Langmuir−Blodgett−Kuhn and Self-Assembled Films of Asymmetrically Substituted Poly(paraphenylene)

• Published in: Langmuir Vol. 21; no. 26; pp. 12146 - 12152
• Main Authors: Fitrilawati, F, Renu, R, Baskar, C, Xu, L. G, Chan, H. S. O, Valiyaveettil, S, Tamada, K, Knoll, W
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 20.12.2005
• Subjects: Adsorption; Chemistry; Exact sciences and technology; General and physical chemistry; Kinetics; Langmuir blodgett films; Microscopy, Atomic Force; Polymers - chemistry; Spectrophotometry, Ultraviolet; Surface physical chemistry; Gas liquid interface; Self assembly; Monolayer; Atomic force microscopy; Compression; Film; In situ; Hydrophobicity; Air water interface; Solid; Characterization; Topography; Calculation; Langmuir Blodgett layer; Hysteresis; Multilayer; Polymer; Surface plasmon; Thickness; Substrate; Adsorption; Isotherm; Surface pressure; Resonance; Surface area; Ultraviolet visible spectrometry
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la0505667

Asymmetrically substituted poly(paraphenylene) (PhPPP) with hydrophilic and hydrophobic side chains was investigated. The polymer behavior at the air−water interface was studied on the basis of surface pressure−area (π−A) isotherms and compression/expansion hysteresis measurements. PhPPP can form stable monolayers with an area per repeat unit of A = 0.20 ± 0.02 nm2 and a collapse pressure in the range of π = 25 mN/m. Then, Langmuir−Blodgett−Kuhn (LBK) films of PhPPP were prepared by horizontally and vertically transferring the Langmuir monolayers onto hydrophilic solid substrates at π = 12 mN/m. Cross-section analysis of the AFM tapping-mode topography images of a single transferred monolayer reveals a thickness of d 0 = 0.9 ± 0.1 nm. Taking into account the obtained monolayer thickness, curve-fitting calculations of angular scan data of LB monolayers measured using surface plasmon resonance (SPR) spectroscopy lead to a value for the refractive index of n = 1.78 ± 0.02 at λ = 632.8 nm. Next, the spontaneous formation of a PhPPP monolayer by adsorption from solution was studied ex situ by atomic force microscopy and UV−vis spectroscopy and in situ by using SPR spectroscopy. Stable self-assembled monolayers of PhPPP can be formed on hydrophilic surfaces with a thickness similar to that of the monolayer obtained using the LB method. The characterization results confirmed the amphiphilic character and the self-assembly properties of PhPPP, as well as the possibility of preparing homogeneous monolayer and multilayer films.