Minimizing Defects in Polymer-Based Langmuir–Blodgett Monolayers and Bilayers via Gluing

Abstract

Polymeric surfactants were prepared by quaternization of poly(4-chloromethylstyrene) with N,N-dimethyl-N-n-dodecylamine and N,N-dimethyl-N-n-octylamine to give 1 and 2, respectively. Each of these polymers formed stable monolayers at the air/water interface. Injection of poly(acrylic acid) (PAA) beneath the surface of these films led to a substantial increase in their cohesiveness (i.e., "gluing"), as evidenced by a dramatic increase in their surface viscosity. Examination of monolayers of 1 by atomic force microscopy, after being transferred to silicon wafers that were surface-modified with n-octadecyltrichlorosilane, showed that the presence of PAA leads to intact film. In contrast, transfer of unglued monolayers resulted in poor coverage. Comparison of the barrier properties of single glued and unglued LB bilayers formed in the presence and in the absence of PAA have shown that PAA minimizes defect formation within these ultrathin assemblies.

Engineering membranes with macrocycles for precise molecular separations

“…167 Regen and coworkers have intensely investigated the gas permeability of surfactant-like calix[n]arenes-containing membranes by the Langmuir-Blodgett (LB) method. [168][169][170][171][172][173][174][175][176][177][178][179] Such membranes would act like molecular sieves and the presence of multiple hydrocarbon chains structure in each surfactant would enhance the cohesiveness of these assemblies, thereby minimizing the defect formation. In order to improve the stability of the LB membrane, the head of calixarene-based surfactants have been designed with specific groups, such as disulfide moieties for photo-cross-linking, amide oxime groups for hydrogen bonding, quaternary ammonium-based groups for ionic crosslinking.…”

Amphiphile nanoarchitectonics: from basic physical chemistry to advanced applications

“…288 The gluing not only improves the quality and stability of the LB films but also their permselectivity characteristics for nanomembranebased applications. 289 The role of porous and nonporous amphiphiles and the effect of counterions on gluing and gas separation have been explored. 290 Further research is needed to improve the membrane characteristics for molecular sieving applications.…”

Structural Transition of Poly(L-lactic acid) Film Induced by Compression at Air/Water Interface

“…As for such amphiphilic copolymers or polymeric surfactants, the hydrophilic block or the polar head groups reside readily in the subphase due to their good affinity with water. 29,30 In contrast, PLLA tends to form intra-or inter-molecular aggregates due to the intra-and inter-molecular interactions of itself and the relatively strong hydrophobicity of the repeat monomer. The multilayer structure is closely consistent with the result of the π-A isotherm and explain why the area of the repeat unit is much smaller than expected.…”