Synthesis, Self-Assembly and Photoresponsive Behavior of Liquid Crystals Based on Azobenzene

Yaoming Wu ,Jianxiang Chen,Runmiao Yang,Yuhai Liu

doi:10.3390/cryst11121560

Yaoming Wu , Jianxiang Chen + Show 2 more

Open Access

https://doi.org/10.3390/cryst11121560

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Abstract

A new amphiphilic surfactant (C4-Azo-C5-HDA) was formed by liquid crystals (LCs) based on azobenzene, whose structures were characterized by 1H-NMR spectroscopy. The reversible hydrogelation upon changes in temperature and light exposure was also studied. Under the irradiation of UV light, the trans-isomer of C4-Azo-C5-HDA rapidly photoisomerized to the cis-isomer, resulting in rapid disruption of the gel. The thermotropic liquid crystal behavior of the gelator was investigated via Differential Scanning Calorimetry (DSC) and Polarizing Optical Microscopy (POM). The biocompatibility experiment of multi-stimulus response of the liquid crystal provides a potential driving force for the development of biomaterials.

Highlights

Gels are topical soft materials that are very suitable for advanced applications in many fields such as the sol-gel process, drug delivery, sensors, etc. [1,2,3]
According to the solvents contained, the gels have been categorized as organogels or hydrogels
Unlike traditional polymer gels that form a three-dimensional network structure through covalent cross-linking, low molecular weight gelators (LMWGs) are a low concentration of low-molecular-mass molecule, which are prepared by gelation to form three-dimensional networks based on non-covalent interactions’ aggregation, such as hydrogen bonds, electrostatic interactions, π–π interactions and van der Waals forces

Summary

Introduction

Gels are topical soft materials that are very suitable for advanced applications in many fields such as the sol-gel process, drug delivery, sensors, etc. [1,2,3]. Unlike traditional polymer gels that form a three-dimensional network structure through covalent cross-linking, low molecular weight gelators (LMWGs) are a low concentration of low-molecular-mass molecule, which are prepared by gelation to form three-dimensional networks based on non-covalent interactions’ aggregation, such as hydrogen bonds, electrostatic interactions, π–π interactions and van der Waals forces. The liquid crystal containing azobenzene attracts much attention due to the combined properties of liquid crystallinity, photoresponsivity and reactivity These make them promising in designing intelligent photo-driven soft materials [16]. In this work, we use azobenzene units, alkyl chains and amine moieties to design and synthesize a supramolecular gelator (C4-Azo-C5-HDA) This liquid crystal showTshperoepfoerret,yicnhtahnigs ews oinrkr,eswpeonuse taozeoxbteenrnzaenl me unltit-s,tiamlkuylil,cshuacihnassapnhdoatomriensepmonosieetainesd ttohedremsiognreasnpdonssyen. AAfftteerr ccoooolliinngg ddoowwnn ttoo 1100 °°CC,, tthhee ssaalltt ssoolliidd wwaass ffoorrmmeedd aanndd ffiilltteerreedd ooffff.

Liquid Crystals’ Characterization a

Self-Assembly Morphology Analysis

Live-Dead Assay of the Hydrogel