Three-dimensional extended nonlocal photopolymerization driven diffusion model Part II Photopolymerization and model development

Li, Haoyu; Qi, Yue; Sheridan, John T.

doi:10.1364/josab.31.002648

Cited by 38 publications

(7 citation statements)

References 46 publications

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“…At one end of the spectrum are accurate physicochemical models accounting for each of the reaction steps (minimally photoinitiation, propagation, and termination) [19][20][21][22], nonuniform distributions of polymer chain length [23,24], generation and diffusion of thermal energy [15], mass transport [25], and intricate optical effects [26,27]. Such models, however, often suffer from an excessive number of parameters, some of which cannot be measured experimentally, and thus they offer limited insight and practical use.…”

Section: Introductionmentioning

confidence: 99%

Controlling frontal photopolymerization with optical attenuation and mass diffusion

et al. 2015

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Frontal photopolymerization (FPP) is a versatile directional solidification process that can be used to rapidly fabricate polymer network materials by selectively exposing a photosensitive monomer bath to light. A characteristic feature of FPP is that the monomer-to-polymer conversion profiles take on the form of traveling waves that propagate into the unpolymerized bulk from the illuminated surface. Practical implementations of FPP require detailed knowledge about the conversion profile and speed of these traveling waves. The purpose of this theoretical study is to (i) determine the conditions under which FPP occurs and (ii) explore how optical attenuation and mass transport can be used to finely tune the conversion profile and propagation kinetics. Our findings quantify the strong optical attenuation and slow mass transport relative to the rate of polymerization required for FPP. The shape of the traveling wave is primarily controlled by the magnitude of the optical attenuation coefficients of the neat and polymerized material. Unexpectedly, we find that mass diffusion can increase the net extent of polymerization and accelerate the growth of the solid network. The theoretical predictions are found to be in excellent agreement with experimental data acquired for representative systems.

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Section: Introductionmentioning

confidence: 99%

Controlling frontal photopolymerization with optical attenuation and mass diffusion

et al. 2015

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“…Recent interest in photopolymerization has sparked the development of a range of models that can be roughly grouped into two categories depending on their complexity. In one group are physicochemical models that accurately account for each of the reaction steps, e.g., photolysis, photoinitiation, propagation, chain transfer, and termination [31][32][33][34]; oxygen inhibition [35,36]; nonuniform distributions in the length of polymer chains [37,38]; heat generation and transport [20]; mass transport due to convection and/or diffusion [25,39]; and optical effects such as scattering [40] and refractive index modulation [41]. Although such models can offer theoretical insights into photopolymerization processes, their practical use is limited by a lack of tractability and large number of parameters, some of which cannot be measured experimentally.…”

Section: Introductionmentioning

confidence: 99%

Role of heat generation and thermal diffusion during frontal photopolymerization

et al. 2015

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Frontal photopolymerization (FPP) is a rapid and versatile solidification process that can be used to fabricate complex three-dimensional structures by selectively exposing a photosensitive monomer-rich bath to light. A characteristic feature of FPP is the appearance of a sharp polymerization front that propagates into the bath as a planar traveling wave. In this paper, we introduce a theoretical model to determine how heat generation during photopolymerization influences the kinetics of wave propagation as well as the monomer-to-polymer conversion profile, both of which are relevant for FPP applications and experimentally measurable. When thermal diffusion is sufficiently fast relative to the rate of polymerization, the system evolves as if it were isothermal. However, when thermal diffusion is slow, a thermal wavefront develops and propagates at the same rate as the polymerization front. This leads to an accumulation of heat behind the polymerization front which can result in a significant sharpening of the conversion profile and acceleration of the growth of the solid. Our results also suggest that a novel way to tailor the dynamics of FPP is by imposing a temperature gradient along the growth direction.

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“…Radical chain polymerization results in the chain growth away from the initial spot. Consequently, the spatial effect of monomer polymerization is nonlocal [30][31][32][33][34]. The diffusion model with nonlocal response is an effective approach in analyzing the actual photopolymerization process.…”

Section: E Theoretical Description Of Swelling Dynamicsmentioning

confidence: 99%

Holographic humidity response of slanted gratings in moisture-absorbing acrylamide photopolymer

et al. 2015

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Holographic humidity response is characterized in detail using transmission and reflection geometry in moisture-absorbing acrylamide photopolymer. The diffraction spectrum and its temporal evolution at various relative humidity are measured and analyzed. The quantitative relations between relative humidity and holographic properties of slanted gratings are determined. The responsibility of holographic gratings for various relative humidity is observed by the spectrum response of gratings. The extracted humidity constants reflect the applicability of reflection and transmission gratings at different humidity regions. The humidity reversibility experiment is achieved for confirming repeatability of the sensor. These experiments provide a probability for improving the applicability of a holographic humidity sensor. Finally, the extended diffusion model is derived by introducing the expansion coefficient to describe the dynamic swelling process. This work can accelerate development of the holographic sensor and provide a novel strategy for exploring the swelling mechanism of photopolymer.

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Three-dimensional extended nonlocal photopolymerization driven diffusion model Part II Photopolymerization and model development

Cited by 38 publications

References 46 publications

Controlling frontal photopolymerization with optical attenuation and mass diffusion

Controlling frontal photopolymerization with optical attenuation and mass diffusion

Role of heat generation and thermal diffusion during frontal photopolymerization

Holographic humidity response of slanted gratings in moisture-absorbing acrylamide photopolymer

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