Nematic solution

Berry, G.C. Static and Dynamic Light Scattering on Moderately Concentraded Solutions Isotropic Solutions of Flexible and Rodlike Chains and Nematic Solutions of Rodlike Chains. VoL 114, pp, 233-290. 

A vibrational analysis (excluding vibrations of the MCO unit) is used in interpreting the results of a H NMR, nematic solution study ofTj4-C4H4Fe(C0)3... 

Yang et al. (15) spun fibers from a partially (biphasic) nematic solution of cellulose in 1 3/NH4SCN. Tenacities of ca. 3 g/d and moduli of ca. 155 g/d were obtained. 

Light Scattering from Nematic Solutions with Complex %xture and Phase Separation in Poor Solvents... 

The Nematic - Isotropic Phase Transition. For nematic solutions kept free from moisture, the phase transformations described in the preceding were not observed, but the nematic phase could be reversibly transformed to the isotropic phase over a temperature interval Tj - Tj lOK. For the sample with w = 0.041, this transition occurred over the range T = 92 C to Tj = 101 0. For temperatures between T and Tj, the sample was biphasic, with the isotropic and nematic phases coexisting. This behavior is similar to that observed in previous studies, in which Tj - Tj is observed to be independent of w over a range of w for which Tj increases with increasing w (3,4). 

The dry nematic solution exhibits a smooth texture after being annealed, with a field of disclinations at any glass-solution interface. A nematic phase produced by cooling the isotropic phase will exhibit a complex, mottled texture that slowly anneals to the smooth texture. The ratio Rvv(q)/ Hv(q) (for e = 20 deg.) for either morphology indicates appreciable orientational averaging of the orientation fluctuation. Photon correlation scattering on the... 

In order to discuss the rheological properties of stiff-chain polymer solutions, we need an expression for stress. The stress a induced in a homogeneous isotropic or nematic solution by a macroscopic flow was formulated by Doi [114], who used the Kirkwood general theory [116] to show... 

Here a is the elastic stress which arises from the change in the (dynamic) free energy in the macroscopic flow, while o(V) and a(S) are the viscous stresses produced by the polymer-solvent friction and the solvent-solvent friction, respectively. In concentrated isotropic polymer solutions, the elastic stress overwhelms the viscous stresses, so the latter are often neglected. However, it should be noticed that the viscous stresses may become significant in more dilute solutions as well as in nematic solutions where the elastic stress diminishes. 

Actual calculations of w,E) for isotropic and nematic solutions will be described in Sects. 8 and 9 respectively. Furthermore, derived approximately for isotropic solutions in a steady shear flow in Sect. 8, but it will be neglected for nematic solutions in Sect. 9. 

Following Larson [154] and Larson and Mead [155], we discuss the rheological behavior of nematic solutions of a rodlike polymer on the basis of Doi s theory... 

With increasing flow rate, the orientational state in the nematic solution should change. Larson [154] solved numerically Eqs. (39) and (40b) with Vscf(a) given by Eq. (41) for a homogeneous system (T[f ] = 0) in the simple shear flow to obtain the time-dependent orientational distribution function f(a t) as a function of k. The non-steady orientational state in the nematic solution can be described in terms of the time-dependent (dynamic) scalar order parameter S[Pg.149]

Tumbling regime At very low shear rates, the birefringence axis (or the director) of the nematic solution tumbles continuously up to a reduced shear rate T < 9.5. While the time for complete rotation stays approximately equal to that calculated from Eq. (85), the scalar order parameter S,dy) oscillates around its equilibrium value S. Maximum positive departures of S(dy) from S occur at 0 n/4 and — 3n/4, and maximum negative departures at 0 x — k/4 and — 5it/4, while the amplitude of oscillation increases with increasing T. 

A NMR study of trans -PtCl2(C2H4)py in a nematic solution in CD2CI2 shows the ratio of dgem dCis to correspond with the structure obtained by neutron diffraction.697 The plane of the pyridine ring is inclined at an angle to the PtCl2 plane with rapid reorientation between the symmetry-related forms.698... 

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