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F-19 spin-lattice relaxation and stable radicals in radiation-modified fluoropolymers

机译：辐射改性含氟聚合物中的F-19自旋晶格弛豫和稳定基团

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摘要

Fluorine-19 spin-lattice relaxation of electron-beam-irradiated poly(tetrafluoroethylene) (PTFE) has been investigated in the temperature range from 250 to 315 K. As shown before. in the initial step, radicals are produced by the electron-beam irradiation and chain scission takes place. The concentrations of radicals and chain end groups after irradiation of PTFE strongly depend on the irradiation conditions. Radicals like other paramagnetic species decrease the Spin-lattice relaxation times. In addition, decreased polymer chain lengths shift the T-1 minimum to lower temperatures. Tetrafluorosuccinic acid in solution was used as a model system and paramagnetic copper sulphate CuSO4 added to quantify the effect on the relaxation times. The shift of the minima in T-1 versus temperature in PTFE are compared with the chain length determined from high-resolution solid-state nuclear magnetic resonance spectra and with the concentration of paramagnetic species.
机译：已经研究了在250至315 K的温度范围内电子束辐照的聚四氟乙烯（PTFE）的氟19自旋晶格弛豫。在初始步骤中，通过电子束辐照产生自由基，并发生断链。 PTFE照射后自由基和链端基的浓度强烈取决于照射条件。像其他顺磁性物质一样，自由基会减少自旋晶格的弛豫时间。另外，减少的聚合物链长将T-1最小值移至较低的温度。将溶液中的四氟琥珀酸用作模型系统，并添加顺磁性硫酸铜CuSO4来量化其对弛豫时间的影响。将T-1最小值的变化与PTFE中温度的关系与从高分辨率固态核磁共振谱确定的链长以及顺磁性物质的浓度进行了比较。

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