ... 

Wu, C.W., Sanborn, T.J., Zuckermann, R.N., and Barron, A. E. Peptoid oligomers with alpha-chiral, aromatic side chains Effects of chain length on secondary structure. /. Am. Chem. Soc. 2001, 723, 2958-2963. 

Various other chemical agents which by their nature are capable of producing cross-linkages between polymer chains effect the same changes in physical properties that are observed in sulfur vulcanization. One of the best known of these agents is sulfur monochloride, which readily combines with two molecules of an olefin (the mustard gas reaction). Applied to rubber, it induces vulcanization even at moderate temperatures, the probable structure of the cross-linkage being... 

Mokrosz JL et al. (1995) Structure-activity relationship studies of CNS agents, XIX Quantitative analysis of the alkyl chain effects on the 5-HTlA and 5-HT2 receptor affinities of 4-alkyl-1-arylpiperazines and their analogs. Arch Pharm (Weinheim) 328(2) 143-148... 

The preparation of helically well-ordered polymers with stable screw-sense, which is able to be transmitted to newly formed polymer main-chains effectively, is highly desired for the development of new methodology for the synthesis of optically active helical polymers. An aromatizing polymerization of 1,2-diisocyanobenzenes is promoted by methylpalladium(II) complexes, producing poly(quinoxaline-2,3-diyl)s.146-148 The polymerization proceeds with successive insertion of the two isocyano groups of the diisocyanobenzene to the carbon palladium bond of... 

Even if one can create the SCO ligand-field around one end of a covalently-bridged dinuclear complex, the SCO might influence the ligand-field at the other end. There are many inter-dependent effects to bear in mind of a bonding, electronic and structural kind, and attempts to delineate these are given below. Inter-cluster or inter-chain effects will play difficult-to-control roles in crystalline SCO polynuclear materials, and these have already been alluded to for mononuclear complexes. 

H.-Z. Tang, M. Fujiki, and M. Motonaga, Alkyl side chain effects of optically active polyfluorenes on their chiroptical absorption and emission properties, Polymer, 43 6213-6220, 2002. 

Fandrich, M., and Dobson, C. M. (2002). The behaviour of polyamino acids reveals an inverse side chain effect in amyloid structure formation. EMBOJ. 21, 5682-5690. Fandrich, M., Fletcher, M. A., and Dobson, C. M. (2001). Amyloid fibrils from muscle myoglobin. Nature 410, 165-166. 

Scaling theories are restricted to long polymer chains in good solvents and do not include finite chain effects and polymer-solvent interactions. These models should be complemented by more detailed mean-field calculations and molecular simulations. 

SIDE-CHAIN EFFECTS IN OTHER AMINO ACIDS... 

FIGURE 1.4 Side-chain effects in other amino acids. 

To study template systems it is important to compare the template process and products of the reaction with conventional polymerization carried out under the same conditions. It is typical to replace template hy a low molecular non-polymerizable analogue. The influences of the template on the process and the product are usually called template effect or chain effect . ... 

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