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).

Deprotection, tethering, and activation of a catalytically active metalloporphyrin to a chemically active metal surface: [SAc](4)P-Mn(III)Cl on Ag(100).

The adsorption and subsequent thermal chemistry of the acetyl-protected manganese porphyrin, [SAc](4)P-Mn(III)Cl on Ag(100) have been studied by high resolution XPS and temperature-programmed desorption. The deprotection event, leading to formation of the covalently bound thioporphyrin, has been characterized and the conditions necessary for removal of the axial chlorine ligand have been determined, thus establishing a methodology for creating tethered activated species that could serve as catalytic sites for delicate oxidation reactions. Surface-mediated acetyl deprotection occurs at 298 K, at which temperature porphyrin diffusion is limited. At temperatures above approximately 425 K porphyrin desorption, diffusion and deprotection occur and at >470 K the axial chlorine is removed.

Glenohumeral joint range of motion in elite male golfers: a pilot study.

BACKGROUND: Shoulder injuries account for up to 17% of all golf related musculoskeletal injuries. One cause may be the repetitive stresses applied to the lead shoulder during the backswing and follow-through phases, which may contribute to the frequency of these injuries. The "elite" golfer may be pre-disposed to developing a shoulder injury based upon the reported adaptations to the glenohumeral joint. OBJECTIVE: To examine and compare bilateral glenohumeral joint rotational range of motion in elite golfers using standard goniometric procedures. METHODS: Twenty-four "elite" male golfers were recruited for this study. Glenohumeral internal (IR) and external rotation (ER) passive range of motion was measured bilaterally at 90° of abduction using a standard universal goniometer. Paired t-tests were utilized to statistically compare the rotational range of motion patterns between the lead and the trailing shoulder. RESULTS: No statistical differences existed between each shoulder for mean IR or mean ER measures. This finding was consistent throughout different age groups. External rotation measurements were greater than IR measurements in both extremities. DISCUSSION AND CONCLUSION: Unlike other sports requiring repetitive shoulder function, the "elite" golfers sampled in this pilot investigation did not demonstrate a unique passive range of motion pattern between the lead and trailing shoulders. Factors, including subjects' age, may have confounded the findings. Further studies are warranted utilizing cohorts of golfers with matching age and skill levels. Additional shoulder range of motion measures should be evaluated.

Indolophanetetrayne cobalt complexes via Nicholas reactions.

[reaction: see text] Indole N-substituted diyne tetracobalt complexes (4) undergo a Lewis acid mediated dimerization-cyclization reaction through the indole 3-position to afford indolophanetetrayne cobalt complexes (7). Substitution of the indole fragment of (4) with a 3-methyl function allows analogous formation of indolophanetetrayne complex (9), linked through the indole 2-position.