Polymers, homologous

Homologous Polymer Blends A subclass of polymer blends limited to mixtures of chemically identical polymers differing in molecular mass. 

The relation finking the sedimentation coefficient with the molecular weight for a homologous polymer series given above is (see [61, 111]) ... 

Apart from salts with homologous polymer anions, Graham s glass always contains trimeta- (6-10%), tetrameta- (up to 4%.) and very small amounts of pentameta- and hexametaphosphate (see Section IV,D) with cyclic anions and also, to a small extent, cross-linked phosphates with tertiary P04 tetrahedra (see Section V) (284, 85, 364) ... 

Diffusion coefficients can be related to molecular weight in three ways first by application of the Stokes-Einstein equation, second by combination with sedimentation data, and third by consideration of homologous polymer solutions. In the first method, an equivalent spherical size of the molecules is calculated from Dt, and an approximate molecular weight is found by combining these data with the appropriate density. In the second method, diffusion measurements are coupled with those of sedimentation velocity to give molecular weights, and in the third method, molecular weights may be determined directly from measurements of diffusion coefficients alone once a calibration has been... 

Homologous Polymers. As the size of a molecule increases, it is expected that its diffusion coefficient will decrease. Figure 5 shows a plot of D° vs. M for solutions of polystyrene in 2-butanone (methyl ethyl ketone) where the relationship between D° and M may be expressed by the semiempirical formula... 

Thus the theories on the conformation of the macromolecules in solution, which have already been well developed, can be proved experimentally. However, in order to attain further progresses in this fields it is necessary to acquire a deeper theoretical knowledge of the relationships between chemical structure and rotatory power and to investigate other series of homologous polymers having simple monomer unit structure in order to facilitate the theoretical interpretation of the experimental results. 

One of the most surprising generalities in the world of polymers is that [r ] values for a series of homologous polymers under a fixed solvent condition (solvent and temperature) follows a simple power law as... 

For a series of homologous polymers A2 depends on M as well as T and the nature of the solvent. Experimental studies have repeatedly shown that for a given polymer there is a combination of poor solvent and temperature 0 for which A2 vanishes regardless of M. This spetial poor solvent at is called the theta solvent, and 0, the theta temperature. 

Taft [109] postulated that the rate of aliphatic ester hydrolysis is a function of substituent type. Using methyl as a standard substituent, he compared, for example, the effects of larger alkyls, and interpreted the results by means of two constants characterizing the steric and polar behaviour of the alkyls. In copolymerization theory, the Taft equation was used many times to describe the relative reactivities (See Chap. 5, Sect. 5.2) in homologous polymer series... 

Virk et al. defined an intrinsic concentration for comparing DR effectiveness of homologous polymers of different MW and also different polymers... 

Since the homologous polymer blends are known to be miscible It Is not surprising that mixtures of HDR with HDR or IDK with U>BE are miscible as well (12, 13). However, due to the diversity of polymerization methods and the variety of resulting molecular characteristics LLDra/LLDra systems are not always miscible (10, 14-15). In our laboratory three series of blends were prepared by Identical procedure of mixing the same LLDPE with two other LLDPE resins and with LDPE. The zero-shear viscosity vs. composition dependence, n vs. W2, of these systems Is presented In Fig. 1. Only the LLDPE s prepared with the same Tl-catalyst were found to be miscible (curve 2). Neither blend of LLDPE with LDPE (curve 3) nor LLDPE prepared with a vanadium catalyst LLDPE (curve 1) were miscible. There are Indications In the literature (8) that... 

The n vs. n dependence is often used while discussing the dynamic data of polymer blends. Since for simple liquids the plot has the form of a semi-circular arc, deviation from a semi-circle is sometimes Identified with Immlsclbillty. However, as frequently demonstrated for homopolymers (16) and homologous polymer blends ( ) the form of the n" vs. n plot is determined by the shape of the relaxation spectrum the molecular polydlsperslty can modify the Cole-Cole plot as much as the presence of the Interphase. As a rule, the presence of (unsubtracted) yield stress appears in the plot as a sudden departure from a semi-circular pattern at higher n level. 

Polymer blend (PB) Homologous polymer blend Miscible polymer blend... 

Mixture of two homologous polymers (usually a mixture of narrow molecular weight distribution fractions of the same polymer). 

Polymer blends, homologous see Homologous polymer blends Polymer blends, terminology 12... 

For lignin polymers with an obviously nonlinear chain topology, formulation of the concept of a homologous polymer may present a quite difficult task. At the current state... 

The elution volumes of a homologous polymer series depend on the molar mass because the hydrodynamic volumes of macromolecules vary regularly with molecular weight. The hydrodynamic volume is proportional to the product rf M. A universal calibration curve of log [rf M) = f Ve) for various linear and branched polymers actually does exist for each gel material (Figure 9-19). 

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