Fourier transform near‐infrared and electron spin resonance studies on the crosslinking reaction of liquid carboxylated poly(acrylonitrile‐co‐butadiene) rubber with dicumyl peroxide in dioxane

Abstract

ABSTRACT:The crosslinking reaction of liquid carboxylated poly(acrylonitrile-co-butadiene) [or nitrile rubber (NBR); acrylonitrile ϭ 10 wt %] with dicumyl peroxide (DCPO) was studied in dioxane by means of Fourier transform near-infrared spectroscopy (FT-NIR) and electron spin resonance spectroscopy (ESR). Among the three butadiene units (1,2, cis-1,4, and trans-1,4 units) of NBR, only the pendant vinyl group of the 1,2 unit showed an absorption at 6110 cm Ϫ1 from the FT-NIR examination of dioxane solutions of NBR, 1-octene, 3,3-dimethyl-1-butene, trans-2-octene, cis-5-octen-1-ol, poly-cis-1,4-butadiene, and poly-1,2-butadiene. The crosslinking reaction was followed in situ in dioxane by the monitoring of the disappearance of the pendant vinyl double bond with FT-NIR. The initial disappearance rate (R 0 ) of the vinyl group was expressed by R 0 ϭ k [DCPO] 0.9 [NBR] Ϫ0.2 (120°C). The overall activation energy of the reaction was calculated to be 20.7 kcal/mol. This unusual rate equation suggests unimolecular termination due to degradative chain transfer and depressed reactivity of the vinyl group caused by crosslinking. ESR study of the reaction mixture revealed that an allyl-type polymer radical was formed in the reaction, and its concentration increased with time and was then saturated.

Hyperbranched Acrylate Copolymer via Initiator‐Fragment Incorporation Radical Copolymerization of Divinylbenzene and Ethyl Acrylate: Synthesis, Characterization, Hydrolysis, Dye‐Solubilization, Ag Particle‐Stabilization, and Porous Film Formation

“…The conversions of DVB and EAwere in situ measured as a function of time by Fourier transform-near infrared (FT-NIR) spectroscopy, where the copolymerization was conducted in a degassed and sealed Pyrex tube (5 mm diameter) in a custom-made aluminium thermostated sample-holder with an FT-NIR measurement system. [9] Preparation of Copolymer-Stabilized Ag Particles A AgNO 3 (4.2 mg, 25 mmol) solution in methanol (0.5 mL) (5.0 Â 10 À2 mol Á L À1 ) was added to a copolymer (100 mg) solution in tetrahydrofuran (THF) (2 mL) and stirred at room temperature for 0.5 h. To this solution, a NaBH 4 (4.2 mg, 11 mmol) solution in methanol (0.5 mL) (2.2 Â l0 À2 mol Á L À1 ) was added and stirred for 3 h. The resulting reaction mixture was poured into a large excess of methanol. The precipitated Ag-containing copolymer was isolated and dried under vacuum.…”

Hyperbranched Polymer through Initiator-Fragment Incorporation Radical Copolymerization of Divinyl Adipate with Allyl Acetate: Synthesis, Characterization, Dye Solubilization, Metal-Nanoparticle Stabilization, and Porous Film Formation

“…The conversions of the vinyl groups of DVA and AAc were followed in situ as a function of time by Fourier transform near-infrared (FT-NIR) spectroscopy, where the copolymerization was performed in a degassed and sealed Pyrex glass tube (5 mm diameter) in a custom-made aluminum furnace with an FT-NIR measurement system. 20 …”

Formation of Soluble Hyperbranched Polymer Nanoparticles by Initiator‐Fragment Incorporation Radical Polymerization of Ethylene Glycol Dimethacrylate

“…Similar underestimations by GPC have often been observed for other hyperbranched polymers. [7,[11][12][13][14][15][16][23][24][25][26] This is because the hyperbranched polymers have a smaller hydrodynamic radius. For comparison, a conventional linear polystyrene sample was also subjected to MALLS measurements and had a M w 2.9 Â l0 5 and a R g of 28 nm.…”

“…[7,[11][12][13][14][15][16][26][27][28][29] We have also viscometrically examined a benzene solution of the same polymer at 30 8C. Figure 8 shows the plot of the reduced viscosity (Z rel ) against the polymer concentration (C).…”

“…The polymerization was performed in a degassed and sealed Pyrex tube (5-mm diameter) in a custom-made aluminum furnace with an FT-NIR measurement system. [16] Measurements The conversion of 1 was estimated with a Jasco INT-400 spectrometer equipped with a mercury-cadmium-telluride detector. The consumption of the vinyl groups of 1 was monitored by the band at around 6 150 cm À1 assigned to the overtone absorption due to the stretching vibration of C-H bonds in the vinyl groups.…”