Segmental relaxation behavior of polystyrene chains in the cores of collapsed dry micelles tethered on the micelle film surface by a poly(acrylic acid) corona

Abstract

We present an experimental investigation of the segmental relaxation behavior of polystyrene (PS) chains that are confined in a micellar core tethered by a poly(acrylic acid) (PAA) block corona on the dry film surface, along with various core density and molecular weight of PS block from below to well above the entanglement molecular weight. The results show that the onset temperature of PS chain rearrangement (T(onset)), which was much lower than the T(bulk)(g) of the corresponding PS block and higher than T(film)(g) of ultrathin PS films with corresponding thickness and molecular weights, generally increases with increasing density of the micelle core. It was found that the difference in ΔT(onset) with increasing relative density ρ/ρmin obtained from PS154-b-PAA49 and PS278-b-PAA47 micelles was large, while these from PS278-b-PAA47 and PS404-b-PAA63 was negligible, suggesting that entanglement has considerable influence on the density dependence of the T(onset) of PS chains under confinement in the micelle core on the film surface.

Programmed supramolecular nanoassemblies: enhanced serum stability and cell specific triggered release of anti-cancer drugs

“…1d), which are slightly lower than the value obtained from DLS. This is possibly due to the shrinkage of the particles in the dry state 64,65 or because of overestimation of the particle size in DLS, as here the average size is measured by taking into account the hydration shells around the particles. The morphology was further supported by atomic force microscopy images (AFM), which showed nearspherical nanostructures with the average height and width in the range of 6-16 nm and 100-120 nm, respectively (Fig.…”

Surface dynamics of poly(methyl methacrylate) films affected by the concentration of casting solutions

“…Effect of the concentration of casting solution on surface dynamics of the corresponding spin-coated PMMA lms Contact angle measurement is one of the most effective and sensitive methods for studying surface reconstruction and chain relaxation. 19,57,58,69,70 The apparent activation energy (E a ) for the surface relaxation of uorine-labeled PMMA lms prepared from various concentrations of casting solutions was examined on the basis of the time-temperature superposition principle for chain dynamics. The above results showed that variation in contact angle on PMMA lms aer being annealed was attributed to changes in chemical components on the lm surface.…”

Segmental Relaxation Dynamics of the Core and Corona in a Single Dry Micelle

“…The micelles were prepared according to our previously reported method. 19 The amphiphilic block copolymers were completely dissolved in dioxane at a concentration of 0.5 wt % and then filtered through a 0.45 μm porous polytetrafluoroethylene (PTFE) film. Subsequently, Milli-Q water was slowly added to the solution to induce aggregation of the PS or PMMA chains.…”

“…The sum frequency generation (SFG) spectra of the micelle film were obtained using a custom-designed EKSPLA SFG spectrometer described previously. 19 The morphology of single micelles was observed on an Ultra 55 scanning electron microscope (SEM) (Zeiss, Germany) and a Multimode 8 AFM (Bruker Co., Germany). Phase image and height image of micelles were obtained using AFM.…”

“…Consequently, these dynamics play an important role in developing nanotechnologies ranging from organic electronics to drug delivery. − The dynamic properties of a polymer approaching the nanometer scale, such as glass transition, − crystallization, − and viscosity, , have been widely reported to deviate from its bulk properties. To date, most studies have focused on the geometry of polymer thin films ,,− because of the convenience of sample preparation and variety of available characterization techniques, whereas few have focused on other geometries. − As polymers confined to higher geometrical dimensionalities become increasingly important in the application of nanotechnologies, understanding the size effects for other geometries is urgently required.…”