Photopolymerization in aqueous solutions initiated by the interaction of excited pyrene derivatives with aliphatic amines

Encinas, M. V.; Lissi, E. A.; Majmud, C.; Cosa, Juan J.

doi:10.1021/ma00075a025

Cited by 34 publications

(16 citation statements)

References 6 publications

(7 reference statements)

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“…A similar dependence of the polymerization rate with the structure of tertiary aliphatic amines was found for the polymerization of 1-vinyl-2-pyrrolidinone employing pyrene derivatives as photoinitiators. 12 In this case TEOHA is two times more efficient than TEA. The differences in polymerization rate for the different amines must be due exclusively to changes in photoinitiation quantum yield since addition of amine up to 0.2 M did not modify the polymerization rate of HEMA photoinitiated by 2,2′-azobis(2-amidinopropane).…”

Section: Chartmentioning

confidence: 97%

Free Radical Polymerization Photoinitiated by Riboflavin/Amines. Effect of the Amine Structure

et al. 2001

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Polymerization rates of 2-hydroxyethyl methacrylate (HEMA) photoinitiated by riboflavin were investigated using as co-initiator several amines of different structure. The photoinitiation efficiency is highly dependent on the structure of the amine. The photochemical behavior of these systems was investigated under the polymerization conditions. The results are explained in terms of the dependence of the amino radicals production and the reactivity of these radicals toward monomer double bonds with the structural features of the amines. IntroductionThe application of photoinitiated polymerization is extensive. Among the most commonly utilized photoinitiators for free radical polymerization stand those where radicals result from a bimolecular process comprising an excited chromophore and a co-initiator that behaves as electron donor. 1 Tertiary amines are the most frequently employed co-initiators in these processes. It is generally accepted that the R-amino radicals generated in these reactions are the species that add to the monomer. 2 In these reactions the yield of the primary photochemical processes is strongly dependent on the structure of the electron donor. Therefore, a strong dependence of the polymerization efficiency with the amine structural features can be expected.Dependence of the polymerization rate with the structure of the amine has been reported for the acrylate polymerization using camphorquinone 3,4 and thioxanthones 5 as photoinitiators. However, there is not a general mechanistic explanation of the experimentally found dependence of the efficiency of the amine as coinitiator with its chemical structure. More recently, Davidson et al. 6 have proposed that for a particular aromatic ketone the efficiency of photoinitiation is determined by the structure and the molecular geometry of the R-aminoalkyl radical produced. On the other hand, Paczkowski et al. 7 have suggested that the initial electron-transfer reaction from an aromatic amines to the excited state of xanthene dyes, is the responsible of the variation of the photoinitiation efficiency.In a previous work, 8 we have shown that riboflavin acts as an efficient photoinitiator of vinyl polymerization in the presence of triethanolamine (TEOHA). Radicals are produced with high yield by a photoinduced electrontransfer process. Therefore, the riboflavin-amine appears as an interesting system to study the effect of the amine structure on the photoinitiation efficiency. Here we report the polymerization of 2-hydroxyethyl methacrylate (HEMA) photoinitiated by riboflavin in the presence of several amines (Chart 1), with the aim of relating the efficiency of generation of radicals and their ability to initiate the polymerization with the structure of the amine.

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Section: Chartmentioning

confidence: 97%

Free Radical Polymerization Photoinitiated by Riboflavin/Amines. Effect of the Amine Structure

et al. 2001

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“…Photopolymerization rates (R p ) at low conversions were measured dilatometrically under anaerobic conditions at 25 8 C, as previously described 4) . The polymer was precipitated by the addition of an excess of water.…”

Section: Experimental Partmentioning

confidence: 99%

Solvent effects on the rate of polymerization of 2-hydroxyethyl methacrylate photoinitiated with aliphatic azo compounds

Alvarez

Encinas²,

Lissi

1999

Macromol. Chem. Phys.

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SUMMARY: The rate of polymerization (R p ) of 2-hydroxyethyl methacrylate, at low conversion, using aliphatic azo compounds as photoinitiators is considerably faster in water than in acetonitrile as a solvent. Active radical production in different solvents was analysed in detail. The quantum yield of active radicals showed only a minor dependence on the medium properties. These differences are due to changes in primary radical recombination reactions and they are unrelated to changes of R p observed in different media. By employing intermittent illumination techniques, it is shown that the increased R p in aqueous solution is due to a reduced rate of termination. Similar propagation rate constants were obtained in acetonitrile and water, whereas the termination rate constant increases by one order of magnitude when acetonitrile is employed instead of water. These results are discussed in terms of the effect of the cosolvent on the medium viscosity and the macroradical conformation.

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“…Neste sentido têm sido utilizadas técnicas como, por exemplo, dilatometria [30,[32][33][34][35] , espectroscopia fotoacústica [36] , espectroscopia de infravermelho (IR) [37,38] , calorimetria diferencial [39][40][41] , espectroscopia Raman [42,43] , espalhamento de luz [44] , e ressonância paramagnética eletrônica [45,46] .…”

Section: Gravimetriaunclassified

Fotopolimerização: princípios e métodos

Rodrigues

Neumann

2003

Polímeros

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Resumo: O interesse na Fotoquímica de Polímeros tem crescido nas últimas décadas devido não somente ao grande número de novas aplicações como também à repercussão do ponto de vista econômico, técnico e ecológico. A fotopolimerização/fotocura tem recebido a atenção especial devido às incontáveis aplicações e a sua importância na área de Materiais. A cinética destes processos necessita de métodos analíticos precisos e rápidos para ser avaliada. Entre os métodos analíticos convencionais, os mais usados são a gravimetria e a medida de propriedades macroscópicas, como resistência à tração, à deformação e dureza. Entretanto, para determinações mais analíticas é conveniente usar métodos que permitam estudar a cinética de fotopolimerização em tempo real. Neste sentido têm sido usadas técnicas como dilatometria, espectroscopia Raman, calorimetria, e espectroscopia de infravermelho por transformada de Fourier em tempo real. A atividade no campo da polimerização continua a se expandir em muitas áreas e, recentemente, o interesse nos sistemas do fotoiniciação envolvendo a polimerização via radicais livres, iniciada por luz visível, tem recebido atenção especial. Recentemente, estudos sobre fotopolimerização catiônica induzida pela luz visível começaram a ser pesquisados novamente devido à grande variedade de monômeros que são polimerizáveis por via catiônica mas não por via radicar, como, por exemplo, oxiranas e éteres vinílicos. Palavras-chave: Fotopolimerização catiônica, fotopolimerização via radicalar, dilatometria, calorimetria, gravimetria, espectroscopia de infravermelho por transformada de Fourier. Photopolymerization: Principles and MethodsAbstract: The interest for Polymer Photochemistry has been growing in the last decades as a consequence not only of the great number of new applications as well as due to the repercussion of economical, technical and ecological characters. The photopolymerization -photocuring processes have received special attention due to the countless and important applications in the area of Materials. The kinetics of these processes needs fast and precise analytic methods to be evaluated. Among the conventional analytic methods, the most used are gravimetry and the determination of macroscopic properties, as resistance to traction, deformation and hardness. However, for a better insight in the reactions it is convenient to use more advanced analytic methods, in order to study the photopolymerization kinetics in real time. Dilatometry, Raman spectroscopy, calorimetry, and real time Fourier transform infrared spectroscopy are some of the techniques that have been used. Activity in the field of photopolymerization continues to expand in many areas and recently, the interest in photoinitiation systems involving the initiation of free-radical polymerization with visible light irradiation has been retaken. Additionally, studies on cationic photopolymerization induced by visible light started again to be studied because of the large variety of monomers that can be photopolymerized by via cation ini...

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Photopolymerization in aqueous solutions initiated by the interaction of excited pyrene derivatives with aliphatic amines

Cited by 34 publications

References 6 publications

Free Radical Polymerization Photoinitiated by Riboflavin/Amines. Effect of the Amine Structure

Free Radical Polymerization Photoinitiated by Riboflavin/Amines. Effect of the Amine Structure

Solvent effects on the rate of polymerization of 2-hydroxyethyl methacrylate photoinitiated with aliphatic azo compounds

Fotopolimerização: princípios e métodos

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