Dipole Moment Of Poly Research Articles

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

The dipole moment of poly(ethylene oxide) (PEO) and its dependence on molecular weight and temperature have been investigated by measuring the dielectric constant and the density of dilute PEO-benzene solutions in the temperature range from 25 to 55°C. The dipole moments of the polymers (μmolecule2)1/2, increased linearly with respect to the square root of the degree of polymerization n, which confirms the theoretical prediction that the long-range excluded volume interactions have little effect on the dipole moment of polymers such as PEO. The estimated value for diethyl ether μDE is 1.20D, according to the relationship between (μmolecule2)1/2 and n1/2 for PEO oligomers,10,17 which leads to a C-O bond moment, mC-O, of 1.07 D. The averaged dipole moment per constitutional repeating unit (μ2)1/2 for PEO polymers is 1.040 ± 0.002 [D] at 25°C. The following dipole moment ratio and the temperature coefficient were obtained for PEO in benzene: (μ2)/m2 = 0.472 ± 0.002 (at 25°C) and d ln(μ2)/dT = (2.11 ± 0.28) × 10−3 K−1 (25–45°C). The experimental results are compared with the conformational characteristics of PEO investigated by the rotational isomeric state (RIS) analyses by Abe et al. and Sasanuma et al.

Effect of methylene spacer length on the molecular mobility and dipole moment of poly(azomethine esters) with azomethinearomatic groups in the ortho position

Relaxation of dipole polarization is studied and dipole moments are measured for poly(azomethine esters) with rigid azomethinearomatic fragments in the ortho position and methylene spacers of various lengths in the backbone chain. These polyesters in solution are shown to be characterized by four relaxation processes. The molecular mobility parameters (relaxation time and activation energies of three local processes) depend nonmonotonically on the length of the methylene spacer and on the evenness or oddness of the number of methylene units in the spacer in particular. For the fourth large-scale process, these activation parameters have high values and monotonically increase with the spacer length. The dipole moment of the polyester is shown to be higher when the number of methylene units in the spacer is odd. This may be due to specific conformational features of the ester part of the macromolecule.

Effect of the Pendant Ester Group Orientations on the Dipole Moment of Poly(alkyl acrylate)s

The dipole moment analysis of vinyl polymers carrying polar side groups such as poly(methyl acrylate) (PMA), poly(methyl methacrylate) (PMMA), and poly(ethyl methyacrylate) (PEMA) has been performed by the expanded matrix algebra method with due consideration of the ester group orientations. The stereochemical characteristics of the pendant ester groups have been exactly treated by introducing a Bernoullian probability λ representing the occurrence of the cis conformation around the first articulated Cα−C* bond. Special care is required for the orientational correlation of the neighboring ester groups when the skeletal conformations around the two successive bonds are both in trans. Such a meso-tt effect has been accommodated by assigning probability λ‘ or (1 − λ‘) to the proper elements of the statistical weight matrix. Experimental observations were found to be satisfactorily reproduced with λ = 0.3−0.4, indicating that the trans conformation is more preferred for the ester group. The orientational corr...

Temperature dependence of static dielectric permittivity and dipole moments of poly(N-vinylcarbazole)

Abstract The dipole moment has been measured for various stereostructural forms of poly( N -vinylcarbazole) (PVK) in solution in 1,4-dioxane and in toluene in the temperature range 288–338 K. The dielectric and dipole moment data were correlated with the stereostructure of PVK. The dipole moment behaviour of various types of PVK, prepared using different catalyst systems, may be explained in terms of 3/1, 2/1 or all- trans sequences of syndiotactic PVK. All PVK samples showed a positive temperature coefficient of dipole moment but to a different extent. PVK with lowest isotacticity (prepared with a free-radical catalyst) had the largest temperature coefficient, suggesting that this structure was more sensitive to changes in temperature. However, the dielectric data for cationically prepared PVK appear to indicate a more random coil-type of configuration or possibly a segmental, rod-like structure in which the dipole moment vectors of groups of carbazole groups are randomly oriented but remain approximately perpendicular to the long axis of the molecule, resulting in only a small temperature coefficient of dipole moment.

Dipole moments of poly(allyl methacrylate) prepared by group transfer polymerization

AbstractDipole moments of poly(allyl methacrylate) prepared by group transfer polymerization and of allyl methacrylate were determined from dielectric constant, refractive index increment and density measurements performed on their dilute benzene and carbon tetrachloride solutions within a temperature range of 25–60°C. Dipole moments ratios and temperature coefficient, d ln〈μ2〉/dT, where 〈μ2〉 is the mean‐square dipole moment of the chain, were calculated. These results are compared with earlier results.

Dipole moment of poly(carbonates) with chlorophenyl or dichlorophenyl side groups

Dipole moment of poly(carbonates) with chlorophenyl or dichlorophenyl side groups

Dipole moments of poly(p‐chlorostyrene) chains determined in benzene, isopropyl benzene and n‐propyl benzene

AbstractDipole moments of poly(p‐chlorostyrene) were determined from dielectric and refractive index measurements performed on their dilute benzene, isopropyl benzene and n‐propyl benzene solutions over a wide range of temperatures. Experimental results are expressed in terms of the dimensionless dipole moment ratios, Dx = 〈μ2〉/xμ02. The temperature coefficients of dipole moments, d In 〈μ2〉/dT were calculated. The presence and importance of the specific solvent‐segment interactions are demonstrated by considering the temperature dependence of the dipole moment ratio in the vicinity of the theta temperature. These results are compared with dipole moments and temperature coefficients which were calculated by Bahar et al. using the appropriate rotational isomeric state model to study the local solvent effect for the poly (p‐chlorostyrene)‐benzene system.

Dipole moment of poly(thiocarbonate)s derived from bisphenol A

The dipole moments of a series of poly(thiocarbonate)s derived from bisphenol A have been determined in 1,4-dioxane and benzene solutions at 298 K. The effect of the side chain structure of the polymer and the solvent on the dipole moment are analysed. A very small influence of the polymer structure on the dipole moment is observed.

Dipole moment of poly(thiocarbonates) with chlorophenyl or dichlorophenyl side groups

Dipole moment of poly(thiocarbonates) with chlorophenyl or dichlorophenyl side groups

Study on dipole moments of macromolecules, 3. Dipole moments of poly(4‐methoxystyrene) and poly(4‐bromostyrene) and their dependences on solvent and temperature

Dipole moments of poly(4-methoxystyrene) (PMeOSt) and poly(4-bromostyrene) (PBrSt) were determined from dielectric constant and density measurements on dilute solutions of the polymers in benzene, 1,4-dioxane and toluene, over the range of temperatures from 25 to 55°C. The average dipole moments per constitutional repeating unit (μ) obtained in benzene (Bz), 1,4-dioxane (Dox), and toluene (Tol) at 25°C are as follows: 1,219 D (Bz), 1,253 D (Dox) and 1,175 D (Tol) for PMeOSt, and 1,371 D (Bz) and 1,413 D (Dox) for PBrSt1 In SI units: 1 D ≈ 3,33564 · 10−30 C · m. . The dipole moment ratio, Dr = 〈μ2〉2/μ20, was found to be 0,942 for PMeOSt and 0,467 for PBrSt in Bz at 25°C, for which the observed values of the dipole moments of 4-methoxytoluene and 4-bromoethylbenzene were used as μ0 for the respective polymer. The variation of the dipole moment ratio with temperature was linear but very small, dDr/dT giving a negative value for PMeOSt but a positive value for PBrSt.

Dipole moments of isotactic and atactic poly(propylene oxide) samples

Dipole moments of poly(propylene oxide) (PPO) samples with different tacticities were determined from dielectric constant and refractive index increment measurements, which were performed on dilute toluene and isooctane solutions. In contrast to previous reports, both refractive index increments and the dipole moment ratios showed a marked dependence on the tacticities of the samples. The dipole moment ratios of isotactic samples were greater than unity and decreased with increasing sequence concentrations of structural irregularities. The temperature coefficients in toluene were negative for both isotactic and atactic samples. No effect of excluded volume was observed.

Polymerization and dipole moment of poly(allyl cyanide)

Polymerization of allyl cyanide was carried out by radiation and chemical catalysis. Polymers obtained by γ-rays under various conditions such as in bulk and in the presence of either air or 0.1 mol% ZnCl 2 were oily or solid dark-brown products with molecular weights up to 1.4 × 10 4. The polymers obtained by n-BuLi was a pale-yellow solid, insoluble in common organic solvents and water. No polymer was obtained with BF 3O(C 2H 5) 2. The mechanism of polymerization was shown by infra-red investigation to be different for radiation and catalyst polymerization. The relation between intrinsic viscosity and number-average molecular weight was found to be [ η] = 4.4 × 10 −4 M 0.51 n. The dipole moment ratio D ∞ of poly(allyl cyanide) in 1,4-dioxane was measured. The relatively large value of D ∞ shows that the polymer chain is not very rigid. A conformational change was observed at 40°C based on dipole moment measurements.

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

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 Halverstadt-Kumler equations (DHK method) and the other on Guggenheim and Smith equations (G-S method). The average dipole moments per repeat unit μ 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.

Theoretical analysis of conformational energies, unperturbed dimensions, and dipole moments of poly(dichlorophosphazene)

AbstractA theoretical analysis of the conformational energies of poly(dichlorophosphazene) (PDCP) is presented. The results indicate that the bond pair PNP possesses a considerable conformational freedom, whereas the bond pair NPN is relatively rigid. This difference explains the low glass transition temperatures Tg and large end‐to‐end distances measured for polyphosphazenes. A statistical model containing four rotational isomers (ie., trans, gauche, cis, and negative gauche) is developed and used to calculate unperturbed dimensions and dipole moments of PDCP. The results, obtained at 25°C with n = 400 skeletal bonds (200 repeating units), were Cn = 〈r2〉0/nl2 = 13.5; CT = 103d(ln〈r2〉0)/dT = −3.0 K−1; Dn = 〈μ2〉/nμ = 0.35; DT = 103d(ln〈μ2〉)/dT = −3.4 K−1. All the calculated magnitudes are extremely sensitive to the energy Eσ that controls the statistical weights of the conformations tg, tc, tg−, gt, ct, and g−t relative to tt for the bond pair PNP. A qualitative explanation for this sensitivity is discussed.

Conformations and dipole moments of poly(methyl) methacrylate molecules

Local conformations of stereospecific PMMA chains have been investigated. For these chains and for atactic PMMA we calculated the mean square dipole moment 〈μ 2〉 and the correlation factor g=( μ/nm 2) n→∞ . In the case of isotactic PMMA chains the share of tt conformations amounts to 75% of the monomer units, and in the syndio chains the amount of tt conformations is increased up to 90%. Vaues of g calculated for the isotactic and atactic chains over the entire interval of values permissible for the energy parameters that may be reconciled with experimental findings are obtainable only if it is assumed that there is a regular alternation of the directions of dipole moments of side polar groups (pendants), the rotation angle being x = 0 and 180°; in the syndio chains the probability of there being an alternation of the directions of dipole moments of the pendants 1 2 </ w x </ 3 4 .

Configurational chracteristics of the polysulfides, 3. Dipole moments of poly(trimethylene sulfide) and comparisons between some polysulfides and the corresponding polyoxides

AbstractConformational energy calculations indicate that poly(trimethylene sulfide) (P3MS) approximates the idealized freely‐rotating chain in that gauche‐trans energy differences in this molecule are very small. This occurs because the relatively long SC bond tends to relieve congestion within the P3MS chain. The bonds in poly(trimethylene oxide) (P3MO) are much more constrained to a particular rotational state because the OC bond is shorter than the SC one, and in this sense P3MO is considerably less flexible. In this study the dipole moments 〈μ2〉0 of P3MS are measured as a function of temperature, and the results analyzed in terms of the rotational isomeric‐state theory. Using conformational energies derived from semiempirical potential energy functions, a three‐rotational‐state model gave values of the dipole moment in good agreement with experiment. Theoretical and experimental values of the temperature coefficient of 〈μ2〉0 were in disagreement, however, and a five‐rotational‐state model based on that adopted by Flory in a similar study of polymethylene failed to remove this discrepancy. Some statistical properties are tabulated for the n‐alkylene polysulfides studied to date and for structurally related polyoxides. In these types of molecules, strong preferences for pairs of gauche states in CH2SCH2SCH2 and CH2 OCH2OCH2 sequences give rise to unusually small values of the dipole moment.

Conformational analysis of poly(oxymethylene)

AbstractThe conformational energies of the lower members of poly(oxymethylene), 2,4‐dioxapentane and 2,4,6‐trioxaheptane were estimated by the empirical force field method. The gauche states of the internal rotation around the skeletal CO bonds were successfully predicted to be of lower energies in both molecules. In order to calculate the unperturbed dimension and dipole moment of poly(oxymethylene), rotational isomeric state approximations were made by using the results obtained from the force field calculations on 2,4,6‐trioxaheptane. The first‐order interaction energy was estimated to be a large negative value, and the second‐order interaction energies for g±g± had non‐zero values. Although these parameters were significantly different from those estimated earlier, they reproduced the observed results fairly well. Thus the “gauche effect” of poly(oxymethylene) was explained by taking account of the effects contributed by the lone pairs of electrons on the oxygen atoms. As adopted in this study, the procedure joining the empirical force field method to the statistical mechanical one was shown to be effective for the investigation of many sorts of configuration‐dependent properties of chain molecules.

Configurational properties of vinyl chains. Dipole moments of poly(vinyl chloride)

Configurational properties of vinyl chains. Dipole moments of poly(vinyl chloride)

Configurational properties of aromatic polyesters with sulfur atoms in their structure

The dipole moments of poly (thiodiethylene glycol terephthalate) chains were determined as a function of temperature by means of dielectric constant measurements in dioxane. The experimental results were found to be in fair agreement with theoretical results based on a rotational isomeric state model in which the required conformational energies were obtained from previous configurational analysis on poly(ethylene terephthalate), poly(diethylene glycol terephthalate) and poly(thiodiethylene glycol). Since poly(thiodiethylene glycol terephthalate) can be considered an alternating copolymer of ethylene terephthalate and thioethylene units, its configuration-dependent properties were compared with those of poly(ethylene terephthalate) and poly(ethylene sulfide). It was found the flexibility of the copolymer, as expressed by the partition function, intermediate to that of its parent homopolymers. The theoretical results also indicate that the dimensions of poly(thiodiethylene glycol) are similar to those of poly(ethylene terephthalate) while its dipole moment ratio resembles that of poly(ethylene sulfide).

Dipole Moments of Poly(oxypropylene), Poly[(S)-oxy(1-isopropylethylene)] and Their Monomeric Model Compounds

Dipole Moments of Poly(oxypropylene), Poly[( S )-oxy(1-isopropylethylene)] and Their Monomeric Model Compounds