Degree of polymerization change

The weight average degree of polymerization changes in the vicinity of gel point according to [70]... 

So, the rate and degree of polymerization change similarly in the presence of 3,6-bis-(ortho-carboxybenzyl)-9-isopropyl-carbazole arrd the polymers synthesized have the higher amount of syndiotactic sequences [3]. 

The family of curves consist of two straight-line portions, with a change of slope occurring at a degree of polymerization in the range 10 -10. ... 

On-line changing of solvent from DMSO to H2O for a starch glucan establishing an absolute calibration function characteristics of mass and molar degree of polymerization distribution for a broad distributed starch sample... 

Figures 4 and 5 show that the degree of polymerization and the intrinsic viscosity increase with increasing the comonomer concentration. Thus, the increase in the comonomer concentration would increase DP and, consequently [rj] Eq. (2). However, the exponent of the monomer concentration for the degree of polymerization decreases at a high comonomer concentration. The abrupt change in the exponent at comonomer concentration >2.1 M/L (Eq. 9) may be ascribed to polydispersity. This was found by others [34] to be at 2.1 and 2.2 M/L, although it starts theoretically at 2.0 M/L.

The molar rate of change of polymeric species of degree of polymerization n in a well-mixed, continuous flow tank reactor is related to the kinetic rate of propagation of unassociated polystyryl anions plus their withdrawal rate in the reactor s effluent. Feed streams are void of polymeric substances, but contain monomer initiator and solvent. 

As suggested by Barrett (2), it is assumed that following the particle nucleation stage, the polymerization proceeds in the particle (monomer/polymer) phase with no mass transfer limitation. Therefore, the dispersion polymerization is similar to a mass or suspension polymerization, and kj can not be assumed to be constant even at isothermal conditions, since kp and even kp are dependent on the degree of polymerization because of a gel effect. (2., ,D However, since the application of the model is for a finishing step, with polymer molecular weight and viscosity fairly well established, further changes in kp and kp should be minimal. 

Random coil conformations can range from the spherical contracted state to the fully extended cylindrical or rod-like form. The conformation adopted depends on the charge on the polyion and the effect of the counterions. When the charge is low the conformation is that of a contracted random coil. As the charge increases the chains extend under the influence of mutually repulsive forces to a rod-like form (Jacobsen, 1962). Thus, as a weak polyelectrolyte acid is neutralized, its conformation changes from that of a compact random coil to an extended chain. For example poly(acrylic acid), degree of polymerization 1000, adopts a spherical form with a radius of 20 nm at low pH. As neutralization proceeds the polyion first extends spherically and then becomes rod-like with a maximum extension of 250 nm (Oosawa, 1971). These pH-dependent conformational changes are important to the chemistry of polyelectrolyte cements. 

The cumulative molar concentration of polymeric species P 0 may be evaluated from the population density distribution, Equation 16. The first two rate expressions represent monomeric additions which do not change the molar concentration of polymeric molecules. A rate constant that describes functionality as a separable function of the molecule s degree of polymerization satisfies this constraint. The simplest, realistic function is the linear expression... 

Generally, these equilibrium constants are very solvent dependent. In particular, the values of KEA are expected to be relatively high in protic solvents because halide anions can be stabilized through solvation in such media [143], Also, on the other hand, Kx values will be likewise affected with changes in solvent polarity [50], Low values of Kx in polar and protic media have direct implications on the degree of polymerization control because of the decreased amounts of deactivator (Mt"+1X/L), as a result of halide anion dissociation from the metal center. 

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