The swelling in various liquids of discs of nylon 66, crosslinked by the radiation from an atomic pile, has been interpreted using the Flory‐Rehner treatment of the swelling of cross‐linked networks. Values of χ1, the polymer‐solvent interaction parameter, found in this way have been discussed in terms of the physical properties of the liquids. The solvent power of about twenty phenols can be correlated with their known ability to form hydrogen bonds. Intramolecular bonding, as in guaiacol or o‐chlorophenol, reduces the solvent power. Partially hindered phenols, i.e., those with one bulky hydrocarbon group ortho to the hydroxyl, show high solvent power, probably because polymer‐solvent interaction is not hindered sterically as much as solvent‐solvent interaction. Other classes of solvents, e.g., inorganic and organic acids, inorganic salts in hydroxylic solvents, are also discussed briefly. Some implications of these results in such technological fields as plasticizers and dyeing assistants are suggested.
The direct photopolymerization of styrene proceeded too slowly for accurate measurements with the usual dilatometric technique, so resource was had to the benzoyl peroxide photosensitized reaction. In this reaction, the rate of polymerization was proportional to the square-root of both the light intensity and the concentration of catalyst. The rate fell off gradually with time and this is attributed to wasteful decomposition of the catalyst. The rate coefficients for the polymerization were determined from a combination of life-time * Tech. Monog. (Dow Chemical Co., 1946).
The copolymerization of styrene and p‐methoxystyrene at 60°C., catalyzed by the thermal decomposition of 2‐azobisisobutyronitrile, has been studied. A combination of rate and molecular weight data has shown that δ = (kt1/2/kp) = 25, kf/kp = 1.1 X 10−4 for styrene and δ = 21, kf/kp = 0.74 X 10−4 for p‐methoxystyrene. The over‐all energy of activation for styrene is shown to be Ep − 1/2Et = 6.2 kcal. The rate of initiation (I) of these monomers does not correspond with the rate of production of free radicals from the catalyst, e.g., experimentally, I = 3.3 X 10−8 and I = 2.1 X 10−8 mole/liter/sec. for styrene and p‐methoxystyrene, respectively, at a catalyst concentration of 1 g./liter. The rate calculated from the rate of fission of the catalyst is 12.2 X 10−8 mole/liter/sec. The rates of copolymerization and initiation have been measured for various monomer mixtures; the former was practically independent of monomer composition but the latter varied directly with monomer composition. A value of ϕ = 1[ϕ = k/(kk)1/2] satisfies the experimental results, in agreement with the theory previously presented, i.e., that ϕ2 = (A212/A11A22)(1/r1r2). The validity and usefulness of this theory are discussed in the light of available data and criticisms, and it is shown that both entropy and polar effects play important roles in cross‐termination reactions.
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