Poly orthoesters structures

In the early 1970s, the ALZA Corporation began its search for polymers suitable for erodible drug delivery systems. The ideal polymer was identified as one undergoing surface erosion in vivo and degrading to non-toxic, low molecular weight products at a rate that could be manipulated over a broad time span. To meet these criteria, a novel family of hydrolyzable polymers was developed, the poly(orthoesters), POEs [285]. The general structure is schematically shown in... 

Fig. 12. The molecular structure of different classes of poly(orthoesters)...

Figure 8 General structure of poly orthoesters. The functional group R can be varied to impart different properties to the polymer. Presence of lactic acid oligomer segments at R catalyzes degradation of the polymer.

Davies, M.C., Khan, M.A., Lvnn, R.A.P., Heller,J. and Watts.J.F, (1991b) X-ray photoelcctron spectroscopy of the surface chemical structure of some biodegradable poly (orthoesters). Biomateriak, 12, 305-308. Davies, M.C., Khan, M..A., Short, R.D., Akhtar, S., Pouton, C. and Watts, J.F. (1990a) XPS and SSIMS analysis of the surface chemical structure of poly (caprolactone) and pol)- (b-h)-droxvbutyrate -b-hydroxy alerate) copolymers. Biomateriak, 11, 228-234. 

Davies, M.C., Lynn, R.A.P., Watts. J.F., Paul,, . J., Vickennan, J.C. and Heller, J. (1991c) ToF-SIMS and XPS analysis of the surface chemical structure of some linear poly (orthoesters). Macromoleciiles, 24, 5508-5514. 

---