References and Notes

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    Lee, P. I. Diffusional release of a solute from a polymeric matrixsapproximate analytical solutions. J. Membr. Sci. 1980, 7, 255275.
  • 3
    Joshi, A.; Himmelstein, K. J. Dynamics of controlled release from bioerodible matrices. J. Controlled Release 1991, 15, 95104.
  • 4
    Cleland, J.; Powell, M.; Lim, A.; Barron, L.; Berman, P.; Eastman, J.; Nunberg, T.; Wrin, X.; Vennari, J. Development of a single shot subunit vaccine for HIV-1. AIDS Res. Human Retrovirus 1994, 10, S21S26.
  • 5
    Shah, S. S.; Cha, Y.; Pitt, C. G. Poly(glycolic acid-co-DL-lactic acid): diffusion or degradation controlled drug delivery?. J. Controlled Release 1992, 18, 261270.
  • 6
    Lewis, D. H. Controlled release of bioactive agents from lactide/glycolide polymers. In Biodegradable Polymers as Drug Delivery Systems; Chasin, X., Langer, X., Eds.; Marcel Dekker: New York, 1990; pp 141.
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    Alonso, M. J.; Gupta, R. K.; Min, C.; Siber, G. R.; Langer, R. L. Biodegradable microspheres as controlled-release tetanus toxoid delivery systems. Vaccine 1993, 11, 18.
  • 8
    Hanes, J.; Hildgen, P.; Edwards, D. A.; Batycky, R. P.; Coleman, S.; Cleland, J.; Langer, R. Poly(D,L-lactic-co-glycolic acid) mi-crosphere degradation and pulsatile release of the globular protein gp 120. Submitted for publication in J. Pharm. Sci.
  • 9
    Van Koevelen, D. W. Properties of PolymerssCorrelations with Chemical Structure; Elsevier: Amsterdam, 1972.
  • 10
    Cha, Y.; Pitt, C. G. A one-week subdermal delivery system for l-methadone based on biodegradable microcapsules. J. Controlled Release 1988, 7, 6978.
  • 11
    As pointed out in the discussion section, the general analysis outlined herein applies to far more general circumstances than those of microparticles into which water tunnels via straight, regularly shaped 'free molecular volume' cylindrical pores.
  • 12
    Shih, C. Chain-end scission in acid catalyzed hydrolysis of poly-(D,L-lactide) in solution. J. Controlled Release 1995, 34, 915.
  • 13
    Shih, C.; Waldron, N.; Zentner, G. M. Quantitative analysis of ester linkages in poly(D,L-lactide) and poly(D,L-lactide-co-gly-colide). J. Controlled Release 1996, 38, 6973.
  • 14
    Mark, H.; Simha, R. Degradation of long chain molecules. Trans. Faraday Soc. 1940, 35, 611618.
  • 15
    Montroll, E. W.; Simha, R. Theory of depolymerization of long chain molecules. J. Chem. Phys. 1940, 8, 721.
  • 16
    Aris, R.; Gavalas, G. R. 1966 On the theory of reactions in continuous mixtures. Phil. Trans. R. Soc. Lond. 1966, A260, 351393.
  • 17
    Ziff, R. M.; McGrady, E. D. The kinetics of cluster fragmentation and depolymerisation. J. Phys. A: Math. Gen. 1985, 18, 30273037.
  • 18
    Ziff, R. M.; McGrady, E. D. Kinetics of polymer degradation. Macromolecules 1986, 19, 25132519.
  • 19
    Kehlen, H.; Rätzsch, M. T.; Bergmann, J. Continuous kinetics of first order degradation reactions in polydisperse mixtures. Chem. Eng. Sci. 1988, 43, 609616.
  • 20
    Wang, M.; Smith, J. M.; McCoy, B. J. Continuous kinetics for thermal degradation of polymer in solution. AIChE J. 1995, 41, 15211533.
  • 21
    Emsley, A. M.; Heywood, R. J. Computer modelling of the degradation of linear polymers. Polymer Degradation Stability 1995, 49, 145149.
  • 22
    Abramowitz, M.; Stegun, I. A. Handbook of Mathematical Functions. Dover: New York, 1965.
  • 23
    In effect, eqs 41-44 are an explicit method for inverting a triangular matrix.
  • 24
    Carslaw, H. S.; Jaeger, J. C. Conduction of Heat in Solids. Oxford, Oxford University 1959.
  • 25
    This method of measurement is obviously approximate. Distinct mesopores become apparent by visual inspection of electron microscopic photos8 when mesopores reach a radius of approximately RM ≡ 1 µm. Measuring the rate of growth of pores in the domain RM ≥ 1 µm may or may not be equivalent to measuring the rate constant kcoal.
  • 26
    Calis, S.; Jeyanthi, R.; Tsai, T.; Mehta, R.; DeLuca, P. P. Adsorption of salmon calcitonin to PLGA microspheres. Pharm. Res. 1995, 12, 10721076.
  • 27
    Saltzman, W. M.; Pasternak, S. H.; Langer, R. Microstructural models for diffusive transport in porous polymers. In Controlled-Release Technology: Pharmaceutical Applications; Lee, X., Good, X., Eds.; Americal Chemical Society: 1987; pp 1633.
  • 28
    Grandfils, C.; Flandroy, P.; Jérôme, R. Control of the biodegradation rate of poly(D,L-lactide) microparticles intended as chemoembolization materials. J. Controlled Release 1996, 38, 109122.
  • 29
    Gref, R.; Minamitake, Y.; Peracchia, M. T.; Trubetskoy, V.; Torchilin, V.; Langer, R. Biodegradable long-circulating poly-meric nanospheres. Science 1994, 263, 1600.
  • 30
    Hausberger, A. G.; Kenley, R. A.; DeLuca, P. P. Gamma Irradiation Effects on Molecular Weight and in Vitro Degradation of Poly(D,L-Lactide- CO-Glycolide) Microparticles. Pharm. Res. 1995, 12, 851856.
  • 31
    Brenner, H.; Edwards, D. A. Macrotransport Processes; Butter-worth-Heinemann, Boston 1993.
  • 32
    Duda, J. L.; Zielinski, J. M. 1996 Free-volume theory. In Diffusion in Polymers; Neogi, P., Ed.; Marcel Dekker: New York, 1996; pp 143171.