Crosslink definition

Note 1 A polyelectrolyte network is sometimes called a cross-linked polyelectrolyte. Use of the latter term is not recommended unless the polyelectrolyte network is formed by the cross-linking of existing polyelectrolyte macromolecules rather than by nonlinear polymerization. (See the definition of a crosslink, definition 1.59, ref [4].)... 

Summarizing this section, we conclude that, from an experimental point of view, the ideal network theory expressed by Eq. (III-9) seems to be obeyed rather well only in the case of swollen networks. The determination of the elasticity parameters is complicated by the presence of a free enthalpy of dilution term. In spite of this, it is possible to conclude that 1/2 is the most likely value for B in Eq. (III-9). The factor A remains undetermined because experimentally the most one can obtain is A g o 2 8. Concerning this memory parameter, a dependence on the stage of dilution during crosslinking definitely exists, (Eq. Ill-19), but its dependence upon the nature of the diluent used in swelling studies needs further investigation. 

The next step in the development of a model is to postulate a perfect network. By definition, a perfect network has no free chain ends. An actual network will contain dangling ends, but it is easier to begin with the perfect case and subsequently correct it to a more realistic picture. We define v as the number of subchains contained in this perfect network, a subchain being the portion of chain between the crosslink points. The molecular weight and degree of polymerization of the chain between crosslinks are defined to be Mj, and n, respectively. Note that these same symbols were used in the last chapter with different definitions. 

Seeding technique, procedure 130, 131 Sequential addition of monomers 164, 167 Silicon-carbide fibers 8 Silicon-nitride fibers 8 Silicone rubber, crosslinked 4, 7-9, 31, 67 Siloxane, definition of 5 Siloxane-acrylate copolymers 27, 29, 56, 57, 64, 70, 71, 73, 74... 

IPNs are found in many applications though this is not always recognised. For example conventional crosslinked polyester resins, where the polyester is unsaturated and crosslinks are formed by copolymerisation with styrene, is a material which falls within the definition of an interpenetrating polymer network. Experimental polymers for use as surface coatings have also been prepared from IPNs, such as epoxy-urethane-acrylic networks, and have been found to have promising properties. 

More definitive evidence of enzymatic attack was obtained with 1 1 copolymers of e-caprolactone and 6-valerolactone crosslinked with varying amounts of a dilactone (98,99). The use of a 1 1 mixture of comonomers suppressed crystallization and, together with the crosslinks, resulted in a low-modulus elastomer. Under in vitro conditions, random hydrolytic chain cleavage, measured by the change in tensile properties, occurred throughout the bulk of the samples at a rate comparable to that experienced by the other polyesters no weight loss was observed. However, when these elastomers were implanted in rabbits, the bulk hydrolytic process was accompanied by very rapid surface erosion. Weight loss was continuous, confined to the... 

The critical gel equation is expected to predict material functions in any small-strain viscoelastic experiment. The definition of small varies from material to material. Venkataraman and Winter [71] explored the strain limit for crosslinking polydimethylsiloxanes and found an upper shear strain of about 2, beyond which the gel started to rupture. For percolating suspensions and physical gels which form a stiff skeleton structure, this strain limit would be orders of magnitude smaller. 

A new type of crosslinking strategy may overcome this problem, as it takes advantage of definitive mass spec identification after the chemical crosslinking of interacting proteins. The... 

The use of PIR compounds to study protein interactions is a significant advance over the use of standard homobifunctional crosslinkers. The unique design of the PIR reagent facilitates deconvolution of putative protein interaction complexes through a simplified mass spec analysis. The software can ignore all irrelevant peak data and just focus analysis on the two labeled peptide peaks, which accompany the reporter signal of appropriate mass. This greatly simplifies the bioinformatics of data analysis and provides definitive conformation of protein-protein crosslinks. 

For small microgels, like crosslinked particles of a microemulsion (diameter below 102 nm), the definition of the gel point is no longer clear. For instance, a... 

Actually, crosslinks control the molecular packing and indeed significantly affect the elastic modulus of the material. As the intermolecular energy of kink formation is also determined by elastic modulus, the yield stress will definitely vary with modulus and thus the cross -linking density. In other words, crosslinks may not seriously affect the activation segment configuration in the molecular chain but will indirectly control the yield stress. 

Butyl acrylate/0.3 moles/kg crosslinker copolymers In toluene. See Experimental for a definition of swell Index. 

Note 4 For components of chain structures that would be expected to be miscible, miscibility may not occur if molecular architecture is changed, e.g., by crosslinking. Modified from Definition 1.3 in [3]. The definition proposed here is preferred because it emphasizes the requirement for homogeneity over miscibility. 

When characterizing polymer networks, the following definitions are typically applied [150] and are illustrated in Fig. 7. When a radical on a polymer chain propagates through a pendant double (i.e. a double bond from a monomer with one double bond already reacted), a crosslink, secondary cycle, or primary cycle can be formed. A crosslink forms when the radical reacts with a pendant... 

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