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Radiation-induced modification of P(VDF/TrFE) copolymers studied by ESR and vibrational spectroscopy

机译：ESR和振动光谱研究P（VDF / TrFE）共聚物的辐射诱导改性

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摘要

Radical species produced in ferroelectric copolymers of vinylidene fluoride (VDF) with trifluoroethylene (TrFE) copolymers with (50/50) and (75/25) composition by fast-electron irradiation were studied by electron spin resonance (ESR). The irradiation was performed in both the para- and ferroelectric phases. The ESR spectra were found to be rather complex and changed with time. Three types of radicals were identified, e.g., the peroxy radical, and alkyl in-chain -CF2-C center dot H-CF2- and end-chain -C center dot H-2 radicals. The decays of the radicals have a similar tendency and show a faster decaying process within a short period followed by a slower decaying process. The fast decay is related to the recombination reaction of alkyl radicals, whereas the slower one is due to the peroxy radicals recombination. In poly(VDF/TrFE) (75/25) copolymer irradiated in the paraelectric phase at T* = 420 K the decay of radicals, which were identified as the long-lived polyenyl radicals -CH2-(CF=CH)(n) -C center dot F-CH2-, is completed within one week and then the concentration of these radicals remains constant. The delocalization of unpaired electrons over up to five C=C bonds was estimated from the infrared studies.
机译：通过电子自旋共振（ESR）研究了偏二氟乙烯（VDF）与三氟乙烯（TrFE）共聚物的铁电共聚物中具有（50/50）和（75/25）组成的自由基电子通过快速电子辐射产生的自由基。在顺电相和铁电相中均进行了照射。发现ESR光谱相当复杂并且随时间变化。确定了三种类型的基团，例如过氧基团和烷基链内-CF 2 -C中心点H-CF 2-和末端链-C中心点H-2自由基。自由基的衰变具有相似的趋势，并且在短时间内显示出更快的衰变过程，随后呈现出更慢的衰变过程。快速衰变与烷基自由基的重组反应有关，而较慢的衰变与过氧自由基的重组有关。在顺电相中以T * = 420 K照射的聚（VDF / TrFE）（75/25）共聚物中，自由基的衰变被确定为长寿命的多烯基-CH2-（CF = CH）（n） -C中心点F-CH2-在一周内完成，然后这些自由基的浓度保持恒定。通过红外研究估计了多达五个C = C键的未配对电子的离域。

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