High-Throughput Screening of the Alkoxide/Oxime-Based Library: An Alternative to Organotin Compounds for the Alkoxysilane Condensation in Adhesives and Sealants.

In this work, a high-throughput screening (HTS) method was used to discover new efficient catalysts to substitute organotin compounds (DBTDL) for the cross-linking of silyl-modified polymers (SMPs). We report here on the use of our HTS method to investigate a library of alkoxide/oxime systems with different metal/ligand (M/L) ratios. Among the 156 candidates tested, 40 interesting hits were detected.

A Theoretical Outlook on the Stereoselectivity Origins of Isoselective Zirconocene Propylene Polymerization Catalysts.

The first three insertion steps of propylene for isoselective metallocenes from the one-carbon-bridged cyclopentadienyl-fluorenyl {Cp/Flu} and silicon-bridged ansa-bis(indenyl) {SBI} families were computed by using a theoretical method implementing the B3PW91 functional in combination with solvent corrections incorporated with the Solvation Model based on Density (SMD) continuum model. For C -symmetric {Cp/Flu}-type metallocenes, two mechanisms of stereocontrol were validated theoretically: more facile and more stereoselective chain "stationary" insertion (or site epimerization backskip) and less stereoselective alternating mechanisms. For the C -symmetric {SBI}-type system, the computation results were in complete agreement with the sole operating chain migratory insertion mechanism.

Organocatalysts for the controlled "immortal" ring-opening polymerization of six-membered-ring cyclic carbonates: a metal-free, green process.

Six-membered cyclic carbonates, namely trimethylene carbonate (TMC), 3,3-dimethoxytrimethylene carbonate (DMTMC) and 3-benzyloxytrimethylene carbonate (BTMC), undergo controlled "immortal" ring-opening polymerization (iROP) under mild conditions (bulk, 60-150 °C), by using organocatalysts, including an amine [4-N,N-dimethylaminopyridine (DMAP)], a guanidine [1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD)], or a phosphazene [2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP)], in the presence of an alcohol [benzyl alcohol (BnOH), 1,3-propanediol (PPD), glycerol (GLY)] that acts as both a co-initiator and a chain-transfer agent.

Highly Effective and Green Catalytic Approach Toward α,ω-Dihydroxy-Telechelic Poly(trimethylenecarbonate).

α,ω-Dihydroxy-telechelic poly(trimethylenecarbonate), HO-PTMC-OH, is synthesized from the controlled "immortal" ring-opening polymerization (ROP) of trimethylene carbonate under mild conditions (bulk, 60 °C), using ZnEt(2) or, more efficiently, [(BDI)Zn(N(SiMe(3) )(2) )] (BDI = CH(CMeNC(6) H(3) -2,6-iPr(2) )(2) ) as catalyst precursor, in the presence of a diol HO-R-OH (R = (CH(2) )(2) or CH(2) C(6) H(4) CH(2) ; 0.5-10 equiv. vs Zn) acting both as co-initiator and chain transfer agent.