The chemical and physical crosslink densities of irradiated polybutadiene were determined using a precise and consistent method. This method included the use of a statistical theory of crosslinking modified to include chain reactions and the use of Langley's theory for calculating the number of trapped chain entanglements. The number of crosslinks formed per unit radiation dose, G(X), was measured for a series of polybutadienes containing various isomeric forms of unsaturation. The physical crosslink density and the molecular weight between entanglements were determined from measurements of the compression modulus of swollen samples.
For most Photodynamic Therapy (PDT) applications a diffuse, broad and uniform source of irradiation is needed to obtain the most effective and consistent treatment. Since many treatments are within the patient's body, an effective. compact fiber optic delivery system is needed for the activation of the photosensitizer drug at the site of the tissue to be treated. High Numerical Aperture (NA) optical fibers have benefits for PDT treatments but possibly even more so for PDT diagnostic applications. These are summarized and new optical fibers with high and ultra high NAs are described. Properties of these fibers are presented as well as advantages they have over other fibers for delivering light in various PDT applications. Silica fibers with enhanced. effective NAs approaching 0.6 are described.
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