High PEO Content Research Articles

Platelet interaction with poly(ethylene oxide) networks

AbstractInterpenetrating polymer networks (IPNs) of poly(ethylene oxide) (PEO) and a polyether substituted polysiloxane were synthesized containing variations of PEO content (35 and 65% dry network weight) and PEO systematically varied from low to high molecular weight (2,000, 8,000, and 20,000). Biocompatibility was assessed by measureing 111In platelet deposition in a baboon femoral ex vivo shunt. Mass transfer analysis revealed that platelet transport to PEO/polysiloxane surfaces was kinetically limited and correlated with both PEO content and molecular weight. Differences in material performance were noted particularly after the initial 30 min blood contact period. In mid and high PEO molecular weight networks (8,000 and 20,000), reduced platelet deposition was noted with increased PEO content. In materials of high PEO content (65%), mid and high PEO molecular weight samples had significantly lower levels of platelet adsorption than PDMS (60 min; p< 0.05) or networks of low PEO molecular weight, coded 2K‐65 (30 and 60 min; p < 0.05). The lowest level of platelet deposition was noted on 20K‐65 networks, less than one platelet per 1,000 μm2.

Miscible blends of poly(ethylene oxide) and an amorphous copolyester-polyurethane

Blends of poly(ethylene oxide) (PEO) with an amorphous copolyester-polyurethane (PU) were prepared by casting from a common solvent. The polymers were found to be miscible and to show a single, composition dependent, glass transition temperature. The techniques used were DSC and optical and scanning electron microscopy. Optical and scanning electron microscopy revealed that blend samples prepared by solution casting crystallized with volume-filling spherulites up to a composition of 40/60 PEO/PU. DSC results showed that there existed crystals in the samples of high PEO content up to 10/90 PEO/PU. Observation of melting point depression of annealed melt-pressed films allowed determination of the B interaction parameter of the two polymers in the melt, using available theory. In order to obtain equilibrium melting point data, the Hoffman-Weeks procedure was employed to take into account the influence of crystal morphology. The value of B obtained was −3.42 cal/cm 3; the negative value is expected for miscible blends.

Novel Design of Microreservoir-Dispersed Matrices for Drug Delivery Formulations: Drug Release from Polybutadiene- and Poly (ethylene oxide)-Based Segmented Polyurethanes in Relation to Their Microdomain Structures

Drug release from monolithic devices of segmented polyether-poly- (urethane-urea) (PEUU)s based on 1,2-polybutadiene (PBD) and poly(ethylene oxide) (PEO) as their soft segments was examined in relation to their micro domain structures. Physical characterization of these PEUU films was carried out in terms of their thermal properties, dynamic mechanical properties, and water structure in water swollen PEUU films. These results reveal that the ter nary microdomain structures are composed of PBD, PEO, and hard segments. The drug release profiles of these PEUU devices are strongly affected by the physicochemical nature of soft segment matrices in PEUUs. The PEUUs with high PEO content exhibited slow and steady (zero-ordered) release of drug in contrast with those with low PEO content from which drug release was en tirely restricted. This result indicates the importance of a matrix to perform the function not only as a drug reservoir but also a transport channel. The solu bility parameters of both constituent segments and the drug must be realized for regulated drug release from microdomain-structured polymeric devices.

The phase behaviour of a poly(ether sulfone) with poly(ethylene oxide)

AbstractBlends of poly(ethylene oxide) with a poly(ether sulfone) were prepared by casting from a common solvent and were found to be miscible and show a single, composition dependent, glass transition temperature. Mixtures in both cyclohexanone and N,N‐dimethylformamide phase, separated on heating and thus conditions need to be carefully chosen to obtain homogeneous blends. At higher PEO contents, PEO crystallised from the blends at lower temperatures. The melting point depression, as determined by trubidity measurements, was used to calculate an interaction parameter which was negative, as expected for miscible polymers. The blends also phase separated on heating, and the cloud point curve could be measured by turbidity measurements and confirmed by both visible and electron microscopy. The cloud point curve was very skew with a minimum at around 10 wt.‐% PES content. This was not a strong function of the molecular weight and the skew nature was thus presumably due to differences in the state parameters of the pure components. The blends showed a very high mobility with sharp and reproducible could points which might make them ideal for future miscibility studies.