Synthesis and SoluSynthesis and SoluCationic Fluorene-Thiophe

Andrea Gutackera), N. Koenena), S. AdamczyJ. Seixas de Melob), A.J.M. VaJ. Seixas de Melob), A.J.M. Va

a) Macromolecular Chemistry Group, Bergische Univa) Macromolecular Chemistry Group, Bergische Univb) Departamento de Química, Universidade

Abst

Water-soluble conjugated copolymers are currently of considerable interest forcomponents for optoelectronic systems. We have looked at novel cationic, conjuwhich have been synthesised in three steps. In the first step, monobromo-termwhich have been synthesised in three steps. In the first step, monobromo-termaverage molecular weight ca. 10 000 in a protocol first described by McCulloug9,9-bis(2-ethylhexyl)fluorene-7-boronic ester using Pd(PPh3)4 as catalyst and B3 4weight of the final diblock copolymer P1 was ca. 18 000, giving ca. 8 000 as thecationic copolymers is a quarternization of the bromoalkyl functions of the non-io

P2 is soluble in polar, protic solvents such as water and methanol. The optical pand solvent mixtures by UV/Visible absorption and photoluminescence (PL) spesolvatochromic effects are observed, which may be associated either with aggsolvatochromic effects are observed, which may be associated either with aggblock. Also results on the aggregation behaviour induced upon addition of oppos

SynthesisSynthesis

C6H12BrO

S n mBr B

O

O

C8H17C8H17(CH2)6Br

Pd(0), 8 h

C8H17 C8H178

SBrHn P1

N(CH3)3(CH2)6N+(CH3)3Br-

P1

C8H17 C8H17

S n m1d, THFP1

Scheme 1: Structure and reaction scheme of the polyfluorene-polythiopheneblock copolymer P1 and P2.

P2

block copolymer P1 and P2.

Atomic Force Microscopy

130 nm

7 μm7 μm0 nm

0 μm

Fig. 5 and 6: Contact-mode atomic force microscopy (AFM) images of drop-Fig. 5 and 6: Contact-mode atomic force microscopy (AFM) images of drop-cast thin layers of P2 onto a glass slide from methanol (0,03 mg/ml). The imageclearly shows the formation of collapsed vesicles with an average size of 2-5microns. (left: view from above; right: 3-dim. view).microns. (left: view from above; right: 3-dim. view).

Conc

• A cationic, water-soluble fluorene-thiophene diblock copolymer has

• The compound P2 is weakly fluorescent in water but more strongly• The compound P2 is weakly fluorescent in water but more strongly

• Solvatochromic changes both in emission and absorption may be at

• With anionic surfactants, such as SDS, marked spectral changes ar

• Future work will be directed to the complexation behaviour of P2 wit

R

1. l. Zhai, R. D. McCullough, Adv. Mater., 14 (202. G. Tu, H. Li, M. Forster, R. Heiderhoff, L. J. B3. U. Scherf, A. Gutacker, N. Koenen, Acc. Che

lution Behaviour oflution Behaviour ofhene Diblock Copolymers czyka), U. Scherfa), J. Pinab), S.M. Fonsecab), Valenteb), and H.D. Burrowsb) Valenteb), and H.D. Burrowsb)

niversität Wuppertal, D-42097 Wuppertal (Germany)niversität Wuppertal, D-42097 Wuppertal (Germany)e de Coimbra, 3004-535 Coimbra (Portugal)

stract

for applications in areas such as fluorescent chemical and biological sensors ornjugated block copolymers containing both polyfluorene and polythiophene blocks,erminated poly(3-bromohexylthiophene) (Br-P3BrHT) was prepared with a meanerminated poly(3-bromohexylthiophene) (Br-P3BrHT) was prepared with a meanugh et al [1]. The seconds step involves a Suzuki-type cross coupling of 2-bromo-

Br-P3BrHT as macromolecular end-capper [2]. The number average molecularhe molecular weight of the polyfluorene segment. The final step in synthesis of theionic precursor P1 with trimethylamine into the block polyelectrolyte P2 [3].

properties of this AB diblock copolymer P2 have been studied in various solventspectroscopy, coupled with atomic force microscopy (AFM) measurements. Markedaggregation or solvent-induced conformational changes within the polythiopheneaggregation or solvent-induced conformational changes within the polythiopheneositely charged surfactants (e.g. SDS) are presented.

Addition of SurfactantUV/Vis and PL Spectra Addition of SurfactantUV/Vis and PL Spectra

UV waterλ = 390 nm = 430 nm

0,8

1,0

0,8

1,0

(a.u

.)

n (a

.u.)

UV water UV methanol PL water PL methanol

λexc

= 390 nm

1200000

λexc

= 430 nm

u.)

0 2.4E-6 M 4E-6 M 1.28E-5 M 1E-4 M

0,4

0,6

0,4

0,6

Em

issi

on (

a.

Abs

orpt

ion

(

400000

800000

I (a.

u.)

300 400 500 600 700 8000,0

0,2

0,0

0,2 EmA

(nm)

500 600 700 8000

(nm)

Fig. 2: Emission spectra of the ionicpolythiophene blocks of P2 for the

Fig. 1: UV/Vis and photoluminescence(PL) spectra of the block copolymer

λ (nm) λ (nm)

polythiophene blocks of P2 for theaddition of sodium dodecyl sulfate(SDS) to aqueous solutions of P2(polymer concentration: 2x10-6 M;

(PL) spectra of the block copolymerP2 in water and methanol (PL spectra- excitation wavelength: 390 nm).

(polymer concentration: 2x10 M;excitation wavelength: 430 nm).

Polarity Effect

0,8

1,01,0

0 % THF 10 % THF 20 % THF30 % THF

λexc

= 430 nm

0,4

0,6

0,8

nm(a

.u.)

0,4

0,6

0,8

I (a.

u.)

30 % THF 40 % THF 50 % THF 60 % THF 70 % THF 80 % THF90 % THF

0,0

0,2

0,4

I 590

nm

0,0

0,2

0,4I 90 % THF

Fig. 3: Normalised fluorescence spectra Fig. 4: Fluorescence intensity at

0 20 40 60 80 1000,0

% THF

500 600 700 8000,0

λ (nm)

Fig. 3: Normalised fluorescence spectraof P2 (polymer concentration: 2x10-6 M)in aqueous solution and in 10, 20, …90 % THF mixtures.

Fig. 4: Fluorescence intensity atemission maximum of P2 (polymerconcentration: 2x10-6 M) as afunction of THF-water composition.90 % THF mixtures. function of THF-water composition.

nclusions

been synthesised and its spectral behaviour studied.

emissive in organic solvents such as methanol, THF and acetone.emissive in organic solvents such as methanol, THF and acetone.

attributed to changes in the polythiophene conformation and aggregation.

are seen that reflect the formation of well-ordered aggregates.

with anionic polyelectrolytes as polystyrene sulfonic acid (PSSA) or DNA.

References

2002) 901.. Balk, R. Sigel, U. Scherf, Small, 3 (2007) 1001.hem. Res., (2008), accepted.