Abstract
Abstract Acrylic acid-modified polyhedral oligomeric silsesquioxane (AC-POSS) was synthesized by the reaction between the amine groups in polyhedral oligomeric silsesquioxane (POSS) and acrylic acid, which could dissolve in water and can be easily purified. Free-radical copolymerization was applied to synthesize azobenzene liquid crystalline polymer silsesquioxane (LCP-POSS) with different proportions of AC-POSS and liquid crystalline monomers. The trans-isomers of azobenzene moieties in LCP-POSS were gradually transformed to cis-isomers with increasing ultraviolet irradiation time. The photoisomerization reaction of liquid crystalline polymer (LCP) and LCP-POSS showed the first-order dynamic reaction. Compared with the LCP, the photoisomerization rate constant of LCP-POSS was decreased due to the space steric hindrance of the POSS as a rigid segment. The phase transition temperature of liquid crystalline in LCP-POSS increased with increasing POSS content, and the liquid crystalline texture in LCP-POSS became smaller under the polarized light. With further increasing the POSS content (>50 wt%) in LCP-POSS, the ordered structure of the liquid crystalline phase was gradually affected, resulting in one-way liquid crystal (LC) phase behavior. The synthesized LCP-POSS has LC properties, light-responsive properties, and thermal stability. When the POSS is introduced into the LC material, the phase state of the LC material will become more abundant and the LC phase will become more stable. The significance of this study is to develop and extend its applications as stimuli-responsive materials and devices.
Highlights
Polyhedral oligomeric silsesquioxane (POSS) has attracted more attention due to the excellent thermal stability and processability in their hybrid organic–inorganic nanocomposites [1,2,3,4,5,6,7,8]
liquid crystalline polymer (LCP)-polyhedral oligomeric silsesquioxane (POSS) with different contents were synthesized by adjusting the amount of substance POSS to 6-(4methoxy-4′-oxy-azobenzene) hexyl methacrylate (AzoM), which are presented in Tables 1 and 2
liquid crystal (LC) birefringence behavior is a phenomenon in which a beam of light is incident into an anisotropic crystal, which is decomposed into two beams and refracted in different directions
Summary
Polyhedral oligomeric silsesquioxane (POSS) has attracted more attention due to the excellent thermal stability and processability in their hybrid organic–inorganic nanocomposites [1,2,3,4,5,6,7,8]. Liquid crystalline polymer (LCP) has attracted increasing attention due to its molecular orientation order, and POSS has the ability of self-assembly with its regular structure. The incorporation of POSS into LCP increased the liquid phase transition temperature and enriched the LC phase. Chen et al [33] prepared the functional POSS-based fluorinated azobenzene polymers, which were expected to be applied on the surface with light-responsive properties with controlled wettability. POSS with different proportions was incorporated into azobenzene LCP through freeradical polymerization. The influence of POSS on the light-responsive properties of azobenzene has been studied, and LCP photoisomerization rate constant was investigated. The LC phase and the thermal stability might be enhanced by the incorporation of low content of POSS to some extent, which may promote and extend its applications as stimuli-responsive materials and devices
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