Sabol, DuĊĦan

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Sabol, DuĊĦan
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Sabol, DuĊĦan

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  • Publication
    Photoinitiation study of Irgacure 784 in an epoxy resin photopolymer
    (American Institute of Physics (AIP), 2010-03-10)
    Sabol, DuĊĦan 
    ;
    Gleeson, M. R. 
    ;
    Liu, Shui 
    ;
    Sheridan, John T. 
    A deeper understanding of the processes, which occur during free radical photopolymerization, is necessary in order to develop a fully comprehensive model, which represents their behavior during exposure. One of these processes is photoinitiation, whereby a photon is absorbed by a photosensitizer producing free radicals, which can initiate polymerization. These free radicals can also participate in polymer chain termination (primary termination), and it is therefore necessary to understand their generation in order to predict the temporally varying kinetic effects present during holographic grating formation. In this paper, a study of the photoinitiation mechanisms of Irgacure 784 photosensitizer, in an epoxy resin matrix, is presented. We report our experimental results and present a theoretical model to predict the physically observed behavior.
      1410ScopusÂİ Citations 56
  • Publication
    Holographic grating evolution in photopolymer materials
    (Optical Society of America, 2007-05-20)
    Gleeson, M. R. 
    ;
    Kelly, John V. 
    ;
    Close, Ciara E. 
    ;
    Sabol, DuĊĦan 
    ;
    Sheridan, John T. 
    A generalized non-local polymerization driven diffusion (NPDD) model is presented, including the effects of absorption and inhibition. Experimentally obtained growth curves are fit using a four-harmonic numerical fitting algorithm and key material parameters are extracted.
      479
  • Publication
    Modeling the photochemical effects present during holographic grating formation in photopolymer materials
    (American Institute of Physics, 2007-07-26)
    Gleeson, M. R. 
    ;
    Kelly, John V. 
    ;
    Sabol, DuĊĦan 
    ;
    Close, Ciara E. 
    ;
    Liu, Shui 
    ;
    Sheridan, John T. 
    The development of a theoretical model of the processes present during the formation of a holographic grating in photopolymer materials is crucial in enabling further development of holographic applications. To achieve this, it is necessary to understand the photochemical and photophysical processes involved and to isolate their effects, enabling each to be modeled accurately. While photopolymer materials are practical materials for use as holographic recording media, understanding the recording mechanisms will allow their limitations for certain processes to be overcome. In this paper we report generalizations of the nonlocal polymer driven diffusion (NPDD) model to include the effects of photosensitive dye absorption and the inhibition effects.
      485ScopusÂİ Citations 60
  • Publication
    Improvement of the spatial frequency response of photopolymer materials by modifying polymer chain length
    (Optical Society of America, 2008-03-01)
    Gleeson, M. R. 
    ;
    Sabol, DuĊĦan 
    ;
    Liu, Shui 
    ;
    Close, Ciara E. 
    ;
    Kelly, John V. 
    ;
    Sheridan, John T. 
    One of the key predictions of the nonlocal photopolymerization driven diffusion (NPDD) model is that a reduction in the extent of the nonlocal effects within a material will improve the high spatial frequency response. The NPDD model is generalized to more accurately model material absorbtivity. By eliminating the necessity for the steady-state approximation to describe the rate of change of monomer radical concentration, a more accurate physical representation of the initial transient behavior, at the start of grating growth, is achieved, which includes the effects of oxygen-based inhibition. The spatial frequency response of an acrylamide/polyvinylalcohol-based photopolymer is then improved through the addition of a chain transfer agent (CTA), sodium formate. Using the NPDD model demonstrates that the CTA has the effect of decreasing the average length of the polyacrylamide (PA) chains formed, thus reducing the nonlocal response parameter, σ. Further independent conïĴrmation of the resulting reduction in the PA average molecular weight is provided using a diffusion-based holographic technique
      499ScopusÂİ Citations 81
  • Publication
    Extended model of the photoinitiation mechanisms in photopolymer materials
    (American Institute of Physics, 2009-11)
    Liu, Shui 
    ;
    Gleeson, M. R. 
    ;
    Sabol, DuĊĦan 
    ;
    Sheridan, John T. 
    In order to further improve photopolymer materials for applications such as data storage, a deeper understanding of the photochemical mechanisms which are present during the formation of holographic gratings has become ever more crucial. This is especially true of the photoinitiation processes, since holographic data storage requires multiple sequential short exposures. Previously, models describing the temporal variation in the photosensitizer (dye)concentration as a function of exposure have been presented and applied to two different types of photosensitizer, i.e., Methylene Blue and Erythrosine B, in a polyvinyl alcohol/acrylamide based photopolymer. These models include the effects of photosensitizer recovery and bleaching under certain limiting conditions. In this paper, based on a detailed study of the photochemical reactions, the previous models are further developed to more physically represent these effects. This enables a more accurate description of the time varying dye absorption, recovery, and bleaching, and therefore of the generation of primary radicals in photopolymers containing such dyes.
      555ScopusÂİ Citations 31