Ultra Violet (UV)-curable resins are widely used for coating, adhesives, composite fillers, and 3D printing because of their many advantages, including high curing rate and energy efficiency. If a UV-curable resin is exposed to UV light irradiation for a fixed amount of time, the polymerization rate and the final degree of conversion (DoC) decline with curing depth due to light attenuation. This will lead to an uneven DoC distribution, especially when photo-curing resin within a large volume. Many material properties of a cured resin are directly linked to DoC. Consequently, the spatial gradient in the DoC that is caused by the light attenuation may degrade the performance of a resin for applications involving large curing depths. Therefore, it is crucial to investigate and predict the evolution of the DoC throughout a volume to better control the properties of a cured resin. Current curing kinetic models provide insight into how DoC evolves with depth for a pure resin cured by a collimated light beam. However, they do not accurately describe how DoC evolves within UV-curable composites or systems in which multi-directional ray propagation is in play. Moreover, they do not provide insight into how polymeric networks form or how they influence the polymerization process. Therefore, this dissertation describes three novel simulation frameworks for predicting the evolution of DoC and polymetric network in UV-curable systems. The first framework uses Maxwell's Laws of Electromagnetic Theory and a series of finite difference time domain (FDTD) simulations to predict light intensity distribution at different reaction time steps. It also uses curing kinetic models and optical properties models to predict DoC and optical properties within a volume. The framework is applied to simulate the photo-induced, free-radical polymerization of acrylate-based composites. It is used to study the influence of resin refractive index, filler refractive index, and filler particle size on the spatial and temporal evolution of DoC. The simulation results reveal that: 1) The change of resin refractive index during polymerization has a significant impact on both light propagation and DoC within a UV-curable composite. 2) Smaller fillers scatter more light than larger fillers. 3) Larger refractive index mismatch between the resin and filler leads to more light scattering and greater light attenuation. In turn, this increases the polymerization rate at shallow depths but decreases it at greater depths. Similar to the first framework, the second framework is also designed to predict the spatial and temporal evolution of DoC within a UV-curable system. However, this framework utilizes the Monte Carlo (MC) method for light transportation to predict light intensity distribution. This framework is used to study the influence of filler volume fraction and filler particle on the curing depth and curing width. The simulation results are in agreement with experimental results published in the research literature. The framework is also applied to simulate the formation of adhesive joints in a PAAW fixture application. The influence of the light source, filler, and workpiece surface on the final DoC distribution are investigated. The study shows that: 1) Both the beam spread from a LED light and the usage of filler have big influences on the curing width of an adhesive joint. However, such influences will not be aggregated. 2)The light scattering by the fillers leads to a higher DoC in the secondary curing zone at shallow depth ranges, while the beam spread of the LED light beam results in a higher DoC in the secondary curing zone at deep depth ranges. 3) If the adhesive is not thick, then a highly reflective workpiece surface can promote the polymerization rate near the workpiece surface. 4) Inside the primary curing zone, diffuse reflection caused by the workpiece surface greatly promotes the polymerization rate near the workpiece surface. The third framework is developed to model photo-induced, free radical polymerization through a molecular dynamics approach. The framework is applied to simulate the photo-polymerization of Bisphenol A (EO)10 Diacrylate under varying conditions of curing light intensity and photo-initiator concentration. The simulation results are compared to the curing kinetic data experimentally derived in this investigation as well as from other studies. The results also reveal that: 1) gelation is highly correlated to the formation of giant molecules, 2) differences in the number of free radicals generated at the beginning of polymerization significantly affect polymer network formation at low to intermediate conversion, and thus affect the gelation point, and 3) increasing light intensity or photo-initiator concentration tends to delay the gelation point, but does not affect ultimate polymer network structure near the latter stages of photo-polymerization.

Design and synthesis of structurally well-defined polymers is one of the areas of current technology interest for niche product applications. Major research efforts are focused on moving from coordination-addition to advanced radical polymerization methodology to produce new polymeric structures using polar and/or non-polar monomer for different end use applications. In this book, the authors present topical research on new developments in radical polymerization. Topics discussed include interface radical reactions of functional polyperoxides for fabrication of three-dimensional polymeric structures; biomacromolecules in radical processes; nitroxide-mediated photo controlled/living radical polymerization; alkaline anion-exchange membranes prepared by plasma polymerization; advancements in controlled radical polymerization for functional polymers and thermal redox and photoinduced ring opening polymerization reactions. (Imprint: Nova)

This report contains a review of the state of the art in photoinitiated polymerisation. The review is divided into two main parts. The first part is devoted to a basic description of the different photoinitiation processes encountered. In the second part photopolymerisation reactions are presented and discussed. This review is published together with an indexed section containing bibliographic references and abstracts to the cited articles.

Atom transfer radical polymerization (ATRP) is the most utilized controlled free-radical polymerization technique. Synthetic polymers can be prepared with predefined molecular weight, low dispersity, precisely selected end groups, and even different shapes via ATRP. In conventional ATRP, thermal stimulation is used to activate the reaction. Light stimulation is more effective and convenient than thermally driven techniques. In addition, transition metal catalysts (most commonly Cu(I)) in the ATRP system limit the potential use in biological and microelectronic applications which are sensitive to metal ion contamination. As a result, the trend in future research and exploration is the metal-free photoinduced ATRP system, in which organic photocatalyst is used.The goal of my research is to find a new photocatalyst. Typically, the catalyst needs to meet the following requirements: strong visible light absorption, high rate of ISC/ high triplet quantum yield, and sufficiently long lifetime for electron transfer to occur. Following these rules, we chose Coumarin 343 and verified whether it can be used as a photocatalyst for photoinduced metal-free ATRP. The first step in this research was the polymerization of methyl methacrylate catalyzed by Coumarin 343. The second step is the chain extension experiment. We used PMMA, which was synthesized in the first step, as a macroinitiator to initiate different monomers. The structure of polymers was studied by 1H nuclear magnetic resonance (NMR) spectroscopy and the molecular weights of polymers were determined by gel permeation chromatography (GPC). The characterization results prove that we have successfully synthesized PMMA and extended the polymer chains. In addition, we found that coumarin 343 can be used not only as a photocatalyst, but also as a photoinitiator, and we hypothesized its mechanism.