From polymer beads

Release and Delayed Release of Water-Soluble Drugs from Polymer Beads with Low Water Swelling... 

Highly water soluble drugs, as they are typical for oral administration, can be released from polymer beads with low (< 10%) water- but high ethanolswelling capacity at controlled rates, for up to 8 hours. The release of oxprenolol-HCl (77% water solubility) and diclofenac Na (2.6% water solubility) from drug loaded monoliths is a function of water content and crosslink density. By partial extraction of the drug loaded beads the release can be further slowed down and, in the case of oxprenolol-HCl, delayed for several hours the delay is dependent on water content of the polymer and is the result of the formation of a hydrophobic surface membrane. 

Polymeric herbicides were prepared with 2,4-D and CMPA covalently or ionically bound to oligoethylenoxylated polystyrene resins at different degrees of crosslinking. These adducts were formed by ion exchange, by nucleophilic displacement on chlo-romethyl groups, and by esterification of hydroxyl groups (Scheme 3.3) [127]. Herbicide release from polymer beads loaded with herbicide was monitored in aqueous solutions buffered at pH 4,7, and 9. For covalently bound herbicides, a release of... 

Figure 5. Blood glucose depression activity of released insulin from polymer beads determined by TV injection in rats (n=4).

Egen, M. and Zentel, R. (2002) Tuning the properties of photonic films from polymer beads by chemistry. Chem. Mater., 14 (5), 2176-2183. 

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