Dendrimer molecular weight

The use of Equation 5.30 can be illustrated using PAMAM as an example. If EDA is used as the eore molecule, then MW = 60 and = 4. The monomers in 

The calculations then yield the values shown in Table 5.4 for g up to 10. If the degree of polymerization DP is required, then 

---

Table 10.1 Core-shell tecto(dendrimer) molecular weight analysis results obtained from MALDI-MS, AFM and PAGE.

Figure 14.12 Dependencies of glass temperature (Tg) (B), fractional free volume (fo/B) (A) and fractional free volume at glass temperature (fg/B) (C) on dendrimer molecular weight (i.e. generation) for the first seven generations of PAMAM dendrimers (according to ref. [40])...

Gadolinium-dendrimer conjugates have been used as blood pool contrast agents in vivo for nuclear magnetic resonance imaging (MRI) of tumors [65]. The efficacy of the conjugates in such applications is dependent on their biodistribution properties, and these properties vary as a function of dendrimer molecular weight and chemical composition [50]. Dendrimer architecture and synthesis... 

Gadolinium has been complexed with dendrimers and it was observed that this complex enhanced conventional MR images in a dendrimer molecular weight dependent way and substantially better, compared with conventional diethylenetri-aminepentaacetic acid Gd (III) chelates [82]. 

However, dendrimeric and hyperbranched polyesters are more soluble than the linear ones (respectively 1.05, 0.70, and 0.02 g/mL in acetone). The solution behavior has been investigated, and in the case of aromatic hyperbranched polyesters,84 a very low a-value of the Mark-Houvink-Sakurada equation 0/ = KMa) and low intrinsic viscosity were observed. Frechet presented a description of the intrinsic viscosity as a function of the molar mass85 for different architectures The hyperbranched macromolecules show a nonlinear variation for low molecular weight and a bell-shaped curve is observed in the case of dendrimers (Fig. 5.18). 

At present, improved methods of dendrimer construction have made possible the commercial availability of these macromolecules with a variety of molecular weight ranges and surface functional groups. Instead of testing the limits... 

Most of the methods of synthesis reported above present some limitations and constraints lack of solubility for polycationic phosphorus-containing dendrimers from generation 3 [2], dendrimers of weak molecular weight [4], difficulties to overcome cross Unking reactions [6], possibility only to incorporate phosphorus groups on the surface of dendrimers [3], etc. 

Phosphorus dendrimers are among the largest dendrimers reported till now (generation 12, molecular weight higher than 3 000000). 

Because of their high molecular weight and their defined structure, dendrimers offer themselves for studying the expression of chirality on a macromolecular level. The construction of configurationally uniform macromolecules is otherwise a complex task but can be achieved more easily with dendrimers because of repetitive synthesis from identical (chiral) building blocks. Comparison of optical rotation values and circular dichroism (CD) spectra should demonstrate what influence there is of the chiral building blocks on the structure of the whole dendrimer. 

Attached to the periphery of a lst-generation dendrimer, Ti(OCHMe2)2-com-plexes of the six TADDOL moieties in 84 catalyze - in homogeneous solution -the enantioselective addition of diethylzinc to benzaldehyde with about the same selectivity ((S) (R) 97 3) as do six monomeric TADDOL units [105],but, with a molecular weight of only 3833 Da, dendrimer 84 had to be separated by column chromatography rather than by ultrafiltration methods. 

Scheme 6. Synthesis of dendrimer 22 a and its TMSI mediated conversion (dedendronization) to 22b. 22b is needed to indirectly determine the molecular weight of 22a...

---