The frequency dependence of dynamic mechanical properties of rat tail tendon (RTT), enzyme-solubilized collagen membranes (ESC), AKM-23 dialysis membranes, and gelatin film have been measured at 110, 11, and 3.5 Hz from - 160 to 220°C. RTT and AKM-23 are devoid of a rubbery region; there are as many as six mechanical loss transitions. Gelatin and ESC membranes behave as rubbery materials above room temperature; only three tan δE peaks can be resolved for these materials. Strain birefringence was used to measure the crystalline and amorphous contribution of orientation induced by strain. Both the birefringence and the strain optical coefficient are sensitive to the amount of water in a sample. The effect of chemical swelling agents and of annealing on birefringence are described. Stress relaxation data on gelatin film were analyzed with the rubber elasticity theory to give the average number of chains per unit volume, the specific polarizability, the stress-birefringence ratio and the average molecular weight between hydrogen bonds were calculated. The intrinsic amorphous birefringence for “wet” gelatin film is 1.25 × 10−2; it is estimated to be about 6 × 10−2 for “dry” gelatin film.

Dynamic mechanical and rheo-optical studies of collagen and gelatin.

The far‐infrared spectra of the Li+, Na+, K+, Cs+ salts and acid forms of polyelectrolytic ethylene‐methacrylic acid copolymers have been examined in the 800–33‐cm−1 region at ambient and low temperatures. A broad band, which shifts to lower frequency as the cation mass is increased, is attributed to cation motion in anionic fields, and the appearance of a low frequency band, whose intensity is related to the cation properties, is assigned to perturbed skeletal motions of a neighboring polymer segment. Models are proposed and analyzed for the vibrational modes involving ion motion. The vibrational force constants for aggregate distortion, as calculated from the observed ion‐motion frequencies, are in agreement with such constants computed here employing an ion‐multipole potential energy function which does not use these experimental data. The spectral and theoretical results are considered in terms of the molecular interactions of importance in polyelectrolytes and in the physical properties of these mate...

Cation Motion in Anionic Fields of the Polyelectrolytic Salts of Ethylenemethacrylic Copolymers

Changes in structure and properties due to mechanical fatigue for polyurethanes containing poly(dimethyl siloxane)

The transition temperature of high-density polyethylene (PE), low-density PE, and hydrogenated poly(butadiene), which was detected by the spin-labeled ESR method, was evaluated. The detected transition corresponded to the β transition of semicrystalline polymer PE. The transition temperature was found to depend on the crystallinity, the molecular weight of the sample, and labeled site. The β relaxation around chain-end segments was observed by the selective spin-labeling method. The mobility of the end segment as well as the inner segments was revealed to depend on the molecular weight (Mn) of the sample. The motional length scale (cooperative segment length) ξ of amorphous PE at Tg was estimated to be around 2 nm, which was the same order as the reported ξ for various polymers and the Kuhn length of PE.

ESR Study on Segmental Motion of Polyethylene in Amorphous Region, Dependent on Crystallinity, Molecular Weight, and Labeled Site

The internal friction of linear high‐density polyethylene (LPE) at cryogenic temperatures was investigated using an inverted free‐oscillating torsion pendulum (1–3 Hz). The results show that LPE is not viscoelastically inactive below its γ peak as had been previously contended. Two new relaxation peaks, δ at 48 °K and e at 20 °K, were observed. The characteristics of these loss maxima are identical to those of the cryogenic relaxations observed for polyethylene terephthalate and polyoxymethylene. A mechanism consisting of the motions of dislocation jogs and their interactions with specific conformational kink defects is proposed. This mechanism is consistent with all the experimental data in that it accounts for the effects of orientation and thermal histories on the relaxation strength of the δ and e internal‐friction peaks.

T. Kajiyama

Papers

The γ Relaxation of a Poly(ethylene-co-methacrylic acid) Polymer and Its Salts