Poly-( I-butene) was separated into atactic and isotactic portions by extraction and these materials were individually fractionated. The two forms obeyed identical intrinsic viscosity-molecular weight relationships in good solvents; however, the isotactic modification exhibited lower values of the osmotic second virial coefficient for molecular weights below 7 x 10'.This type of behavior in good solvents has been reported by other workers for the two forms of polystyrene and polypropylene, and hence appears to be quite general. Precipitation temperature measurements in anisole gave a higher entropy parameter, $1, for the stereoregular poly-( 1-butene), in agreement with the result reported by Kinsinger and Wessling for polypropylene in phenyl ether. On the other hand, the latter workers found a lower theta, temperature for isotactic polypropylene, whereas we obtained a higher theta temperature for the stereoregular poly-( 1-butene). Thus, atactic poly-( 1-butene) is more soluble in anisole than its stereoregular counterpart for all molecular weights, whereas atactic polypropylene should be the form of lower solubility in phenyl ether for molecular weights above 39,000. Isotactic poly-( 1-butene) appears to have a more highly extended molecular conformation than its atactic counterpart, as judged from unperturbed dimensions estimated from light scattering data obtained using a good solvent. Parameters are given which permit a comparison of the relative extensions of a number of polyolefins. IntroductionThe method of preparation and the physical properties of a number of linear, stereoregular polyolefins were described by Natta and eo-workers in 1955.' Since that time there has been considerable interest in comparing the molecular dimensions and thermodynamic interactions of the isomeric forms of these polymers in solution. The majority of this work has involved the measurement of intrinsic viscosities, molecular sizes and second virial coefficients in thermodynamically good solveiits.2-11 The conclusions drawn from these investigat'ions are that the perturbed molecular dimensions in good solvents are indistinguishable for the atactic and isotactic forms, but that the stereoregular polymers exhibit smaller second virial coefficients (at least, for lower molecular weights) in these solvents. This latter conclusion is in agreement with the earlier work of Muthana and Mark,12 mho compared crystalline and amorphous samples of poly-(vinyl isobutyl ether). Finally, in the

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IntroduetionIn curing conventional epoxy resins, considerable study has been devoted to the effect of structure of polycarboxylic acid anhydrides on reactivity and resin properties. The resistance of cured resins to stress at elevated temperatures, for example, increases as the functionality or the compactness of the anhydride increases.' Pyromelletic dianhydride,2 chlorendic anhydride13 and methyl Nadic anhydride4 have been developed as curing agents leading to high softening resins. More recently, attention has also been given to the synthesis of new types of epoxides as another method of modifying the resin forming properties. The approach was stimulated by the development of economical and efficient methods of epoxidation with the use of peracetic acid.6 This paper is concerned with one of these epoxides, namely endo-dicyclopentadiene dioxide (Union Carbide Chemicals Co., Unox epoxide 207, m.p. 185OC.) : Unox 207 Anhydride Curing AgentsA variety of polycarboxylic acid anhydrides is available as curing agents for polyepoxides. The reactivities of anhydrides toward epoxides differ greatly and are related to 'the strength of the respective acids and to steric hindrance. Maleic anhydride, which is derived from a strong acid, reacts very rapidly, whereas alkenylsuccinic anhydride reacts slowly because of the bulky side chain. We have observed that maleic anhydride and Unox 207 have several unique and desirable properties in forming resins.The thermal stability of resins from Unox 207, maleic anhydride, and 2-ethyl-2-(hydroxymethyl)-l,3-propanediol (trimethylolpropane) was examined as a criterion for optimum formulations. The polyol was added to initiate the reaction. The mixtures, which are homogeneous, mobile

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The rates of diffusion, R, of helium through four glasses of varied composition have been measured as a function of temperature up to and including the "transformation points" of the glasses. Two borosilicates, a lead glass, and a soda glass were studied, and the effect of heat treatment was investigated. A plot of log R vs. 1/T, in general, proved to be made up partly of a straight line and partly of a curving line at temperatures where the glass became soft enough to relieve strain. The borosilicates showed either no break or only a slight break a t the "transformation point," whereas the lead and soda glasses showed more pronounced changes in slope near the "transformation point." The borosilicates showed a shift to higher rates with heat treatment; and the lead glass, a shift to lower rates. It is believed that completely annealed glass would show a linear log R vs. 1/T relation over the entire temperature range.The permeability of the glass to the diffusion of helium at any temperature decreases as the percentage of basic oxides or of cations increases. This may be interpreted in terms of the atomic arrangement in these glasses