One-pot Polymerization Process Research Articles

One-Pot Fabrication of Kinetically Inert Ultrasmall Manganese(II) Chelate-Backboned Polymer Contrast Agents for High-Performance Magnetic Resonance Imaging.

Traditional macromolecules or nanoscale Mn2+ chelate-based magnetic resonance imaging (MRI) contrast agents (CAs) suffer from complicated and laborious synthesis processes, relatively low kinetic stability and T1 relaxivity, limiting their clinical applications. Herein, we fabricated a series of kinetically inert Mn2+ chelate-backboned polymers, P(MnL-PEG), through a facile and one-pot polymerization process. Particularly, P(MnL-PEG)-3 demonstrates a significantly higher T1 relaxivity of 23.9 Mn mM-1 s-1 at 1.5 T than that of previously reported small molecules and macromolecules or nanoscale Mn2+ chelate-based CAs. Due to its high T1 relaxivity, extended blood circulation, hepatocyte-specific uptake, and kidneys metabolism, P(MnL-PEG)-3 presents significantly enhanced contrast in blood vessel, liver, and kidneys imaging compared to clinical Gd3+-based CAs (Gd-EOB-DTPA and Gd-DOTA) at a dosage of 0.05 mmol Mn/Gd kg-1 BW, and can accurately diagnose orthotopic H22 liver tumors in vivo in animal models. We anticipate that this work will promote the development of clinically relevant MRI CAs.

Ultrahigh temperature ablation resistant HfB2-SiC composites: From liquid SiHfCB precursor synthesis to light weight bulk preparation and characterization

The current generation of ultrahigh temperature ceramic precursors typically encounters obstacles in achieving high ceramic yields (<40 wt.%) due to the challenges in integrating significant amounts of boron, which hampers their conversion into boride-based ultrahigh temperature ceramics. To tackle these challenges, a serious of pioneering liquid multi-component hafnium-containing ceramic SiHfCB precursors (with different Hf/Si ratios) have been developed. These novel precursors are featured with stable molecular structure and high ceramic yield which were successfully created through a novel one-pot polymerization process. They present in liquid form and their structure is characterized by C-C bonds forming its main chain with branched chains of O-Si-O, Si-O-Hf, Si-O-B, and B-O-Hf which have untapped advantages including uniform component dispersion, and excellent fluidity. The ceramic yield of SiHfCB precursor with Hf/Si of 0.2 is remarkably up to 68.6 wt.% at 1500 °C, and their Hf content exceeded 50 wt.%. Of particular interest, the pyrolyzed product HfB2-SiC nanopowders derived from the SiHfCB precursor with Hf/Si of 0.2, consist of nanopowders in the 40–60 nm range with a density of 5.23 g cm−3. Remarkably, this material demonstrates exceptional performance in ultrahigh temperature oxygen-containing environments at 2500 °C, showing near-zero ablation with a linear ablation rate of just 2.5 × 10−4 mm s−1. Post-ablation analysis of the microstructure reveals that the formation of a lava-like HfO2 and HfO2-SiO2 oxide layer effectively blocks oxygen penetration and provides excellent oxidation resistance. The innovative SiHfCB hafnium-containing ceramic precursor offers a groundbreaking solution for the preparation of lightweight ultrahigh-temperature ceramics. This development is poised to provide robust technical support for the use of ultrahigh temperature ceramics in non-ablative thermal protective systems, particularly in the construction of hypersonic vehicles, where ultrahigh temperature resilience is crucial.

Synthesis of stereoblock polybutadiene possessing cis-1,4 and syndiotactic-1,2 segments by imino-pyridine cobalt complex-based catalyst through one-pot polymerization process

The iminopyridylcobalt complexes Co1-Co5 bearing bulky phenethyl or benzhydryl substituents were synthesized. Determined by single crystal X-ray crystallographic analysis, complexes Co3 and Co4 displayed tetrahedron geometries. The present complexes displayed high cis-1,4 selectivity for 1,3-butadiene polymerization upon activation with ethylaluminum sesquichloride (EASC). While upon activation with either methylaluminoxane (MAO) or trialkylaluminum-free MAO (dMAO) cocatalyst, these complexes exhibited moderate activities, addition of PPh3 into the catalyst system resulted in the increase in catalytic activities and the change of the selectivity from cis-1,4 to 1,2 manner. Moreover, the livingness of Co4/dMAO system enabled synthesis of cis-1,4-b-syn-1,2 stereodiblock polybutadiene with PPh3 as a selectivity regulating agent in one-pot polymerization process. Crystallization of syn-1,2 block and attendant expulsion of cis-1,4 block from the crystalline structure led to micro-phase separation in this stereoblock polymer.

Dual Layer Coating Strategy Utilizing N-doped Carbon and Reduced Graphene Oxide for High-Performance LiFePO4 Cathode Material

Lithium iron phosphate (LiFePO4, LFP) has two major drawbacks such as low lithium ion diffusivity and poor electric conductivity, which limit the wider application as a cathode material for lithium ion batteries. In this work, we report a dual carbon layer coating strategy for LFP, which uses polydopamine-derived nitrogen-doped carbon (N-doped carbon) and reduced graphene oxide (RGO). These dual carbon layers are prepared by a one-pot polymerization process and thermal treatment. The dual carbon coated LFP has a rate capability with a discharge capacity of 98mAh/g at 30C, cycling performance with a discharge capacity of 115mAh/g at 10C, and 96.18% capacity retention after 700 cycles. The high rate performance and the excellent long-term cycling stability can be attributed to the enhanced electric conductivity with N-doped carbon coating, the well-connected electron pathway, and the fast Li+ ion diffusion induced by the small size of the particles. Consequently, coating of LFP with polydopamine derived N-doped carbon and RGO produces a material suitable for high-performance lithium-ion batteries.