The properties of the molecular ferroelectric diisopropylammonium bromide (C 6 H 16 BrN, DIPAB) particles embedded into a nanoporous opal matrix were studied by high-resolution nuclear magnetic resonance (NMR) in the temperature range from 295 to 450 K. The 13 C NMR spectra were obtained using CP-MAS technique. The results showed that structural changes in nanostructured DIPAB particles are more complex than it was previously expected. The NMR spectra of DIPAB embedded into the opal matrix revealed the coexistence of two different crystalline structures within a wide temperature range. The monoclinic ferroelectric and orthorhombic non-polar phases were seen in nanoconfined DIPAB at room temperature, meanwhile the orthorhombic phase only was found in the bulk DIPAB crystalline powder. The NMR spectra showed that the transition from the orthorhombic to the ferroelectric phase upon heating is reconstructive. The total nanocomposite transforms into the ferroelectric structure at a temperature much higher than that for the relevant transition in bulk. The size effect also leads to the increase of the temperature of the phase transition from the ferroelectric P2 1 phase to the P2 1 /m paraphrase.

中文翻译：

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基于分子铁电二异丙基溴化铵的纳米复合材料的核磁共振研究

通过高分辨率核磁共振 (NMR) 在 295 至 450 K 的温度范围内研究了嵌入纳米多孔蛋白石基质中的分子铁电二异丙基溴化铵 (C 6 H 16 BrN, DIPAB) 颗粒的性质。 13 C NMR使用 CP-MAS 技术获得光谱。结果表明，纳米结构 DIPAB 颗粒的结构变化比以前预期的更复杂。嵌入蛋白石基质中的 DIPAB 的 NMR 光谱揭示了两种不同晶体结构在很宽的温度范围内共存。室温下在纳米限制的 DIPAB 中观察到单斜铁电相和正交非极性相，而正交相仅在块状 DIPAB 结晶粉末中发现。核磁共振谱表明，加热时从正交相到铁电相的转变是重建的。整个纳米复合材料在比相关体相转变温度高得多的温度下转变为铁电结构。尺寸效应还导致从铁电 P2 1 相到 P2 1 /m 释义的相变温度升高。