Radical concentrations, environments, and reactivities during crosslinking polymerizations

Anseth, Kristi S.; Anderson, Karin J.; Bowman, Christopher N.

doi:10.1002/macp.1996.021970306

Cited by 94 publications

(142 citation statements)

References 51 publications

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“…Excellent reviews have summarized the developments of both areas. 11,12,13 More recently, Selli et al 14 and Bowman and co-workers 15 have studied in detail the bulk photopolymerization of multifunctional (meth)acrylate monomers. Hamielec et al 16 have also published studies on thermally initiated copolymerization of MMA/EGDMA followed by ESR.…”

Section: Introductionmentioning

confidence: 98%

Kinetic investigations on the photopolymerization of di- and tetrafunctional (meth)acrylic monomers in polymeric matrices. ESR and calorimetric studies. I. Reactions under irradiation

Bosch

Serrano

Mateo

et al. 1998

J. Polym. Sci. A Polym. Chem.

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The photopolymerization of several di‐ and tetrafunctional (meth)acrylic monomers in the presence of a styrene–butadiene–styrene polymeric matrix (SBS) has been studied. Electron spin resonance spectroscopy (ESR) and differential scanning photocalorimetry (photo‐DSC) were used as monitoring techniques to identify the photogenerated radicals and analyze photopolymerization profiles, radical environments, and radical secondary reactions. The study of the photopolymerization and/or photocrosslinking reactions of these monomers in the solid media was carried out by taking into consideration different factors, such as the influence of both monomer and photoinitiator structures on the hydrogen abstraction in the binder with formation of benzylic and allylic radicals, the polymerization of the monomers itself and the hydrogen abstraction reaction in the polymerized acrylic chains. Finally, irradiation of the system SBS/photoinitiator in the absence of monomer was also accomplished. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2775–2783, 1998

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Section: Introductionmentioning

confidence: 98%

Kinetic investigations on the photopolymerization of di- and tetrafunctional (meth)acrylic monomers in polymeric matrices. ESR and calorimetric studies. I. Reactions under irradiation

Bosch

Serrano

Mateo

et al. 1998

J. Polym. Sci. A Polym. Chem.

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“…9,10 Reactive microgel particles, multifunctional polymer chains with pendant double bonds, and inter-and intramolecular cyclization affected considerably the structure of the synthesized networks, at least on the submicron level. 1,3,11,12 The increased density of chemical crosslinks and physical entanglements lead to the restricted mobility of the molecules, even polymer chain segments. The consequence of this phenomenon, observed during free-radical crosslinking polymerization, is radical trapping.…”

Section: Introductionmentioning

confidence: 99%

Dark reactions of free radicals trapped in densely crosslinked polymer networks after photopolymerization

Pavlineč

Moszner

2003

J of Applied Polymer Sci

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Difunctional methacrylate monomers containing stiff or flexible spacers were combined with a vinylcyclopropane derivate in a copolymerization to form densely crosslinked networks. The high rate of visible light photoinitiation at 20 -22 o C was used for starting the polymerization. By switching off the light after 40 s, the longlived free radicals, trapped in the polymer network, retain radical processes, however, at substantially retarded rates. The postcuring development of the network structure in the investigated samples lasting at least 12 weeks was proved by the increasing density of the crosslinks, by the increasing amount of the gel fraction, and by the decreasing of the residual unsaturation. The relaxation spectra from dynamic mechanical thermal analyses (DMTA) show curves with two evident maxima. The first one belonged the glass transition (T g ) of original network and increases in the postcuring period. The second one belonged to the final structure to which the crosslinked polymer approaches slowly during aging. The final state develops fast during a DMTA thermal scan to 200°C. All procedures proceeded in the dark, but in the presence of air oxygen. The chemiluminescence (CL) response of the postcured samples proved the accumulation of hydroperoxides. The oxidation chain reaction took place in the postcuring time and competed with the building up of additional crosslinks. The majority of postcuring changes were observed during the first 3 weeks of aging. Nine weeks later, the long-lived radicals were still present in the network and maintained the sensibility of the crosslinked polymer to free-radical reactions.

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“…The network structure that is created is very complex, especially because of its very heterogeneous nature. 8 Bowman and coworkers have undergone numerous studies on the structural evolution of photopolymerized networks by studying the kinetics of reactions, 9 by monitoring the radical concentrations within the networks during polymerization, 10 and by using "living" radical polymerization. 11 They concluded that networks produced by the photopolymerization of multifunctional monomers contain very highly crosslinked regions, called microgels, as well as much less crosslinked regions that connect the microgels.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and photopolymerization of acrylic acrylate copolymers

Valette

Massardier

Pascault

et al. 2002

J of Applied Polymer Sci

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Acrylate-functionalized copolymers were synthesized by the modification of poly(butyl acrylate-coglycidyl methacrylate) (BA/GMA) and poly(butyl acrylateco-methyl methacrylate-co-glycidyl methacrylate).13 C-NMR analyses showed that no glycidyl methacrylate block longer than three monomer units was formed in the BA/ GMA copolymer if the glycidyl methacrylate concentration was kept below 20 mol %. We chemically modified the copolymers by reacting the epoxy group with acrylic acid to yield polymers with various glass-transition temperatures and functionalities. We studied the crosslinking reactions of these copolymers by differential scanning calorimetry to point out the effect of chain functionality on double-bond reactivity. Films formed from acrylic acrylate copolymer precursors were finally cured under ultraviolet radiation. Network heterogeneities such as pendant chains and highly crosslinked microgel-like regions greatly influenced the network structure and, therefore, its viscoelastic properties.

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Radical concentrations, environments, and reactivities during crosslinking polymerizations

Cited by 94 publications

References 51 publications

Kinetic investigations on the photopolymerization of di- and tetrafunctional (meth)acrylic monomers in polymeric matrices. ESR and calorimetric studies. I. Reactions under irradiation

Kinetic investigations on the photopolymerization of di- and tetrafunctional (meth)acrylic monomers in polymeric matrices. ESR and calorimetric studies. I. Reactions under irradiation

Dark reactions of free radicals trapped in densely crosslinked polymer networks after photopolymerization

Synthesis and photopolymerization of acrylic acrylate copolymers

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