High‐output polymer screening (HOPS) combines automated polymerization with online reaction monitoring, rapid polymer characterization and novel fingerprint technology useful in polymer preparation as well as polymer processing and polymer additive development. Originally, HOPS was introduced to develop polymerization catalysts and polyolefin materials more effectively. In comparison to conventional high‐throughput screening, focusing on ultrahigh speed of catalyst screening using arrays of miniaturized reactors, output‐oriented, process‐relevant HOPS is aiming at generating and exploiting high information density (useful information/experiment). Catalyst systems for olefin polymerization are evaluated in automated workstations with multiparallel as well as semi‐ and fully automated, upgraded lab reactors. Automated polymerizations under standardized conditions afford large families of well‐characterized polymers which serve as calibration samples for data analysis. Data analysis, using multivariate calibration, is the key to basic correlations between spectroscopic information and catalyst and polymer properties as well as reaction parameters and processing conditions. IR spectroscopic fingerprints are used to measure chemical copolymer composition, density, molecular weight as well as thermal and even mechanical properties. This fingerprint technology can be applied in online quality control and facilitates transfer from lab results into pilot and production plants. Fingerprint methods are important components of rapid online analysis and can reduce the need for time‐ and money‐consuming polymer testing. Fingerprint technology combines spectroscopic analysis by means of “cheap” spectrometers with multivariate calibration.magnified imageFingerprint technology combines spectroscopic analysis by means of “cheap” spectrometers with multivariate calibration.
As a consequence of developing fully automated reactors for organic and organometallic synthesis and polymerizations combined with rapid on-line analysis, databases, and data mining, the analysis of polymers with respect to composition and properties has been speeded up. High-throughput evaluation of olefin copolymers requires fast measurements and high accuracy without tedious sample preparation such as pressing KBr pellets. This has been achieved by using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR spectroscopy) in conjunction with multivariate calibration in order to determine the composition of olefin copolymers such as ethene/propene, ethene/1-hexene and ethene/1-octene copolymers.
Bismethacrylate monomers and macromonomers bearing various alkoxysilyl units were prepared by convenient Michael addition of ethylene glycol acrylate methacrylate (EGAMA) and ethylene glycol bisacrylate (EGBA) to various α,ω-alkoxysilylamines. The resulting monomers and macromonomers have been characterized in detail by NMR spectroscopy, VPO measurements and FAB−MS. Average molecular weights M n ranged between 530 and 1600 (VPO) in addition reactions with bisacrylates. FAB−MS evidenced the formation of a homologous macromonomer series. Viscosities of the liquid monomers are relatively low, ranging from 52 to 305 mPa·s. This renders these compounds interesting as reactive diluents in dental composite formulations. Polymerization of the monomers and macromonomers resulted in low volumetric shrinkage in the range of ΔV = 2.2−7.8% at high methacrylate conversion. Cross-linking was monitored by photo-DSC. Furthermore, composites were prepared by mixing Bis-GMA with the new hybrid monomers, initiator and glass filler. The composites showed compressive strengths of 190−329 MPa, flexural strengths from 23 to 53 MPa and Young's moduli between 2090 and 5060 MPa. Low volumetric shrinkage was observed also for the composites upon photopolymerization, ranging from only 0.8% to 2.2% in comparison to over 3% shrinkage of commercially available composites. Besides the viscosity reducing effect due to the branched structure, the pendant alkoxysilyl groups of the synthesized hybrid monomers can be polymerized to form nanoparticles with reactive acrylate surface, permitting the in situ preparation of nanocomposites.
The melt miscibility of stereoregular polypropene with branched ethene homopolymers, prepared by Ni- and Pd-based catalysts, was investigated by means of transmission electron microscopy, atomic force microscopy, and differential scanning calorimetry. The number of branched C atoms per 1000 C atoms, referred to as degree of branching (DB), was varied from 6 to 112. Miscibility increases with increasing DB. Blends of branched ethene homopolymers and poly(ethene-co-1-octene) with isotactic (i-PP) and syndiotactic polypropylene (s-PP) were compared and show slightly improved miscibility for s-PP. For DBs of 98 and 112 partial miscibility with polypropene was found. The miscibility of polyethenes with longer branches resemble that of polyethene/1-octene copolymers, whereas short branched polyethenes behave more like polyethene/1-butene copolymers.
The High‐Output Polymer Screening (HOPS) combines process‐relevant automated reactor systems and rapid polymer characterization with on‐line polymerization monitoring and automated data acquisition (“electronic notebook”) in order to make effective use of advanced data mining tools. This has led to the development of fingerprint technology based upon correlations between spectroscopic data and polymerization process conditions, catalyst compositions, as well as polymer end‐use properties. Infrared spectroscopic fingerprints proved to be very useful for accelerating polymer analyses including characterization of polymer molecular architectures as well as non‐destructive testing of the mechanical, thermal and other end‐use polymer properties. Such spectroscopic fingerprints represent important components of effective on‐line quality control systems. With ATR‐FT‐IR probes on‐line monitoring of catalytic olefin copolymerization was performed in solution to measure in real time copolymerization kinetics, catalyst productivities, catalyst deactivation as well as copolymerization parameters and copolymer sequence distributions. Monomer consumption and comonomer incorporation were monitored simultaneously. Advanced fingerprint technology can reduce significantly the need for time‐ and money consuming polymer testing and can also stimulate the search for new catalyst systems and polymeric materials.
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