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Temperature field distribution in polymer particles during surface-selective laser sintering
摘要： The dynamics of polymer particle heating by laser irradiation during surface-selective laser sintering (SSLS) has been studied both experimentally and theoretically. Water aerosol wetting of the polymer particle surface was applied to increase the absorbance of thulium fiber laser radiation at 1.96 μm. Theoretical modeling of the laser-induced thermal processes was performed in thermolabile polylactic-co-glycolic acid powder coated with a thin water layer. Temperature gradients on the surface and inside the sintered particle volume were evaluated and analyzed. It was shown that for certain optimized SSLS parameters an effective sintering process can be achieved by delicate melting of the particle surface only, without noticeable changes in the chemical and phase compositions of the internal domains.
关键词： surface-selective laser sintering,thermal imaging,polymer particles,wetting,analysis of thermal processes
更新于2025-09-23 15:19:57
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Direct Observation of Chain Lengths and Conformations in Oligofluorene Distributions from Controlled Polymerization by Double Electron–Electron Resonance
摘要： Synthetic polymers are mixtures of chains with different lengths, and their chain length and chain conformation is often experimentally characterized by ensemble averages. We demonstrate that Double-Electron-Electron-Resonance (DEER) spectroscopy can reveal the chain length distribution, and chain conformation and flexibility of the individual n-mers in oligo-(9,9-dioctylfluorene) from controlled Suzuki-Miyaura Coupling Polymerization (cSMCP). The required spin-labeled chain ends were introduced efficiently via a TEMPO-substituted initiator and chain terminating agent, respectively, with an in situ catalyst system. Individual precise chain length oligomers as reference materials were obtained by a stepwise approach. Chain length distribution, chain conformation and flexibility can also be accessed within poly(fluorene) nanoparticles.
关键词： controlled polymerization,polymer particles,wormlike chain model,conjugated polymers,Electron paramagnetic resonance,double-Electron-Electron resonance (DEER),distance determination
更新于2025-09-12 10:27:22