Low-Temperature Plasma Induced Grafting of 2-Methacryloyloxyethyl Phosphorylcholine onto Poly(tetrafluoroethylene) Films

Modification of poly(tetrafluoroethylene)(PTFE) films with 2-methacryloyloxyethyl phosphorylcholine(MPC) was performed by low-temperature plasma treatment and grafting polymerization.Surface properties of PTFE were characterized by attenuated total reflectance Fourier transform infrared(ATR-FTIR) spectra,X-ray photoelectron spectroscopy(XPS) ,and static contact angle.The results show that MPC has been grafted onto PTFE film surface successfully.Contact angle for the modified PTFE films in the water decreased from 108°to 58.25°,while surface energy increased from 17.52 mN/m to 45.47 mN/m.The effects of plasma treatment time,monomer concentration and grafting time on degree of grafting were determined.In the meanwhile,blood compatibility of the PTFE films was studied by checking thrombogenic time of blood plasma.

The Fourier space restricted Hartree-Fock method for the electronic structure calculation of linear poly(tetrafluoroethylene)

Building on the pioneering work of Jean-Marie Andre and working in the laboratory he founded, the authors have developed a code called FT-1D to make Hartree-Fock electronic structure computations for stereoregular polymers using Ewald-type con- vergence acceleration methods. That code also takes full advantage of all line-group symmetries to calculate only the minimal set of two-electron integrals and to optimize the computation of the Fock matrix. The present communication reports a bench- mark study of the FT-1D code using polytetrafluoroethylene （PTFE） as a test case. Our results not only confirm the algorith- mic correctness of the code through agreement with other studies where they are applicable, but also show that the use of con- vergence acceleration enables accurate results to be obtained in situations where other widely-used codes （e.g., PLH and Crys- tal） fail. It is also found that full attention to the line-group symmetry of the PTFE polymer leads to an increase of between one and two orders of magnitude in the speed of computation. The new code can therefore be viewed as extending the range of electronic-structure computations for stereoregular polymers beyond the present scope of the successful and valuable code Crystal.

NaF-rich protective layer on PTFE coating microcrystalline graphite for highly stable Na metal anodes

The practical application of Na metal anode is plagued by the dendrite growth,unstable solid electrolyte interphase(SEI)formation and volume change during the cycling process.Herein,poly(tetrafluoroethylene)(noted as PTFE)coating microcrystalline graphite is designed as the sodium metal anode host by a facile and cost-effective strategy.The isotropous microcrystalline graphite(MG)is conducive to guiding Na+to form a co-intercalation structure into MG.And the PTFE coating layer can form NaF as artificial SEI film for uniform ion transport and deposition.As a result,the gained PTFE coating MG electrode can deliver a long-life span over 1,200 cycles with an average Coulombic efficiency(CE)of 99.88%.To note,almost the CE in each cycle is around 99.8%–100%.When assembled with Na_(3)V_(2)(PO_(4))_(2)F_(3)cathode as full cells,the full cell paired with PTFE coating MG electrode can operate much stable than that of MG electrode for the existence of PTFE coating layer.Even utilized as sodium-free Na metal anode paired with Na_(3)V_(2)(PO_(4))_(2)F_(3)cathode,it can also deliver a high initial CE of 76.27%at 0.5 C.After 100 cycles,it still has a high discharge capacity of 83.5 mAh·g^(−1).

In situ Synthesis of Oligonucleotide and Detection of Gold-label-silver-stain on PTFE Slices

Poly（tetrafluoroethylene） （PTFE） was treated with plasma in a mixture of nitrogen and hydrogen （1 ： 2 in volume）. X-ray photoelectron spectroscopy （XPS） demonstrated the success of amino group grafting. The as-treated PTFE slices were successively applied to the in situ synthesis of oligonucleotides. With the detection of gold-label-silver-stain, the hybridization signals were recorded with a gel document and analysis system. A target DNA concentration as low as 10 pmol/L could be detected. The complementary and mismatched sequences were distinguished clearly, and the ratio of background-subtracted gray scale values for perfect match ： 1 base mismatch ： 2 base mismatch ： 3 base mismatch was 72 ： 44.4 ： 22.5 ： 11.4. The sensitivity of in situ synthesis system was 1 order of magnitude higher than that of spotting system, and the signal of the former was about 1.5 times stronger than that of the latter under the same target DNA concentration. These plasma modified PTFE slices might open novel prospects for the in situ synthesis of DNA micro-arrays.

In vitro mineralisation of grafted ePTFE membranes carrying carboxylate groups

In vitro mineralisation in simulated body fluid(SBF)of synthetic polymers continues to be an important area of research as the outcomes cannot be predicted.This study evaluates a series of ePTFE membranes grafted with carboxylate-containing copolymers,specifically using acrylic acid and itaconic acid for grafting.The samples differ with regards to graft density,carboxylate density and polymer topology.The type and amount of mineral produced in 1.5×SBF was dependent on the sample characteristics as evident from XPS,SEM/EDX,and FTIR spectroscopy.It was found that the graft density affects the mineral phases that form and that low graft density appear to cause co-precipitation of calcium carbonate and calcium phosphate.Linear and branched graft copolymer topology led to hydroxyapatite mineralisation whereas crosslinked graft copolymers resulted in formation of a mixture of calcium-phosphate phases.This study demonstrates that in vitro mineralisation outcomes for carboxylate-containing graft copolymers are complex.The findings of this study have implications for the design of bioactive coatings and are important for understanding the bone-biomaterial interface.