Biodegradable Alkali-Swellable Emulsion Polymers: Industrial and Commercial Thickeners.

Sustainability and circularity are key issues facing the global polymer industry. The search for biodegradable and environmentally-friendly polymers that can replace conventional materials is a difficult challenge that has been met with limited success. Alternatives must be cost-effective, scalable, and provide equivalent performance.

Material Flows of Polyurethane in the United States.

Today, polyurethanes are effectively not recycled and are made principally from nonrenewable, fossil-fuel-derived resources. This study provides the first high-resolution material flow analysis of polyurethane flows through the U.S.

TEMPO-Mediated Catalysis of the Sterically Hindered Hydrogen Atom Transfer Reaction between (CPh)Cr(CO)H and a Trityl Radical.

We have demonstrated the ability of TEMPO to catalyze H· transfer from (CPh)Cr(CO)H to a trityl radical (tris( p- tert-butylphenyl)methyl radical). We have measured the rate constant and activation parameters for the direct reaction, and for each step in the catalytic process: H· transfer from (CPh)Cr(CO)H to TEMPO and H· transfer from TEMPO-H to the trityl radical. We have compared the measured rate constants with the differences in bond strength, and with the changes in the Global Electrophilicity Index determined with high accuracy for each radical using state of the art quantum chemical methods.

Kinetics and thermodynamics of H. transfer from (eta5-C5R5)Cr(CO)3H (R = Ph, Me, H) to methyl methacrylate and styrene.

The rates of H/D exchange have been measured between (a) the activated olefins methyl methacrylate-d(5) and styrene-d(8), and (b) the Cr hydrides (eta(5)-C(5)Ph(5))Cr(CO)(3)H (2a), (eta(5)-C(5)Me(5))Cr(CO)(3)H (2b), and (eta(5)-C(5)H(5))Cr(CO)(3)H (2c). With a large excess of the deuterated olefin the first exchange goes to completion before subsequent exchanges begin, at a rate first order in olefin and in hydride. (Hydrogenation is insignificant except with styrene and CpCr(CO)(3)H; in most cases, the radicals arising from the first H.

Polynuclear catalysis: enhancement of enchainment cooperativity between different single-site olefin polymerization catalysts by ion pairing with a binuclear cocatalyst.

A new multicenter ethylene polymerization process is described whereby two different single-site catalysts, one competent for producing vinyl-terminated oligomers or macromonomers and one competent for producing high-molecular weight ethylene-alpha-olefin copolymers, are held in close spatial proximity via ion-pairing with a dianionic binuclear bis-borate cocatalyst. Ethylene polymerizations mediated by stoichiometrically appropriate quantities of Me2Si(tBuN)(eta5-3-ethylindenyl)ZrMe2 and Me2Si(tBuN)(eta5-C5Me4)TiMe2 activated by the bis-borate cocatalyst [Ph3C+]2[1,4-(C6F5)3BC6F4B(C6F5)3-2] yield a more homogeneous polyethylene product when compared to control polymerizations using the mononuclear activator [Ph3C+][B(C6F5)4-]. The bulk and spectroscopic properties of the polymer produced using the binuclear activator are consistent with highly branched polyethylene.