V-Branched, Amide Connectivity

Related dendrimers possessing primary amines were synthesized135 from hexaacrylo-nitrile, a by-product in acrylonitrile polymerization, which was converted to the corresponding hexaester. Aminolysis with ethylenediamine and Michael addition with ethyl acrylate follow Tomalia s process the sequence was repeated to generate the higher generations. 

De Gennes and Hervet 46 statistically found that these cauliflower polymers 8 (Tomalia s PAMAMs) exhibit restricted idealized growth, also known as dense packing , when the number of generations m = mi, where mi = 2.88 (In P + 1.5). This relates in space to the limiting radius Ru which increases linearly with P monomers. Below this limit, the radius R(M) of the dendrimer, when plotted as a function of molecular weight (M), should increase (m0,2) whereas above this limit (R Ri), compact structures (R == A/0,33) should result. 

These starburst dendrimers have been subjected 47 to two different fractal analyses I48 49 (a )A c/2 D)/2, where A is the surface area accessible to probe spheres possessing a cross-sectional area, o, and the surface fractal dimension, D, which quantifies the degree of surface irregularity and (b) A = dD, where d is the object size. Both methods give similar results with D = 2.41 0.04 (correlation coefficient = 0.988) and 2.42 0.07 (0.998), respectively. Essentially, the dendrimers at the larger generations are porous structures with a rough surface. For additional information on dendritic fractality, see Section 2.3. 

Yu and Russo 52a reported the fluorescence photobleaching recovery and dynamic light 

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