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It has been reported that the water-swollen crosslinked poly(2-hydroxyethyl methacrylate) (PHEMA) gel displays an increase of entropy on extension at constant volume in a simple tensile experiment. In this paper, the authors report a new technique for measuring the entropy contribution to tensile load in a solvated polymer. Samples immersed in water at a reference temperature (T//0 equals 30 degree C) are extended to a series of lengths at each of which equilibration with the neighboring solvent is permitted. At each of these lengths, the tensile force is measured as a function of temperature with the sample uptake of water constant by changing the temperature of the sample in a much shorter time than that necessary for changes in water uptake to occur to reestablish osmotic equilibrium at the new temperature. The principle of the experiment is thus the measurement of load at different temperatures at thermal but not osmotic equilibrium. Experimental data are presented and evaluated by using mathematical techniques.

New stereospecific polymerization systems for methyl methacrylate are reported. The temperature dependence of the internal friction of the stereoregular forms of polymethyl methacrylate (PMMA) has been determined at frequencies of ca. 1 cycle/sec. Isotactic PMMA does not exhibit a side chain relaxation and its main chain relaxation is 66°C. lower than that of conventional PMMA. Syndiotactic PMMA exhibits exactly the same relaxations as conventional PMMA. Since the density and infrared absorption spectra of syndiotactic and conventional PMMA are also comparable and differ from the isotactic form, it is concluded that conventional radical-initiated polymer is not truly atactic but has considerable syndiotactic character.

A torsion pendulum has been used to measure the internal friction of polytetrafluoroethylene. The crystallinity of the specimens varied form 48 to 92%, and the measurements were made over a wide temperature range. The site of each relaxation was assigned by observing the variation of relaxation strength and peak height with crystallinity. In this way amorphous relaxations were found to occur at 176.5°K. (0.60 cycle/sec.) and 399°K. (0.62 cycle/sec.). The crystallite relaxations occur at 291°K. (0.28 cycle/sec.) and the crystallite melting point, 600°K. It is concluded that the amorphous regions of polytetrafluoroethylene exist in three phases between 4.2°K. and the crystallite melting point. The supercooled liquid which exists below 600°K. is transformed into an amorphous solid at a temperature in the region of 400°K. This solid undergoes another transformation at approximately 176°K. to form a third phase which is stable down to 4.2°K. The crystallite realaxation centered at 291°K. consists of a series of disordering transitions including the well-known first-order transition. There is evidence that hindered rotation occurs within the crystallites at temperatures as low as 220°K.

The temperature variation of the internal friction of tetrafluoroethylene-hexafluore propylene (TFE-HFP) copolymers was studied using a torsion pendulum at frequencies ca. 1 cps. The compositions varied from 0 to 14 mole% HFP. Increasing HFP content was found to, 1 depress the temperature of the crystal disordering transition. 2 increase the size and depress the temperature of the glass I peak 400° to 348°K. 3 decrease the size of the glass II peak. The temperature remined constant at 177°K. The glass I and II peaks were assigned to relaxation mechanisms involving long side branched and linear segments of the molecule and short linear segments, respectively. The depression of the crystal disordering transition was attributed to a decrease in the crystal lite size with increasing HFP content. An analogous glass I peak was observed in high density polyethylene at 333°K. in addition to the previously reported glass II peak at 156°K. Polypropylene exhibits glass I and II Peaks at 273° and 170°K. and two smaller peaks at 53° and 32°K due to hindered rotation of the methyl groups. Further work is required to elucidate the nature of the motions of the molecular backbone responsible for the glass I and II and crystal disordering peaks in the above Polymers. Die Temperaturabhangigkeit der inneren Reibung von Tetrafluorathylen-Hexafluor propylen-Copolymeren (TFE-HFP) wurde mittels eines Torsionspendels bei Frequenzen von ca. 1 Hz untersucht. Ihre Zusammensetzung wurde von 0 bis 14 Mol-% HFP variiert. Es wurde gefunden, das mit zunehmendem Anteil von HFP 1 die Temperature der Unordnungs-Umwandlung im Kristall herabgesetzt wird, 2 die Hohe des I. amorphen Maximum zunimmt und die zugehorige Temperature von 400° auf 348°K abnimmt, 3 die Hohe des II. amorphen Maximum abnimmt, wahrend die zugehorige Temperature bei 177°K konstant bleibt. Als Ursache des I. und II. amorphen Maximum wurden Relaxationsmechanismen angenommen, die den langen Seitenketten und linearen Molekulsegmenten bzw. den kurzen linearen Segmenten zuzuordnen sind. Die Erniedrigung der Temperatur, bei der die Unordnungs-Umwandlung im Kristall stattfindet, wurde als eine Folge der mit zunehmendem Gehalt an HFP abnehmenden Kristallitgrose angenommen. Bei Niederdruck-Polyathylen wurde ein analoges I. amorphes Maximum bei 333°K gefunden, zusatzlich zu einem 11. amorphen Maximum bei 156°K, uber das fruher schon berichtet wurde. Polypropylen zeigt ein I. und 11. amorphes Maximum bei 273° und 170°K sowie zwei kleinere Maxima bei 53° und 32°K, die durch die gehemmte Rotation der Methylgruppen verursacht werden. Weitere Arbeiten sind erforderlich, um die Art der Bewegung des Molekulskeletts aufzuklaren, die fur den I. und II. Glaspunkt und fur die Unordnungs-umwandlung in den betrachteten Polymeren verantwortlich ist.

Mechanical relaxation was studied in bulk polyoxymethylene by means of a torsion pendulum. The magnitude of the large γ peak at 203°K. (for f = 1.1 cycles/sec.) decreases with increasing density. The magnitudes of the β peak at 260°K, and the α peak at 400°K. do not depend on density. The β peak is small unless the specimen contains water or has just been cooled from a temperature above ca. 370°K. The activation enthalpies of the α and γ relaxations are 24 and 27 keal./mole, respectively. The relaxation time distribution and activation enthalpy of the γ relaxation do not depend on density.

Mechanical relaxation has been studied at 0.67 cps in linear polyethylene (LPE) and polytetrafluoroethylene (PTFE) between −190 and −20°C. Specimens were prepared by use of various thermal treatments to produce in LPE a range of crystalline fractions from 0.690 to 0.825 and in PTFE from 0.615 to 0.870. An empirical theory is proposed relating the modulus of the crystalline–amorphous composite solid to the moduli and the volume fractions of the two phases. The empirical theory is shown to be in accord with the bounds of Hill and of Hashin and Shtrikman. The theory is used to determine the magnitudes of the crystalline and amorphous components of the low temperature relaxations in LPE and PTFE from measurements of logarithmic decrement and shear modulus. In PTFE the γ relaxation occurs in the amorphous fraction alone. In LPE the γ relaxation is a composite one, formed from the superposition of a small crystal relaxation and a large amorphous relaxation. For the crystal relaxation in LPE the ratio of relaxed to unrelaxed modulus equals 0.78; for the amorphous relaxation, the ratio equals 0.23. In a specimen of LPE with crystal fraction 0.69 the crystal contribution to the relaxation is 25% of the total. The magnitude of the unrelaxed modulus of the crystal fraction of LPE (modulus of polycrystalline LPE at −190°C) is in reasonable agreement with theoretical calculations of Odajima and Maeda.