Studies of cyclic and linear poly(dimethyl siloxanes): 5. Diffusion behaviour in dilute solution

Edwards, C.J.C; Stepto, R. F. T.; Semlyen, J.A.

doi:10.1016/0032-3861(80)90296-7

Cited by 56 publications

(19 citation statements)

References 16 publications

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“…As the data of Fig. 8 show, the dependence of diffusion coefficient on ring size seen here for the three different benzene-d 6 solutions of dimethylsiloxane mixtures parallels that seen earlier in toluene and bromocyclohexane 21,22 for samples containing only single species. All the data for non-overlapping signals fit well to a straight line in a log-log plot, showing that the diffusion coefficients scale approximately as the inverse square root of the ring size.…”

Section: Resultssupporting

confidence: 83%

“…All the data for non-overlapping signals fit well to a straight line in a log-log plot, showing that the diffusion coefficients scale approximately as the inverse square root of the ring size. This is the scaling expected both for a rigid highly oblate ellipsoid or thin disc 23 (an appropriate model for very small ring sizes) and for a cyclic random coil in a y-solvent 21 (appropriate for flexible rings). The straight lines in Fig.…”

Section: Resultssupporting

confidence: 52%

“…The diffusion coefficients of individual cyclic dimethylsiloxane oligomers have been investigated extensively in their own right 21,22 using the boundary-spreading technique. As the data of Fig.…”

Section: Resultsmentioning

confidence: 99%

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2D and 3D DOSY methods for studying mixtures of oligomeric dimethylsiloxanes

Stchedroff

Kenwright

Morris

et al. 2004

Phys. Chem. Chem. Phys.

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Diffusion-ordered spectroscopy (DOSY) is a powerful method for the NMR analysis of many types of mixture without the need for physical separation, and requires only relatively standard spectrometer hardware. The principal requirements for high resolution analysis using DOSY, that the basic NMR spectrum be well-resolved and that it have good signal-to-noise ratio, pose a dilemma where multiple chemically similar species with NMR-active heteronuclei are involved. Generally the 1 H spectrum of such a mixture has good sensitivity but relatively poor chemical shift resolution, while for heteronuclei the situation is reversed. The dilemma is illustrated for the case of a mixture of cyclic dimethylsiloxanes, and the results of a range of 1 H 2D DOSY, 29 Si 2D DOSY and 1 H { 29 Si} 3D DOSY-HMQC experiments are compared. In selecting the most appropriate technique to use for a given sample it is necessary to balance conflicting requirements for speed, resolution and accuracy, and to consider the balance between systematic and random errors. Results are presented for three different concentrations of a mixture of cyclic siloxanes containing between 4 and 20 monomer units. The diffusion coefficients measured show an inverse half power law relationship with molecular mass.

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Section: Resultssupporting

confidence: 83%

Section: Resultssupporting

confidence: 52%

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2D and 3D DOSY methods for studying mixtures of oligomeric dimethylsiloxanes

Stchedroff

Kenwright

Morris

et al. 2004

Phys. Chem. Chem. Phys.

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“…This coincidence may be due to the insensitivity of g H to chain length and local conformation for not‐too small x . However, we wish to remark that our g H values (0.82–0.84) for a = 0.1 nm (corresponding to a moderately good solvent) and for 17 < x < 100 are lower than or comparable to the asymptotic Gaussian‐chain value 0.849 (as is the case with g s in Figure 3) and rather close to the experimental value28, 29 of 0.84 for poly(dimethylsiloxane) in good solvents. Such an experimental g H should not be interpreted as due to small excluded‐volume effects on R H of ring polymers compared to those in linear chains.…”

Section: Resultssupporting

confidence: 81%

Monte Carlo study of cycloamylose: Chain conformation, radius of gyration, and diffusion coefficient

2002

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Cyclic (1 --> 4)-alpha-D-glucan chains with or without excluded volume have been collected from a huge number (about 10(7)) of linear amylosic chains generated by the Monte Carlo method with a conformational energy map for maltose, and their mean-square radii of gyration and translational diffusion coefficients D (based on the Kirkwood formula) have been computed as functions of x (the number of glucose residues in a range from 7 to 300) and the excluded-volume strength represented by the effective hard-core radius. Both /x and D in the unperturbed state weakly oscillate for x < 30 and the helical nature of amylose appears more pronouncedly in cyclic chains than in linear chains. As x increases, these properties approach the values expected for Gaussian rings. Though excluded-volume effects on them are always larger in cycloamylose than in the corresponding linear amylose, the ratios of and the hydrodynamic radius of the former to the respective properties of the latter in good solvents can be slightly lower than or comparable to the (asymptotic) Gaussian-chain values when x is not sufficiently large. An interpolation expression is constructed for the relation between the gyration-radius expansion factors for linear and cyclic chains from the present Monte Carlo data and the early proposed asymptotic relation with the aid of the first-order perturbation theories.

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“…The ratio of the center of mass diffusion coefficients D * /D 0 is found to be 0.84$0.02, which compares favorably with 0.85, predicted in the case of absent-free draining and excluded volume effects [130]. The absolute values of D * and D 0 agree quite well with those obtained by boundary spreading [131] and quasi-elastic light-scattering techniques [132].…”

Section: Dilute Solutions Of Cyclic Polymerssupporting

confidence: 69%

Neutron Spin Echo Investigations on the Segmental Dynamics of Polymers in Melts, Networks and Solutions

Ewen

Richter

Neutron Spin Echo Spectroscopy Viscoelasticity Rheology

114

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Neutron spin echo (NSE) spectroscopy, an advanced high-resolution quasi-elastic neutron scattering technique, provides the unique opportunity to investigate long-range relaxation processes of macromolecules simultaneously in space and time on nano-scales. In particular, information on the single-chain behavior is not restricted to dilute solutions, but may also be obtained from concentrated solutions and melts, if labelling by proton deuterium exchange is used. Thus, this method facilitates a direct microscopic study of molecular models developed to explain the macroscopic dynamic properties of polymers, e.g. transport and viscoelastic phenomena.This article gives a short outline of the method and reviews the relevant experimental results obtained from polymer melts and networks and from dilute and semi-dilute solutions of chain molecules with different architectures since the first successful NSE work on polymers was published in 1978. The experimental observations are compared with the predictions of the related microscopic models and other theoretical approaches, which are briefly introduced and adapted accordingly.

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Studies of cyclic and linear poly(dimethyl siloxanes): 5. Diffusion behaviour in dilute solution

Cited by 56 publications

References 16 publications

2D and 3D DOSY methods for studying mixtures of oligomeric dimethylsiloxanes

2D and 3D DOSY methods for studying mixtures of oligomeric dimethylsiloxanes

Monte Carlo study of cycloamylose: Chain conformation, radius of gyration, and diffusion coefficient

Neutron Spin Echo Investigations on the Segmental Dynamics of Polymers in Melts, Networks and Solutions

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