Light responsive thin films of micelles of PS-b-PVP complexed with diazophenol chromophore

Abstract

We have incorporated push-pull azobenzene units into diblock-copolymer micelles by supramolecular assembly. Specifically, we encapsulated a phenol-functionalized chromophore, DO13, within PS-b-P4VP micelles in toluene by means of H-bond interactions developed between DO13 molecules and pyridine groups of P4VP block. The solutions were spin-coated onto glass substrates resulting in multi- or mono-layered thin films of micelles with P4VP(DO13) core and PS corona. We show that the use of DO13 as a building block of micellar aggregates allowed us to manipulate the developed nanostructures. Spherical to cylindrical micellar transition was found when we increased the degree of chromophore complexation. Also, it was found that the polymer concentration in the solution plays an important role in determining the micellar nanostructures. The chain extension and change in composition of the P4VP core in the presence of the chromophore may be responsible for the structural changes observed in the micelles. The optical properties of the thin films have been investigated focusing on the effect of the micellar morphology over the photoinduced birefringence. The optical anisotropy (Δn) increased with respect to the analogous homogeneous system P4VP(DO13), indicating that the protective micelle environment can enhance the optical properties of the embedded chromophores significantly. Furthermore, we show very interesting new results in which we have related changes in optical properties to the film morphology (spheres to cylinders). This can be exploited for producing optical devices having improved optoelectronic properties and stability.

Effect of molecular architectures in photoinduced birefringence in films of azo-modified diblock copolymers

“…Block copolymers in a selective solvent for one of the blocks are known to form micelles or aggregates as a result of the association of the insoluble blocks [19][20][21][22]. In our case, micelles with a P4VP core and a PS corona are formed as shown in a previous work [17]. Micellar size is the order of 40-50 nm.…”

“…Furthermore, the writing times were also shorter for the LB and LS films fabricated from toluene solutions. The enhanced properties with toluene are ascribed to the formation of micelles consisting of a P4VP core and a PS corona [17], owing to a cooperative effect arising from the confinement effect over azo chromophores. (ANPCyT, Argentina) and the University of Mar del Plata (Argentina).…”

“…In a previous work, we encapsulated a phenol-functionalized chromophore (Disperse Orange 13, DO13) within poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) micelles in toluene by means of H-bond interactions between the phenol group of DO13 molecules and pyridine groups of P4VP block. DO13 was used as building block of micellar aggregates to manipulate the morphology, which allowed birefringence to be induced in spincoated films produced with the micellar solutions [17].…”

Successful in vivo hyperthermal therapy toward breast cancer by Chinese medicine shikonin-loaded thermosensitive micelle

“…17,18 In order to improve drug-specific accumulation in tumors, various novel stimulus-sensitive polymeric micelles were designed such as the temperature, 19 pH, 20 reduction, 21 light, 22 magnetic field, 23 and ultrasound. 24 Among these newly developed functional carriers, nanomicelles are ideal candidates for the delivery of hydrophobic shikonin.…”

“…19 The intracellular release of such drug-loaded nanomicelles with hydrophilic PNIPAM corona (thermosensitive nanomicelle [TN]) is also successfully regulated by the temperature in vitro. 21,22 On the contrary, the drug-loading content, release, and micellar stability are also strongly dependent on the hydrophobic core. 26 The China Food and Drug Administration-approved hydrophobic polymers, such as poly(ε-caprolactone) and polylactic acid (PLA), are widely used for making biodegradable micelles.…”