Self-Assembly of Conjugated Polymers at the Air/Water Interface. Structure and Properties of Langmuir and Langmuir-Blodgett Films of Amphiphilic Regioregular Polythiophenes
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- 作者：Niels Reitzel ; Daniel R. Greve ; Kristian Kjaer ; Paul B. Howes ; Manikandan Jayaraman ; Steve Savoy ; Richard D. McCullough ; John T. McDevitt ; and Thomas Bj
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- 刊名：Journal of the American Chemical Society
- 出版年：2000
- 出版时间：June 21, 2000
- 年：2000
- 卷：122
- 期：24
- 页码：5788 - 5800
- 全文大小：412K
- 年卷期：v.122,no.24(June 21, 2000)
- ISSN：1520-5126
文摘
This paper provides the first direct structural evidence describing conjugated polymer self-assemblyat the air-water interface. Grazing-incidence X-ray diffraction (GIXD) and X-ray reflectivity measurementson a number of derivatives of amphiphilic regioregular polythiophenes (e.g., poly(3'-dodecyl-3-(2,5,8-trioxanonyl)-2',5-bithiophene), polymer 1) show that these conjugated polymers self-assemble as 2-dimensionalpolycrystalline monolayers at the air/water interface with the amphiphilic polymers preorganized into rigidboards standing edge-on on the water surface. The monolayer consists of highly ordered (~70% crystalline)domains, with a centered rectangular unit cell having the polymer backbone along the a-axis and the thiophene
pi.gif" BORDER=0 >-stack along the b axis with a distance of 3.85-3.94 Å depending on the applied surface pressure. Thesedomains are connected by soft, more disordered boundaries. This is evidenced by the macroscopic compressibilityof the entire LB film (Cmacro 
p.gif"> 4-7 m/N) being one order of magnitude larger than the microscopiccompressibility (Cmicro p.gif"> 0.6 m/N) of the polycrystalline domains. The alkyl chains in the 3-position of thethiophene rings are in a crystallographically disordered state due to their cross-sectional mismatch with thepacking of the thiophenes. The importance of having the side chains coupled in a regioregular fashion to the3-position of the thiophene rings is evidenced by a dramatic increase in the coherence length of the crystallinedomains for highly regioregular samples (>95% head-tail couplings) as compared to less regioregularly coupledpolymers (~80% head-tail couplings). Transfer to solid support by the Langmuir-Blodgett technique inducesan overall orientation of the domains in the film, giving rise to a dichroic ratio of up to 4. Reflection-absorption infrared spectroscopy (RAIRS) shows that the alkyl chains of transferred films are in an all-transconformation with a locally ordered environment, having only few gauche defects.
pi.gif" BORDER=0 >-stack along the b axis with a distance of 3.85-3.94 Å depending on the applied surface pressure. Thesedomains are connected by soft, more disordered boundaries. This is evidenced by the macroscopic compressibilityof the entire LB film (Cmacro p.gif"> 4-7 m/N) being one order of magnitude larger than the microscopiccompressibility (Cmicro p.gif"> 0.6 m/N) of the polycrystalline domains. The alkyl chains in the 3-position of thethiophene rings are in a crystallographically disordered state due to their cross-sectional mismatch with thepacking of the thiophenes. The importance of having the side chains coupled in a regioregular fashion to the3-position of the thiophene rings is evidenced by a dramatic increase in the coherence length of the crystallinedomains for highly regioregular samples (>95% head-tail couplings) as compared to less regioregularly coupledpolymers (~80% head-tail couplings). Transfer to solid support by the Langmuir-Blodgett technique inducesan overall orientation of the domains in the film, giving rise to a dichroic ratio of up to 4. Reflection-absorption infrared spectroscopy (RAIRS) shows that the alkyl chains of transferred films are in an all-transconformation with a locally ordered environment, having only few gauche defects.