Adsorption Of Triblock Copolymers Research Articles

Physical and chemical insights into molecular adsorption of copolymer’s monomers on Rutile surface

The adsorption of triblock copolymer’s moieties such as DME, 1,2-DME, and 1,2-DMP on a Rutile surface has been studied by DFT. The insights into their adsorption mechanism have been investigated by analyzing various physical and chemical properties such as the adsorption energies, the structural properties, difference of charge density, density of state, bond overlap population, and the atomic partial charge. Dispersion interaction plays a major role on the absorption energy in 1,2-DME, and the upward bridging oxygen configurations of DME and 1,2-DMP; whilst electrostatic and polarization energies are insignificant. A new Ob-Ti bond has been formed from the overlap of lone-pair electrons between orbital O 2p and Ti 3d in downward bridging oxygen configurations of DME and 1,2-DMP, which results in a significantly larger adsorption energies compared with other configurations. The molecular torsion is considered as a barrier that prevent Ob-down of 1,2-DME to create the bond with Ti.

Adsorption of triblock copolymers and their homopolymers at laponite clay/solution interface. Role played by the copolymer nature

The adsorption thermodynamics of copolymers, based on ethylene oxide (EO) and propylene oxide (PO) units, at the laponite (RD) clay/liquid interface was determined at 298 K. The copolymer nature was tuned at molecular level by changing the hydrophilicity, the architecture and the molecular weight (Mw) keeping constant the EO/PO ratio. Polyethylene (PEGs) and polypropylene (PPGs) glycols with varying Mw and their mixture were also investigated to discriminate the role of the EO and the PO segments in the adsorption process. Enthalpies of transfer of RD, at fixed concentration, from water to the aqueous macromolecule solutions as functions of the macromolecule molality were determined. They were treated quantitatively by means of a model based on two equilibria: (1) one-to-one binding between the macromolecule and the site on the solid and (2) two-to-one binding following which one macromolecule interacts with another one adsorbed onto the solid. The good agreement between the equilibrium constants obtained from calorimetry and those determined from kinetic experiments confirmed the reliability of the experimental and theoretical approaches. Almost all of the systems investigated are highlighted by the one-to-one binding; the L35 and 10R5 systems present both equilibria. The insights provided by the thermodynamics of adsorption of their homopolymers onto RD were fruitful in obtaining detailed information on the nature of the forces involved between RD and the copolymers. The data obtained in the present work clearly evidenced that for comparable polymer Mw, PPG is more suitable in building up a steric barrier around the RD particles and, indeed, exhibits several advantages and no drawbacks. Moreover, the parent copolymers may properly functionalize the RD surface by exploiting both their high affinity to the solid surface and the ability to self-assemble onto it as L35 and 10R5 clearly showed.

Adsorption of triblock copolymers on rough surfaces

The adsorption of ABA triblocks in a good solvent for the B block and a bad solvent for the A segment onto a corrugated sat face is studied. Under favorable conditions, the A moieties bind to the ridges of the bumpy surface surface and the B segments span the wells that lie between two ridges. The effect of the chain length and the value of χ BS , the interaction energy between the B block and the surface, are studied