1. Contribution from the Laboratory of Organic Chemistry, Dutch Polymer Institute/Wageningen University, Dreijenplein 8, 6703 HB Wageningen, The Netherlands, Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands, and Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands