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/marc.1998.030190206

Cited by 17 publications

(17 citation statements)

References 8 publications

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“…A family of dendrimers consists of a series of molecules whose molecular weight increases exponentially with each generation. Scattering experiments on higher generation dendrimers suggest that these polymeric species form spheres with a uniform density (12)(13)(14). Due to the ever increasing number of monomers incorporated into the periphery with succeeding generations, a uniform density can be obtained only by a folding of the end groups back into the center of the sphere (15).…”

Section: Introductionmentioning

confidence: 99%

Viscosity of Colloidal Suspensions in Aqueous Gelatin

Hone

Howe

2002

Journal of Colloid and Interface Science

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Section: Introductionmentioning

confidence: 99%

Viscosity of Colloidal Suspensions in Aqueous Gelatin

Hone

Howe

2002

Journal of Colloid and Interface Science

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“…Scattering experiments [2][3][4][5][6][7][8][9][10][11][12] and computer simulation [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] can give valuable information about the shape and internal structure of dendrimers in terms of radial density distributions and the overall dimension of dendrimers. Both methods approach the problem from different directions.…”

Section: Introductionmentioning

confidence: 99%

Structure of star-burst dendrimers: A comparison between small angle x-ray scattering and computer simulation results

Rathgeber

Pakuła

Urban

2004

The Journal of Chemical Physics

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We investigated the generation dependent shape and internal structure of star-burst dendrimers under good solvent conditions using small angle x-ray scattering and molecular modeling. Measurements have been performed on poly(amidoamine) dendrimers with generations ranging from g=0 up to g=8 at low concentrations in methanol. We described the static form factor P(q) by a model taking into account the compact, globular shape as well as the loose, polymeric character of dendrimers. Monomer distributions within dendrimers are of special interest for potential applications and have been characterized by the pair correlation function gamma(r), as well as by the monomer and end-group density profile, rho(r) and rho(e)(r), respectively. Monomer density profiles and gamma(r) can be derived from P(q) by modeling and via a model independent approach using the inverse Fourier transformation algorithm first introduced by Glatter. Experimental results are compared with computer simulations performed for single dendrimers of various generations using the cooperative motion algorithm. The simulation gives direct access to gamma(r) and rho(r), allows an independent determination of P(q), and yields in addition to the scattering experiment information about the distribution of the end groups. Excellent qualitative agreement between experiment and simulation has been found.

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“…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 al 14 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 theory 18 and modeling 19 or a dense core model as obtained by simulation.…”

Section: Introductionmentioning

confidence: 99%

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

Bodnár¹,

Silva²,

Deitcher³

et al. 2000

J. Polym. Sci. B Polym. Phys.

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ABSTRACT: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 D 2 O 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.

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

Cited by 17 publications

References 8 publications

Viscosity of Colloidal Suspensions in Aqueous Gelatin

Viscosity of Colloidal Suspensions in Aqueous Gelatin

Structure of star-burst dendrimers: A comparison between small angle x-ray scattering and computer simulation results

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

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