title: Langmuir-Blodgett-Kuhn and self-assembled films of asymmetrically substituted poly(paraphenylene).
abstract: 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 (pi-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 pi=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 pi=12 mN/m. Cross-section analysis of the AFM tapping-mode topography images of a single transferred monolayer reveals a thickness of d0=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 lambda=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.
authors.affiliation: Departments of Chemistry and of Materials Science, National University of Singapore, 10 Science Drive 4, Singapore 117543.
authors.forename: F
authors.initials: F
authors.lastname: Fitrilawati
authors.forename: R
authors.initials: R
authors.lastname: Renu
authors.forename: C
authors.initials: C
authors.lastname: Baskar
authors.forename: L G
authors.initials: LG
authors.lastname: Xu
authors.forename: H S O
authors.initials: HS
authors.lastname: Chan
authors.forename: S
authors.initials: S
authors.lastname: Valiyaveettil
authors.forename: K
authors.initials: K
authors.lastname: Tamada
authors.forename: W
authors.initials: W
authors.lastname: Knoll
mesh_terms: D000327:Adsorption; D007700:Kinetics; D018625:Microscopy, Atomic Force; D011108:Polymers / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D011108:Polymers