Macromolecules requires one complete initiator molecule. Furthermore, if po- lymerization occurs much faster than disulﬁde lysis, such pro- cesses can be accomplished with presumably little damage to surrounding proteins and peptides. Researchers should be aware, however, that the disulﬁde degradation does occur and will presumably occur at a greater rate in the absence of unreacted monomer, such as occurs when polymers are overcured with signiﬁcant radical generation after the polymerization reaction is otherwise completed. ’ CONCLUSION The results presented herein demonstrate the versatility of radical rearrangement of disulﬁde bonds in hydrogels, but the implications extend to broad areas of polymer and biopolymer engineering. The radical lysis of disulﬁdes and resulting fragmen- tation reactions of thiyl radicals with disulﬁdes allowed for photodegradation, photoadaptation, and photohealing of hydro- gel materials. The application of photoradical generators for the initiation of these processes should expand to the manipulation of various disulﬁde-containing materials ranging from proteins and peptides to stabilized self-assembled amphiphilic materials to bulk adaptable materials generally. ’ AUTHOR INFORMATION Corresponding Author *E-mail: kristi.anseth@colorado.edu. Present Addresses §CSIRO Materials Science and Engineering, Clayton, Victoria 3169, Australia. ’ ACKNOWLEDGMENT The authors acknowledge funding from the National Science Foundation, grants CBET-0626023 and DMR-1006711. The authors also acknowledge Josh McCall for photographic assistance. ’ REFERENCES (1) Sawhney, A. S.; Pathak, C. P.; Hubbell, J. A. Macromolecules 1993, 26, 581–587. (2) Lutolf, M. P.; Lauer-Fields, J. L.; Schmoekel, H. G.; Metters, A. T.; Weber, F. E.; Fields, G. B.; Hubbell, J. A. Proc. Natl. Acad. Sci. U.S. A. 2003, 100, 5413–5418. (3) DeForest, C. A.; Polizzotti, B. D.; Anseth, K. S. Nature Mater. 2009, 8, 659–664. (4) Polizzotti, B. D.; Fairbanks, B. D.; Anseth, K. S. Biomacromole- cules 2008, 9, 1084–1087. (5) Fairbanks, B. D.; Schwartz, M. P.; Halevi, A. E.; Nuttelman, C. R.; Bowman, C. N.; Anseth, K. S. Adv. Mater. 2009, 21, 5005–5010. (6) Goessl, A.; Tirelli, N.; Hubbell, J. A. J. Biomater. Sci., Polym. Ed. 2004, 15, 895–904. (7) Hahn, S. K.; Park, J. K.; Tomimatsu, T.; Shimoboji, T. Int. J. Biol. Macromol. 2007, 40, 374–380. (8) Li, C. M.; Madsen, J.; Armes, S. P.; Lewis, A. L. Angew. Chem., Int. Ed. 2006, 45, 3510–3513. (9) Zhao, Y.; Kang, J.; Tan, T. W. Polymer 2006, 47, 7702–7710. (10) Huang, G.; Gao, J.; Hu, Z. B.; John, J. V. S.; Ponder, B. C.; Moro, D. J. Controlled Release 2004, 94, 303–311. (11) Kloxin, A. M.; Kasko, A. M.; Salinas, C. N.; Anseth, K. S. Science 2009, 324, 59–63. (12) Kloxin, A. M.; Tibbitt, M. W.; Kasko, A. M.; Fairbairn, J. A.; Anseth, K. S. Adv. Mater. 2010, 22, 61–66. ARTICLE (13) Wong, D. Y.; Griﬃn, D. R.; Reed, J.; Kasko, A. M. Macro- molecules 2010, 43, 2824–2831. (14) Amamoto, Y.; Kamada, J.; Otsuka, H.; Takahara, A.; Matyjas- zewski, K. Angew. Chem., Int. Ed. 2011, 50, 1660–1663. (15) Favaudon, V.; Tourbez, H.; Houee-Levin, C.; Lhoste, J. M. Biochemistry 1990, 29, 10978–10989. (16) Tobolsky, A. V.; Takahashi, M.; Macknight, W. J. J. Phys. Chem. A 1964, 68, 787. (17) Endo, K.; Shiroi, T.; Murata, K. J. Polym. Sci., Part A: Polym. Chem. 2001, 39, 145–151. (18) Thang, S. H.; Chong, Y. K.; Mayadunne, R. T. A.; Moad, G.; Rizzardo, E. Tetrahedron Lett. 1999, 40, 2435–2438. (19) Majima, T.; Schnabel, W.; Weber, W. Macromol. Chem. Phys. 1991, 192, 2307–2315. (20) Fairbanks, B. D.; Schwartz, M. P.; Bowman, C. N.; Anseth, K. S. Biomaterials 2009, 30, 6702–6707. (21) Scott, T. F.; Schneider, A. D.; Cook, W. D.; Bowman, C. N. Science 2005, 308, 1615–1617. (22) Kloxin, C. J.; Scott, T. F.; Adzima, B. J.; Bowman, C. N. Macromolecules 2010, 43, 2643–2653. (23) Kloxin, C. J.; Scott, T. F.; Park, H. Y.; Bowman, C. N. Adv. Mater. 201110.1002/adma.201100323. (24) Stockmayer, W. H. J. Phys. Chem. A 1944, 12, 125–131. (25) Odian, G., Ed. Principles of Polymerization; Wiley: New York, 1991. (26) Chiefari, J.; Chong, Y. K.; Ercole, F.; Krstina, J.; Jeﬀery, J.; Le, T. P. T.; Mayadunne, R. T. A.; Meijs, G. F.; Moad, C. L.; Moad, G.; Rizzardo, E.; Thang, S. H. Macromolecules 1998, 31, 5559–5562. (27) Moad, G.; Rizzardo, E.; Thang, S. H. Aust. J. Chem. 2005, 58, 379–410. (28) Daniel, K. A.; Kopﬀ, L. A.; Patterson, E. V. J. Phys. Org. Chem. 2008, 21, 321–328. (29) Tulla-Puche, J.; Barany, G. J. Org. Chem. 2004, 69, 4101–4107. (30) Yang, Y. C. Acc. Chem. Res. 1999, 32, 109–115. (31) Eunju, K.; Dongwoo, K.; Hyuntae, J.; Jiyeong, L.; Somak, P.; Narayanan, S.; Yosep, Y.; Namseok, L.; Chan Gyung, P.; Kimoon, K. Angew. Chem., Int. Ed. 2010, 49, 4408–4408. (32) Kim, W.; Thevenot, J.; Ibarboure, E.; Lecommandoux, S.; Chaikof, E. L. Angew. Chem., Int. Ed. 2010, 49, 4257–4260. (33) Hartgerink, J. D.; Beniash, E.; Stupp, S. I. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 5133–5138. (34) Lee, Y.; Mo, H.; Koo, H.; Park, J. Y.; Cho, M. Y.; Jin, G. W.; Park, J. S. Bioconjugate Chem. 2007, 18, 13–18. (35) Liu, J. Q.; Liu, H. Y.; Jia, Z. F.; Bulmus, V.; Davis, T. P. Chem. Commun. 2008, 6582–6584. (36) Lin, C. C.; Metters, A. T. Adv. Drug Delivery Rev. 2006, 58, 1379–1408. (37) Wedemeyer, W. J.; Welker, E.; Narayan, M.; Scheraga, H. A. Biochemistry 2000, 39, 4207–4216. (38) Wrighton, N. C.; Farrell, F. X.; Chang, R.; Kashyap, A. K.; Barbone, F. P.; Mulcahy, L. S.; Johnson, D. L.; Barrett, R. W.; Jolliﬀe, L. K.; Dower, W. J. Science 1996, 273, 458–463. 2450 dx.doi.org/10.1021/ma200202w |Macromolecules 2011, 44, 2444–2450