Amphiphilic diblock copolymers containing poly(N‐hexylisocyanate): Monolayer behavior at the air–water interface

Abstract

The behavior of amphiphilic diblock copolymers containing 80-89% of poly(N-hexylisocyanate) (PHIC) with different hydrophobic segments spread at the air-water interface has been studied. Surface pressure-area isotherms (p-A) at the air-water interface were determined. It was found that these diblock copolymers form stable monolayers and the isotherms present a pseudoplateau region at low surface pressure, irrespective of the nature of the partner block: poly(styrene) (PS) or poly(isoprene). Surface pressure variation at the semidilute region of the monolayer was expressed in terms of the scaling laws as power function of the surface concentration. The critical exponents of the excluded volume m obtained for copolymers with PHIC and PS blocks are 0.58 for the copolymer with 85% of PHIC and 15% of PS, and 0.63 for the copolymer with 89% of PHIC and 11% of PS. The hydrophobicity degree of the diblock copolymers was estimated from the determination of the surface energy values by wettability measurements. The morphology of the monolayers was determined by means of Brewster angle microscopy. Molecular dynamic simulation was performed to explain the experimental behavior of diblock copolymers at the air-water interface.

Constraining Polymers into β-Turns: Miscibility and Phase Segregation Effects in Lipid Monolayers

“…This is approximately a doubling of the mean molecular area in regard to 6 and is thus in good agreement with the doubling of the molecular weight, as it has been seen before for the PIB conjugates. A shift of the transition to lower mean molecular area has previously been observed for PHICs with higher molecular weights due to the loss of rigidity [ 55 ] and for copolymers with PS and PI [ 58 ]. Thus, we assume that the β-turn mimetic structure leads to a higher packing density of the PHIC chains, which should lift out of the plane due to the hydrophilic anchor.…”

“…The surface properties of pure PHIC [ 54 , 55 , 56 , 57 ] and of copolymers with poly(2-vinyl pyridine), polyisoprene or polystyrene [ 58 , 59 ] have been previously investigated. Kawaguchi et al [ 54 ] found that pure PHIC forms a stable film on the air–water interface and comparison of experimental data with theoretical calculations suggested that the PHIC rods lay on the surface.…”

“…Once formed, these aggregates are difficult to deform upon expansion. Gargallo et al [ 58 ] observed a second pseudoplateau for pure PHIC at a surface pressure of around 12 mN·m −1 and an area around 15 Å 2 per repeating unit. They supposed that either a phase transition or the collapse of the monolayer is taking place.…”

Molecular Dynamics Simulation of Synthetic Polymers

“…A macromolecular complex system is formed by the interaction between the macromolecules of the same system. There are many macromolecular complex systems; this chapter will refer to complex systems of synthetic polymer blends (Donald R. P., 2000) and synthetic polymer at the airwater interface (Gargallo et al, 2011). The most synthetic polymers are characterized by flexible structure able to adopt multiple and variable forms.…”