Rigid chain polymers molecular weight

Monofunctional, cyclohexylamine is used as a polyamide polymerization chain terminator to control polymer molecular weight. 3,3,5-Trimethylcyclohexylamines ate usehil fuel additives, corrosion inhibitors, and biocides (50). Dicyclohexylamine has direct uses as a solvent for cephalosporin antibiotic production, as a corrosion inhibitor, and as a fuel oil additive, in addition to serving as an organic intermediate. Cycloahphatic tertiary amines are used as urethane catalysts (72). Dimethylcyclohexylarnine (DMCHA) is marketed by Air Products as POLYCAT 8 for pour-in-place rigid insulating foam. Methyldicyclohexylamine is POLYCAT 12 used for flexible slabstock and molded foam. DM CHA is also sold as a fuel oil additive, which acts as an antioxidant. StericaHy hindered secondary cycloahphatic amines, specifically dicyclohexylamine, effectively catalyze polycarbonate polymerization (73). 

Equations (4) and (5) show that when the parameter x = 2 L/A changes from 0 to the hydrodynamic properties of a worm-like chain change from those of a thin straight tod to those of an undrained Gaussian coil. In accordance with this the dependence of intrinsic viscosity (nl and diffusion coefficient D on molecular weight M of a rigid-chain polymer cannot be described by the usual Mark-Kuhn dependence... 

Therefore, the axis of the highest polarizability of the monomer unit of polystyrene is inclined to the axis of the main chain by a wide angle, i.e. the Aa value is negative and, accordingly (see Eq. (67), p. 137), FB is also negative. However, in this case, in contrast to rigid-chain polymers, the Kerr constant is positive, independent of molecular weight and close to the value of K of the monomer. 

This behavior is an evidence of the small-scale mechanism of the molecular motion of polystyrene in the electric field each monomer unit of the polymer chain is oriented virtually independently of other units, just as in the monomeric styrene. Equation (99) shows that for high molecular weight polymers K is proportional to S, This accounts for the much higher values of K for rigid-chain polymers than for flexible-chain polymers (Table 13) since the corresponding values of S are of order of m nitudes 10—10 for flexible and approximately unity for i%id polymers in the electric field. 

The validity of Eqs. (102) - (105) for both low molecular weight liquids ) and rigid-chain polymer solutions was confirmed by appropriate experiments. Examples are given in Figs. 80 and 81 which reveal the dependences of ctg 2 a on E (3/(e + 2)) at constant g. In accordance with Eqs. (109) and (105) the points fit straight lines the intercepts of which yield ctg 2 ag and the slope can be used for the determination of m. 

On the other hand, the peculiarities of the molecular structure of rigid-chain polymers favor the use of EB whereas the application of this method to flexible-chain polymers is much less effective. To a certain extent, this also refers to FB which permits the determination of both the anisotropy and the rigidity of the polymer chain using the molecular weight dependence of the shear optical coefficient when chain rigidity is relatively h. ... 

Structure of which is identical to their corresponding low molecular weight disk-like counterparts. Rigid chain polymers, such as nucleic acids and polypeptides [5b, 66], are also well known to produce lyotropic columnar mesophases with appropriate solvents. The poly(di-n-alkylsilanes) and poly(di-n-alkylsiloxanes). Fig. 12, with only alkyl side groups and deprived of any mesogen [67] are examples of polymers showing thermotropic columnar mesophases which need to be analyzed in more detail. 

In polymer systems such a mutually independent dipole orientation is inapplicable because dipole orientation is highly correlated. The very essence of a pd3mer chain generally renders independent orientation of a main chain dipole component impos-rible and frequently, coupling between side chain and main chain modes are involved. For a rigid chain polymer in solution, dipole orientation requires rotatory diffusion of a macromolecule as a whole, and no component due to local modes is involved, but this situation is the exception. Flexible polymers permit polarization by local mode motions as well as rotatory diffusion as illustrated in Fig. 5. Equation (5) is also inapplicable for polymers because of dispersity in molecular weight, since if the relaxation involves molecular wel t dependent modes there will be a tead of relax-... 

Early work on NMR of polymers in dilute solution was reviewed by Heatley(29). It was already clear in that early review that relaxation times of dilute polymers were independent of polymer molecular weight, at least for molecular weights above a few to ten thousand, and were nearly independent of polymer concentration for concentrations up to 100-150 g/1 or so. A revealing exception to this rule was provided by polymers plausibly expected to rotate as nearly rigid bodies, for which Ti continued to depend on M up to much larger M. From these observations, it was plausibly inferred that local chain motions are primarily responsible for the observed relaxation times. Dependences of Ti on solvent temperature and viscosity were concluded to scale linearly with solvent viscosity, at least in most systems, a matter treated in more detail below. Heatley also considers correlations between Ti and chain structure. 

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