رفتارهای خود سازماندهی شده و خصوصیات فتوفیزیکی پلیمرهای کریستالی مایع
Abstract
1- Introduction
2- Experimental section
3- Results and discussion
4- Conclusion
References
Abstract
A series of hemiphasmidic luminescent liquid crystalline polymers, in which the hemiphasmidic mesogen containing cyanostilbene were linked to the polymethacrylate main-chains via flexible spacers with different lengths, named poly {(Z)-m-(4-(1-cyano-2-(3,4,5-tris(octyloxy)phenyl)vinyl)phenoxy)alkyl methacrylate} (donated as Pr-m, m = 2, 4, 6, 8, 10) were synthesized via free radical polymerization. The phase structures and photophysical properties of Pr-m were investigated in detail by a combination of techniques including differential scanning calorimetry (DSC), polarizing optical microscopy (POM), small-angle X-ray scattering (SAXS), UV–Vis absorption spectra (UV–Vis spectra), photoluminescence spectra (PL spectra) and particle size analyzer. The results revealed that the phase structures of Pr-m transformed from hexagonal columnar phase (m = 2, 4) to smectic A phase (m = 6, 8, 10) with the increasing of flexible spacer length. All of the polymers featured similar AIEE properties, however, the solid state quantum yields of Pr-m decreased with the increasing flexible spacer length, and the solid quantum yields of Pr-m decreased from 8.55 (Pr-2) to 3.71 (Pr-10) with the increasing flexible spacer length.
Introduction
Over the past few decades, liquid crystals (LCs) have been widely studied as a type of functional material [1-9]. A substantial number of LCs have been synthesized, and their physical and chemistry properties have been investigated because the LCs show excellent anisotropic physical properties that can be used in many classical fields, such as stimuli-responsive [10-12], information storage [3, 4], and photomechanical materials [13, 14] etc. Among various applications of LCs, display materials is always the most important application direction of LCs. However, the conventional liquid crystal materials are non-self-luminescent, so that a backlight needs to be added in the liquid crystal display device, which violates the development trend of energy saving and thinning of liquid crystal display device [15]. Therefore, new strategy toward more efficient liquid crystal display device is highly desirable. Luminescent liquid crystals (LLCs), which combines optoelectronic characteristics of luminescent materials with the unique properties of anisotropic fluids, is expected to be an effective way to solve those problems mentioned above. LLCs can overcome the shortcomings of traditional liquid crystals as display materials and enjoy tremendous advantages for the construction of linear or circular polarized light emitting materials [16, 17]. In view of the traditional luminogens, researchers have tried to construct fluorescent liquid crystal materials [18-20]. However, due to the aggregation caused quenching (ACQ) effect, these fluorescent liquid crystal materials usually emit strong fluorescence only in dilute solution while hardly emit light in aggregate state, which makes the preparation of LLCs with excellent performance intractable [21-24].