The main aim of this work is to obtain heterogeneous, zirconocene aluminohydride/methylaluminoxane (MAO) polymerization catalysts, without using inorganic carriers like silica. The syntheses of zirconocenium ion‐based clathrates, formed from aluminohydride zirconocene complexes activated with MAO, are reported here. Several different approaches were examined for the synthesis of these clathrate compositions; in one approach the catalyst (nBuCp2ZrH3AlH2/MAO) was first prepared in toluene solution, and the clathrate phase then generated by addition of silicone oil. An alternate approach involved reaction of silicone oil or another clathrate‐forming additive (e.g. KCl) with MAO to form a solidified clathrate, and then introducing the zirconocene aluminohydride complex (nBuCp2ZrH3AlH2). The clathrate catalysts were probed in the polymerization of ethylene in hydrocarbon slurry, without using additional co‐catalyst (MAO), or at very low concentrations of modified MAO (MMAO 7, 13 wt‐% in iso‐octane). The catalytic activities of the solid clathrate catalysts were compared as well as the morphology and properties of the polyethylene synthesized in slurry.
The implementation of a dialysis method for the simultaneous purification of different polymer materials in a commercially available automated parallel synthesizer (APS) is discussed. The efficiency of this “unattended” automated parallel dialysis (APD) method was investigated by means of proton nuclear magnetic resonance (1H-NMR) measurements, which confirmed that the method enables the removal of up to 99% of the unreacted monomer derived from the synthesis of the corresponding polymers in the APS. Size-exclusion chromatography (SEC) revealed that the molar mass and molar mass distribution of the investigated polymers did not undergo significant changes after the application of the APD method. The method discussed herein can be regarded as a good alternative to the “unattended” and reliable purification of polymer libraries prepared in APS. This method may be useful for overcoming current limitations of high-throughput/-output (HT/O) synthesis of polymer libraries, where purification of the generated materials currently represents a significant constraint for establishing fully automated experimental workflows necessary to advance towards a full digitalization of research and development of new polymers for diverse applications.
In this work, poly(alkylmethacrylates) based on poly(n-alkyl methacrylate) s (PnAMAs), that is, poly(hexyl methacrylate) (PHMA), poly(lauryl methacrylate) (PLMA), and poly(stearyl methacrylate) (PSMA), with similar molar masses (M n ), are synthesized via reversible addition-fragmentation chain transfer technique using a high-throughput approach.
Analyses by dynamic light scattering (DLS) of PnAMAs in nonpolar solvents show the presence of nanoparticles distributions (unimers or single chains). Interactions of methylaluminoxane (MAO) and MAO/metallocene compounds withPnAMA nanoparticles, lead to self-assembled micellar-like structures useful as "nanoreactors" for coordination polymerizations of ethylene. The inverse micellarlike structures of the three kinds of polymethacrylates, formed in the presence of MAO are confirmed by DLS experiments and by transmission electron microscopy using energy dispersive spectrometry analyzer, in dyed PnAMAs/ MAO samples. The encapsulation of the metallocene catalyst into the PSMA/ MAO nanoparticles reveals stable catalytic systems that have a clear effect on the morphology of the polyethylenes synthesized through this method.
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