Colloidal nature of star polymer dilute and semidilute solutions

Dozier, W. D.; Huang, John S.; Fetters, Lewis J.

doi:10.1021/ma00010a026

Cited by 136 publications

(160 citation statements)

References 7 publications

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“…In this way, the only contribution to scattering is the form factor P (Q) of the stars, which is related to the Fourier transform of the monomer density ϕ(r) [6,69,70]. A common and successful fit for the form factor, which is consistent with the predictions of the Daoud-Cotton theory, is provided by the Dozier expression [11]:…”

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confidence: 86%

“…Second, from an experimental point of view, the recent synthesis of regular star polymers with various possible numbers of arms by Roovers and coworkers [9,10] made it possible to explore the physics of well-defined model systems, which are monodisperse in both the number of arms and in the degree of polymerization. Important examples are polyisoprene stars with f = 8, 18 [11] and polybutadiene stars with f = 32, 64, 128 [10], both synthesized by anionic polymerization. Thereafter, the static properties of stars can be studied by small-angle neutron scattering (SANS), light scattering and small-angle X-ray scattering (SAXS).…”

Section: Introductionmentioning

confidence: 99%

“…It is essentially in the limit f ≫ 1 where a description of star polymers as sterically stabilized colloidal particles holds. This polymer-colloid hybrid character of star polymers has been explored in a number of publications dealing with the structural [4,6,11,[24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] and dynamical [4,27,28,[39][40][41][42][43][44][45][46][47][48] properties of the same.…”

Section: Introductionmentioning

confidence: 99%

“…According to Dozier et al [11], the quantities V W , α, ξ and R g are to be treated as free fit parameters, whereas the exponent ν is fixed at its Flory value 3/5, yielding µ = 2/3. The Dozier form factor yielded excellent fits for an array of data obtained for stars with f = 8 − 128 arms [30].…”

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confidence: 99%

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Star Polymers: From Conformations to Interactions to Phase Diagrams

Likos¹,

Harreis²

2002

Condens. Matter Phys.

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We review recent progress achieved in the theoretical description of the interactions, correlations, and phase behavior of concentrated solutions of star polymers, sterically stabilized colloids, and micelles. We show that the theoretical prediction of an ultrasoft, logarithmically diverging effective interaction between the star centers, which has been confirmed by SANSexperiments and computer simulations, lies in the core of a host of unusual phenomena encountered in such systems. These include anomalous structure factors, reentrant melting behavior, as well as a variety of exotic crystal phases. Extensions to polydisperse stars and the role of many-body forces are also discussed. A particular 'mean-field' character of star polymer fluids is presented and it is shown that it manifests itself in the shape and structure of sedimentation profiles of these systems.

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mentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Star Polymers: From Conformations to Interactions to Phase Diagrams

Likos¹,

Harreis²

2002

Condens. Matter Phys.

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“…Within a so-called ''blob'', a spherical volume with radius , the dendrons have to be described as a selfavoiding random walk and excluded-volume interaction has to be considered. 36 Following a similar ansatz of Dozier et al 37 for highfunctionality stars, which has also, in a different modification, been successfully applied to polymeric micelles, 38 we split the dendrimer form factor into the sum of two terms…”

Section: Sphere With Fuzzy Shell and Internal Density Fluctuationsmentioning

confidence: 99%

Dynamics of star-burst dendrimers in solution in relation to their structural properties

Rathgeber

Monkenbusch

Kreitschmann³

et al. 2002

The Journal of Chemical Physics

135

160

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We have measured both the static and dynamic structure factors of a single dendrimer with small-angle x-ray scattering ͑SAXS͒ and neutron spin-echo spectroscopy under good solvent conditions with the aim of finding a consistent correlation between the structural properties of dendrimers and their dynamic behavior. The samples under investigation were star-burst polyamidoamine dendrimers with generations gϭ0 to 8 in dilute methanol solutions. A model independent approach employing inverse Fourier transformation and square root deconvolution methods has been used to analyze the SAXS data to obtain the pair distance distribution function p(r) and the radial excess electron density profile ⌬ (r). In addition, we formulated a model that takes both the colloidal ͑globular, compact shape with form polydispersity or fuzzy surface͒ as well as the loose, polymeric ͑self-avoiding random walk͒ character of dendrimers into account. With this model we were able to describe the spectra of all dendrimer generations consistently. Parameters discussed as a function of the dendrimer generation are, among others, the correlation length of the density fluctuations ͑blob radius͒ , the radius of gyration R g , the sphere radius R s , the form polydispersity s or analogously, the width of the fuzzy surface region 2 f . Both the model-independent approach and the model fits reveal that at least down to the third generation the dendrimers exhibit a rather compact, globular shape. These findings are in agreement with the dynamic results obtained by NSE spectroscopy which probes length scales both larger and much smaller than the dimension of a single dendrimer. The method reveals that the dynamics throughout is dominated by the center-of-mass diffusion-the internal dynamics is suppressed. The diffusion coefficients obtained are close to the values calculated from the Stokes-Einstein relation using the sphere radius R s determined from the SAXS spectra. Dynamically, the dendrimers behave like ''hard'', solid spheres.

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