Phosphatidylcholine-based nonaqueous photorheological fluids: effect of geometry and solvent

• Published in: Colloid and polymer science Vol. 292; no. 7; pp. 1599 - 1609
• Main Authors: Shrestha, Rekha Goswami, Agari, Naoko, Tsuchiya, Koji, Sakamoto, Kazutami, Sakai, Kenichi, Abe, Masahiko, Sakai, Hideki
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.07.2014; Springer; Springer Nature B.V
• Subjects: Benzene; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Colloidal state and disperse state; Complex Fluids and Microfluidics; Exact sciences and technology; Fluid dynamics; Fluid flow; Food Science; General and physical chemistry; Isooctane; Micelles; Micelles. Thin films; Nanotechnology and Microengineering; Original Contribution; Photochemistry; Physical Chemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Polymer Sciences; Rheological properties; Rheology; Rings (mathematics); Soft and Granular Matter; Reverse wormlike micelles; Photosensitive; Trans-cinnamic acid; NMR; Rheology; Photochemistry; Solvent effect; Wormlike micelle; Cinnamic acid; Fluid; Phosphatidylcholine; Nuclear magnetic resonance; Reverse micelle
• ISSN: 0303-402X; 1435-1536
• DOI: 10.1007/s00396-014-3202-3

We report a detail study on photoinduced rheological changes in nonaqueous photorheological (PR) fluids obtained with 1,2-diacyl-sn-glycero-3-phosphocholine-based reverse wormlike micelles, 1-palmitoyl-2-oleophosphatidylcholine (POPC)/cyclohexane/H 2 O, POPC/isooctane/H 2 O, and L-α-dioleophosphatidylcholine (DOPC)/isooctane/H 2 O systems. Initially, the mixtures form highly viscoelastic fluids of long, reverse wormlike micelles as confirmed by the rheological measurements. When photosensitive molecule, trans -CA, is added to these mixtures, they exhibit photosensitivity, and the viscoelasticity increases that decreases on UV irradiation. The nature of the substituent on the benzene ring of trans -CA influences the rheology. When hydroxycinnamic acid (HCA) (hydrophilic, −OH group attached to the benzene ring of CA) is added to DOPC/isooctane/H 2 O phase, separation occurs; while with the methoxycinnamic acid (MOCA) and methylcinnamic acid (MCA) (hydrophobic groups, −OCH 3 , and –CH 3 attached to the benzene ring of CA respectively) led to higher viscoelasticity. The study on the effects of position of the substitution on CA reveals the viscosity enhancement is in the order of p-  >  m-  >  o- isomers. The different geometries obtained because of substitution and photoinduced trans - cis isomerisation is responsible for the different rheology as confirmed by the dynamic rheology, the UV absorption, and the 1 H NMR spectrums. The 1 H NMR spectra revealed a change in the solubilization site of CA with irradiation. cis -CA (high solubility in water) is solubilized in the vicinity of water (at the hydrophilic end of DOPC) as compared with trans- CA. This disrupts the 3D networks of reverse wormlike micelles, decreasing the η 0 , plateau modulus, G 0, and relaxation time, τ R of solution.