ARTICLES
3. Segura, J. L. & Martin, N. o-Quinodimethanes: Efficient intermediates in organic
synthesis. Chem. Rev. 99, 3199–3246 (1999).
4. Deeter, G. A., Venkataraman, D., Kampf, J. W. & Moore, J. S. Reactivity of
disubstituted benzocyclobutenes: Model compounds of cross-linkable high-
performance polymers. Macromolecules 27, 2647–2657 (1994).
5. Kraus, A., Gugel, A., Belik, P., Walter, M. & Mu¨llen, K. Covalent attachment of
various substituents in closest proximity to the C60-core: A broad synthetic
approach to stable fullerene derivatives. Tetrahedron 51, 9927–9940 (1995).
6. Harth, Eva. et al. A facile approach to architecturally defined nanoparticles via
intramolecular chain collapse. J. Am. Chem. Soc. 124, 8653–8660 (2002).
In conclusion, ketenes formed by the thermolysis of modular
Meldrum’s acid derivatives have been demonstrated to have signifi-
cant potential for general materials functionalization with the
approach being versatile in both monomer and polymer backbone
selection. The inherent chemistry of ketenes, specifically the
ability to provide crosslinking, act as a reactive chemical handle,
or both, allows this simple and modular chemistry to be applied
to a variety of challenges in materials, including covalent microcon-
tact printing of crosslinked thin films. This strategy highlights the
robust, efficient and orthogonal nature of Meldrum’s acid as a
monomer building block and the significant opportunities
afforded by the traditionally neglected ketene functional group in
polymer chemistry.
´
7. Kim, Y., Pyun, J., Frechet, J. M. J., Hawker, C. J. & Frank, C. W. The dramatic
effect of architecture on the self-assembly of block copolymers at interfaces.
Langmuir 21, 10444–10458 (2005).
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8. Pyun, J., Tang, C., Kowalewski, T., Frechet, J. M. J. & Hawker, C. J. Synthesis and
direct visualization of block copolymers composed of different macromolecular
architectures. Macromolecules 38, 2674–2685 (2005).
9. Ryu, D. Y., Shin, K., Drockenmuller, E., Hawker, C. J. & Russell, T. P.
A generalized approach to the modification of solid surfaces. Science 308,
236–239 (2005).
10. Leiston-Belanger, J. M., Russell, T. P., Drockenmuller, E. & Hawker, C. J.
A thermal and manufacturable approach to stabilized diblock copolymer
templates. Macromolecules 38, 7676–7683 (2005).
11. Wang, Z. Y., Kuang, L., Meng, X. S. & Gao, J. P. New route to incorporation of
[60]fullerene into polymers via the benzocyclobutenone group. Macromolecules
31, 5556–5558 (1998).
12. Staudinger, H. Ketenes, a new compound class. Ber. Dtsch. Chem. Ges. 38,
1735–1739 (1905).
13. Tidwell, T. Ketenes (John Wiley & Sons, 2006).
14. Tidwell, T. T. Ketene chemistry after 100 years: Ready for a new century. Eur. J.
Org. Chem., 563–576 (2006).
15. Zarras, P. & Vogl, O. Ketenes and bisketenes as polymer intermediates. Prog.
Polym. Sci. 16, 173–201 (1991).
16. Staudinger, H., Felix, F., Meyer, P., Harder, H. Helv. Chim. Acta, 8,
322–332 (1925).
17. Pregaglia, G., Binaghi, M. Ketene polymers. Enc. Polym. Sci. Technol. 8, 45–57 (1968).
18. Sudo, A., Uchino, S. & Endo, T. Development of a living anionic polymerization
of ethylphenylketene: A novel approach to well-defined polyester synthesis.
Macromolecules 32, 1711–1713 (1999).
19. Nagai, D., Sudo, A. & Endo, T. Anionic alternating copolymerization of ketene
and aldehyde: Control of enantioselectivity by bisoxazoline-type ligand for
synthesis of optically active polyesters. Macromolecules 39, 8898 (2006).
20. Wolfgang, K., 100 years of the Wolff rearrangement. Eur. J. Org. Chem.,
2193–2256 (2002).
21. Dammel, R. R. Diazonaphthoquinone-Based Resists (SPIE Optical Engineering
Press, 1993).
22. Goodwin, A. P., et al. Synthetic micelle sensitive to IR light via a two-photon
process. J. Am. Chem. Soc. 127, 9952–9953 (2005).
Methods
Diels-Alder reaction for the synthesis of 20,20-dimethyl-spiro[bicyclo[2.2.1]hept-
5-ene-2,50-[1,3]dioxane]-40,60-dione (9). To a solution of freshly cracked
cyclopentadiene (820 mg, 12.4 mmol) in CH3CN (10 ml) was added acetic acid
(750 mg, 12.5 mmol). To the solution was added a suspension of 1-[(6-hydroxy-2,2-
dimethyl-4-oxo-4H-1,3-dioxin-5-yl)methyl]pyridinium hydroxide, inner salt (8)
(1.95 g, 8.30 mmol) in CH3CN (20 ml) at 0 8C. The yellow colour gradually
disappeared upon addition. After stirring for 1 h at 0 8C, water (30 ml) was
added and the mixture was extracted with EtOAc (3 ꢀ 100 ml). The combined
ether layer was dried over MgSO4, filtered and concentrated in vacuo to yield a
crude product as a yellowish white solid (2.38 g). The crude product was
further purified by flash column chromatography to afford the desired product 9
as a white solid. All new compounds were fully characterized
(see Supplementary Information).
Copolymerization of 7 with styrene via ATRP. The statistical copolymerization of 7
with styrene is illustrated by conditions that provide a polymer containing 2 mol% of
7 to styrene. ATRP initiator (1-bromoethyl)benzene (16.9 mg, 0.091 mmol), styrene
(2.50 g, 24.5 mmol), 5-benzyl-2,2-dimethyl-5-(4-vinylbenzyl)-[1,3]dioxane-4,6-
dione (7) (175 mg, 0.50 mmol), and 4,40-dinonyl-2,20-bipyridine (74.4 mg,
0.18 mmol) were added to a 20 ml scored ampule and the solution was
deoxygenated by freezing in liquid nitrogen under vacuum and subsequent thawing
to room temperature. This process was repeated twice, the ampule was filled with
nitrogen and CuBr (13 mg, 0.091 mmol) was added. The ampule was again frozen
by liquid nitrogen under vacuum and subsequently thawed to room temperature.
This process was repeated twice, the ampule was sealed, and the brown solution was
placed in an oil bath at 110 8C for 17 hours. The viscous solution was quenched by
exposing to air, diluted with 15 ml THF, and precipitated into 200 ml methanol. The
resulting product was a white powder (conversion ¼ 74%, Mn ¼ 23.7 kg mol–1
,
PDI ¼ 1.12).
´
Synthesis of polymer PMANB (14) by ROMP. A vial was charged with Grubbs
catalyst III (9 mg, 11 mmol) and 1 ml of dry CH2Cl2 under nitrogen atmosphere.
A solution of monomer 9 (100 mg, 0.45 mmol) in 3 ml of dry CH2Cl2 was
added at room temperature. After 30 min, the reaction was quenched by adding
excess ethyl vinyl ether (ꢁ10 equivalents). The solution was dripped into methanol
to precipitate the desired polymer. The resulting product was a white powder.
Yield: 92%, conversion: 100%, Mn: 11,200 g mol–1, PDI: 1.06.
23. Mynar, J. L., Goodwin, A. P., Cohen, J. A., Ma, Y., Fleming, G. R. & Frechet, J. M.
Two-photon degradable supramolecular assemblies of linear-dendritic
copolymers. Chem. Commun. 2007, 2081–2082 (2007).
24. Kumbaraci, V., Talinli, N. & Yagci, Y. Photoinduced crosslinking of polymers
containing pendant hydroxyl groups by using bisbenzodioxinones. Macromol.
Rapid Commun. 28, 72–77 (2007).
25. Tasdelen, M. A., Kumbaraci, V., Talinli, N. & Yagci, Y. Photoinduced cross-
linking polymerization of monofunctional vinyl monomer without conventional
photoinitiator and cross-linker. Macromolecules 40, 4406–4408 (2007).
26. Durmaz, Y. Y., Kumbaraci, V., Demirel, A. L., Talinli, N. & Yagci, Y. Graft
copolymers by the combination of ATRP and photochemical acylation process
by using benzodioxinones. Macromolecules 42, 3743–3749 (2009).
27. Meldrum, A. N. A b-lactonic acid from acetone and malonic acid. J. Chem. Soc.
93, 598–601 (1908).
28. Brown, R. F. C., Eastwood, F. W. & Harrington, K. J. Methyleneketenes and
methylenecarbenes. I. Formation of arylmethyleneketenes and alkylideneketenes
by pyrolysis of substituted 2,2-dimethyl-1,3-dioxan-4,6-diones. Aust. J. Chem.
27, 2373–2384 (1974).
mCP of TAMRA cadaverine fluorescent dye. A thin film of 10 was prepared by
spin casting a 20 wt% solution of 10 onto an 18 ꢀ 18 mm2 glass slide (spin
rate ¼ 1,500 rpm for 45 seconds). A poly[(mercaptopropyl)methylsiloxane]
stamp was fabricated by previously reported procedures39. The stamp was immersed
in a 0.02 M solution of TAMRA cadaverine in deionized water to ink for three
minutes. The stamp was removed from the solution, dried under a stream of
nitrogen, placed in conformal contact and pressed against the polymer surface for
two minutes. The stamp was observed to stick to the glass slide and was carefully
peeled off. The polymer film used as a control was stamped after spin casting.
In order to prepare a reactive surface of ketenes for covalent attachment of TAMRA
cadaverine, a polymer film was placed on a microscope hot stage for two minutes
at 225 8C. Fluorescence images were obtained after printing. The slides were
immersed in water under slight convection (60 rpm) for 12 hours. The slides
were removed from water, dried and reimaged.
29. Baxter, G. J., Brown, R. F. C., Eastwood, F. W. & Harrington, K. J. Pyrolytic
generation of carbonylcyclopropane (dimethylene ketene) and its dimerization
to dispiro-[2,1,2,1]-octane-4,8-dione. Tetrahedron Lett. 16, 4283–4284 (1975).
30. Hyatt, J. A. & Raynolds, P. W. Ketene cycloadditions. Org. React. 45,
159–646 (1994).
Received 30 July 2009; accepted 15 December 2009;
published online 31 January 2010
31. Zia-Ebrahimi, M. & Huffman, G. W. Synthesis and utility of a novel methylene
Meldrum’s acid precursor. Synthesis 215–218 (1996).
32. Matyjaszewski, K. & Xia, J. Atom transfer radical polymerization. Chem. Rev.
101, 2921–2990 (2001).
33. Hiraoka, H. Photochemistry of glutaric anhydride type polymers.
Macromolecules 9, 359–360 (1976).
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34. Lucas, N. C., Netto-Ferreira, J. C., Andraos, J. & Scaiano, J. C. Nucleophilicity
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211
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