Thermally stable optical force probes for technical high-performance polymer materials

• Applicant: Professor Dr. Robert Göstl
• Subject Area: Preparatory and Physical Chemistry of Polymers ; Organic Molecular Chemistry - Synthesis and Characterisation ; Polymer Materials
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 508998124

In this project, we will devise and synthesize several thermally stable, spectrally tunable optical force probes (OFPs) with expected thermal decomposition temperatures above the processing temperatures of technically used polymers. Therefore, [4+4] photodimers of anthracenes, [4+2] photodimers of π-extended anthracenes, [4+2] cycloadducts of benzyne and anthracene (triptycenes), and [4+2] cycloadducts of triazolinedione and anthracene will be investigated. After the successful synthesis of the aforementioned OFPs, thermal analysis of the OFP samples will reveal their thermal stability at elevated temperatures, which will also provide thermal dissociation rate constants, activation energies, dissociation onset temperatures, and possible solvent- as well as concentration-dependent characteristics as parameters to describe their thermal stability. Afterwards, the OFPs will be incorporated into diverse linear polymer chains including technically important polystyrene (PS) and polyethylene (PE). To obtain polymers with narrow dispersity, we will use Cu0-mediated controlled radical polymerization for acrylate and methacrylate polymers, especially poly(methyl acrylate) (PMA), living anionic polymerization for PS, and entropy-driven ring-opening metathesis polymerization for PE. To examine the mechanochemical reactivities of acquired OFP-functionalized linear polymer chains, those with a single central mechanophore unit (PMA, PS) will subsequently be subjected to sonochemical treatment, which will lead to chain scission and eventually provide the apparent scission rate constants. Then, OFP-containing polymers will be prepared under different technical conditions. We will blend OFP-functionalized linear poly(methyl methacrylate) (PMMA) either into MMA monomers with following cell casting process, or into commercial PMMA granules with subsequent extrusion at 180-240 °C and injection molding. OFP-functionalized linear PS will be blended with commercial high molar mass PS either through extrusion and following injection molding (150-220 °C), or through solution blending with subsequent hot pressing (150 °C). The latter approach is suitable for both general purpose PS (GPPS) and composites such as high-impact PS (HIPS). For PE, besides the aforementioned methods, we will also produce OFP-PE doped PE fibers by blending with ultra-high-molecular-weight PE (UHMWPE) and spinning fibers thereof. Finally, by combining subsequent mechanical testing of the obtained polymer samples with photon quantitative confocal laser scanning microscopy (CLSM), we expect to shed light on the yielding and fracture behavior of these authentically manufactured technical polymers.

• DFG Programme: Research Grants