Poly molecular weight dependence

The intrinsic viscosity of poly(7-benzyl-L-glutamate) (Mq = 219) shows such a strong molecular weight dependence in dimethyl formamide that the polymer was suspected to exist as a helix which approximates a prolate ellipsoid of revolution in its hydrodynamic behaviorf ... 

Rymden, R. Stilbs, P. (1985b). Concentration and molecular weight dependence of counterion self-diffusion in aqueous poly(acrylic acid) solutions. Journal of Physical Chemistry, 89, 3502-5. 

For homopolyelectrolyte, we first studied the ellipsometric measurement of the adsorption of sodium poly(acrylate) onto a platinum plate as a function of added sodium bromide concentration (5). We measured the effect of electrolyte on the thickness of the adsorbed layer and the adsorbances of the polyelectrolyte. It was assumed that the Donnan equilibrium existed between the adsorbed layer and the bulk phase. The thickness was larger and the adsorbance of the polyelectrolyte was lower for the lower salt concentration. However, the data on the molecular weight dependence of both the adsorbance and the thickness of the adsorbed polyelectrolyte have been lacking compared with the studies of adsorption of nonionic polymers onto metal surfaces (6-9). 

The aim of this paper is to offer experimental results for the molecular weight dependence of adsorption of polystyrene-sulfonate) onto a platinum plate from aqueous NaCl solution at 25 °C. Measurements of poly(styrenesulfonate) adsorption were carried out by ellipsometry. The dependences of molecular weight and added salt concentration on the thickness of the adsorbed layer and also the adsorbances of polymer and salt are examined. 

The Lewis basicity of the solvents was found to be more important for the solvatochromism than the solvent polarity, since such Si... solvent and Si... F interactions are competitive in the presence of solvents with donor atoms. In contrast, the analogous non-fluorinated polysilane, poly(methyl-/z-propylsilylene), revealed a disordered conformation in both coordinating and non-coordinating solvents. Additionally, the UV spectra of various molecular weight fractions of 87 showed an unusual molecular weight dependency an isosbestic point is apparent, suggesting an equilibrium between globule- and rod-like conformations at room temperature, which was also evident from the... 

In addition, polyelectrolytes such as poly(acrylic acid-alt-maleic anhydride) (pyran) are reticuloendothelial stimulants, induce resistance to tumor growth [462,463] and show interferon-inducing ability and antiviral activity. The pyran activity may be dependent upon molecular weight. Low molecular weight materials of narrow polydispersity activate macrophages however antitumor activity does not appear to be molecular weight dependent [460]. 

A frequency dependence of complex dielectric permittivity of polar polymer reveals two sets or two branches of relaxation processes (Adachi and Kotaka 1993), which correspond to the two branches of conformational relaxation, described in Section 4.2.4. The available empirical data on the molecular-weight dependencies are consistent with formulae (4.41) and (4.42). It was revealed for undiluted polyisoprene and poly(d, /-lactic acid) that the terminal (slow) dielectric relaxation time depends strongly on molecular weight of polymers (Adachi and Kotaka 1993 Ren et al. 2003). Two relaxation branches were discovered for i.s-polyisoprene melts in experiments by Imanishi et al. (1988) and Fodor and Hill (1994). The fast relaxation times do not depend on the length of the macromolecule, while the slow relaxation times do. For the latter, Imanishi et al. (1988) have found... 

Yu, Z., Yahsi, U., McGervey, J.D., Jamieson, A.M., Simha, R. (1994) Molecular weight-dependence of free volume in polystyrene studied by positron annihilation measurements . J. Poly. Sci. B. 32,2637. 

As shown in part A of Table IV, fg increases slightly with PTMG MW, while decreases. A similar trend was observed with low molecular weight polymers of poly(vinyl acetate) and polystyrene (6). It is reasoned that the molecular weight dependence of fg arises because longer soft segment length requires more volume to accommodate the increased number of conformations available to such a chain. 

Ellingson PC, Strand DA, Cohen A, Sammler RL and Carriere C (1994) Molecular weight dependence of polystyrene/poly(methyl methacrylate) interfacial tension probed by imbedded-fiber retraction. Macromolecules 27 1643-7. 

The transition between the two regions of molecular weight dependence is well demonstrated by poly(a-methylstyrene) (26). Figure 2 shows the dependence of the initial rate on the initial chain length or twice the DP of a series of fractions. The variation is linear for small N, indicating that initiation occurs at random. A plateau is approached at a molecular weight of about 6 X Since... 

Cao BH, Kim MW (1995) Molecular weight dependence of the surface tension of aqueous poly(ethylene oxide) solutions. Faraday Discuss 98 245-252... 

Goh, C. et al.. Molecular-weight-dependent mobilities in regioregular poly(3-hexyl-thiophene) diodes. A/ /)/. Phys. Lett. 86, 122110, 2005. 

Umemoto, S. et al.. Molecular weight dependence of primary nucleation rate of poly(ethylene succinate), J. Macromol. ScL, Part B Phys. 42, 421 30, 2003. 

Table 17.1 shows a test of this predicted molecular weight dependence for polystyrene latex particles, sterically stabilized by thin layers of poly(oxyethylene) of molecular weight 750, using poly(oxyethylene) of different molecular weight as the free polymer. These experimental results were reported by Cowell et al. (1978). It is apparent that V2 decreased with molecular weight with an exponent of ca —0 5, as expected from the crude theory. 

M. Brinkmann and P. Rannou, Molecular weight dependence of chain packing and semicrystal-hne structure in oriented films of regioregular poly(3-hexylthiophene) revealed by high-resolution transmission electron microscopy. Macromolecules, 42, 1125 (2009). 

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