A small angle X-ray scattering study of sizes and shapes of poly(benzyl ether) dendrimer molecules

Kleppinger, Ralf; Reynaers, Harry; Desmedt, Kurt; Forier, Bart; Dehaen, Wim; Koch, Michel H. J.; Verhaert, Peter

doi:10.1002/(sici)1521-3927(19980201)19:2<111::aid-marc111>3.3.co;2-m

Cited by 4 publications

(5 citation statements)

References 9 publications

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“…There are at least two mechanisms capable of explaining this effect: either these polymers interpenetrated at a higher concentration, analogous to polymer coils in a good solvent, or the dendrimers deswelled with increasing concentration, expelling solvent. The latter was reported for poly(benzylether) dendrimers by Kleppinger et al14 In either case, this suggests that the hydrodynamic volume of the dendrimers decreased with increasing concentration, such that the rescaling of the weight fraction by the intrinsic viscosity yielded an overestimate of the true volume fraction. For comparison, the solid line in Figure 3 is the Krieger–Dougherty correlation for hard spheres, with a maximum packing fraction of φ max = 0.63 24.…”

Section: Resultsmentioning

confidence: 62%

“…In addition to the usual range of polymer characterization methods, the tools appropriate for the characterization of dendrimer and hyperbranched polymer architecture include small‐angle neutron scattering (SANS),11, 12 small‐angle X‐ray scattering (SAXS),13, 14 and rheology and dilution viscometry 11, 15, 16. Some of the literature relevant to this investigation is summarized briefly as follows.…”

Section: Introductionmentioning

confidence: 99%

“…They found that dendrimer scattering can be reasonably fitted by a homogeneous sphere model, again suggesting a relatively uniform density profile. SAXS experiments on dilute solutions of poly(benzyl ether) dendrimers in tetrahydrofuran (THF) were performed by Kleppinger et al14 From Fourier inversion of the scattering patterns, they concluded that for this type of dendrimer, the shape is slightly ellipsoidal but there is a uniform electron density distribution inside. All of these experiments contradicted predictions of a dense shell model by self‐consistent field theory18 and modeling19 or a dense core model as obtained by simulation 20.…”

Section: Introductionmentioning

confidence: 99%

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Structure and rheology of hyperbranched and dendritic polymers. I. Modification and characterization of poly(propyleneimine) dendrimers with acetyl groups

Bodnár

Silva

Deitcher

et al. 2000

J. Polym. Sci. B Polym. Phys.

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Commercially available fourth and fifth generation poly(propyleneimine) (PPI) dendrimers were functionalized with acetyl chloride and deuterated acetyl chloride. Their solution properties in water and D2O were measured with dilution viscometry, densitometry, rheology, and small‐angle neutron scattering (SANS) and compared to molecular modeling. Both the acetylated and PPI dendrimers exhibited Newtonian rheology in solution at all concentrations, but the functionalized dendrimers were less viscous than the nonacetylated dendrimers at an equal weight fraction (50 wt %). The acetylated dendrimers exhibited a pronounced structure peak in SANS, however, that was not evident for PPI in solution and a greatly enhanced solubility. This structure peak, evident at concentrations as low as 0.2 wt %, was evidence for long‐range electrostatic interdendrimer forces, which were screened by added salt. A quantitative agreement was obtained between the dilute‐limiting absolute scattering spectra of both the nonacetylated and acetylated dendrimers in solution with model calculations via a homogeneous spherical model and input parameters independently obtained from dilution viscometry or direct calculation. The combined measurements verified significant solvent penetration for both dendrimer types. The form factors measured in this manner were also in good quantitative agreement with the results of molecular dynamics simulations, which pointed to significant backfolding of the terminal groups. SANS and rheology measurements at higher concentrations suggested dendrimer clustering and interpenetration with increasing concentration, leading to less structure and lower viscosity than would be predicted from the dilute‐limiting behavior. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 857–873, 2000

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Section: Resultsmentioning

confidence: 62%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure and rheology of hyperbranched and dendritic polymers. I. Modification and characterization of poly(propyleneimine) dendrimers with acetyl groups

Bodnár

Silva

Deitcher

et al. 2000

J. Polym. Sci. B Polym. Phys.

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“…Other functional core moieties include: stable TEMPO-based radicals for controlled radical polymerization, 342 crown ethers, 343,344 hexacyclenes, 170 poly-(quarternary ammonium) cations, 345 ethylene thiolates, 346,347 calixarenes, [348][349][350][351][352] cyclodextrins, 178 inorganic clusters, [93][94][95]340,353,354 dichalcogenides, 355 and silsesquioxanes. 356…”

Section: Other Core Functionalitiesmentioning

confidence: 99%

Convergent Dendrons and Dendrimers: from Synthesis to Applications

2001

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I. Introduction 3819 A. Structure 3820 B. Applications 3821 C. Synthetic Approaches 3821 1. Divergent Approach 3821 2. Convergent Approach 3822 D. Features of the Convergent Synthesis 3823 1. Structural Purity 3823 2. Synthetic Versatility 3823 II. Convergent Synthesis of Dendrons and Dendrimers 3824 A. Single-Stage Convergent Syntheses 3824 1. Poly(aryl ether) Dendrimers 3824 2. Poly(aryl alkyne) Dendrimers 3826 3. Poly(phenylene) Dendrimers 3827 4. Poly(alkyl ester) Dendrimers 3827 5. Poly(aryl alkene) Dendrimers 3828 6. Poly(alkyl ether) Dendrimers 3828 7. Other Convergent Dendrimer Syntheses 3829 B. Accelerated Approaches 3829 1.

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“…11 The number of flavors and types of dendrimers has flourished over the past few years, but the characterization of physical properties has tended to lag behind. [12][13][14][15][16][17][18][19][20][21] In fact, much of the progress in understanding the underlying physics that controls the molecular and bulk properties has come from investigations via computer simulation. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] These studies have resulted in a variety of expectations about the molecular organization and resulting properties of these materials.…”

Section: Introductionmentioning

confidence: 99%

From Stars to Spheres: A SAXS Analysis of Dilute Dendrimer Solutions

2001

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The progression of intramolecular organizations within a series of dilute poly(amido amine) (PAMAM) dendrimer/methanol solutions is examined by use of small-angle X-ray scattering (SAXS) combined with comparisons to electron density models and radial density distributions extracted by the indirect transformation for the calculation of P(r) (ITP) method. The SAXS from generation 3 (G3) dendrimers are shown to possess scattering features similar to those of star molecules. This contrasts with the SAXS of the much larger G9 and G10 dendrimers. The G10 SAXS exhibits at least five resolvable secondary maxima. These features are successfully reproduced for a model consisting of constant-density spheres with a small amount of polydispersity in molecular size. Scattering from the intermediately sized G4 through G8 dendrimers reflects a consistent evolution of internal structure progressing from "starlike" to "hard-sphere-like" organizations.

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A small angle X-ray scattering study of sizes and shapes of poly(benzyl ether) dendrimer molecules

Cited by 4 publications

References 9 publications

Structure and rheology of hyperbranched and dendritic polymers. I. Modification and characterization of poly(propyleneimine) dendrimers with acetyl groups

Structure and rheology of hyperbranched and dendritic polymers. I. Modification and characterization of poly(propyleneimine) dendrimers with acetyl groups

Convergent Dendrons and Dendrimers: from Synthesis to Applications

From Stars to Spheres: A SAXS Analysis of Dilute Dendrimer Solutions

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