The crosslinking statistics for the post-gel stage of a stepwise alternating polyaddition of a bi-and tri-functional component has been developed. The treatment includes formation of elastically inactive cycles and their activation resulting in formation of elastical!y active network chains (EANCs). Model calculations have shown that in networks formed from telechelic polymers the fraction of bonds wasted in elastically inactive cycles amounts only to several percent, but their effect on lowering the concentration of EANC's is rather important. The effect of cyclisation on the concentration of EANC's can be strongly reduced if the concentration of EANC's is compared at the same relative conversion with respect to that at the gel point or at the same gel fraction. The concentration is rather sensitive to incompleteness of the reaction or to deviations from the stoichiometrically equivalent ratio of the functional groups.

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An equation has been derived allowing calculation of the penetration modulus A for the indentation of a hard sphere having the radius R' into a sample in the shape of a cylinder having the radius R in a direction transverse to cylinder axis. The correction function (determined by the elliptic integrals), X i f i =f(R'IR) needed in the calculation ofA, has been tabulated. An approximative equation has also been sug ested which the range 0 < R'IR 5 1 it describes this dependence with an accuracy of2.5 percent. While in the case ofthe penetration ofa cylinder the geometry is fully defined and the derived equation is generally valid, in the case of indentation of a plane sheet the equation holds only if the thickness of the sheet is infinite. Experimental results for the penetrdion of a steel sphere with various R' on samples of vulcanized silicone rubber in the shape of cylinders with different R gave an A independent of R'IR, which was in agreement with the shear modulus G, = El3 ( E is Young's modulus) with an average deviation of 2.3 percent. Further, it has been found experimentally that in the case of penetration of a cylinder the equilibrium is attained more readily than in the case of indentation of a plane.adequately describes the dependence of m X i ? 2 on R'iR; in

The effect of concentration of the crosslinking agent (ethylene dimethacrylate) and diluent (water) during the crosslinking copolymerization on the shape and position of retardation spectra in the dry state has been investigated for poly(2‐hydroxyethyl methacrylate) networks. With increasing water content during network formation, the maxima of the retardation spectra, Lm, increase and the position of the spectra is shifted toward shorter retardation times, τ. The results are in quantitative agreement with the modified Rouse–Mooney (R–M) molecular theory and suggest the influence of deformation due to the diluent during network formation on the viscoelastic behavior. With increasing content of the crosslinking agent, the retardation spectra are shifted toward longer times. At a constant reference temperature T0 = 115°C the retardation time, τm, at the maxima of the spectra increases with increasing content of effective chains in the network, νe. However, after a correction for the effect of the monomeric frictional coefficient, ξ M0, τm/ξ M0 decreases with increasing ve at a rate which agrees quantitatively with the R–M theory. The slope of the retardation spectra in the main transition region and the value of their maxima decrease with increasing ve; a comparison of these dependences with theory leads to the most probable distribution of submolecules in the chains. The contribution of long retardation times to the equilibrium compliance, Je, of the systems under investigation was estimated; it was shown that the application of the Thirion–Chasset extrapolation method for the determination of Je of loose networks requires a certain type of dependence of the retardation or relaxation spectra on τ.

The free volume theory of Cohen and Turnbull, the results of which are identical with the empirical relationship of Williams, Landel and Ferry (WLF), was compared with the theory of conformational entropy of Adam and Gibbs (AG) using experimental results of measurements of the temperature dependence of the relaxation times of poly(viny1 acetate). In spite of being different in their mathematical form, both theories were found to describe the experiment with similar adequacy. A procedure was also suggested permitting to obtain the AG parameters if the WLF parameters are known. The procedure was applied to 59 compounds, the WLF parameters of which were found in the literature. The results are tabulated. E inle it ungAus der Frequenzlage v, dielektrischer oder mechanischer Absorptionsmaxima la& sich bekanntlich nach der Beziehung 2rcv,t = 1(1) die (wahrscheinlichste) Relaxationszeit T der zugrundeliegenden Relaxationsmechanismen bestimmen. Die Relaxationszeit zeigt fur polymere Substanzen eine charakteristische Temperaturabhangigkeit, die sich fur Gruppenrelaxation durch die fur thermisch aktivierte Prozesse gultige Arrhenius-Gleichung beschreiben 1aBt. Fur Segmentrelaxation ergibt sich dagegen im Bereich oberhalb der Glastemperatur Tg, daB die scheinbare Aktivierungsenergie stets mit abnehmender Temperatur sehr stark ansteigt'). Das ist durch die kooperative Bewegung einer groDen Anzahl aufeinanderfolgender Molekulgruppen der Polymerkette bedingt. Zur theoretischen Deutung der Temperaturabhangigkeit der Segmentrelaxation sind verschiedene Theorien entwickelt worden, von denen im folgenden die beiden wesentlichsten kritisch miteinander verglichen werden sollen. Es sind dies die Theorie des freien Volumens von Cohen und Turnbull'), die in ihrer mathematischen Form mit der von Williams, Landel und Ferry') empirischgewonnenenBeziehung (WLF) identisch ist und die Theorie der Konformationsentropie von Adam und Gibbs3) (AG). Beide Theorien WLF und AG konnen im Aussagegehalt erweitert