Crosslinkers intra-molecular

Branching and crosslinking processes can be treated as a combinatorial problem which is not too complicated when the functionalities are equally reactive and unreacted functionalities are considered as the only kind of defects. If loop formation (intra-molecular cyclization) is involved, the complexity increases considerably. The same holds if the monomers contain groups of unequal reactivity or if the reactivity is influenced by substitution effects. 

The extreme hardness and lack of formability of thermoset plastics is due to the extremely large number of primary valence bonds between the plastic s atoms. In an extreme case of crosslinking with covalent bonds practically no secondary valence bonds exist that can be loosened by increasing the temperature. This means that no thermoplastic processing of the polymer is possible. A thermoset plastic can be depicted as being a huge single molecule. The removal of these intra molecular bonds by increased tempera-... 

Andreev OA, Reshetnyak Y, Goldfarb RH. Evidence of inter- and intra-molecular crosslinking of tyrosine residues of carmodulin induced by photo-activation of ruthenium(II). Photochem Photobiol Sci 2002 1 834-6. 

It can be noted that this reaction Is closely analogous to the free radical inter-intra-molecular polymerization discovered by Butler and Angelo (11) In which a difunctional monomer undergoes such efficient ring closure that a soluble linear polymer is obtained instead of a crosslinked or three-dimensional product. 

STUDY OF INTRA-MOLECULAR CROSSLINKING OF POLYACRYLAMIDE IN Cr(III)-POLYACRYLAMIDE GELATION BY SIZE-EXCLUSION CHROMATOGRAPHY, LOW-ANGLE LASER LIGHT SCATTERING, AND VISCOMETRY... 

Intra-molecular Crosslinking was determined to occur in the Cr(III)-PAAM gelation process. The effect of IMC is more pronounced in crosslinking systems with relatively low PAAM concentrations. 

The molecule, schematically shown in Fig. 2, is now subjected to reaction, which can be either intermolecularly or intra-molecularly. The probability that a group A of this particular macromolecule reacts, either internally or externally, in a volume element dx, dy, dz located at x, y, z, is proportional to the concentration of A groups of this macromolecule in that volume element. This concentration is proportional to p(r), where r = x + y + z. The proposed crosslinking reaction, however, is of the second order. Therefore the probability that this... 

Crosslinking reactions, depending on whether the functional groups are present on different molecules or in the same molecule, are classified as inter- or intra-molecular reactions. The chemical reactions which are mainly used for this purpose are condensation reactions, addition reactions or ionic polymerizations. The type of chemical reaction involved varies with the type of binder resin used in the paint formulation. In the following section, the crosslinking reactions for some of the important classes of resins used in the coatings industry will be briefly discussed. 

To explain the formation of non-crosslinked polymers from the diallyl quaternary ammonium system, Butler and Angelo proposed a chain growth mechanism which involved a series of intra- and inter-molecular propagation steps (15). This type of polymerization was subsequently shown to occur in a wide variety of symmetrical diene systems which cyclize to form five or six-membered ring structures. This mode of propagation of a non-conjugated diene with subsequent ring formation was later called cyclopolymerization. 

For example, the respective values at pH 10.6 are 0.262, 0.494, and 1.04 mole per cent (ratio of about 1 2 4) at pH 11.2 the values are 0.420, 0.780, and 1.32 mole per cent and at pH 12.5 (pH of 1% protein solution in 0.IN NaOH), the respective values are 0.762, 0.780, and 2.62 mole per cent. (Note that the value of casein approaches that of gluten at this pH). The observed differences in lysinoalanine content of the three proteins at different pH values are not surprising since the amino acid composition, sequence, protein conformation, molecular weights of protein chains, initial formation of intra- versus intermolecular crosslinks may all influence the chemical reactivity of a particular protein with alkali. Therefore, it is not surprising to find differences in lysinoalanine content in different proteins treated under similar conditions. These observations could have practical benefits since, for example, the lower lysinoalanine content of casein compared to lactalbumin treated under the same conditions suggests that casein is preferable to lactalbumin in foods requiring alkali-treatment. 

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