Infinite‐dilution viscoelastic properties of poly‐γ‐benzyl‐L‐glutamate in helicogenic solvents

Abstract

synopsisThe storage and loss shear moduli, G , and G", have been measured for solutions of three samples of poly-y-benzyl-L-glutamate with molecular weights from 16 to 57 X lo4, by use of the Birnboim-Schrag multiple-lumped resonator. The frequency range was 106 to 6060 Hz, the concentration range 0.0015-0.005 g/ml, and the temperature 25OC. Two helicogenic solvents with widely different viscosities, dimethylformamide and m-cresol, were used to provide a broader effective frequency range. The intrinsic moduli, extrapolated to infinite dilution, were compared with the predictions of the theory of Ullman for rigid rods; agreement was rather good at the lowest frequencies, but unsatisfactory at high frequencies. The data over the entire frequency range of three logarithmic decades could be described closely by a relaxation spectrum consisting of one terminal relaxation time separated by a gap from a sequence of relaxtion times spaced as in the Zmm theory. The terminal time agrees approximately with that calculated for end-overend rotation of a rigid rod. The additional relaxation mechanisms are tentatively attributed to modes of flexural deformation of the helix.

Spontaneous evolution of self-assembled phases from anisotropic colloidal dispersions

“…The yield stress,  0 obtained from the flow curves showed a power-law dependence on clay concentration which is illustrated in Fig. 1b and this data could be correlated to concentration through 0~c The aforementioned expression is interpreted as originating from a superposition of several Debye relaxations 22,23 . The mean relaxation time is given by  cc .…”

“…Such phases possess a relaxation time spectrum as mentioned earlier. Previous works showed that plotting the two components of dynamic viscoelastic characteristics (modulus or viscosity) against each other yields an arc shaped curve if the process can be depicted with a single relaxation time [21][22][23][24][25][26] . The arc transforms to a semicircle or a skewed semicircle if the material owns a distribution of relaxation times 23,24 .…”

“…As the sample aged, an unambiguous tail started appearing which indicated network formation in these systems [21][22][23][24][25][26] . In a diverse example, the silicate network was detected by the increase in the complex viscosity and storage modulus with decreasing frequency, in the small frequency range of the mechanical spectrum [22][23][24][25] . The increase in the elastic component of the viscosity and modulus is most probably due to the formation of a network structure and the network obviously deforms with different relaxation times than the homogeneous melt, thus we expect a deviation from a semicircle in the afore-mentioned representation.…”

Viscoelastic properties of dilute polymer solutions

“…whose spacings correspond to the ratios given by the Zimm theory (13,14). This specifies (9) (10) where Z' and Z" are the reduced intrinsic moduli given by Eqs.…”

“…8 and 11, Wada (21) obtained the convenient equation (13) and, if 'F can be identified with T 1 of the hybrid spectrum, we calculate for paramyosin B = 4.0 x 10-19 dyn/cm 2 at 20°C. For poly(y-benzyl-L-glutamate), Wada calculated 5 x 10-19 dyn/cm 2 from persistence length data.…”