Controlling Growth of Poly (Triethylene Glycol Acrylate-Co-Spiropyran Acrylate) Copolymer Liquid Films on a Hydrophilic Surface by Light and Temperature

Abstract

A quartz crystal microbalance with dissipation monitoring (QCM-D) was employed for in situ investigations of the effect of temperature and light on the conformational changes of a poly (triethylene glycol acrylate-co-spiropyran acrylate) (P (TEGA-co-SPA)) copolymer containing 12–14% of spiropyran at the silica–water interface. By monitoring shifts in resonance frequency and in acoustic dissipation as a function of temperature and illumination conditions, we investigated the evolution of viscoelastic properties of the P (TEGA-co-SPA)-rich wetting layer growing on the sensor, from which we deduced the characteristic coil-to-globule transition temperature, corresponding to the lower critical solution temperature (LCST) of the PTEGA part. We show that the coil-to-globule transition of the adsorbed copolymer being exposed to visible or UV light shifts to lower LCST as compared to the bulk solution: the transition temperature determined acoustically on the surface is 4 to 8 K lower than the cloud point temperature reported by UV/VIS spectroscopy in aqueous solution. We attribute our findings to non-equilibrium effects caused by confinement of the copolymer chains on the surface. Thermal stimuli and light can be used to manipulate the film formation process and the film’s conformational state, which affects its subsequent response behavior.

Thermoresponsive Behavior of Binary Waxes

“…The absorbed water in the deposited film could help to preserve the interface and structural uniformity since the smooth spiral shape in the change of energy dissipation as a function of the negative frequency shift demonstrated the interactions between bulk water and rapeseed wax composite without deformation (Figure 5a). [35,36] On the contrary, coconut and stearin waxes have single bonds and saturated fatty acid chains which result in their hydrophobic nature. Therefore, no frequency drop in the coconut wax composite profile at higher temperatures was observed (Figure 4c).…”

Temperature-responsive bioactive glass/polymer hybrids allow for tailoring of ion release

“…[26][27][28] Stimuli-responsive polymers can change their characteristics in a controlled way when activated by external factors. Depending on the polymer's structure, the triggering factors can be physical (such as temperature, light, mechanical force, magnetic fields, electric forces), [29][30][31][32] chemical (such as pH, redox reactions, presence of certain molecules) 33 or even biological (via enzymes). 27,28,32 Stimuli-responsive nanoparticles have recently gained significant attention due to their ability to regulate the dispersion or aggregation of colloidal particles.…”

Artifact Correction of Light Induced Detuning in QCM-D Experiments

“…Quartz crystal microbalance with dissipation (QCM-D) is a measurement technique, which is nowadays widely utilized for investigation of hard and soft interfaces. − The measurement technique can monitor in situ changes in interfacial molecular organization and is tolerant to several types of different adsorbents ranging from inorganic to organic molecules, macromolecules, or discrete nanosized objects in the size range ∼1 nm to 1 μm, and the technique can be applied for several liquids. This makes the QCM-D technique one of the most versatile and key research technologies for the investigation of dynamics of soft, solvated interfaces. , Especially the investigation of dynamic response becomes very attractive with the QCM-technique, which includes the response investigation of nano- and microstructural materials on different stimuli such as pH, , temperature, − light, − or chemical gradients. − However, the QCM-D investigations of photosensitive soft interfaces with respect to light triggered dynamic changes in interfacial properties have not been widely reported, since the quartz crystal itself is quite sensitive to illumination. Under exposure to light a frequency and dissipation shift is seen (see example plot in Figure ) and has been reported in the literature as the “light induced detuning” (LID). − The LID depends on many parameters such as light power and wavelength as well as on surrounding conditions.…”