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. Author manuscript; available in PMC: 2014 Sep 10.
Published in final edited form as: MRS Bull. 2013 Mar 1;38(3):260–268. doi: 10.1557/mrs.2013.54

Figure 3.

Figure 3

(a) Photolabile nitrobenzyl ether acrylic monomer. (b) Polyethylene glycol) di-photodegradable acrylate (PEGdiPDA) macromer, composed of PEG (black), photolabile moieties (blue), and acrylate end groups (red), polymerizes to form a gel. (c) Irradiation with specific wavelengths of light cleaves the nitrobenzyl ether moiety, degrading network cross-links. (d) Wavelength and intensity of the light controls degradation time, as determined by in situ rheometry to measure elastic modulus (G′) normalized to initial modulus (G′0), which is directly proportional to cross-linking density. (i) 365 nm at 20 mW/cm2, (ii) 365 nm at 10 mW/cm2, and (iii) 405 nm at 25 mW/cm2. (e) The degradation reaction only proceeds during exposure to light. (i) Continuous or (ii) periodic irradiation with 365 nm at 10 mW/cm2. Adapted from Reference 27. Note: n, number of repeat units.