Angew SI Rev2 - Wiley-VCH

Supporting Information

for

Angew. Chem. Int. Ed. 200460382

© Wiley-VCH 2004

69451 Weinheim, Germany

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Recognition of Polyimide Sequence-Information by a Molecular Tweezer

H.M. Colquhoun* and Z. Zhu

School of Chemistry, University of Reading, Whiteknights, Reading, UK RG6 6AD

Fax: (+)44 118 378 8454. Email: [email protected]

________________________________________________________________________

Materials and Instrumentation

Pyromellitic dianhydride (PMDA) and 5,5’-(hexafluoroisopropylidene)di-o-toluidine were obtained

from Aldrich and were used as received. The sulfone-based diamine 4,4’-bis[4-(3-aminophenoxy)-

benzenesulfonyl)]biphenyl (4) was synthesised as previously reported (ref. 14). The polymerisation

solvent N,N-dimethylacetamide (DMAc) was distilled over calcium hydride before use. Proton and

13C NMR spectra were recorded on a Bruker DPX 250 MHz spectrometer with chemical shifts

referenced to residual solvent resonances. Assignments of proton resonances were made with

reference to 2-dimensional (COSY) spectra. UV-visible spectra were measured at 20 °C on a Perkin

Elmer Lambda-25 spectrometer. Polymer glass transition onset temperatures were determined by

DSC under nitrogen, at a heating rate of 10°C min-1, using a Mettler DSC20 system. Inherent

viscosities (ηinh) of polyimides were measured at 25 °C on 0.1% polymer solutions in 1-methyl-2-

pyrrolidinone using a Schott-Geräte CT-150 semi-automated viscometer. Molecular weights of

polyimides relative to polystyrene standards were determined by gel permeation chromatography

(GPC) on a Polymer Laboratories PL-220 instrument equipped with a differential refractive index

detector and 2 × PLgel 10 µm Mixed B columns. Analyses were carried out in DMF/LiBr solution

(0.01 M in LiBr) at 60 °C, at a flow rate of 1.0 mL min-1 and with an injection volume of 100 µl.

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Samples were dissolved in DMF/LiBr at a concentration of 1 mg mL-1, and both eluent and sample

solutions were filtered through a 0.02 µm PTFE membrane prior to injection.

Synthesis and characterisation of polyimides 3, 7 and 8

The synthesis of homopolyimide 3 is taken as an example. Diamine 4 (0.811 g, 1.25 mmol) was

dissolved in DMAc (5 mL) by stirring at room temperature, and when the diamine was completely

dissolved, pyromellitic dianhydride (0.273 g, 1.25 mmol) was added in one portion. The anhydride

dissolved over ca. 1 h to give a highly viscous, pale yellow solution which was stirred for a further

20 h, then transferred to a Petri dish and heated at 80 °C under vacuum for 2 h to remove the

solvent. The resulting film of polyamic acid was imidized by heating sequentially to 120 °C for 10

min, 150 °C for 10 min, 180 °C for 10 min, 210 °C for 10 min and finally at 250 °C for 30 min. The

polyimide film was dissolved in DMF and reprecipitated in methanol to give uniform beads of

polymer which were dried at 80 °C for 2 h. These were extracted with refluxing chloroform in a

Soxhlet apparatus for 15 h to remove traces of macrocyclic by-products, and were finally dried

under vacuum at 100 °C for 2 h.

Polyimide 3: Yield 92%, Tg 300 °C, ηinh = 1.00 dL g-1; Mn = 161 x 103 daltons; Mw = 289 x 103

daltons; 1H NMR (CDCl3/hexafluoro-propan-2-ol 6:1 v/v): δ = 8.44 (s), 7.95 (d, J = 8.4 Hz), 7.89 (d,

J = 8.8 Hz), 7.70 (d, J = 8.4 Hz), 7.59 (non-1st order t), 7.31 (d, J = 7.9 Hz), 7.17 (m); IR (film from

DMF): 1777, 1734 (imide νC=O), 1369 (νC-N), 1245 (νC-O-C), 1107, 725 cm-1.


daltons1; 1H NMR (CDCl3/hexafluoro-propan-2-ol, 6:1 v/v): δ = 8.47 (s), 8.44 (s), 7.95 (d, J = 8.4

Hz), 7.88 (d, J = 8.8 Hz), 7.70 (d, J = 8.4 Hz), 7.59 (non-1st order t), 7.47 (d, J = 8.3 Hz), 7.30 (d, J

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= 8.5 Hz), 7.16 (m); IR (film from DMF): 1779, 1728 (imide νC=O), 1365 (νC-N), 1244 (νC-O-C),

1107, 727 cm-1.


daltons; 1H NMR (CDCl3/hexafluoro-propan-2-ol, 6:1 v/v): δ = 8.52 (s), 8.45 (m), 7.95 (d, J = 8.4

Hz), 7.88 (d, J = 8.8 Hz), 7.70 (d, J = 8.4 Hz), 7.59 (non-1st order t), 7.47 (d, J = 8.4 Hz), 7.30 (d, J

= 7.8 Hz), 7.16 (m); IR (film from DMF): 1779, 1728 (imide νC=O), 1367 (νC-N), 1243 (νC-O-C),

1107, 726 cm-1.

Complexation studies

Determination of the stoichiometry of binding between tweezer 1 and homopolymer 3.

The stoichiometry of complexation betwen homopolymer 3 and tweezer 1 was determined by Job’s

method. Stock solutions (6mM) of polymer 3 and tweezer 1 in CHCl3/6FiPA (6:1, v/v) were

prepared in 20 ml volumetric flasks and, by varying the ratio of polymer 3 and tweezer 1 from 9:1 to

1:9 respectively, the sum of the concentrations of polymer 3 and tweezer 1 was maintained constant

at 3 mM. Ultraviolet-visible spectra were recorded using a 3.5 ml quartz curvette (1 cm path length),

and the absorbance at λmax (500 nm) for each solution was plotted against the fractional

concentration of tweezer 1. See Supporting Figure 5.

Determination of the 1:1 binding constant for tweezer 1 with homopolymer 3 (ref. 16)

A standard solution containing equimolar amount of polymer 3 (2 mM with respect to total imide

residues) and tweezer 1 in CHCl3/hexafluoro-propan-2ol (6:1, v/v) was made up in a 10 mL

volumetric flask, and the absorbance “A” of this solution at 500 nm was recorded. The solution was

then diluted accurately and the absorbance re-measured. This process of accurate dilution and re-

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measurement of absorbance was repeated six times to obtain seven sets of data. The experiment was

repeated with a second standard solution (1.75 mM), and seven-fold dilution yielded eight sets of

data. For full details of the method and of the data treatment see ref. 16.

1H NMR studies of the binding of tweezer 1 to polyimides 3, 7 and 8.

A stock solution of each polyimide (4mM with respect to total imide residues) in CHCl3/hexafluoro-

propan-2-ol (6:1 v/v) was prepared in a 5 mL volumetric flask, and 0.8 mL of this solution was

added to an NMR tube using a micropipette. The solution was slowly evaporated under nitrogen-

flow and the residue dried at 80 °C under vacuum for 4 h. A solution of tweezer molecule 1 in

CDCl3/hexafluoro-propan-2-ol (6:1 v/v) and having the required concentration of tweezer was

similarly prepared in a 5 mL volumetric flask. An aliquot of this solution (0.8 mL) was added to the

NMR tube by micropipette and mixed well to re-dissolve the polyimide before carrying out NMR

analysis. Peak assignments were made by reference to chemical shift data for known cyclic and

linear oligo-imides (ref. 14), by 2-dimensional (COSY) analyses (e.g. Supplementary Figure 10), by

evaluation of integrals, and by tracking incremental changes in peak positions on progressive

addition of tweezer 1.

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A = absorbance

c = concentration (mole L-1) of imide units (equimolar with tweezer)

Intercept, y0 = 1.468 x 103 (standard error = 0.054 x 103)

Slope, α = 0.414 (standard error = 0.029)

Error bars show the standard errors of estimate.

Ka = y0/α2 = 8565 M-1 (standard error = 940 M-1)

So that: Ka = 8.6 (± 0.9) x 103 M-1

Supporting Figure 4. Binding constant plot for polymer 3 with tweezer 1 (UV-visible dilution

method in CHCl3/hexafluoropropan-2-ol, 6:1 v/v).

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Supporting Figure 5. Job plot (based on the charge-transfer absorption band at 500 nm) for complexation oftweezer 1a with homopolymer 3 in chloroform/hexapropan-2-ol (6:1 v/v.), confirming 1:1 stoichiometry ofbinding between the tweezer and the pyromellitimide residue.

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Supporting Figure 6. GPC chromatogram of homopolymer 3 in NMP/LiBr (0.01 M). Mn = 161 x 103

daltons; Mw = 289 x 103 daltons.

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Supporting Figure 7. GPC chromatogram of copolymer 7 in NMP/LiBr (0.01 M). Mn = 60 x 103 daltons;Mw = 96 x 103 daltons.

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Supporting Figure 8. GPC chromatogram of copolymer 8 in NMP/LiBr (0.01 M). Mn = 103 x 103 daltons;Mw = 188 x 103 daltons.

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Supporting Figure 9. Infra-red spectrum of co-polyimide 8 (film from DMF).

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Supporting Figure 10. Two-dimensional (COSY) 1H NMR spectrum of copolymer 7 plus tweezer 1(1:4 mole ratio).

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