耐高温无色透明聚酰亚胺的研究进展

Recent Progress in Colorless and Transparent Polyimide with High Thermal Stability

聚酰亚胺(PI)以其优异的耐热稳定性、化学稳定性及介电性能,在航空航天、微电子、光电工程、液晶显示、分离膜等领域得到广泛应用。传统PI显示棕色或棕黄色,限制了其在光电工程领域的应用。因此,近年来发展耐高温无色透明PI备受关注。针对近年来国内外耐高温无色透明PI的研究现状,从分子结构设计出发,总结了耐高温无色透明PI的制备策略,包括引入强电负性基团、脂环结构、大取代基团、不对称和刚性非共平面结构,以及可聚合的无机纳米粒子等;并讨论了分子结构对PI的热稳定性、尺寸稳定性、光学性能、溶解性等的影响;最后对耐高温无色透明PI的发展趋势和应用前景进行了展望。

Polyimides(PIs)have extensive applications in the aerospace industry,microelectronic and optoelectronic engineering,liquid crystal display,and separation membrane due to their high-temperature resistance,outstanding mechanical properties,chemical and radiation resistance,and excellent dielectric properties.Conventional PIs possess strong inter-and intra-molecular charge transfer interactions,resulting in an intense stack of the molecular chains,which leads to strong absorption in the visible region and brings deep color to PIs.This has considerably restricted their applications in the area of optoelectronic and microelectronic engineering.With the rapid development of display technology,PIs with excellent optical and thermal performance are desired to serve as substrate materials.However,achieving a breakthrough in the molecular design of the satisfied PIs remains challenging with regarding to the trade-off between good transparency and thermal stability of PI films.Recently,enormous research efforts have been devoted to the development of colorless and transparent PIs with high thermal stability via rational molecular structure design,as summarized in this review.These fabrication strategies mainly include the introduction of strong electronegative groups,alicyclic structures,bulky pendent units,asymmetric and rigid noncoplanar segments,and polymerizable inorganic nanoparticles.The incorporation of these structures plays an important role in disrupting the conjugation between the PI chains.This disruption reduces the regularity and weakens the stack of the molecular chains,while increasing the free volume of the PI chains,thus prohibiting the formation of inter-and intra-molecular charge transfer complex.All these are beneficial to minimize the absorption in the visible region and the formation of colorless PIs.Then,the influences of molecular structures on the properties of PI,such as thermal properties,optical performance and solubility,are discussed.Finally,the prospect of colorless and transparent PI with high thermal stability is discussed with respect to their development trends and potential applications.