A synthetic concept of preparing dense polymer brushes on planar surfaces is described, in which a self-assembled monolayer (SAM) of biphenyllithium moieties on gold substrates is used to initiate anionic polymerization of styrene. The thickness of the resulting dry polystyrene brush, as estimated by ellipsometry and atomic force microscopy (AFM), is 18 ( 0.2 nm. These techniques also reveal a smooth, homogeneous polymer surface throughout the entire substrate on the macroscopic, as well as on the microscopic, scale, with a roughness of 0.3-0.5 nm (rms). On the basis of results from in situ swelling experiments, monitored by ellipsometry, a polymerization degree of N ) 382 and a grafting density of approximately 7-8 chains/R g 2 , or 3.2-3.6 nm 2 /chain, were calculated with use of mean-field theory. Polarized external reflection (ER) FTIR spectra of the grafted layer confirm highly stretched preferentially oriented polystyrene chains. Upon annealing, spin-coated polystyrene films dewet immediately the brush surface to give polymer droplets with a contact angle of 3°. All obtained results indicate that the described synthetic approach yields densely grafted polymer brushes whose experimental investigations were till now very limited.

Solubilization of highly hydrophobic drugs with carriers that are non-toxic, non-immunogenic and well-defined remains a major obstacle in pharmaceutical sciences. Well defined amphiphilic di- and triblock copolymers based on poly(2-oxazolines) were prepared and used for the solubilization of Paclitaxel (PTX) and other water-insoluble drugs. Probing the polymer micelles in water with the fluorescence probe pyrene, an unusual high polar microenvironment of the probe was observed. This coincides with an extraordinary large loading capacity for PTX of 45 wt.% active drug in the formulation as well as high water solubility of the resulting formulation. Physicochemical properties of the formulations, ease of preparation and stability upon lyophilization, low toxicity and immunogenicity suggest that poly(2-oxazoline)s are promising candidates for the delivery of highly challenging drugs. Furthermore, we demonstrate that PTX is fully active and provides superior tumor inhibition as compared to the commercial micellar formulation.

Poly(2-oxazoline)s (POx) are currently discussed as an upcoming platform for biomaterials design and especially for polymer therapeutics. POx meets several requirements needed for the development of next-generation polymer therapeutics such as biocompatibility, high modulation of solubility, variation of size, architecture as well as chemical functionality. Although in the early 1990s first and promising POx-based systems were presented but the field lay dormant for almost two decades. Only very recently, POx based polymer therapeutics came back into the focus of very intensive research. In this review, we give an overview on the chemistry and physicochemical properties of POx and summarize the research of POx-protein conjugates, POx-drug conjugates, POx-based polyplexes and POx micelles for drug delivery.