Size Effect of the End-Attached Particle on the Adsorption-Responsive Polymer Switches

Abstract

Using analytical theory and self-consistent field calculations, we study the conformation behaviors and switching properties of an adsorption-active polymer chain with its free end attached to a hard-core nanoparticle included in an inert brush. The conformation switches are induced by the short-ranged adsorption from the substrate. Particularly, we focus on the influence of particle size and quantify the switching properties by evaluating the transition point, transition width, and transition barrier. Our results indicate that the particle–polymer system exhibits different phases and transition features compared to the particle-free system only when the particle is large enough. To characterize the particle size, we define two critical particle radii R* and R c. If R > R*, the particle could be stuck at the brush surface exhibiting a partially exposed state, which cannot be observed in the particle-free polymer switches. On the contrary, if the particle is small, only two states, the exposed state and the adsorbed state, are involved. When R > R c, the transition properties show different dependence on the system parameters like the grafting density of the brush, the solvent quality, and the length of the polymer chains. Analytical expressions for the transition point, transition width, and transition barrier are derived. The obtained scaling formulas at the small particle and large particle limits are verified by the self-consistent field calculations. Our analysis concludes that a large particle attached to the end of the active chain mainly broadens the transition width while keeps the transition barrier as small as that in the free-particle system as the system parameters are carefully tuned. Strong osmotic repulsion imposed on the finite volume particle is responsible for the particular phase and transition characteristics observed in the present particle–polymer switches.

Controlling Adsorption of Diblock Copolymer Nanoparticles onto an Aldehyde-Functionalized Hydrophilic Polymer Brush via pH Modulation

“…70,71 On close approach to a well-solvated brush, proteins (and other biomacromolecules) typically experience a strong repulsive interaction owing to an increase in osmotic pressure. 72,73 The magnitude of this force depends on the inter-separation distance, brush grafting density, 72 and particle size, 74,75 as well as the precise geometry. 76 If nanoparticle adsorption is desired, then an attractive interaction force between the brush and the nanoparticles must be introduced to overcome the repulsive force.…”

“…Non-ionic and zwitterionic hydrophilic polymer brushes are well-known for their ability to minimize biofouling. , On close approach to a well-solvated brush, proteins (and other biomacromolecules) typically experience a strong repulsive interaction owing to an increase in osmotic pressure. , The magnitude of this force depends on the inter-separation distance, brush grafting density, and particle size, , as well as the precise geometry …”

Height-Switching in a Mixed Polymer Brush Induced by the Collapse Transition of Attractive Polymer Chains

“…They noted that longer responsive polymers and a smaller fraction of responsive polymers would be more effective . Similarly, a sufficiently large nanoparticle attached to the adsorption-active longer polymer chain can change from the exposed state at the weak surface attraction to a partially exposed state at the mediate surface attraction and finally to the immersed state at the strong surface attraction …”

“…40 Similarly, a sufficiently large nanoparticle attached to the adsorption-active longer polymer chain can change from the exposed state at the weak surface attraction to a partially exposed state at the mediate surface attraction and finally to the immersed state at the strong surface attraction. 41 Inspired by the studies of height-switching in mixed polymer brushes, we built a polymer brush consisting of repulsive polymers and attractive longer polymers and studied the height-switching phenomenon induced by the collapse transition of the attractive polymer chains. Our Langevin dynamics (LD) simulation results show that, for the brush with low grafting density, the collapse transition of the sparsely grafted attractive polymer chains can induce a height-switching phenomenon; e.g., the attractive polymer chains are in the exposed state above the collapse transition temperature T c whereas they are in the immersed state below T c .…”