The critical conditions in which the classical Flory−Stockmayer gelation theory (F−S theory) is applicable to monovinyl−divinyl copolymerizations were pursued in detail. Thus, the cross-linking copolymerizations of styrene (St) with m-divinylbenzene (m-DVB) as a most typical monovinyl−divinyl system were discussed under the specified conditions where the occurrence of a thermodynamic excluded volume effect and intramolecular cross-linking as the primary and secondary factors, respectively, for the greatly delayed gelation in the free-radical monovinyl−divinyl copolymerizations was reduced. The ratio of the actual gel point to the theoretical one reached 1.3, supporting the good applicability of F−S theory. In addition, the more tailed molecular-weight distribution (MWD) curves were observed with conversion as a result of occurrence of intermolecular cross-linking reaction leading to ideal network formation governed by F−S theory. Also, the swelling ratio of the gel obtained just beyond the gel point was very high, suggesting no microgelation up to the gel-point conversion. On the contrary, in the solution copolymerization of St with m-DVB in toluene at a dilution of 1/3 in the presence of a rather high amount of cross-linker, the considerable occurrence of intramolecular cross-linking reaction was clearly reflected on the greatly delayed gelation and the markedly changed MWD curve from a tailed one at a higher conversion.

Un-ionized polyurethane was obtained by the reaction of an isocyanate-terminated urethane prepolymer, which was synthesized from 4,4Ј-diphenylmethane diisocyanate and poly(oxytetramethylene)-␣,-glycol, with 2,2-bis(hydroxymethyl)propionic acid. A carboxylate-based polyurethane anionomer was then derived from the polyurethane by the use of the sodium, potassium, or magnesium salt of acetic acid as a neutralizer. The ionomerization resulted in the following changes in the characteristics of the polyurethane: (1) an increase in the tensile strength, (2) a decrease in the glass-transition temperature, (3) an increase in the wettability and hygroscopicity with respect to water, and (4) susceptibility to thermal decomposition. A sulfonatebased polyurethane was also synthesized for comparison with the carboxylate-based polyurethane.

The polymerization of vinyl monomers with various xanthates (potassium tert‐butylxanthate, potassium benzylxanthate, zinc n‐butylxanthate, etc.) were carried out at 0°C in dimethylformamide. N‐Phenylmaleimide, acrylonitrile, methyl vinyl ketone, and methyl methacrylate were found to undergo polymerization with potassium tert‐butylxanthate; however, styrene, methyl acrylate, and acrylamide were not polymerized with this xanthate. In the anionic polymerization of methyl vinyl ketone with potassium tert‐butylxanthate, the rate of the polymerization was found to be proportional to the catalyst concentration and to the square of the monomer concentration. The activation energy of methyl vinyl ketone polymerization was 2.9 kcal/mole. In the polymerization, the order of monomer reactivity was as follows: N‐phenylmaleimide > methyl vinyl ketone > acrylonitrile > methyl methacrylate. The initiation ability of xanthates increased with increasing basicity of the alkoxide group and with decreasing electronegativity of the metal ion in the series, lithium, sodium, and potassium tert‐butylxanthate. The relative effects of the aprotic polar solvents on the reactivity of potassium tert‐butylxanthate was also determined as follows: diethylene glycol dimethyl ether > dimethylsulfoxide > hexamethylphosphoramide > dimethylformamide > tetrahydrofuran (for methyl vinyl ketone); dimethyl sulfoxide > hexamethylphosphoramide > dimethylformamide ≅ diethylene glycol dimethyl ether (for acrylonitrile).