Molecular weight polydispersities

Tne derivation of eq 10 was undertaken with the assumption that the sample effluent was monodisperse in molecular weight at any V. In reality this is never the case. First, if the frequency of branching varies with molecular weight, species of different molecular weight (but equivalent hydrodynamic volume) may elute at the same V (1 ). Second, molecular weight polydispersity at V results from assorted hardware mixing volumes and band-spreading of the SEC columns 0,11). 

Polymer Typical solvents Typical molecular weight Polydispersity Vendors... 

Stafford, C.M., Russell, T.P, and McCarthy T.J., Expansion of polystyrene using supercritical carbon dioxide, effects of molecular weight, polydispersity, and low molecular weight components, Macromolecules, 32, 7610, 1999. 

In order to determine g as a function of molecular weight, one approach is to use universal calibration with SEC analysis of molecular-weight polydisperse samples (31-33). For a multiarm (MA) branched material, the intrinsic viscosity of polymer eluting in v is ... 

Chin, Y.-P., G. Aiken, and E. O Loughlin, Molecular weight, polydispersity, and spectroscopic properties of aquatic humic substances , Environ. Sci. Technol., 28, 1853-1858 (1994). 

A central question is that of the size and the polydispersity of the polymeric supramolecular species produced. Of course, their size is expected to increase with concentration. The molecular weight polydispersity depends on the stability constants for successive associations. 

The series of ten different segmented poly(ester-urethane)s obtained was characterized by SEC (molecular weight, polydispersity), DMA (thermo-mechanical properties), DSC (thermal properties) and Instron (mechanical properties). Before the mechanical testing could be performed, it was necessary to establish procedures for film production. 

Usually the adjustment of properties is carried out by using mixtures of high molecular weight polydispersed telechelic prepolymers and simple low molecular weight molecules. Recently, we produced a review about the prepolymers mentioned above [8] which we will not describe in this paper. This work concerns the synthesis of low molecular weight monodispersed molecules, their properties and eventually their applications. 

The polymer properties of cellulose are usually studied in solution, using solvents, such as CED or Cadoxen (see Section 9.2). On the basis of the solution properties, conclusions can be drawn concerning the average molecular weight, polydispersity, and chain configuration. However, the... 

Hence the key economic control objectives for polymer reactors are typically average molecular weight, polydispersity, viscosity, composition, partical size distribution, and production rate (plus color, phase... 

The anisotropic phase is separated from the Isotropic by a two-phase region. The size of the two-phase gap depends on parameters such as temperature, molecular weight, polydispersity, etc. In figure 2, the extent of the two-phase region is not represented, but the average values are indicated. 

Molecular weight polydispersity may also markedly affect the determination of the equilibrium rigidity of the macromolecule from the experimental dependence of [n]/[r)] on M. In fact,... 

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