title: Dielectric and thermodynamic properties of biodegradable poly(D,L-lactide-co-glycolide) and the effect on the micro-encapsulation and release of captopril.
abstract: The mechanical and dielectric properties of three kinds of poly(lactic acid-coglycolic acid) (PLG) with different molecular weights and polydispersities fractioned by ultrafiltration were investigated by dynamic mechanical thermal analysis (DMTA) and dielectric measurement. All samples showed typical behaviour of amorphous polymer under different fields. Two relaxation processes were found, a secondary relaxation in glassy state at low temperature and a glass transition relaxation. The molecular weights and polydispersities of PLGs influenced significantly both relaxation, especially the relaxation strength and location. The strength of secondary relaxation was reduced and the glass transition shifted to a higher temperature when the molecular weight of PLG increased and the polydispersity decreased. The shift of glass transition temperature (Tg) might decrease the motion of the macromolecules and resulted in a higher moduli of rubbery PLG at the temperature of the drug system (37 degrees C) and lowered the diffusivity of the drug in polymeric matrix and then the initial burst and fast diffusional release of captopril from commercial PLG were improved.
authors.affiliation: Department of Physical Chemistry, Philipps-University Marburg, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Schartel
authors.forename: C
authors.initials: C
authors.lastname: Volland
authors.forename: Y X
authors.initials: YX
authors.lastname: Li
authors.forename: J W
authors.initials: JW
authors.lastname: Wendorff
authors.forename: T
authors.initials: T
authors.lastname: Kissel
mesh_terms: D001672:Biocompatible Materials; D001673:Biodegradation, Environmental; D002214:Capsules; D002216:Captopril / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics*; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D016503:Drug Delivery Systems; D004563:Electrochemistry; D019344:Lactic Acid; D008863:Microspheres; D008970:Molecular Weight; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers; D013816:Thermodynamics; D014462:Ultrafiltration
chemical_list: D001672:Biocompatible Materials; D002214:Capsules; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D011108:Polymers; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D002216:Captopril