The Influence of Molecular Architecture and Solvent Type on the Size and Structure of Poly(benzyl ether) Dendrimers by SANS

Evmenenko, Guennadi; Bauer, Barry J.; Kleppinger, Ralf; Forier, Bart; Dehaen, Wim; Amis, Eric J.; Mischenko, N; Reynaers, Harry

doi:10.1002/1521-3935(20010301)202:6<891::aid-macp891>3.0.co;2-k

Cited by 30 publications

(39 citation statements)

References 25 publications

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“…Hence, from the molecular weight dependence of the dendrimer dimensions conclusions can be drawn whether or whether not dendrimers grow in a self-similar manner when a new generation is added. Some computer simulations ͑Scherrenberg et al, 6 Karatasos et al, 15 Giupponi and Buzza, 16 Murat and Grest, 21 Lyulin et al, 23 Cavallo and Fraternali 26 ͒ as well as scattering experiments ͓Evmenenko et al 5 (gϭ1 -5), Scherrenberg et al, 6 Prosa et al 12 (gϭ2 -9)] obtain a fractal dimension of DϷ3 indicating that dendrimers are compact, space filling ͑homogeneous͒ structures. The Monte Carlo simulations of Lue 24 on dendrimers under good solvent conditions yield values between Ϸ0.67 (DϷ1.49) and 0.60 (DϷ1.67) depending on the size of the beads from which the dendrimers are build.…”

Section: Radius Of Gyration and Fractal Growth Of Dendrimerssupporting

confidence: 91%

“…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%

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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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Section: Radius Of Gyration and Fractal Growth Of Dendrimerssupporting

confidence: 91%

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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“…Similar rigidity in dendrimers has been observed experimentally for poly(amido amine) (PAMAM) and poly(benzyl ether) dendrimers where the size of the dendrimer measured by small-angle neutron scattering (SANS) remains nearly constant as the solvent is changed from a poor to a good solvent. 60,61 This seems to be related to the uniform space-filling feature of the PAMAM dendrimer we observed from our previous study. 62 This insensitivity is due to the converging architecture of the dendrimer that restricts the degrees of freedom for conformational changes.…”

Section: The Nanophase-segregated Structure Of the Dendrionmentioning

confidence: 99%

Nanophase Segregation and Water Dynamics in the Dendrion Diblock Copolymer Formed from the Fréchet Polyaryl Ethereal Dendrimer and Linear PTFE

et al. 2005

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We propose a new material consisting of a dendrion copolymer formed from (a) a water-soluble dendritic polymer and (b) a hydrophobic backbone. Using molecular dynamics simulations techniques, we determine the structure and dynamics of the dendrion formed by second-generation Fréchet polyaryl ethereal dendrimer as the hydrophilic component and linear polytetrafluoroethylene (PTFE) as the hydrophobic polymer, with 5 and 10 wt % of water. We find that this material produces a well-developed nanoscale structure in which water forms a continuous nanophase, making this new family of compounds promising candidates for applications in fuel cell membranes. We find that the water molecules are incorporated into the dendrimer block of the copolymer to form a nanophase-segregated structure. The well-developed nanophase-segregated structures rendered by this material have characteristic dimensions of segregation ( approximately 30 Angstrom) and dendrimer conformational properties that are independent of water content. Calculations of water dynamics and proton transport in these nanophase-segregated structures indicate that the dendrion copolymer membrane with 10 wt % of water content has a water structure and transport properties equivalent to that of the hydrated Nafion membrane with 20 wt % of water content.

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“…This discrepancy could be attributed to the fact that the shape of the dendrimer (discussed below) is far from spherical, an assumption that was made to extract R g when using Eq. for PAMAM and PPI dendrimer both theoretically and experimentally 18,19,44 . Such nonuniversal scaling law behavior was recently found to be true for flexible dendrimers 45 .…”

Section: Size and Shapementioning

confidence: 99%

“…The number of bound waters calculated this way is listed in Table 5. This significant penetration of solvent molecules inside the dendrimer structure is in agreement with the recent SANS studies on poly (benzyl ether) 51 and polycarbosilane dendrimers 52 . In these experiments the number of solvent molecules inside the dendrimer was calculated from the change in neutron scattering density.We find that the number of bound water for the G-th generation of the PETIM is larger than the number of water in same generation PAMAM dendrimer.…”

Section: Water Penetrationmentioning

confidence: 99%

Structure of poly(propyl ether imine) dendrimer from fully atomistic molecular dynamics simulation and by small angle x-ray scattering

Jana

Jayamurugan

Ganapathy

et al. 2006

The Journal of Chemical Physics

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Abstract:We study the structure of carboxylic acid terminated neutral poly (propyl ether imine) (PETIM) dendrimer from generation 1 through 6 (G1-G6) in a good solvent (water) by fully atomistic molecular dynamics (MD) simulations. We determine as a function of generation such structural properties as: radius of gyration, shape tensor, asphericity, fractal dimension, monomer density distribution, and end-group distribution functions. The sizes obtained from the MD simulations have been validated by Small Angle X-Ray Scattering (SAXS) experiment on dendrimer of generation 2 to 4 (G2 -G4). A good agreement between the experimental and theoretical value of radius of gyration has been observed. We find a linear increase in radius of gyration with the generation. In contrast, R g scales as ~x N with the number of monomers. We find two distinct exponents depending on the generations: x = 0.47 for G1-G3 and x = 0.28 for G3-G6 which reveals their non-space filling nature. In comparison with the amine terminated PAMAM dendrimer, we find R g of G-th generation PETIM dendrimer is nearly equal to that of (G+1)-th generation of PAMAM dendrimer as observed by Maiti et. al. [Macromolecules, 38, 979 2005]. We find substantial back folding of the outer sub generations into the interior of the dendrimer. Due to their highly flexible nature of the repeating branch units, the shape of the PETIM dendrimer deviates significantly from the spherical shape and the molecules become more and more spherical as the generation increases. The interior of the dendrimer is quite open with internal cavities available for accommodating guest molecules suggesting using PETIM * For correspondence: maiti@physics.iisc.ernet.in (PKM) or jayaraman@orgchem.iisc.ernet.in (NJ)or asood@physics.iisc.ernet.in (AKS) 2 dendrimer for guest-host applications. We also give a quantitative measure of the number of water molecules present inside the dendrimer.3

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The Influence of Molecular Architecture and Solvent Type on the Size and Structure of Poly(benzyl ether) Dendrimers by SANS

Cited by 30 publications

References 25 publications

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

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

Nanophase Segregation and Water Dynamics in the Dendrion Diblock Copolymer Formed from the Fréchet Polyaryl Ethereal Dendrimer and Linear PTFE

Structure of poly(propyl ether imine) dendrimer from fully atomistic molecular dynamics simulation and by small angle x-ray scattering

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