Cyclization During Crosslinking Free-Radical Polymerizations

Dotson, Neil A.; Macosko, Christopher W.; Tirrell, Matthew

doi:10.1007/978-1-4615-3016-9_23

Cited by 16 publications

(4 citation statements)

References 50 publications

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“…Deviation from these theories increases further as the secondary hydroxyl content approaches 100%. Similar deviations of theoretical gel points reported in previous studies have been explained by such phenomena as intramolecular cyclization, intramolecular cross-linking, microgelation, and excluded volume effects especially at high molecular weights. − We attribute such deviation in the present work to two different reasons. One is the catalyst choice, because dibutyltin dilaurate catalyzes the isocyanate reaction with primary hydroxyls and water much more effectively than it catalyzes the reaction of isocyanate with secondary hydroxyls .…”

Section: Results and Discussionsupporting

confidence: 85%

Spectroscopic and Rheological Cross-Analysis of Polyester Polyol Cure Behavior: Role of Polyester Secondary Hydroxyl Content

Tilly¹,

Pervaje²,

Inglefield

et al. 2019

ACS Omega

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The sol–gel transition of a series of polyester polyol resins possessing varied secondary hydroxyl content and reacted with a polymerized aliphatic isocyanate cross-linking agent is studied to elucidate the effect of molecular architecture on cure behavior. Dynamic rheology is utilized in conjunction with time-resolved variable-temperature Fourier-transform infrared spectroscopy to examine the relationship between chemical conversion and microstructural evolution as functions of both time and temperature. The onset of a percolated microstructure is identified for all resins, and apparent activation energies extracted from Arrhenius analyses of gelation and average reaction kinetics are found to depend on the secondary hydroxyl content in the polyester polyols. The similarity between these two activation energies is explored. Gel point suppression is observed in all the resin systems examined, resulting in significant deviations from the classical gelation theory of Flory and Stockmayer. The magnitude of these deviations depends on secondary hydroxyl content, and a qualitative model is proposed to explain the observed phenomena, which are consistent with results previously reported in the literature.

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Section: Results and Discussionsupporting

confidence: 85%

Spectroscopic and Rheological Cross-Analysis of Polyester Polyol Cure Behavior: Role of Polyester Secondary Hydroxyl Content

Tilly¹,

Pervaje²,

Inglefield

et al. 2019

ACS Omega

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“…Dusek reviewed the network formation by chain cross-linking (co)polymerization, especially emphasizing the importance of cyclization leading to the formation of microgel-like particles. Recently, Dotson et al. , tested the predictions of classical Flory−Stockmayer's theory for the establishment of a network by free-radical cross-linking polymerization, and Zhu et al . summarized their studies on the elucidation of the cross-linking mechanism and kinetics, the characterization of network microstructures, and the development of kinetic gelation models; both research groups have dealt with the copolymerization of methyl methacrylate with ethylene dimethacrylate, a historical copolymerization system which was first investigated in 1945 by Walling .…”

Section: Introductionmentioning

confidence: 99%

Free-Radical Cross-Linking Polymerization of Diallyl Terephthalate in the Presence of Microgel-like Poly(allyl methacrylate) Microspheres

Matsumoto¹,

Kawasaki²,

Shimatani³

2000

Macromolecules

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The cross-linking polymerization of diallyl terephthalate (DAT) was explored in detail in the presence of microgel-like poly(allyl methacrylate) (PAMA microsphere) as an extension of our continuing studies concerned with the elucidation of cross-linking reaction mechanism and the control of network formation in the free-radical cross-linking polymerization of multivinyl compounds. Thus, PAMA microspheres were prepared by the emulsion polymerization of AMA as reactive cross-linked polymer microspheres having abundant pendant allyl groups. The polymerization of DAT in the presence of microsphere was conducted in bulk using BPO as initiator at 80 °C. The gel-point conversion became higher with an increase in the feed amount of microsphere. No gel effect was observed. Variation of RI-monitored SEC curves with conversion suggested the copolymerization of the pendant allyl groups present on the surface of microsphere with DAT; this was also supported by light scattering and 1H NMR spectroscopy. The swelling ratios of the gels in the presence of microsphere were not high even just beyond the gel points, suggesting a preferential incorporation of microsphere into the gel. These are discussed mechanistically.

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“…Here it is worthy to note that the main trend in this field for the past decades was to extend the F−S theory to more realistic polymerization cases in the presence of cyclization and unequal reactivities. Since numerous papers have been published to report that gelation occurs 1−2 orders of magnitude than predicted, Dotson et al and Zhu et al made efforts to embellish the theory by removing the assumptions of the classical F−S theory, including no cyclizations and equal reactivities of all types of double bonds. In this connection, the establishment of the other extreme case governed by F−S theory would be significant.…”

Section: Introductionmentioning

confidence: 99%

Approach to Ideal Network Formation Governed by Flory−Stockmayer Gelation Theory in Free-Radical Cross-Linking Copolymerization of Styrene with m-Divinylbenzene

Matsumoto

Kitaguchi

Sonoda³

1999

Macromolecules

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The critical conditions in which the classical Flory−Stockmayer gelation theory (F−S theory) is applicable to monovinyl−divinyl copolymerizations were pursued in detail. Thus, the cross-linking copolymerizations of styrene (St) with m-divinylbenzene (m-DVB) as a most typical monovinyl−divinyl system were discussed under the specified conditions where the occurrence of a thermodynamic excluded volume effect and intramolecular cross-linking as the primary and secondary factors, respectively, for the greatly delayed gelation in the free-radical monovinyl−divinyl copolymerizations was reduced. The ratio of the actual gel point to the theoretical one reached 1.3, supporting the good applicability of F−S theory. In addition, the more tailed molecular-weight distribution (MWD) curves were observed with conversion as a result of occurrence of intermolecular cross-linking reaction leading to ideal network formation governed by F−S theory. Also, the swelling ratio of the gel obtained just beyond the gel point was very high, suggesting no microgelation up to the gel-point conversion. On the contrary, in the solution copolymerization of St with m-DVB in toluene at a dilution of 1/3 in the presence of a rather high amount of cross-linker, the considerable occurrence of intramolecular cross-linking reaction was clearly reflected on the greatly delayed gelation and the markedly changed MWD curve from a tailed one at a higher conversion.

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Cyclization During Crosslinking Free-Radical Polymerizations

Cited by 16 publications

References 50 publications

Spectroscopic and Rheological Cross-Analysis of Polyester Polyol Cure Behavior: Role of Polyester Secondary Hydroxyl Content

Spectroscopic and Rheological Cross-Analysis of Polyester Polyol Cure Behavior: Role of Polyester Secondary Hydroxyl Content

Free-Radical Cross-Linking Polymerization of Diallyl Terephthalate in the Presence of Microgel-like Poly(allyl methacrylate) Microspheres

Approach to Ideal Network Formation Governed by Flory−Stockmayer Gelation Theory in Free-Radical Cross-Linking Copolymerization of Styrene with m-Divinylbenzene

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