Polyethylene Glycol Polyester Block Copolymers: Biocompatible Carriers for Nanoparticulate Drug Delivery - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 61

PVL in the center of the star with PEO at the terminal ends [32].
Polymerization of PVL was initiated off of dipentaerythritol and PEO
was coupled to the PVL ends. These micelles had somewhat lower
CMC's on the order of 10 -6 M than the diblock PEO-PVL micelles.
As much as star copolymers have contributed to our knowledge of
the range of copolymer block geometries that will form micelles, the
development to this point has only slightly increased their stability.
Therefore, PEO-PCL diblock copolymers with functional groups
coupled to the PCL were developed.

Figure 3.4 Structure of (a) four-arm star PEO-PCL block copolymer. From
reference [66].

3.2.5 Drug Delivery from Substituted Diblock PEO-PCL

Copolymer Micelles

Lavasanifar and coworkers synthesized α -substituted ε -caprolactone
monomers (Figure 3.5) with functional substituents of benzyl
carboxylate or carboxylic acid to produce PEO-poly( α -benzyl
carboxylate ε -caprolactone) (PBCL) and PEO-poly( α -carboxylate
ε -caprolactone) (PCCL) [68]. Also, functional groups such as
hydroxyls, carboxylic acids and epoxides can be grafted onto the PCL
chain post-post polymerization via atom transfer radical addition
reactions or Michael-type additions [69-71].
The addition of benzyl carboxylate or carboxylic acid
demonstrated how the CMC can be tuned within a PEO-PCL copolymer
with nominally the same block lengths. A 5 kDa PEO block was used