Poly-benzyl-L-glutamate PBLG

Supported in part by the National Science Foundation and the Office of Naval Research. 

If the solvent is good, the only important intermolecular interactions are then steric short range excluded volume repulsions. 

The mesomorphic behavior of a solution of rigid rods has been studied by several authors.i-iZ-Ll In particular, for long rods of length b and radius a, OnsagerL has shown that the effective excluded volume per rod in the isotropic phase is of order b a. The actual volume occupied per rod is ira b. A lyotropic transition to a nematic phase occurs at a rod concentration O given by 

In Section II, we shall briefly recall the statistical mechanics of the helix-coil transition for isolated chains. We shall then present an argument showing that there is little tendency for non-interacting molecules to exhibit substantial mesomorphic fluctuations. A mean field theory for incorporating the interchain interactions will be developed in Section III in the cooperative limit for helix-coil transition. Some final remarks will be made in Section IV. 

The helix-coil transition of a polypeptide chain consisting of N monomers is usually described in terms of two parameters  

---

For aprotic polar organic solvents only few widely applicable alignment media are known. The lyotropic mesophase of poly(y-benzyl-L-glutamate) (PBLG) with DMF [37] has the disadvantage of a relatively strong minimum alignment. Bicellar... 

PolyCy-benzyl L-glutamate) (PBLG), 15 109 Poly(y-ketosulfide)s, optically active, 23 711 Poly(P-alanine), 1 292 Poly-P-hydroxybutyrate (PHB), 12 482 Polybetaines, 20 479-482 applications of, 20 482 preparation of, 20 480-481 solution properties of, 20 481-482 synthesis of, 20 479-481 Polyborates, 4 256-258 Polyborosiloxanes, in silicon carbide manufacture and processing, 22 533 Polybrominated diphenyl ethers (PBDEs), 13 142-143 20 56... 

Fig. 7. Comparison of experimental phase boundary concentrations between the isotropic and biphasic regions for various liquid-crystalline polymer solutions with the scaled particle theory for wormlike hard spherocylinders. ( ) schizophyllan water [65] (A) poly y-benzyl L-glutamate) (PBLG)-dimethylformamide (DMF) [66-69] (A) PBLG-m-cresoI [70] ( ) PBLG-dioxane [71] (O) PBLG-methylene chloride [71] (o) po y(n-hexyl isocyanate) (PHICH°Iuene at 10,25,30,40 °C [64] (O) PHIC-dichloromethane (DCM) at 20 °C [64] (5) a po y(yne)-platinum polymer (PYPt)-tuchIoroethane (TCE) [33] ( ) (hydroxypropyl)-cellulose (HPC)-water [34] ( ) HPC-dimethylacetamide (DMAc) [34] (N) (acetoxypropyl) cellulose (APC)-dibutylphthalate (DBP) [35] ( ) cellulose triacetate (CTA)-trifluoroacetic acid [72]...

In fact, for random-coil conformations, b in Equation 41 is explicitly related to the exponent in the Mark-Houwink equation by 3b = a 1. In this way values of M may be determined directly from measurements of D° provided KD and b are known. Although both these parameters could in principle be calculated from a detailed knowledge of the geometry of the solute, it is usual to regard them as experimentally determinable parameters. A similar relationship has also been found to hold true for the polypeptide poly(y-benzyl L-glutamate) (PBLG) dissolved both in 1,2-dichloroethane and in dichloroacetic acid. These results are shown in Figures 6 and 7, respectively. 

Poly-y-benzyl-L-glutamate (PBLG) CDCI3, CD2C12, DMF, THF, Dioxane Chiral 95,96... 

Poly(y-benzyl-L-glutamate) (PBLG), whose structure is given by the formula... 

Figure 33 shows similar dependences of [nj/lnl on M for solutions of poly(7-benzyl-L-glutamate) (PBLG) > (Curve 1). These are compared with data for poly(chk>rohexyl isocyanate) (Curve 2). Experimental values of In]/[r)J for PBLG do not permit the determination of the limiting value ((n]/[r)l)a. because they covet only the initial part of the curve [nJ/lnl = f (M). 

Poly(7-benzyl-L-glutamate) (PBLG) is a typical repre ntative of the polymers. Its solutions in spiralizing solvents exhibit very high positive birefringence both in mechanical (Table 9, Fig. 33) and electric fields. 

Figure 6.17 Normalized intrinsic viscosity [r ]/[)7]o for a dilute solution of poly(y-benzyl-L-glutamate) (PBLG) = 208,000) in m-cresol. The line is a calculation for the rigid-dumbbell model, with the relaxation time t = lj6Dro adjusted to the value 10- sec to obtain a fit. The stress tensor for a suspension of rigid dumbbells is given by Eq. (6-36) with Cstr replaced by k T/Dro-(From Bird et al. 1987 data from Yang 1958, Dynamics of Polymeric Liquids, VoL 2, Copyright 1987. Reprinted by permission of John Wiley Sons, Inc.)...

Figure 6.20 (a) Viscosity of solution of poly(y-benzyl-L-glutamate) (PBLG molecular weight 231,000), in m-cresol as a function of shear rate at 29 C for various mass percentages ranging from dilute ( 0.31%) to semidilute (0.31-2.5%) to concentrated isotropic (5-9.5%). The different symbols and lines refer to data taken on different instruments, (b) Zero-shear viscosity as a function of concentration, (reprinted with permission from Mead and Larson, Macromolecules 23 2524. Copyright 1990 American Chemical Society.)... 

---