Flow birefringence studies of polymer conformation: cellulose tricarbanilate in two characteristic solvents

Noordermeer, Jacobus W.M.; Daryanani, R.; Janeschitz‐Kriegl, H.

doi:10.1016/0032-3861(75)90032-4

Cited by 29 publications

(10 citation statements)

References 26 publications

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“…22 The chain expansion of CTC with decreasing temperature was reported by several workers. [22][23][24][25][26] The values of k 0 are normal, indicating no aggregation of CTC in THF upon cooling. Figure 2 plots [] vs. M w double-logarithmically of CTC in THF at 0 and À25 C as well as the previous results at 25 C. 9 The molecular weight dependencies of [] become slightly stronger with lowering temperature.…”

Section: Resultsmentioning

confidence: 98%

Local Conformation of the Cellulosic Chain in Solution

Yanai

Sato

2006

Polym J

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ABSTRACT:The temperature and molecular weight dependencies of the intrinsic viscosity [] were investigated for cellulose tris(phenyl carbamate) (CTC) in tetrahydrofuran (THF). By the analysis of the [] data in terms of the wormlike cylinder model, the persistence length q of CTC was determined as a function of the temperature. With decreasing the temperature from 25 to À20 C, q increases from 10.5 to 13.7 nm. This temperature dependence of q was successfully explained by the broken wormlike chain model, where each glucose residue in the cellulosic chain is assumed to take left-handed 3/1 or 2/1 helical state and occasionally a kink state generated by a glucosidic bridge angle fluctuation. While the torsional fluctuation in each glucosidic bond is considerably small, there are two energetically favored helical (3/1 and 2/1) states, so that the cellulosic chain may not be regarded as a regular helix in solution. [DOI 10.1295/polymj.38.226] KEY WORDS Cellulose Derivative / Intrinsic Viscosity / Persistence Length / Broken Wormlike Chain / Local Conformation / Helicity of polymer chains plays important roles in chain rigidity, liquid crystallinity, and chiral discrimination. Recently, several synthetic polymers have been found to take more or less regular helical conformations in solution, and extensive arguments have been made on the relationship among their chemical structure, helicity, chain rigidity, liquid crystallinity, and cholesteric structure. Many review articles deal with recent advances in this subject. [1][2][3][4][5] Cellulose derivatives are known as semiflexible polymers exhibiting liquid crystallinity 6,7 and important materials in chiral chromatography.8 These features imply helical nature in the cellulosic chain. Conformations of cellulose derivatives in solution were studied both experimentally and theoretically for a long time. However, as mentioned in a previous paper, 9 their conformational analysis was not an easy task because both chain stiffness and excluded volume effect must be taken into account simultaneously due to their intermediate chain rigidity. Only recent literature provides proper analyses for the conformation of cellulosic chains 9,10 and also for solution properties (e.g., liquid crystallinity, 11 viscosity, 12 and diffusivity 13 ) based on the properly analyzed conformation. On the other hand, theoretical studies on the conformation of the cellulosic chain were carried out by Brant et al.14-17 in 1970s, who made an extensive conformational energy analysis and found two energetically stable conformations implying left-handed 3/1 and 2/1 helices for the cellulosic chain. However, the characteristic ratio C 1 and its temperature dependence estimated from their conformational energy did not satisfactorily agree with experimental results for cellulose derivatives. 15,16 The disagreement was argued occasionally afterward, 17,18 but satisfactory explanation has not been made yet. Thus, the local conformation of the cellulosic chain is still unclear.In this study, we have revisited...

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Section: Resultsmentioning

confidence: 98%

Local Conformation of the Cellulosic Chain in Solution

Yanai

Sato

2006

Polym J

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“…First, approximate values of M L and q were estimated from the intercept and slope of the ( M w /〈 S 2 〉*) 1/2 vs M w -1 plot constructed in Figure a according to eq 8 with 〈 S 2 〉 0 replaced by 〈 S 2 〉*; the pronounced downward deviations of the six plotted points at small M w -1 may be ascribed to excluded-volume effects on 〈 S 2 〉. The first approximate values of M L and q were then used to find ε which allows eq 7 to best fit the experimental δ vs M w relation in Figure ; ε for CTDC was taken to be negative on the basis of flow birefringence data , for cellulose tris(phenylcarbamate) in various solvents. With the values of M L , q , and ε thus estimated, f U v in eq 10 was calculated to obtain first-approximate values of 〈 S 2 〉 z as a function of M w .…”

Section: Resultsmentioning

confidence: 99%

Chain Stiffness and Excluded-Volume Effects in Dilute Polymer Solutions: Cellulose Tris[(3,5-Dimethylphenyl)carbamate]

1996

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Nineteen fractions of cellulose tris[(3,5-dimethylphenyl)carbamate] (CTDC) ranging in weight-average molecular weight M w from 2.5 × 104 to 7.5 × 106 have been studied by static light scattering, sedimentation equilibrium, and viscometry in 1-methyl-2-pyrrolidone at 25 °C. Since this cellulose derivative exhibits pronounced optical anisotropy, light-scattering data are corrected for the anisotropy effect on the basis of Nagai theory for the Kratky−Porod (KP) wormlike chain with cylindrically symmetric polarizabilities. It is shown that the data for 〈S 2〉z (the z-average mean-square radius of gyration), δ (the optical anisotropy factor), and [η] (the intrinsic viscosity) and those reported previously for 11 fractions are described accurately by the known theories for the unperturbed KP chain if M w is lower than 7 × 105. From the comparison, the persistence length and the monomeric projection of the CTDC chain are estimated to be 7.8 and 0.52 nm, respectively. When M w exceeds 106, i.e., when n K (the Kuhn segment number) increases above 50, excluded-volume effects on 〈S 2〉z and [η] become experimentally observable. Though such a large n K value for the appearance of volume effects has been considered inconsistent with the Yamakawa−Stockmayer−Shimada (YSS) theory for KP or helical wormlike chains, the observed excluded-volume effects are found to be explained quantitatively in the YSS scheme, i.e., by the YSS perturbation theory combined with the Domb−Barrett function for the radius expansion factor and the Barrett function for the viscosity expansion factor. Thus, this theoretical scheme should have a wider applicability than what might be anticipated from earlier studies.

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“…Such a change is observed for CC in a mixture of dioxane and phenyl benzoate. 24 From the present data one can calculate the persistence dipole moment of the CC chain in the following manner. For a macromolecule bearing dipole moments along the chain skeleton, the Kratky and Porod treatment26 can be applied for dipole moment vectors:…”

Section: Discussionmentioning

confidence: 99%

“…The trend of decreasing radius of gyration with increasing temperature has also been found for higher molecular weight samples; limiting viscosity numbers were also found to decrease strongly with rising temperature. 24,33 For a quantitative comparison with the dielectric measurements we make a very crude assumption, that the particles behave like rigid cylinders. Their mean-square endto-end distance L5 = 12 (S2) is compared with the length of the rod calculated according to eq 1, using b = 9.2 Á as deduced from small-angle X-ray scattering measurements on acetone solution34 (£2)i/2 (from <S2» = 970 Á L(from D) = 1300 Á It can also be assumed that the real volume V of the rod is equal to its hydrodynamic volume.…”

Section: Discussionmentioning

confidence: 99%