A New Interpretation of Apparent Induction Period in Ring‐Opening Polymerization of Octamethylcyclotetrasiloxane in Acid Emulsion

Suzuki, Kiyoshi; Totsuka, Takahiro; Ishiguro, Daisuke; Okubo, Shun; Tobita, Hidetaka

doi:10.1002/mren.202000040

Cited by 3 publications

(10 citation statements)

References 9 publications

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“…It is clear from Figure 7 that the development of the solids content (i.e., the development of the silicone polymer formation) in the first 0.5 h of the process was retarded, especially in the case of the polymerization of D4 alone. This observation confirmed the conclusions from the earlier studies [ 3 ], where it was proved that there was an induction period of ca. half an hour in the cationic emulsion polymerization of D4.…”

Section: Resultssupporting

confidence: 93%

“…D3 (hexamethyloctatrisiloxane), D5 and alkoxysilanes were not detected in samples taken in the course of the polymerization of D4 in the mixtures with alkoxysilanes. The lack of D3 in all samples taken in the course of the polymerization of D4 alone confirmed the conclusion from the studies on the mechanism of the cationic emulsion polymerization of D4 alone, that D3 may only be formed as an intermediate and not as a side product [ 3 ]. The formation of D5 in the course of the polymerization of D4 alone was also confirmed [ 3 , 11 ].…”

Section: Resultssupporting

confidence: 73%

“…The cationic polymerization of octamethylcyclotetrasiloxane (D4) catalysed by acids leads to the formation of polydimethylsiloxane (PDMS), though higher molecular weight cyclosiloxanes are also formed as side products ( Figure 1 ) [ 1 , 2 , 3 , 4 ].…”

Section: Introductionmentioning

confidence: 99%

“…The emulsion polymerization of D4, first described in 1959 [ 5 ], is preferred over polymerization carried out in bulk because, usually, the monomer conversion is higher, the polymer molecular weight (MW) distribution is lower and less cyclic oligomers of a higher MW than D4 are formed [ 6 ]. When dodecylbenzenesulfonic acid (DBSA) is applied as a surfactant and at the same time as a polymerization initiator, the cationic emulsion polymerization proceeds smoothly at a relatively low temperature [ 1 , 3 , 4 , 6 , 7 , 8 , 9 ].…”

Section: Introductionmentioning

confidence: 99%

“…The effect of various factors on D4 conversion, MW of the polymer and dispersion average particle size observed in the studies conducted on the cationic emulsion polymerization of D4 in the presence of DBSA is summarised in Supplementary Table S1 in the Supplementary Materials . The mechanism of the cationic emulsion polymerization of D4 in the presence of DBSA was proposed [ 7 ] and the role of the induction period was explained based on detailed studies of intermediate products formed in this reaction [ 3 ].…”

Section: Introductionmentioning

confidence: 99%

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Cationic Emulsion Polymerization of Octamethylcyclotetrasiloxane (D4) in Mixtures with Alkoxysilanes

et al. 2022

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The cationic emulsion polymerization of octamethylcyclotetrasiloxane (D4) in mixtures with methyltriethoxysilane (MTES) and vinyltriethoxysilane (VTES) was studied by FTIR ATR, GC, the development of a toluene insoluble fraction of the polymer and a gravimetric analysis. The polymerization of D4 alone was also conducted for comparison and, additionally, the development of molecular weight of polydimethylsiloxane (PDMS) obtained in that process was studied by GPC. Dodecylbenzenesulphonic acid (DBSA) was used as a surfactant and catalyst. The process was carried out in a “starved feed” mode by adding dropwise the monomer mixture to the aqueous solution of DBSA. FTIR ATR spectra were recorded by the sensor placed in the probe tip of a ReactIR 15TM apparatus. It was found that the silicone polymer formation proceeded faster when D4 was polymerized in the mixture with alkoxysilanes, especially in the beginning of the process, and that already at the beginning of the process, the partly crosslinked polymer was formed. The induction period of ca. 30 min was observed and the concentration of cyclic siloxanes (D4 and decamethylcyclopentasiloxane—D5) remained at a very low level in the course of the reaction and only traces were detected in the final product. The particle size development in the course of the reaction was also studied and it was found that the particle size distribution was bimodal and was broadening as the reaction proceeded, though this phenomenon was less distinct when D4 was polymerized in the mixtures with alkoxysilanes. The structure of the reaction product was confirmed by 29Si NMR.

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Section: Resultssupporting

confidence: 93%

Section: Resultssupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Cationic Emulsion Polymerization of Octamethylcyclotetrasiloxane (D4) in Mixtures with Alkoxysilanes

et al. 2022

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A Tandem Continuous Flow Process for the Synthesis of Functionalized PDMS

Wang,

2024

Ind. Eng. Chem. Res.

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The traditional industrial production of functionalized polydimethylsiloxane (PDMS) consists of a two-stage batch process, i.e., the ring-opening polymerization (ROP)/equilibrium of cyclic siloxane monomer followed by attaching functional groups to PDMS through hydrosilylation. In this study, we developed a continuous tandem flow process combining the two stages for the synthesis of functionalized PDMS using octamethylcyclotetrasiloxane (D 4 ) as the monomer. We investigated the kinetics of ROP/equilibrium reaction of D 4 using a flow tube reactor filled with the cationic resin catalyst Amberlyst 35. The reaction was found to be complete within a short residence time, 2−3 min, giving steady flow-out of the reaction mixture containing ca. 80% nonvolatile content for a period of up to 90 min. The catalyst was reusable for up to 80 times by rinsing with methyl isobutyl ketone (MIBK). The resulting PDMS-SiH, bearing two terminal -SiH groups, was used for subsequent hydrosilylation reaction with different vinyl compounds in the presence of the Speier catalyst. PDMSs possessing functionalities such as ethylene glycol (EG), epoxy (EPO), methacrylate (MA), and hydrocarbon chain were prepared through continuous tandem ROP/equilibrium and hydrosilylation reaction. These products exhibit excellent defoaming performance that is comparable with the commercial products from a batch process. The present study paves the way to a more efficient production of functionalized silicone oil through a flow reaction process.

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Radical-Mediated C–C Coupling of Alcohols Induced by Plasmonic Hot Carriers

Koo

Kim

2022

J. Phys. Chem. Lett.

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The C−C coupling reactions of aliphatic alcohols to aromatics and largermass compounds have large endothermicities and activation energies, calling for catalysts operating at high temperatures. Here, we demonstrate that plasmon-excited nanoparticles catalyze the C−C coupling of aliphatic alcohols at room temperature to produce polyaromatic hydrocarbons and graphene oxide. The conversion is quenched by radical and electron scavengers and by the surface passivation of metals, suggesting that the reaction proceeds through alkoxy, peroxyl, hydroxyalkyl, and alkyl radical intermediates created by the metal to molecule transfer of plasmonic hot carriers. Besides being the first realization of C−C coupling of aliphatic alcohols at room temperature, the result constitutes a rare example of an endothermic plasmon-induced reaction producing new bonds and a new method for photogenerating graphene derivatives. More importantly, the result demonstrates the facile generation of organic radicals directly from alcohols, which may be used as precursors for radical-based organic reactions.Letter pubs.acs.org/JPCL

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A New Interpretation of Apparent Induction Period in Ring‐Opening Polymerization of Octamethylcyclotetrasiloxane in Acid Emulsion

Cited by 3 publications

References 9 publications

Cationic Emulsion Polymerization of Octamethylcyclotetrasiloxane (D4) in Mixtures with Alkoxysilanes

Cationic Emulsion Polymerization of Octamethylcyclotetrasiloxane (D4) in Mixtures with Alkoxysilanes

A Tandem Continuous Flow Process for the Synthesis of Functionalized PDMS

Radical-Mediated C–C Coupling of Alcohols Induced by Plasmonic Hot Carriers

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