Study on Dipole Moments of Macromolecules I. Apparatus for Dielectric Measurements and Dipole Moment of Poly(p-methoxystyrene)

Abstract

ABSTRACT:A three-terminal cell for the dielectric measurement of liquid was made and the cell capacitance was determined using a capacitance bridge. The accuracy of the dielectric constant measurement with the apparatus was examined by measuring standard materials such as benzene and cyclohexane. The mean square dipole moments of poly(p-methoxystyrene) in benzene were determined by accurate measurements of dielectric constants on the polymer dilute solutions and the values were estimated according to two procedures, i.e., one based on Debye and HalverstadtKumler equations (DHK method) and the other on Guggenheim and Smith equations (G-S method). The average dipole moments per repeat unitµ were obtained as 1.214 (25°C) and 1.221 (40°C) by the DHK method and 1.204 (25°C) and 1.209 (40°C) by the G-S method (in debye unit). The slight disagreement in µ values obtained by two different procedures was interpreted as arising from differences in assumptions used in the DHK method and the G-S method.KEY WORDS Dipole Moment / Dielectric Constant / Molecular Polarization / Electronic Polarization / Atomic Polarization / Molecular Refraction / Poly(p-methoxystyrene) / Dielectric Cell / Dilute Solution / Dipole moment is a configurationdependent property of polymer chains carrying polar groups in their monomer units and the observed dipole moment is the statistical average of molecular conformations. Theory predicts that the dipole moments of polymer molecules cannot be affected greatly by longrange excluded volume interactions when the molecules have the dipole components perpendicularly attaching to the chain axis. 1 • 2 The probable absence of the effect of the excluded volume on dipole moments, in contrast with its pronounced effect on chain dimensions, is of great advantage in investigating the influence of intramolecular interactions on the conformation of polar polymers.We have been studying since early in the 1960's the dipole moments µ of polar vinyl polymers to investigate configurational properties such as the stereochemical structure of the vinyl chains and the monomer sequence distribution in the copolymers.

Dipole Moment of Poly(ethylene oxide) in Solution and Its Dependence on Molecular Weight and Temperature

“…Both of these methods are based on the Debye theory, but the assumptions used for estimating P E þ P A differ between the respective methods. We have previously examined the discrepancy between these two methods, 14,21 and can summarize our conclusions as follows; if the solvent has a small value of " À n 2 , as in the case of benzene with a value of " À n 2 ¼ 0:022 at 25 C, then the G-S method provides almost equivalent results to those obtained using the H-K-D method. 14,15,21 The discrepancy that appears in Figure 3 of PEO-2 is the smallest (2:1 Â 10 4 , n ¼ 477) among the PEO samples, which may suggest that the OH end groups influence the observed dipole moment.…”

“…As previously reported, 14,21 two different methods were used for evaluation of the dipole moments of polymers in solution. In this paper, the authors evaluated the dipole moments of the polymers based on measurements of the dielectric constants and densities of the polymer solutions, using eqs (1-5) (Halverstadt-Kumler-Debye method, (H-K-D) method 15,16 ).…”

“…In order to obtain more reliable data, the present investigation has focused on precise measurement of the dipole moments of PEO in benzene and their dependence on molecular weight and temperature, in addition to measurement of PEO with higher molecular weights, using improved equipment that enables very precise measurement of the dielectric constants of liquids. 14…”

Application of a ferrocene-chelating heteroscorpionate ligand in nickel mediated radical polymerization

“…Therefore, the presence of the radical initiator leads to an increased control over the polymerization. While not unprecedented, [54][55] these results suggest that the homopolymerizations of p-MOS and EVE mediated by [(fc P,B )NiBr][BAr F ] undergo radical polymerization instead of the far more common cationic polymerization mechanism.…”

Study on Dipole Moments of Macromolecules II. Dipole Moments of p-Methoxytoluene, p-Bromoethylbenzene and p-Bromotoluene as Structural Units of Poly(p-methoxystyrene) and Poly(p-bromostyrene)

“…In the preceding paper, 1 we reported the dielectric measurements of organic solvents, and poly(p-methoxystyrene) in solution, introducing a new apparatus consisting of capacitance bridge and a three-terminal platinum electrodes cell. The dielectric constants obtained using the new apparatus were accurate and the accuracy of the dipole moment was improved by one more order than that obtained before.…”