142 Advances in Polymer Science Editorial Board: A. Abe. A.-C ...

Dendrimers and Dendrimer-Polymer Hybrids 219
Scheme 19
conditions are required during the redistribution in order to avoid oxidative polymerization
and oxidative side reactions. The star polymers are different from
the previously described model star polymers obtained by anionic polymerization
because the arm MW has a most probable MWD. Interestingly, it was observed
that the hydrodynamic volume of the star polymers as measured by SEC
does not vary much with increasing functionality from f=4 to f=64 [143], although
measured [h] and calculated MW suggest an important increase in R h
[144]. The hydrodynamic volume measured by dynamic light scattering is clearly
an increasing function of the functionality of the stars at constant arm length,
as well as under conditions of increasing arm length and constant dendrimer
functionality. This apparent difference may be due to different averages probed
by the two methods. The SEC maximum is close to a weight average while the
dynamic light scattering measures a z-average value of the hydrodynamic volume.
The method of transetherification or the related transesterification should be
applicable to other dendrimer polymer systems. Transamidation has been performed
with poly(propylene imine) dendrimer and poly(e-caprolactone). The
linear chain is fragmented according to Scheme 19b, and a mixture of star and
linear polymer is formed [135]. The average MW of the arms is equal to the MW
of the linear fragments.
5
Hybrids of Dendrimers and Biological Polymers
5.1
Dendrimer-Peptide Hybrids
Tam has pioneered the use of dendrimers as templates for simultaneous growth
of identical polypeptides [145]. Tam et al. were also the first to use the Merrifield
approach to the synthesis of dendrimers [145–148]. Starting from phenylaceta-