Effect of chain flexibility

Values of B calculated from the ordinate intercepts are shown in Fig. 23 as a plot of B/(2q)3 against the number of the Kuhn segments N. For N<4, the data points for the indicated systems almost fall on the solid curve which is calculated by Eq. (78) along with Eqs. (43), (51), (52), and Cr = 0. A few points around N 1 slightly deviate downward from the curve. Marked deviations of data points from the dotted lines for the thin rod limit, obtained from Eq. (78) with Le = L and de = 0, are due to chain flexibility the effect is appreciable even at N as small as 0.5. The good lit of the solid curve to the data points (at N 4) proves that the effect of chain flexibility on r 0 has been properly taken into account by the fuzzy cylinder model. 

The effect of chain flexibility is also evidenced by replacing aromatic hardeners by aliphatic ones. This produces an increase in the fracture resistance at room temperature (Kinloch and Young, 1983). 

It is not always as easy to draw such conclusions. For the effect of chain flexibility... 

Wallin T, Linse P. Monte Carlo simulations of polyelectrolytes at charged micelles. 1. Effects of chain flexibility. Langmuir 1996 12 305-314. 

If the semi-flexible liquid crystalline polymers are well stretched along the director and thus the order parameter is high, the underlying equations are valid and can demonstrate qualitatively the effect of chain flexibility on the splay elastic constant. 

Table 3.9 Effect of Chain Flexibility of Crystalline Melting Point...

TABLE 5.4 Effect of Chain Flexibility on the Transition Temperatures of Side-Chain Liquid Crystal Polymers Having a Common Mesogen [4]... 

In the present paper, we first review briefly the rigid rod models for liquid crystalline phase transitions. In these models, emphasis is placed on the anisotropic form and on the orientation dependent intermolecular interactions between rigid particles. Conformational studies on isolated chains have shown that liquid crystalline polymers are rather semi-rigid in character although only a narrow range of deformations is possible due to intrachain interactions. The effect of chain flexibility on the formation of liquid crystalline phases has been pointed out both experimentally and the-oretically J. 

Figure 9.2 The effect of chain flexibility of macromolecules on their conformations in solution, in the molten state, or in the solid state. The flexibility of a macromolecule can be correlated to the type of crystal and physical properties of the corresponding solid polymer. (Reprinted from Samulski, Physics Today 35(5) 40. Copyright 1982, with permission from the American Institute of Physics.)...

Fig. 1 Schematic illustrations of effects of chain flexibilities on stmctural motifs and associated entropic effects occurring on polyelectrolyte complex formation. Complexation of flexible polyanions and polycations a may lead to non-stoichometric release of counterions being an important contribution to the increased entropy associated with PEC formation. Complexation of semiflexible polyanion and flexible polycation may lead to non-stochiometric release of counterions relative to the overall valence of the polycation (b). Complexation between semiflexible polyanions and polycations may yield a near stoichiometric release of counterions associated with the counterion exchange reaction in an idealized ladder-lUse structure (c). The associated structures are often referred to as d scrambled egg and e railway track structural motifs for the flexible and inflexible, respectively, pairs of interacting polymers. Panels d and e are reproduced from ref [25]with permission from John Wiley and Sons...

In conclusion, the work of Picken et al has provided a theoretical framework supported by many experimental data on the formation of order in a quiescent nematic polymer solution. It explains the concentration dependence of the nematic-isotropic transition temperature and deals with the effects of chain flexibility and molecular weight distribution. Moreover, the structure and properties of a nematic solution under shear and elongational flow have been clarified to a great extent. 

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