2 2 azobis 2 methylpropionamidine dihydrochloride v50

Nano-SiO₂ (Aerosil 200, Degussa, Piscataway, NJ, USA) with an average particle size of 12 nm, vinyl trimethoxysilane (VTS) (Sigma-Aldrich, St. Louis, MO, USA) and ammonia solution (25% NH₄OH, Fisher Scientific, Fair Lawn, NJ, USA) were used as received for silica modification. Isoprene monomer (IP) (Sigma-Aldrich, St. Louis, MO, USA), sodium styrene sulfonate (NaSS) (Sigma-Aldrich) and 4-cyanopentanoic acid dithiobenzoate (RAFT agent, Sigma-Aldrich) were used without further purification. 4,4′-azobis (4-cyanopentanoic acid) (ACP) (Sigma-Aldrich) and 2,2′-Azobis (2-methylpropionamidine) dihydrochloride (V50, Wako Pure Chemical Industries, Ltd., Tokyo, Japan) were used as water-soluble initiators. The methyl ethyl ketone (MEK) (Fisher Scientific) was used for the rubber coagulation. The products were washed with petroleum ether (PE) (J.T.Baker, Inc., Phillipsburg, NJ, USA) to remove residual monomer and homopolymer.
For the preparation of prevulcanized natural rubber nanocomposites, natural rubber (NR) latex (total solid content of 60 wt %), sulfur as vulcanizing agent, zinc oxide (ZnO) and zincdiethyl dithiocarbamate (ZDEC) as vulcanization accelerators were obtained from the Rubber Research Institute of Thailand, Bangkok, Thailand.

SH end group PVA (PVA-SH: 100% hydrolyzed, average Mw = 198,000) was obtained from Kuraray Co., Ltd., Tokyo, Japan. Sodium p-styrenesulfonate (SSS) was purchased from Tosoh Co., Tokyo, Japan. 2,2′-Azobis(2-methylpropionamidine) dihydrochloride (V-50) and analytical grade glutaraldehyde (GA) (25 wt.% solution in water) were purchased from Wako Pure Chemical Industries, Osaka, Japan. Sodium chloride, hydrochloric acid, and potassium chloride (all analytical grade) were purchased from Nacalai Tesque, Kyoto, Japan.