Thermal rearrangement of ortho-allyloxypolyimide membranes and the effect of the degree of functionalization†,Polymer Chemistry

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Thermal rearrangement of ortho-allyloxypolyimide membranes and the effect of the degree of functionalization†
Polymer Chemistry ( IF 4.1 ) Pub Date : 2018-05-25 00:00:00 , DOI: 10.1039/c8py00530c
David Meis _{1,

2,

3,

4} , Alberto Tena _{1,

2,

3,

4} , Silvio Neumann _{1,

2,

3,

4} , Prokopios Georgopanos _{1,

2,

3,

4} , Thomas Emmler _{1,

2,

3,

4} , Sergey Shishatskiy _{1,

2,

3,

4} , Sofia Rangou _{1,

2,

3,

4} , Volkan Filiz _{1,

2,

3,

4} , Volker Abetz _{1,

2,

3,

4,

5}

Affiliation

Aromatic polyimides containing an ortho-allyloxy group with different ratios (in the range of 10–100%) of the ortho-allyloxy to ortho-hydroxy units were synthesized. The allyl ether synthesis was done via a post-polymerization Williamson etherification reaction. Thermally induced Claisen-rearrangement of the allyloxy-phenyl unit was conducted in the solid-state, followed by isothermal treatments at 250 °C leading to a crosslinked ortho-hydroxy containing polyimide. Further thermal annealing at 350 °C was employed to achieve a high imide-to-benzoxazole conversion, commonly described as the thermal rearrangement process (TR). The influence of the degree of modification on the crosslinking reaction as well as the imide-to-benzoxazole conversion temperature and the rate were studied by means of TG-FTIR, DSC and dielectric spectroscopy. A nearly linear change of the material properties, such as film density, d-spacing and gel-fraction, with an increasing number of allylated units was observed. Additionally, an incline of the permeability, due to an increase of the free volume elements, was observed. Moreover, the polymer chain mobility in terms of relaxation times was demonstrated to depend on the degree of allylation, which in turn led to a reduction of the TR temperature of about 80 °C compared to the pristine polyimide. The thermally induced imide-to-benzoxazole rearrangement occurred already to a large extent of 77% at 350 °C. In comparison, the pristine polymer showed only a conversion of 20%. Furthermore, the observed HPI-to-PBO conversions at 350 °C surpassed those of various other reported TR polyimides treated at even higher temperatures of 400 to 450 °C. Side-reactions and degradation that usually accompany treatments at 400 °C and above might be avoided at lower treatment temperatures of 350 °C.

中文翻译：

邻位烯丙氧基聚酰亚胺膜的热重排及其功能化程度的影响†

含有芳族聚酰亚胺邻的具有不同比例的烯丙基（在10-100％的范围内）的邻位烯丙氧基到邻合成羟基单元。烯丙基醚的合成是通过后聚合的Williamson醚化反应完成的。固态进行烯丙基氧基苯基单元的热诱导克莱森重排，然后在250°C下等温处理，导致交联的邻位含羟基的聚酰亚胺。采用350°C的进一步热退火来实现高酰亚胺到苯并恶唑的转化率，通常将其描述为热重排工艺（TR）。通过TG-FTIR，DSC和介电谱研究了改性程度对交联反应以及酰亚胺-苯并恶唑转化温度和反应速率的影响。材料特性（例如薄膜密度，d）几乎呈线性变化观察到间隔和凝胶分数随烯丙基化单元数目的增加而增加。另外，由于自由体积元素的增加，观察到渗透率的倾斜。此外，证明聚合物链迁移率的弛豫时间取决于烯丙基化的程度，与原始的聚酰亚胺相比，这又导致TR温度降低了约80°C。热诱导的酰亚胺到苯并恶唑的重排在350°C时已经发生了77％的程度。相比之下，原始聚合物仅显示20％的转化率。此外，在350°C时观察到的HPI到PBO的转化率超过了其他各种报道的TR聚酰亚胺的转化，甚至在400至450°C的更高温度下进行了处理。

更新日期：2018-05-25

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