To understand how polymers physisorb onto solid surfaces, we investigated the physisorption behavior of non-charged, semiflexible poly(9,9-dioctylfluorene) (PF8) with three different number-average degrees of polymerization (DPn) as photoluminescent and chromophoric probes onto cuboidal γ-alumina in toluene at 5, 25, and 50 °C. PF8 revealed noticeable DPn and temperature dependencies in its physisorption behaviors. Molecular mechanics (MM)/molecular dynamics (MD) simulations [consistent valence force field (CVFF)] and Møller–Plesset second-order perturbation theory (MP2) with 6-31 G(d,p) calculations suggested that the PF8 in toluene has multiple interactions from CH/π to C–H/O interactions on the (110) surface of γ-alumina. The competition between multiple intermolecular CH/π and C–H/O interactions was crucial for the spontaneous physisorption of PF8 to occur in the presence of a solvent quantity of toluene. Calculations by time-dependent density functional theory (TD-DFT) with Becke three parameter Lee-Yang-Par (B3LYP) method and 6–31 G(d,p) basis set of a model fluorene 9-mer indicated that the π–π* absorption wavelength largely depends on the regularity of the dihedral angles between fluorene rings, while the intensity and spectral width of the π–π* absorption band are largely influenced by the regularity of the dihedral angles. Solution-phase physisorption systems are a result of the inherent nature of several competitive weak intermolecular interactions coexisting among the polymers, surface, and solvents.
Subscribe to Journal
Get full journal access for 1 year
only $24.92 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Parfitt GD, Rochester CH, Editors. Adsorption from solution at the solid/liquid interface. New York: Academic; 1983.
Jones RAL, Richards RW. Polymers at surface and interfaces. Cambridge, UK: Cambridge University Press; 1999.
Butt H-J, Graf K, Kappl M. Physics and chemistry of interfaces. Germany: Wiley–VCH, Weinheim; 2006.
Israelachvili YN. Intermolecular and surface forces. 3rd edn. New York: Academic; 2011.
Langmuir I. The adsorption of gases on plane surface. J Am Chem Soc. 1918;40:1361–403.
Brunauer S, Emmett PH, Teller E. Adsorption of gases in muitimolecular layers. J Am Chem Soc. 1938;60:309–19.
Simha R, Frish HL, Eirich RR. The adsorption of flexible macromolecules. J Phys Chem. 1953;57:584–9.
Dąbrowski A. Adsorption–from theory to practice. Adv Colloid Interface Sci. 2001;93:135–224.
Sagiv J. Organized monolayers by adsorption. 1. Formation and structure of oleophobic mixed monolayers on solid surfaces. J Am Chem Soc. 1980;102:92–8.
Netzer N, Sagiv J. A new approach to construction of artificial monolayer assemblies. J Am Chem Soc. 1983;105:674–6.
Park J-W, Park YJ, Jun C-H. Post-grafting of silica surfaces with pre-functionalized organosilanes: new synthetic equivalents of conventional trialkoxysilanes. Chem Commun. 2011;47:4860–71.
Guo G, Naito M, Fujiki M, Saxena A, Okoshi K, Yang Y, Ishikawa M, Hagihara T. Room-temperature one-step immobilization of rod-like helical polymer onto hydrophilic substrates. Chem Commun. 2004;276–7.
Yamamoto K, Otsuka H, Takahara A. Preparation of novel polymer hybrids from imogolite nanofiber. Polym J. 2007;39:1–15.
Porter MD, Bright TB, Allara DL, Chidsey CED. Spontaneously organized molecular assemblies. 4. Structural characterization of n-alkyl thiol monolayers on gold by optical ellipsometry, infrared spectroscopy, and electrochemistry. J Am Chem Soc. 1987;109:3559–73.
Berndt P, Kurihara K, Kunitake T. Adsorption of poly(styrenesulfonate) onto an ammonium monolayer on mica: A surface forces study. Langmuir. 1992;113:2486–90.
Kumar A, Whiteside GM. Features of gold having micrometer to centimeter dimensions can be formed through a combination of stamping with an elastomeric stamp and an alkanethiol “ink” followed by chemical etching. Appl Phys Lett. 1993;63:2002–4.
Lvov Y, Decher G, Möhwald H. Assembly, structural characterization, and thermal behavior of layer-by-layer deposited ultrathin films of poly(vinyl sulfate) and poly(allylamine). Langmuir. 1993;9:481–6.
Brust M, Walker M, Bethell D, Schiffrin DJ, Whyman R. Synthesis of thiol-derivatised gold nanoparticles in a two-phase liquid–liquid system. J Chem Soc Chem Commun. 1994;1801–2.
Lvov Y, Ariga K, Ichinose I, Kunitake T. Assembly of multicomponent protein films by means of electrostatic layer-by-layer adsorption. J Am Chem Soc. 1995;117:6117–23.
Kotov NA, Dekany I, Fendler JH. Layer-by-layer self-assembly of polyelectrolyte–semiconductor nanoparticle composite films. J Phys Chem. 1995;99:13065–9.
Decher G. Fuzzy nanoassemblies: toward layered polymeric multicomposites. Science. 1997;277:1232–7.
Caruso F. Nanoengineering of inorganic and hybrid hollow spheres by colloidal templating. Science. 1998;282:1111–4.
Ejaz M, Yamamoto S, Ohno K, Tsujii Y, Fukuda T. Controlled graft polymerization of methyl methacrylate on silicon substrate by the combined use of the Langmuir-Blodgett and atom transfer radical polymerization techniques. Macromolecules. 1998;31:5934–6.
Zhao B, Brittain WJ. Polymer brushes: surface-immobilized macromolecules. Prog Polym Sci. 2000;25:677–710.
Matyjaszewski K, Xia J. Atom transfer radical polymerization. Chem Rev. 2001;101:2921–90.
Pyun J, Matyjaszewski K. Synthesis of nanocomposite organic/inorganic hybrid materials using controlled “living” radical polymerization. Chem Mater. 2001;13:3436–48.
Zhou F, Huck WTS. Surface grafted polymer brushes as ideal building blocks for “smart” surface. Phys Chem Chem Phys. 2006;8:3815–23.
Mizukami M, Kurihara K. Macrocluster formation of alcohol on silica surface in cyclohexane: analysis of interfacial energy between adsorption layer and bulk solution. E J Surf Sci Nanotech. 2006;4:244–8.
Tsubokawa N. Surface grafting of polymers onto nanoparticles in a solvent-free dry-system and applications of polymer-grafted nanoparticles as novel functional hybrid materials. Polym J. 2007;39:983–1000.
Budarin VL, Clark JH, Hale SE, Tavener SJ, Mueller KT, Washton NM. NMR and IR study of fluorobenzene and hexafluorobenzene adsorbed on alumina. Langmuir. 2007;23:5412–8.
Pietropaolo A, Wang Y, Nakano T. Predicting the switchable screw sense in fluorene-based polymers. Angew Chem Int Ed. 2015;54:2688–92.
Zhang W, Gomez ED, Milner ST. Surface-induced chain alignment of semiflexible polymers. Macromolecules. 2016;49:963–71.
Grell M, Bradley DDC, Long X, Chamberlain T, Inbasekaran M, Woo EP, Soliman M. Chain geometry, solution aggregation and enhanced dichroism in the liquid crystalline conjugated polymer poly(9,9-dioctylfluorene). Acta Polym. 1998;49:439–44.
Grell M, Bradley DDC, Ungar G, Hill J, Whitehead KS. Interplay of physical structure and photophysics for a liquid crystalline polyfluorene. Macromolecules. 1999;32:5810–7.
Scherf U, List EJW. Semiconducting polyfluorenes towards reliable structure-property relationships. Adv Mater. 2002;14:477–87.
Knaapila M, Garamus VM, Dias FB, Almásy L, Galbrecht F, Charas A, Morgado J, Burrows HD, Scherf U, Monkman AP. Influence of solvent quality on the self-organization of archetypical hairy rods-branched and linear side chain polyfluorenes: rodlike chains versus “beta-sheets” in solution. Macromolecules. 2006;39:6505–12.
Chen J-H, Chang C-S, Chang Y-X, Chen C-Y, Chen H-L, Chen S-A. Gelation and its effect on the photophysical behavior of poly(9,9-dioctylfluorene-2,7-diyl) in toluene. Macromolecules. 2009;42:1306–14.
Cone CW, Cheng RR, Makarov DE, V Bout DA. Molecular weight effect on the formation of β-phase poly(9,9-dioctylfluorene) in dilute solutions. J Phys Chem B. 2011;115:12380–5.
Evans RC, Marr PC. Chain confinement promotes β-phase formation in polyfluorene-based photoluminescent ionogels. Chem Commun. 2012;48:3742–4.
Liu C, Wang Q, Tian H, Liu J, Geng Y, Yan D. Morphology and structure of the β-phase crystals of monodisperse polyfluorenes. Macromolecules. 2013;46:3025–30.
Mei J, Leung NLC, Kwok RTK, Lam JWY, Tang BZ. Aggregation-induced emission: together we shine, united we soar! Chem Rev. 2015;115:11718–940.
Taguchi M, Suzuki N, Fujiki M. Intramolecular CH/π interaction of poly(9,9-dialkylfluorene)s in solutions: Interplay of the fluorene ring and alkyl side chains revealed by 2D 1H-1H NOESY NMR and 1D 1H-NMR experiments. Polym J. 2013;45:1047–57.
Suzuki N, Matsuda T, Nagai T, Yamazaki K, Fujiki M. Investigation of the intra-CH/π interaction in dibromo-9,9′-dialkylfluorenes. Cryst Growth Des. 2016;16:6593–9.
Nakao A, Fujiki M. Visualizing spontaneous physisorption of non-charged π-conjugated polymers onto neutral surfaces of spherical silica in nonpolar solvents. Polym J. 2015;47:434–42.
Nakao A. Molecular weight dependency of physisorption behavior. In: Elucidation of physisorption behaviors of π-conjugated polymers and characterization thereof, Chapter 3. PhD thesis, Nara Institute of Science and Technology; 2015, pp 64–96.
Bhowmik R, Katti KS, Katti D. Molecular dynamics simulation of hydroxyapatite–polyacrylic acid interfaces. Polym (Guildf). 2007;48:664–74.
Møller C, Plesset MS. Note on an approximation treatment for many-electron systems. Phys Rev. 1934;46:618–22.
Head-Gordon M, Pople JA, Frisch MJ. MP2 energy evaluation by direct methods. Chem Phys Lett. 1988;153:503–6.
Nishio M, Hirota M, Umezawa Y. The CH/π interaction: evidence, nature, and consequences. New York: John Wiley & Sons; 1998.
Tsuzuki S, Fujii A. Nature and physical origin of CH/π interaction: significant difference from conventional hydrogen bonds. Phys Chem Chem Phys. 2008;10:2584–94.
Takahashi O, Kohno Y, Nishio M. Relevance of weak hydrogen bonds in the conformation of organic compounds and bioconjugates: Evidence from recent experimental data and high-level ab initio MO calculations. Chem Rev. 2010;110:6049–76.
Sutor DJ. The CH···O hydrogen bond in crystals. Nature. 1962;195:68–9.
Desiraju GR. The C–H···O hydrogen bond: structural implications and supramolecular design. Acc Chem Res. 1996;29:441–9.
Gu Y, Kar T, Scheiner S. Fundamental properties of the CH···O interaction: is it a true hydrogen bond? J Am Chem Soc. 1999;121:9411–22.
Hohenberg P, Kohn W. Inhomogeneous electron gas. Phys Rev. 1964;136:B864–71.
Marques MAL, Ullrich CA, Nogueira F, Rubio A, Burke K, Gross EKU, Editors. Time-dependent density functional theory. Berlin, Germany: Springer-Verlag; 2006.
Ullrich C. Time-dependent density-functional theory: concepts and applications. Oxford: Oxford University Press; 2012.
Hildebrand JH, Scott RH. The solubility of nonelectrolytes: monograph series. American Chemical Society, No. 17; 2012.
Hansen CM. The three dimensional solubility parameter and solvent diffusion coefficient. Copenhagen: Danish Technical Press; 1967.
Wu L, Sato T, Tang. H-Z, Fujiki M. Conformation of a polyfluorene derivative in dolution. Macromolecules. 2004;37:6183–8.
Shiraki T, Shindome S, Toshimitsu F, Fujigaya T, Nakashima N. Strong main-chain length-dependence for the β-phase formation of oligofluorenes. Polym Chem. 2015;6:5103–9.
Marciniak J, Bakowicz J, Dobrowolski MA, Dziubek KF, Kazmierczak M, Paliwoda D, Rajewski KW, Sobczak S, Stachowicz M, Katrusiak A. Most frequent organic interactions compressed in toluene. Cryst Growth Des. 2016;16:1435–41.
Nakano Y, Liu Y, Fujiki M. Ambidextrous circular dichroism and circularly polarised luminescence from poly(9,9-di-n-decylfluorene) by terpene chirality transfer. Polym Chem. 2010;1:460–9.
Bondi A. van der Waals volumes and radii. J Phys Chem. 1964;68:441–51.
Rowland RS, Taylor R. Intermolecular nonbonded contact distances in organic crystal structures: comparison with distances expected from van der Waals radii. J Phys Chem. 1996;100:7384–91.
Guo G, Suzuki N, Fujiki M. Oligo- and polyfluorenes meet cellulose alkyl esters: Retention, inversion, and racemization of circularly polarized luminescence (CPL) and circular dichroism (CD) via intermolecular C-H/O=C interactions. Macromolecules. 2017;50:1778–89.
Guo S, Kamite H, Suzuki N, Wang L, Ohkubo A, Fujiki M. Ambidextrous chirality transfer capability from cellulose tris(phenylcarbamate) to nonhelical chainlike luminophores: Achiral solvent-driven helix-helix transition of oligo- and polyfluorenes revealed by sign inversion of circularly polarized luminescence and circular dichroism spectra. Biomacromolecules. 2018;19:449–59.
Saxena A, Guo G, Fujiki M, Yang Y, Ohira A, Okoshi K, Naito M. Helical polymer command surface: Thermodriven chiroptical transfer and amplification in binary polysilane film system. Macromolecules. 2004;37:3081–3.
KY acknowledges Profs. Hiroshi Fujisawa, Hironari Kamikubo, and Hiroharu Ajiro for stimulating discussion and profession guidance throughout his doctoral course work. We thank Noritake Koike and Shohei Katao for assistance with the SEM and WAXD observations and analyses. KY thanks Daichi Hirose at Dassault Systemes Biovia Co. (Tokyo, Japan) for generous technical help with the MM/MD simulations. KY acknowledges financial support from the NAIST Presidential Special Fund.
Conflict of interest
The authors declare that they have no conflict of interest.
About this article
Cite this article
Yamazaki, K., Nakao, A., Suzuki, N. et al. Molecular weight-dependent physisorption of non-charged poly(9,9-dioctylfluorene) onto the neutral surface of cuboidal γ-alumina in toluene. Polym J 50, 865–877 (2018). https://doi.org/10.1038/s41428-018-0046-6