Link structures

The novolak resins themselves contain no reactive methylol groups and do not form cross-linked structures on heating. If, however, they are mixed with compounds capable of forming methylene bridges, e.g. hexamethylenetetramine or paraformaldehyde, they cross-link on heating to form infusible, thermoset structures. 

As these condensation reactions can occur at the two ortho and the para positions in phenol, w-cresol and 3,5-xylenol, cross-linked structures will be formed. It has been pointed out by Megson that because of steric hindrance the amount of cross-linking that can take place is much less than would involve the three reactive groups of all the phenolic molecules. It is now generally considered that the amount of cross-linking that actually takes place is less than was at one time believed to be the case. 

Since this reaction may occur at both ends of the molecule (in case of glycidyl ether resins) a cross-linked structure will be built up. 

Many polymers containing boron in the main chain have been prepared but most of them have either been of low molecular weight or intractable cross-linked structures. Some interest has been shown in the tri-3-aminoborazoles, which polymerise on heating (Figure 29.15f. ... 

Liquid crystal polymers Cross-linked Structures Polyblends... 

In previous works [18-20,23,102] water-soluble polymers such as polyacrylamide (pAM), polysodium acrylate (pAA Na), poly(acrylamide-sodium acrylate) (pAM-AA Na), poly(acrylamide-diallyethylamine-hy-drochloride) (pAM-DAEA-HCl), and poly(acrylamide-sodium acrylate-diallyethylamine-hydrochloride) (pAM-AANa-DAEA-HCl) were used in the recovery of cations and some radioactive isotopes from aqueous solutions. It was found that the floe is formed between the added polymer and ions of the solution in the flocculation process with the formation of a crosslinked structure. The formed cross-linked structure is characterized by [103-105] ... 

Cross-linked structure of pAM CuS0 5H20 complenes... 

Cross-linked structure of pDAA-HCl-CuS0 5H20... 

A new polymer type which emerged as important materials for circuit hoards are polycyanurates. The simplest monomer is the dicyanate ester of hisphenol A. When polymerized, it forms three-dimensional, densly cross-linked structures through three-way cyanuric acid (2,4,6-triazinetriol) ... 

Figure 8.20 shows the first five iterations of a system starting from a four neighbor lattice with a single non-zero site at its center. The link structure is given... 

Fig. 10. Possible collagen-linke structure depending on the hydrogen-bonding capacity of certain polypeptides based on their proline content...

Our laboratory has planned the theoretical approach to those systems and their technological applications from the point of view that as electrochemical systems they have to follow electrochemical theories, but as polymeric materials they have to respond to the models of polymer science. The solution has been to integrate electrochemistry and polymer science.178 This task required the inclusion of the electrode structure inside electrochemical models. Apparently the task would be easier if regular and crystallographic structures were involved, but most of the electrogenerated conducting polymers have an amorphous and cross-linked structure. 

Cross-linked structure of polypyrrole, 311 Cross-linking, 330... 

Divinyl monomers such as divinylbenzene, divinyl adipate, and ethylene dimethacrylate, in which the reaction of one double bond does not alter greatly the reactivity of the other, polymerize to highly cross-linked structures. 

Thermosetting materials, which have a rigid, cross-linked structure for example, the polyester and epoxy resins. 

Ceramic materials have a cross-linked structure and are therefore brittle. 

Figure 39 The enantioselective polymer-supported catalysts (61) of chiral oxazaborolidinone with cross-linking structures for use in the Diels-Alder reaction of methacrolein with cyclopentadiene. (Adapted from ref. 85.)...

Generally, during hydroboration polymerization of dicyano compounds, the formation of the borazine structures that have a six-membered boron-nitrogen ring (scheme 19a) and dihydroborated end groups (scheme 19b) as a structural defect is unavoidable. The borazine cross-linked structures often cause the gelation, and dehydroboration causes a decrease in molecular weight. 

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