Cross-link number average molecular weight

Figure 8. SANS measurements of R /Fg° and R /Rg° versus A of tetrafunctional polydimethylsiloxane networks. Mw and Mn are weight and number average molecular weights before crosslinking, cp is the polymer fraction in solution before cross-linking. Data from Ref. 20.

The degree of cross-linking can be expressed in terms of cross-links per gram or per unit volume. If C is the moles of cross-links per unit volume, n the number of network chains per unit volume, d the density of cross-linked polymer, and Me the number-average molecular weight of the polymer segments between cross-links, then... 

Number average molecular weight between cross-links. 

Increases in number average molecular weight, Mn, and cross-link density will both act to increase the T. The addition of plasticizers, such as in the case of PVC, will decrease the value of the glass transition temperature. The glass transition temperature of the plasticized... 

Using shear modulus obtained from compression tests for noncovalent gels to calculate the association constant for the formation of junction zones., the number average molecular weight of the junction zones and the number of cross-linking loci per junction zone... 

There are two parameters used as a measure of cross-Unk density the number of network chains, v, usually expressed as v/ V, where V is the volume of the unstrained network and the number of cross-links (p) per unit volume, p/F. The relationship between p and v is established by knowing the number of chains starting from a particular cross-linking point, (functionality). The two most important types of network are the tetrafunctional (c ) =z 4) and the trifunctional ( = 3). Another characteristic parameter of a network is the number-average molecular weight between cross-links,... 

Me is the number-average molecular weight between polymer cross-links M is the number-average molecular weight of the uncross-Unked polymer M is a critical molecular weight between cross-links (p is polymer volume fraction n is solute radius... 

Neutral cross-linked hydrogels are commonly described in terms of the polymer volume fraction in the swollen and unswollen state and the number average molecular weight of the polymer chain between adjacent cross-links. The difference between polymer volume fractions can be determined from the swelling ratio of the gel (Figure 16.9) [63]. 

Me is the number average molecular weight of the polymer chain between cross-links... 

Equations 16.6 and 16.7 can be combined to give a quadratic expression in [RL] which can be used to determine the fraction of receptor, which is bound to immobilized hgand (Figure 16.13). From these equations, the number average molecular weight (Me) between affinity cross-links can be determined ... 

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