Intrinsic viscosity complexes

In this section alone, in order to avoid confusion the intrinsic viscosity [rf] represents that of a particle and is dimensionless and the intrinsic viscosity [rj] represents that of a polymer and has units of gem-3. From these expressions we know that as we increase the volume fraction above each of these values, the product demarcates the structural transition. For particles there are many situations where it is relatively easy to determine the volume fraction, but for polymers the situation is more complex and it is most convenient to use a mass concentration. We can rewrite this relationship in terms of the mass of added particles in gem-3 ... 

Viseometry and rheology Intrinsic viscosity [t ] can be related to complex size via MHKS, a coefihcient... 

The presence of a second type of repeat unit causes the dilute solution behavior to be more complex than that of homopolymers [1], Copyolymer composition and sequence distribution directly effect the intrinsic viscosity. Interactions between unlike chain segments and preferential interaction of solvent molecules with one of the comonomers are also of considerable importance. 

Table 4 was unity, which indicated the five-coordinate structure as in the PVMI-heme complex. PBLGIm forms an a-helix, and the helix content and intrinsic viscosity were unchanged in the PBLGTm ferriheme complex. The formation constant of the ferriheme complex with PBLGTm was not so different from that of the imidazole complex (Table 4). The strong coordination was thought to be due to an additional hydrogen bond between a propionic residue of ferriheme and a carbonyl residue in the side chain of PBLGTm, as shown in Fig. 4(d)w ...

O rate constant for reaction between [Co(III)(en)2(PNVl)CllCl2 and Fe(ll)edta, A rate constant for reaction between monomeric [Co(IIlXen)2(NEI)CllCli and Fe(II)edta, intrinsic viscosity of PVMI-Co complex solution, PVNI = poly(N-vinyl-2-methylimidazole),... 

Degradation in bulk. Davis and Golden (85) have studied the degradation of PTHF in bulk at various temperatures. The polymers that they studied were prepared using a THF/PF5 complex either in an open flask (polymer A) or in vacuum with exposure to air during the work up (polymer V). The intrinsic viscosity of polymer A. heated at fixed temperatures up to 150° C in a sealed system, fell rapidly to a constant value. Polymer V behaved similarly but the decrease was considerably smaller. When heated in air at a fixed temperature the viscosity of both polymers decreased continuously with eventual destruction of the polymer. Temperatures well in excess of 150° C were required for complete degradation of polymer A or V in vacuum. 

The bimolecular initiation leads to much more complex results. The essential difference between the former kinetic scheme and the bimolecular initiation (or a similar kinetic scheme) lays in the dependence in the latter case of Mn and Mw on the rate of addition of monomer. Increasing the rate of addition results in a higher Mw and produces, therefore, a polymer of higher intrinsic viscosity. 

Particle asymmetry has a marked effect on viscosity and a number of complex expressions relating intrinsic viscosity (usually extrapolated to zero velocity gradient to eliminate the effect of orientation) to axial ratio for rods, ellipsoids, flexible chains, etc., have been proposed. For randomly orientated, rigid, elongated particles, the intrinsic viscosity is approximately proportional to the square of the axial ratio. 

Experimental evidence on whether L or other molecular parameters (Stokes radius, viscosity radius, radius of gyration, the product of intrinsic viscosity and molecular weight, etc.) govern partitioning in SEC supports has been summarized by Dubin [29]. He concludes that none of these parameters perfectly correlates with SEC partitioning when a wide variety of macromolecules, of both rigid and flexible structure, are used as test probes. This may result from the complex uncharacterized nature of the pore space occupying the porous supports commonly utilized. 

The absorption spectrum studies presented above merely reflect the electronic environment of the molecule and do not give specific information about the type of interaction. The data which must be accounted for in considering a physical mode for the binding process can be derived from several different approaches. Hydro-dynamic measurements on the DNA-drug complex are of interest, since Lerman58, S9 has established that an increase in the intrinsic viscosity of DNA and a decrease in the sedimentation coefficient of the polymer are two criteria for intercalation of ring systems between base pairs of a double-helical DNA. 

The relationship between the intrinsic viscosity of DNA and the amount ( r ) of bound tilorone was studied28. The intrinsic viscosity of the complex increases with r up to a limiting value of about 0.05. The maximum relative enhancement of viscosity was about 1.7. In addition, at the same ionic strength and at a ligand to DNA-P molar ratio of 0.1, the sedimentation rate of DNA was decreased to 78% of the value in the absence of ligand. 

As has been pointed out, for SEC of complex polymers no simple correspondence exists between elution volume and molar mass. It is, therefore, useful to determine the molar mass not via a calibration curve but directly from the SEC effluent. This can be done by using molar-mass-sensitive detectors based on Rayleigh light scattering or intrinsic viscosity measurements [45]. 

Another very useful approach to molar mass information of complex polymers is the coupling of SEC to a viscosity detector [55-60]. The viscosity of a polymer solution is closely related to the molar mass (and architecture) of the polymer molecules. The product of polymer intrinsic viscosity [r ] times molar mass is proportional to the size of the polymer molecule (the hydrodynamic volume). Viscosity measurements in SEC can be performed by measuring the pressure drop AP across a capillary, which is proportional to the viscosity r of the flowing liquid (the viscosity of the pure mobile phase is denoted as r 0). The relevant parameter [r ] is defined as the limiting value of the ratio of specific viscosity (qsp= (n-noVflo) and concentration c for c—> 0 ... 

If a continuous viscosity detector is coupled to an FFF channel, viscosity distributions and intrinsic viscosities can be measured without calibrating the channel [76]. The coupling of one FFF instrument to another opens the possibility of obtaining two-dimensional property distributions of complex materials the combination of sedimentation- and flow-FFF provides the size-density distribution of complex colloids, whereas a combination of thermal- and flow-FFF yields the composition-molecular weight distribution of copolymers. 

The formation of polymer-polymer complexes as a rule is observed in aqueous media5,33. The viscosity of complexes in water is about 0.05-0.10 dl/g and close to that of globular proteins. Aqueous solutions have some features low intrinsic viscosity values are independent of the matrix molecular weight, the absence both of the concentration dependence of the reduced viscosity and the polyelectrolyte anomaly, and high values (about 30 s) of the sedimentation constant. 

The stability of PMAA-PVP complexes5 27 S7) has been investigated as a function of temperature, ionization of the polyelectrolyte component of the complex, and organic solvent. The complexes have been found to be very stable even at elevated temperature (Fig. 7, curve 4). The intrinsic viscosity is about 0.10 dl/g and does not depend on temperature up to 70 °C. The compact structure of the complex is retained up to some value of the degree of neutralization, the viscosity is low and does not change. As neutralization proceeds, the viscosity sharply increases and the PMAA-PVP system behaves as a usual polyelectrolyte (Fig. 8). It should be noted that the stabilization of the compact structure of the complex, due to complex formation, was also observed on the ionization of other systems52). 

PMAA-PVP complexes were found to be the most stable among the investigated complexes. Such stability should be expected because hydrophobic interactions favor the additional stabilization of the compact structure of the complex in water. Thus, the structure of the PMAA-PVP complex in a water-dimethyl sulfoxide mixture remains compact up to 70 vol-% DMSO (Fig. 9) as follows from the low intrinsic viscosity values obtained in these mixtures. 

Fig. 9. Dependence of sedimentation constants (1) and intrinsic viscosities (2,3,4) of complex solutions on the composition of H20-DMS0, PAA-PVP (1,3), PMAA-PVP (2), PMMI-PVP (4). . >...

A further dependence of the intrinsic viscosity on the content of water-dimethyl sulfoxide mixed solvent for the PVP-MAA/St copolymer system76 has been found the viscosity increases already beyond 30 vol-% of DMSO in the mixture. This indicates the dissociation of the polymer complex. At the same time, in the PMAA-PVP system27, the compact structure of the complex remains intact up to 70 vol-% content of DMSO, i.e. these complexes are very stable to the organic solvent. 

The different shape of the [ -composition curves for binary polymer mixtures (PMAA and PVP) in water and DMSO indicates the absence of the complexes in DMSO, The intrinsic viscosity passes through a minimum in water while in DMSO the viscosity is an additive function of the intrinsic viscosities of the individual components (Fig. 14). 

The PAA-PVP system in methanol and the PMAA-PVP system in DMF display the typical properties of polycomplexes, namely low values of intrinsic viscosity independent of the matrix molecular weight (for PVP with molecular weight of 50 MO and 560000, the intrinsic viscosity [ /], of PA A-PVP complexes in methanol is equal to 0.07 dl/g), the absence both of the concentration dependence of the reduced viscosity, and of the polyelectrolyte anomaly. 

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