Effect of Phenols on the Free-Radical Photopolymerization of Vinyl Monomers in Aqueous Solution

Valdebenito, A.; Lissi, E. A.; Encinas, M. V.

doi:10.1002/1521-3935(20010801)202:12<2581::aid-macp2581>3.0.co;2-o

Cited by 12 publications

(5 citation statements)

References 15 publications

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“…The reaction pathways leading to the formation of cross-linked structure shown in Scheme involve radical recombination. In a bulk melt polycondensation of BPAPC, even if radicals are generated, they quickly react with phenol which acts as a free-radical scavenger. , Unlike in bulk (melt) polymerization and polymerization in partially crystallized polymer microlayers and particles, the polymerization in amorphous polymer microlayers provides a very efficient removal of phenol due to either a very short diffusion path and the absence of a crystalline structure which gives extra diffusional resistance of phenol. The presence of a residual amount of casting solvent might have acted as a plasticizer also to ease the transport of phenol to the microlayer surface by diffusion.…”

Section: Resultsmentioning

confidence: 99%

UltraHigh Molecular Weight Nonlinear Polycarbonates Synthesized in Microlayers

Baick

Luciani

et al. 2013

Ind. Eng. Chem. Res.

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Ultrahigh molecular weight bisphenol A polycarbonate (BPAPC) with nonlinear chain structures has been synthesized by solid-state polymerization in microlayers at 230°C. It has been found that the molecular weights of the microlayers of low molecular weight prepolymers with thickness ranging from 5 to 35 μm increased rapidly to ultrahigh molecular weight (300,000−600,000 g/mol) without any discoloration. The amorphous prepolymers exhibited much higher reaction rate than the partially crystallized prepolymers. Although the reactive end group mole ratios of the prepolymers prepared by semibatch melt polycondensation deviated significantly from the stoichiometric value, branching and partial cross-linking reactions have been found to occur to rapidly increase the polymer molecular weight. These nonlinear chain structures observed were due to Fries rearrangement, Kolbe-Schmitt rearrangement reactions, and radical-induced scission/cross-linking reactions. The microstructures of the high molecular weight polymers have been analyzed by 13 C NMR, 1 H NMR, pyrolysis-gas chromatography mass spectrometry, and atomic force microscopy.

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Section: Resultsmentioning

confidence: 99%

UltraHigh Molecular Weight Nonlinear Polycarbonates Synthesized in Microlayers

Baick

Luciani

et al. 2013

Ind. Eng. Chem. Res.

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“…A small amount of radical species can be formed from homolytic scission of carbonate groups between the oxygen and carbonyl group in BPAPC at high temperatures and from hydrogen abstraction, which result in methylene radicals on carbonate groups and phenoxy radicals, respectively . The byproduct, phenol, is a known radical scavenger . Thus, in the conventional SSP with relatively large spherical particles or pellets where diffusional transport of phenol is rather slow, high concentration of phenol in the polymer particles may prohibit the formation of crosslinked PC but in the SSP m , phenol is almost instantly removed from the micro‐layers, making the recombination of macro‐radical species more favorable to form cross‐linked chain structures than in conventional solid‐state polymerization.…”

Section: Resultsmentioning

confidence: 99%

Structure and properties of ultra‐high molecular weight bisphenol a polycarbonate synthesized by solid‐state polymerization in amorphous microlayers

Baick

Yang

Ahn

et al. 2014

J of Applied Polymer Sci

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The structure and properties of ultrahigh molecular weight polycarbonate synthesized by solid-state polymerization in micro-layers (SSP m ) are reported. A low molecular weight prepolymer derived from the melt transesterification of bisphenol A and diphenyl carbonate as a starting material was polymerized to highly amorphous and transparent polycarbonate of molecular weight larger than 300,000 g mol 21 in the micro-layers of thickness from 50 nm to 20 mm. It was observed that when the polymerization time in micro-layers was extended beyond conventional reaction time, insoluble polymer fraction increased up to 95%. Through the analysis of both soluble and insoluble polymer fractions of the high molecular weight polycarbonate by 1 H NMR spectroscopy and pyrolysis-gas chromatography mass spectrometry (Py-GC/MS), branches and partially crosslinked structures have been identified. The thermal, mechanical and rheological properties of the ultra-high molecular weight nonlinear polycarbonates synthesized in this study have been measured by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and rheometry. The nonlinear chain structures of the polymer have been found to affect the polymer's thermal stability, mechanical strength, shear thinning effect, and elastic properties.

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“…The reaction of phenols as efficient inhibitors implies two facts: the H atoms in PhOH have a high reactivity to readily be abstracted [37][38][39] and the formed PhOÁradicals have a strong ability to scavenge carbon-centered chain radicals. 40 In this work, acetone as photoinitiator and different phenols [including 4-hydroxylbenzene sulfonic acid (HBSA), p-aminophenol, tyramine, and 4-hydroxythiophenol and tyrosine] with a para substituent XR (denoted XRPhOH) as the reactants were proposed to incorporate a broad range of functional X groups with an R spacer onto the polymeric surface as illustrated in Scheme 1. The triplet state of the excited acetone would either abstract surface H of the polymer substrate to generate a carbon-centered surface radical or abstract H of OH group of phenol to produce oxygen-centered phenoxy radical (XRPhO).…”

Section: Resultsmentioning

confidence: 99%

Functionalization of polymeric surfaces by simple photoactivation of CH bonds

Xie

et al. 2011

J. Polym. Sci. A Polym. Chem.

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A universal photoassisted pathway to functionalize polymeric surfaces is presented by transferring the inert surface sp3 CH bonds into reactive groups, such as SO3H, NH2, SH, and COOH. The proposed method uses acetone as photoinitiator and different phenols with a para substituent XR as the reactants. Acetone excited by UV irradiation acts as a pair of scissors cutting both the surface CH bonds of the polymer substrate and the OH bonds of phenol, leading to the formation of carbon‐centered surface chain free radicals and oxygen‐centered phenoxy free radicals. By coupling of these two radicals, a variety of functional X groups with an R spacer from XR species of different phenol reactants were readily bonded to the polymeric surfaces, where phenol reactants included 4‐hydroxylbenzene sulfonic acid for SO3H, p‐aminophenol and tyramine for NH2, 4‐hydroxythiophenol for SH, and tyrosine for COOH. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

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Effect of Phenols on the Free-Radical Photopolymerization of Vinyl Monomers in Aqueous Solution

Cited by 12 publications

References 15 publications

UltraHigh Molecular Weight Nonlinear Polycarbonates Synthesized in Microlayers

UltraHigh Molecular Weight Nonlinear Polycarbonates Synthesized in Microlayers

Structure and properties of ultra‐high molecular weight bisphenol a polycarbonate synthesized by solid‐state polymerization in amorphous microlayers

Functionalization of polymeric surfaces by simple photoactivation of CH bonds

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