Photochemically Reversible Liquefaction and Solidification of Multiazobenzene Sugar-Alcohol Derivatives and Application to Reworkable Adhesives

Abstract

Multiazobenzene compounds, hexakis-O-[4-(phenylazo)phenoxyalkylcarboxyl]-D-mannitols and hexakis-O-[4-(4-hexylphenylazo)phenoxyalkylcarboxyl]-D-mannitols, exhibit photochemically reversible liquefaction and solidification at room temperature. Their photochemical and thermal phase transitions were investigated in detail through thermal analysis, absorption spectroscopy, and dynamic viscoelasticity measurements, and were compared with those of other sugar-alcohol derivatives. Tensile shear strength tests were performed to determine the adhesions of the compounds sandwiched between two glass slides to determine whether the compounds were suitable for application as adhesives. The adhesions were varied by alternately irradiating the compounds with ultraviolet and visible light to photoinduce phase transitions. The azobenzene hexyl tails, lengths of the methylene spacers, and differences in the sugar-alcohol structures affected the photoresponsive properties of the compounds.

Photoswitchable Nanomaterials Based on Hierarchically Organized Siloxane Oligomers

“…[33][34][35][36] Introduction of pendant groups at the 2-or 3-position can reduce intermolecular π-π interactions and allow photoisomerization in the bulk state on the time scale of minutes. [28] Recent work has also suggested that lamellar or monolayer azobenzene morphologies facilitate fast photoisomerization, [26,27,37] presumably by providing increased molecular freedom. In our exfoliated monolayer system, rapid photoliquefaction is enabled by the presence of highly disordered and fluidic ODMS surrounding monolayers of crystalline azobenzene.…”

“…[24,25] Furthermore, few examples have demonstrated the photocontrolled switching of liquid and solid phases in azobenzene materials. [26][27][28][29] Given the importance of molecular arrangement in photoresponsive materials, self-assembly strategies that facilitate ordering of functional motifs are prudent. Recently, we reported on the synthesis of a class of well-defined and discrete end-functionalized siloxane oligomers that form highly ordered multidomain nanomaterials with sub-5 nm periodicities.…”

Photoinduced Phase Transitions in Rod-shaped Azobenzene with Different Alkyl Chain Length

“…In an application point of view, this phase transition is of importance because this kind of phase transition material can be potentially be used in reusable light adhesives (dismantlable adhesives), photoresists, and other functional materials. Actually, it has been demonstrated that azobenzene-based materials can be used as dismantlable adhesives, that drastic decrease and recovery of the adhesion force were observed by the irradiation with ultraviolet and visible light, respectively [19][20][21][22].…”

Synthesis of star‐shaped poly(n‐butyl acrylate) oligomers with coumarin end groups and their networks for a UV‐tunable viscoelastic material

“…The aqueous layer was separated and extracted with CHCl 3 . The combined CHCl 3 phases were washed with water, dried over MgSO 4 , and concentrated to dryness to afford 2. The yield was 8.34 g (69%).…”

“…[1][2][3] This strategy is preferable for photoreversible adhesive applications, which enables ON-OFF attachment and detachment of surfaces coated by them without using solvent fractions. 4 Although the IRLNC strategy should, in principle, be applicable for tuning viscoelasticity of materials, only two physical states, i.e., solid and liquid ones are allowed for such small molecules. Therefore, the development of materials exhibiting solvent-free IRLNC with tunable viscoelasticity remains a challenge.…”