ABSTRACT
Polymeric vesicles are a form of vesicular self-assembly (Fig. 1). As has been emphasized elsewhere in this volume, vesicular systems arise when amphiphilic molecules self-assemble in aqueous media in an effort to reduce the high-energy interaction between the hydrophobic portion of the amphiphile and the aqueous disperse phase and maximize the low-energy interaction between the hydrophilic head group and the disperse phase (Fig. 1). Vesicular self-assemblies reside in the nanometer to micrometer-size domain. Excellent reviews exist on the self-assembly of amphiphiles (1,2), and hence this topic will not be dealt with in great detail here. The most well-known vesicular assemblies, the liposomes (3), have formed the basis of licensed medicines (4), and although the anticancer doxorubicin formulation (Doxil1 or Caelyx1) does contain an amphiphilic poly(oxyethylene) derivative, such vesicles, with bilayers comprising relatively small proportions of amphiphilic polymers, be they nonionic surfactant vesicles (niosomes) (5) or liposomes (6), are not to be dealt with in this chapter, especially as the
latter are well explored in other parts of the volume. Rather this chapter will focus on polymeric vesicle self-assemblies arising from polymers bearing lipid pendant groups (Fig. 2) (8-10). Such vesicles are formed from the self-assembly of linear soluble polymers bearing hydrophobic pendant groups. An early form of these vesicles, in which amphiphilic groups were attached to a polymer chain via a hydrophilic spacer (Fig. 2), were first investigated as a means of stabilizing the metastable vesicles formed from low-molecular-weight amphiphiles, with the polymer providing a kinetic trap for the self-assembled system (9,11).
