Unreacted group

The fraction of unreacted groups is l p. If it is assumed that a tetramer is formed because of the reaction between 4 reactant molecules, 2 of AA and 2 of B-B, in which 3 pairs of reactive groups have reacted. The probability of a tetramer formation is, P3. 

Unreacted groups Groups engaged in bonds With infinite continuation With finite continuation Unit is a part of... 

The number of ring forming functionalities per unit is obtained by considering all probabilities of ring closures between an unreacted group of a unit in the root (remember that we have all units as roots) and all unreacted groups on units in all generations g, g>0. Allowance can be made for the case when cycllzatlon can occur within... 

The principle of the calculation is to derive an expression for the number of unreacted groups on sol molecules (r ) by summing over finite species of all sizes and to find the number of unreacted groups on the gel (Tg) as the difference... 

One may first check qualitatively whether the desired reaction has taken place, especially by means of solubility tests and NMR or IR spectroscopy it is also necessary to examine whether unreacted groups, or groups other than those desired, are present. Quantitative analysis is aimed at evaluating the proportions of A, C, and D in Eq. 5.2, for which one may employ not only the usual methods of determination, but also special procedures, such as spectroscopy and pyrolysis gas chromatography. It is also sometimes expedient to choose the low-molecular-weight reactant so that an easily determinable element is introduced (e.g., by using chloroacetic acid for esterifications). 

We can assume that on average for one macromolecule of product obtained, there are X units with ladder-type structure, Y unreacted groups with double bonds, and Z points of crosslinking. The scheme of copolymerization of multimethacrylate with acrylic acid and a possible structure of the product obtained are presented in Figure 5.2. 

This regular structure is obtained when polymerization proceeds at 70°C and at rather low concentration of monomer. The material obtained in more concentrated solutions has more complex structure composed of ladder-type blocks, branchings, and unreacted groups. It can be illustrated by the scheme represented in the Figure 9.5. 

Such branched or slightly crosslinked materials possess unreacted groups and ladder blocks. The products after drying are usually insoluble in common solvents, therefore precise structure investigation is difficult. 

The reaction of the vinyl groups of activated supports with ligand residues is not quantitative. The excess of the ligand must be removed by washing the adsorbent with buffer. Unreacted groups of the sup-... 

We are interested in determining the time dependence of the number of unreacted groups. We now introduce the idea of a /-tuplet again. We denote the number of /-clusters by Bs and the number ofy -tuplets by Ps. Since there are j 1-tuplets in a /-cluster, j-1 2-tuplets (doublets) in a y -cluster, etc., one gets for the relation between the Pj and Bj,... 

Network defects in the form of unreacted groups serve as sites for crack initiation and propagation. When such defects are non-randomly distributed within the network a nodular morphology will be observed upon fracture or chemical etching of the bulk network. 

The second shell substitution effect (SSSE) is operative when the reactivity of a group depends not only on the substitution degree of the unit it belongs to, but on the substitution degree of all units that are first neighbors to that unit. Unless stated otherwise, we shall assume for simplicity that all the unreacted groups of a unit have an equal chance of reacting. 

Fig. 2. A single molecule formed in RA3 polymerization. The molecule contains various types of units. The labels of units are the same as the dummy variables in Eq. (130) u - monosub-stituted unit with two unreacted groups (solid lines), v - disubstituted unit, x - disubstituted unit engaged in cycle,/ - trisubstituted unit engaged in cycle...

All the reactants are individual compounds of high chemical purity with epoxy equivalent close to theoretical values. It has been shown 6,7,16,17) that, at Tcure iS 110-120 °C and especially with diglycidyl ether of resorcinol (DGER) or Bis-phenol-A (DGEBA) and w-phenylenediamine (w-PhDA) as reactants, Eq. (I) proceeds practically without side reactions and yields a polymer with a chemical structure very close to that shown in above. Using different initial ratios of reactants (P = [NH]0/[EP]0 molar ratio), one can prepare a family of polymers with rather broad variations of crosslink concentration per unit volume or number of unreacted groups of different type and properties of the final products. 

T values of the networks prepared from different components of the initial mixtures are shown in Fig. 11, as measured by different techniques. The T values reflect the chemical composition of the networks. T decreases linearly with the content of unreacted amine and epoxy groups. Unreacted groups in networks play the same role as end groups in linear polymers. The stronger influence of epoxy groups... 

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