Hydroxyl end-capped macromers of N-vinyl-2-pyrrolidinone as precursors of amphiphilic block copolymers

Telechelic N-vinyl-2-pyrrolidinone (NVP) oligomers terminated by hydroxyl groups were prepared by radical polymerization in the presence of functional chain transfer agents. Then hydroxy-terminated poly(NVP) was used as initiator in the ring opening polymerization of ε-caprolactone (ε-CL). Experiments were performed either under basic conditions or by using SnOct₂ or ZnEt₂ as catalyst. The resulting amphiphilic AB-type block copolymers were thoroughly characterized by spectroscopic and thermal techniques. These data and fractionation in protic solvents indicated that the copolymerization products are constituted by a mixture of copolymers with a wide composition range. The water-soluble copolymer fractions formed micelles and nanoaggregates that showed an appreciable capacity of loading piroxicam, a hydrophobic non-steroidal anti-inflammatory drug. Contact angle measurements, atomic force microscopy, and surface plasmon resonance measurements indicated that the surface of films prepared from the insoluble fractions does not have antiopsonizing properties in spite of their high hydrophilicity.