PAMAM dendrimers morphology

Fig. 36. Comparison of change in Starburst PAMAM dendrimer morphology (aspect ratios, J y) as a function of generation...

SEM observations showed that the most crystals obtained in the absence and the low concentration of the G4.5 PAMAM dendrimer were rhombohedral. In the high concentration of the G4.5 PAMAM dendrimer, the vaterite products were spherical. Each shape of CaCOj is a typical morphology for each polymorph. The particle sizes of the spherical vaterite particles obtained in the presence of the PAMAM dendrimer were depended on the concentration of the dendrimer. As the concentration of -COONa increased from 5.3 to 10.6 mmol/1, the particle sizes of the spherical vaterite particles were reduced from 8.7 1.0 to 5.2 3.0 pm. 

Figure 13.1 Simulated dendrimer morphology (aspect ratio, l/IJ as a function of generation for PAMAM dendrimers. Adapted from ref. 1...

The surface morphologies of PAMAM dendrimers have been studied extensively by Turro and co-workers [16-23]. As shown in Scheme 4, one approach was to study the adsorption of organic dye molecules and metal complexes on the dendrimer surface by UY-Vis and fluorescence spectroscopy another approach took advantages of electron transfer processes between two adsorbed species on a single dendrimer surface or between the adsorbed species on a dendrimer surface and other species in aqueous solution. 

Scheme 4 Approaches to study the surface morphologies of PAMAM dendrimers...

Langmuir films prepared at air/water interface are transferred on solid substrates and LB firms are constructed. The morphologies of the LB films and their molecular arrangements depend on the characters of hydrophilic and hydrophobic moieties of amphiphiles and the affinity of the moieties to the substrates. Transition of molecular arrangement in LB films of third generation amphiphilic PAMAM dendrimers with dodecyl terminal groups was elucidated [77]. The LB films were transferred by horizontal lifting onto hydrophobic silicon wafers and were devoted to their structural characterization. Since silicon wafers are ahead treated (that is, oxidized) by an aqueous solution of... 

The size and shape of dendrimers have been estimated using transmission electron microscopy [14]. Producing better images of dendrimers may supply answers to fundamental questions such as whether dendrimers have truly uniform sizes, spherical shapes, and dense cores. The visualization of dendrimer assemblies would also be helpful to confirm the structure and morphology for many applications of dendrimers. The positively stained PAMAM dendrimers are shown in Fig. 2 for G10 to G5, respectively. The dendrimer molecules appear as dark objects on a light background of the amorphous carbon substrate and they are well separated from each other. The shapes of the stained molecules are spherical to a first approximation for G10 to G7, with some molecules showing... 

Khopade, A. J. Moehwald, H. Statistical megamer morphologies and materials from PAMAM dendrimers. Macromol Rapid Commun. 2005, 26,445-449. 

The effect of 5th generation polyamidoamine (PAMAM G5) dendrimers on multilamellar dipalmitoylphosphocholine (DPPC) vesicles was investigated. PAMAM was added in 2 different concentrations to the lipids (10 and 10 dendrimer/lipid molar ratios). The thermal behavior of the evolved systems was characterized by DSC while the structure and the morphology were investigated with small- and wide-angle X-ray scattering (SWAXS), freeze-fracture electron microscopy (FFTEM) and P NMR spectroscopy, respectively. The obtained results show that the dendrimers added in 10 molar ratio to the lipids generate minor perturbations in the multilamellar structure and thermal character of... 

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