Fast, Efficient, Catalyst-Free Epoxidation of Butyl Rubber Using Oxone/Acetone for Improved Filler Dispersion

Incorporation of a polar filler such as silica into a nonpolar rubber matrix is challenging and energy consuming due to their large difference in polarity. Epoxidation of carbon–carbon double bonds in unsaturated rubber, especially for rubber with low unsaturation such as butyl rubber, is an effective method to introduce polar functional groups to the rubber macromolecules for better filler dispersion. Although different epoxidation reagents including hydrogen peroxide (H2O2), peracid, and meta-chloroperoxybenzoic acid (mCPBA) have been previously reported, these reagents have different drawbacks. In this article, a metal-free epoxidation reagent, dimethyl dioxirane (DMDO), generated from acetone and Oxone is explored for efficient epoxidation of rubber with low unsaturation. The effects of the addition manner of the reactant Oxone and buffer sodium bicarbonate (NaHCO3) and reaction temperature on the epoxide formation are studied. Compared to peracid, a faster and more efficient epoxidation without the generation of a ring-opened product is achieved when DMDO is used as the epoxidation reagent. Furthermore, it is found that the epoxidation using DMDO is not sensitive to the water concentration in the rubber solution up to 20 wt %. The addition of quaternary ammonium salt as a phase transfer catalyst not only improves the conversion but also further increases the water tolerance to 25 wt %. The reaction conditions for preparation of epoxidized butyl rubber with different percentages of epoxide group are optimized by Design of Experiments (DoE). At the end, improved dispersion of silica in the matrix of epoxidized butyl rubber is achieved, as revealed by the rubber process analyzer (RPA) and atomic force microscopy (AFM)

Effect of flagellin treatment on hTERT-EECs NF-κB activity.

<p>(A) hTERT-EECs and (B) Ishikawa 3-H-12 cells transfected with the SEAP reporter gene were co-cultured with 0, 10, 100 or 500 ng/ml of flagellin for 24 hours. Samples were collected at 0, 2, 4 and 24 hours and analyzed using Quantiblue™. Data of NF-κB activity are reported as the fold induction of SEAP activity over untreated controls. Different letters mean significant difference (p<0.05). (C) Electrophoretic mobility shift assays (EMSA) analysis of DNA-binding activity of NF-κB in hTERT-EECs treated with (flagellin group) or without (control group) 100 ng/ml of flagellin for 24 hours. Control reactions were incubated with either excess (1000 fold) unlabeled κB (cold specific; CS) or nonspecific cold probe (N) before reaction with labeled NF-κB probe.</p

Effect of glass beads on hTERT-EECs NF-κB activity.

<p>hTERT-EECs transfected with the SEAP reporter gene were co-cultured either with: (A) 0, 100, or 500 glass beads; or (B) cultured in the absence of both glass beads and flagellin (control), cultured with 100 glass beads, cultured with 100 ng/ml of flagellin, or pre-incubated with 100 glass beads for 1 h before the addition of 100 ng/ml of flagellin. Samples were collected at 0, 24 hours and analyzed using NovaBright™ Secreted Placental Alkaline Phosphatase (SEAP) Enzyme Reporter Gene Chemiluminescent Detection System 2.0. Control Data of NF-κB activity are reported as the fold induction of SEAP activity over untreated controls. Different letters mean significant difference (p<0.05).</p

Effect of different concentrations of JAr spheres on hTERT-EECs NF-κB activity and attachment to the endometrial cell monolayer.

<p>(A) hTERT-EECs and (B) Ishikawa 3-H-12 cells transfected with the SEAP reporter gene were co-cultured with 0, 20, 50 or 100 JAr spheroids for 24 hours. Samples were collected at 0, 2, 6 and 24 hours and analyzed using NovaBright™ Secreted Placental Alkaline Phosphatase (SEAP) Enzyme Reporter Gene Chemiluminescent Detection System 2.0. Data of NF-κB activity are reported as the fold induction of SEAP activity over untreated controls. Different letters mean significant difference (p<0.05). (C) hTERT-EECs were co-cultured with 20, 50 or 100 JAr spheroids for either 1 or 24 hours. The plates were then washed and the percentage of the attached spheroids was calculated.</p

Effect of JAr spheres on the endometrial response to flagellin.

<p>A 2×2 factorial experimental design was developed were (A) hTERT-EECs or (B) Ishikawa 3-H-12 cells transfected with the SEAP reporter were either: cultured in the absence of both JAr spheres and flagellin (control); cultured with 100 JAr spheres; cultured with 100 ng/ml of flagellin or pre-incubated with 100 JAr spheres for 1 h before the addition of 100 ng/ml of flagellin. Samples were collected at 0, 2, 6 and 24 hours and analyzed using NovaBright™ Secreted Placental Alkaline Phosphatase (SEAP) Enzyme Reporter Gene Chemiluminescent Detection System 2.0. Control Data of NF-κB activity are reported as the fold induction of SEAP activity over untreated controls. Different letters mean significant difference (p<0.05).</p