A differential scanning calorimeter has been used to measure the heat capacity of both melt and solution crystallized samples of isotactic polypropylene from 200 to 500°K. An estimate has been made of heat capacity values below 200°K. Values of the heat capacity, entropy, enthalpy, and free energy have been estimated for 100 yo crystalline isotactic polypropylene and are listed at 10°K intervals. The glass transition occurs at about 265°K in both samples. A value of 207 * 5 J .g-1 is obtained for the heat of fusion of isotactic polypropylene. Z U S AMMENF AS SUN G: Die Warmekapazitat von schrnelzkristallisierten und losungskristallisierten isotaktischen Polypropylenproben wurde zwischen 200 und 500°K mit Hilfe eines Differentialkalorimeters gemessen. Fur Temperaturen unterhalb 200°K wurde die Warmekapazitat naherungsweise rnittels eines Extrapolationsverfahrens berechnet. Die Warmekapazitlt, Entropie, Enthalpie und freie Energie eines zu 100 yo kristallinen Polymeren wurden abgeschatzt. Die Werte werden in Intervallen von 10 Grad angegeben. In den beiden Proben wurde ein Einfriervorgang (265 OK) beobachtet. Die Schmelzwarme von isotaktischem Polypropylen ist 207 * 5 J-g-l.

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Well-resolved electron spin resonance (e.s.r.) spectra are reported and analyzed for the radicals produced when samples of solid adamantane doped with alkyl substituted cycloalkenes are y-irradiated at room temperature.Canadian Journal of Chemistry, 49, 20 (1971) Introduction Pyrolysis experiments (1) revealed the ease with which cycloalkenyl radicals can be generated by removal of one hydrogen atom from cycloalkene molecules. The radicals formed possess unusual resonance stability as no further hydrogen elimination is observed even at temperatures up to 400 "C. Ohnishi et al. (2) and Ayscough and Evans (3) subsequently attributed e.s.r. spectra observed following the irradiation of cycloalkene glasses to these cycloalkenyl radicals. These workers concluded that hydrogen elimination preferentially occurred from a carbon atom adjacent to the unsaturated linkage and that the radical generated was stabilized by electron delocalization on three carbon atoms.In a successful attempt to improve the e.s.r. spectral resolution of these radicals, Helcke and Fantechi (4) generated cyclohexenyl and cycloheptenyl radicals by irradiating polycrystalline thiourea adducts of the parent hydrocarbons with fast electrons. We have recently initiated a systematic study of silver cycloalkenyl radicals in y-irradiated silver cycloalkene complexes (5), and have extended the study to alkyl substituted olefins. However, a literature search reveals that little e.s.r, information is known about the parent alkyl substituted cycloalkenyl radicals. To extend this study to alkyl cycloalkenyl radicals we found that spectral resolution could be improved by slightly modifying the recently developed technique of Wood and co-workers (6). These workers achieved well resolved isotropic e.s.r. spectra of a series of amino radicals by selective radiation

Paramagnetic species have been detected in y-irradiated polycrystalline silver perchlorate -cycloalkene complexes at room temperature and identified as Ag+cycloalkenyl radicals, with spin density on Ag decreasing from 4.6 to 1.5% with increasing size of the cycloalkenyl ring. The extent of the spin density on Ag increases with the stability of the parent complexes.

A precision, adiabatic vacuum calorimeter and a differential scanning calorimeter have been used to measure the heat capacities of eight ethylene/propylene copolymers, containing from 15 to 70 mole-% propylene, over the temperature range 180 t o 450°K. An estimate has been made of heat capacity values below 180°K. The entropy of the amorphous copolymers at 450 "K may be represented by the relationship -S : = 19.5 + 9.2 .10-2y caldeg-1 mole-I (y = propylene content of the copolymer in mole-yo). The glass transition temperatures of the copolymers lie in the range 210 to 235'K. ZUSAMMENFASSUNG:Die Wivmekapazitiit von acht bthylen/Propylen-Copolymeren, die zwischen 15 und 70 Mol-% Propylen enthalten, wurde zwischen 180 und 450°K mit Hilfe eines prazisionsadiabatischen Vakuumkalorimeters und eines Differentialkalorimeters gemessen. Fiir Temperaturen unterhalb 180 OK wurde die Wivmekapazitiit niiherungsweise durch ein Extrapolationsverfahren berechnet. Die Entropie der amorphen Copolymeren bei 450°K kann in der folgenden Gleichung dargestellt werden : -S : = 19,5 + 9,2 .10-2y cal Grad-' Mol-I (y = Propylengehalt des Copolymeren in M01-y~). Die Einfriertemperatur des Copolymeren liegt zwischen 210 und 235'K.