No abstract

A series of aliphatic poly(ether-ester)s based on flexible poly(tetramethylene oxide) (PTMO) and hard poly (butylene succinate) (PBS) segments were synthesized by the catalyzed two-step transesterification reaction of dimethyl succinate, 1,4-butanediol, and a,x-hydroxy-terminated PTMO (M n 5 1000 g/mol) in the bulk. The content of soft PTMO segments in the polymer chains was varied from 10 to 50 mass %. The effect of the introduction of the soft segments on the structure, thermal, and physical properties, as well as on the biodegradation properties was investigated. The composition and structure of the aliphatic segmented copolyesters were determined by 1 H NMR spectroscopy. The molecular weights of the polyesters were verified by viscometry of dilute solutions and polymer melts. The thermal properties were investigated using DSC. The degree of crystallinity was determined by means of DSC and WAXS. Biodegradation of the synthesized copolyesters, estimated in enzymatic degradation tests on polymer films in phosphate buffer solution with Candida rugosa lipase at 378C, was compared with hydrolytic degradation in the buffer solution. Viscosity measurements confirmed that there was no change in molecular weight of the copolyesters leading to the conclusion that the degradation mechanism of poly(ester-ether)s based on PTMO segments occurs through the surface erosion.

Poly(ε-caprolactone) (PCL), a biodegradable and biocompatible aliphatic polyester has a great potential as a drug carrying material in controlled drug delivery/release systems. The most simple and economical way to tailor the release profile of active substances from biodegradable polymer matrix is by the addition of the second polymeric component in the polymer matrix, i.e. by blending. This study describes the preparation and characterization of a carbamazepine-loaded microspheres by the use of PCL blended with poly(ethylene oxide) as a drug carrying material. By the use of two-component hydrophilic/hydrophobic polymer blend as a microspheres' matrix material, release profile of the drug can be modified and dictated. The microspheres prepared by classical oil-in-water emulsion solvent evaporation technique were characterized with respect to particle size and morphology, polymer matrix composition, encapsulation efficiency, physical state of the drug and in vitro release behaviour. It was presented that the release profile can be modified by the presence and the amount of hydrophilic component in the starting formulation of microspheres.

The aim of this study was to determine the optimal conditions for the fabrication of porous microspheres based on poly(butylene succinate), PBS. The biodegradable non-porous PBS microspheres were prepared by the oil-in-water (o/w) emulsion solvent evaporation method using poly(vinyl alcohol), PVA, as the surfactant. Fabrication conditions, such as stirring rate, organic/aqueous ratio, PBS concentration and surfactant (PVA) concentration, which have an important influence on both the particle size and the morphology of the microspheres, were varied. Scanning electron microscopy, SEM, observations confirmed the size, size distribution and surface morphology of the microspheres. The optimal conditions for the preparation of the non-porous microspheres were found to be: concentration the PBS solution, 10 mass%; PVA concentration, 1 mass%; the organic/ aqueous ratio CHCl3/H2O = 1/20 and stirring rate 800 rpm. Porous PBS microspheres were fabricated under the optimal conditions using various amounts of hexane and poly(ethylene oxide), PEO, as porogens. The influence of the amount of porogen on the pore size and the particle size was investigated using SEM and the apparent density. The microspheres exhibited various porosities and the pore sizes. The average particle size of the microspheres with PEO as the porogen was from 100 to 122μm and that of the microspheres with hexane as the porogen was from 87 to 97μm. The apparent density of the porous microspheres with PEO as the porogen, from 0.16 to 0.23 g/cm3, was much smaller than the non-porous microspheres, 0.40 g/cm3. In the in vitro degradation experiments, the porous microspheres were incubated in phosphate buffer solution (pH 7) at 37°C. After incubating for one month, the microspheres showed significant extent of the hydrolytic degradation of the porous PBS microspheres

Novel poly(ester-ether)s based on poly(butylene succinate) (PBS) as the hard segments and 30 mass % of poly(propylene oxide) (PPO) as the soft segments were synthesized with varying amount of the antioxidant (N,N'-diphenyl-p-phenylenediamine, DPPD). The influences of the addition of DPPD and the impact of post-synthetic treatment by precipitation on the molecular structure, thermal and physical properties, as well as on the storage stability of the biodegradable aliphatic copolyesters, were investigated. The structure and composition of the copolymers were determined by means of 1H-NMR spectroscopy. The molecular weight and polydispersity of the poly(ester-ether)s were evaluated from solution viscosity and GPC measurements. The thermal properties and stability were evaluated, respecttively, by means of DSC and non-isothermal thermogravimetry in an inert nitrogen atmosphere. The biodegradability potential of the polymers was studied in hydrolytic and enzymatic degradation tests with Candida cylindracea lipase by monitoring the weight loss of polymer films after incubation. The weight losses of the samples increased with time and were in the range from 1 to 5 mass % after 4 weeks. GPC analysis confirmed that there were changes in the molecular weight of the copolyesters during both hydrolytic and enzymatic degradation tests, leading to the conclusion that the degradation mechanism of poly(butylene succinate)s modified with PPO occurred through surface erosion and bulk degradation.