Photoresponsive polycarbonates and polyesters
Photoresponsive materials have several advantages due to their spatial and temporal control of the input. Such polymer have been used as actuators, light activated shape memory polymers, polymers with variable refractive indices, photoresponsive mechanophores, controlled release devices and in surface patterning. The Joy Lab has developed two families of photoresponsive materials.
Alkoxyphenacyl based polycarbonates and polyesters:
The PI’s lab (Joy Lab) has developed alkoxyphenacyl based polymers that undergo polymer chain scission upon irradiation at 300 nm (Fig. 2). These polymers have an absorption spectrum from 250-320 nm with a lmax at 280 nm. The photoactive chromophore is part of the polymer backbone and undergoes photoinduced rearrangement resulting in cleavage of the ester or carbonate bond between repeat units. We have used this methodology to develop photocleavable polycarbonates and polyesters and demonstrated their use in creating micropatterned surfaces and for the release of model compounds from nanoparticles. We have also designed rhodamine patterned surfaces by the use of alkoxyphenacyl polyesters wherein the co-monomer, glutamic acid, provides the functional handle to selectively tether rhodamine to the surface. The rearrangement and resulting chain scission is a very efficient reaction and polymer chain scission occurs rapidly for polymers in solution and as thin films. Solution irradiation of the polymer results in polymer chain scission resulting in oligomers in a matter of 4-8 min (Figure 1).
Coumarin containing polyesters:
The PI’s lab (Joy Lab) has also developed a family of coumarin based polyesters wherein coumarin units are part of the polyester backbone. These polymers have an absorption spectrum from 250-370 nm with a lmax at 322 nm. These coumarin polyesters upon irradiation at 350 nm undergo [2+2]-cycloaddition resulting in crosslinked polymers which can then be un-crosslinked by irradiation at 254 nm. Irradiation at 254 nm also results in chain scission due to cleavage of the 4’-ester bond between the coumarin and the diacid (Fig. 2). Complementary patterns from thin films of these polyesters can be created by irradiation at 350 nm through a mask (Rayonet reactor RPR-200; 22 mW/cm2) which crosslinks the exposed areas and the non-exposed areas can be washed away. Alternatively irradiation at 254 nm causes chain scission of the polymer film and enables its removal. The obtained patterns in the two instances are complementary to each other (Fig. 2)
We are currently exploring the utility of such coumarin polyesters for the fabrication of patterned surfaces for cellular guidance. For example, micropatterned coumarin thin films exhibit cortical neural cell guidance (Fig 3). We are exploring the utility of such polymers for creating patterned biodegradable nerve guidance conduits and for the fabrication of small diameter matrices for the guidance of endothelial cells.
|Fig. 3: Micropatterned coumarin thin films (left) and guidance of cortical neurons on such substrates (right) (ACS Appl. Mat. Inter. 2014, 6, 19655)|
- A. McCormick, M.V.S.N. Maddipatla, S. Shuojia, E.A. Chamsaz, H. Yokoyama, A. Joy, N. Leipzig; Micropatterned coumarin polyester thin films direct neurite orientation; ACS Applied Mat. Interfaces, 2014, 6, 19655
- D. Wehrung, E.A. Chamsaz, A. Joy, M.O. Oyewumi; Formulation and photoirradiation parameters that influence photoresponsive drug delivery with alkoxyphenacyl based polycarbonates; Europeon Journal of Pharmaceutics and biopharmaceutics, 2014, in press
- J. Lee, M.V.S.N. Maddipatla, A. Joy, B. Vogt; Kinetics of UV induced chain scission and cross-linking of coumarin-containing polyester ultrathin films; Macromolecules, 2014, 47, 2891
- E. A. Chamsaz, S. Sun, M.V.S.N. Maddipatla, A. Joy; Photoresponsive polyesters by incorporation of alkoxyphenacyl or coumarin chromophores along the backbone; Photochem. Photobiol. Sci., 2014, 13, 412
- M.V.S.N. Maddipatla, D. Wehrung, C. Tang, W. Fan, M. O. Oyewumi, T. Miyoshi, A. Joy; Photoresponsive coumarin polyesters that exhibit cross-linking and chain scission properties; Macromolecules, 2013, 46, 5133
- D. Wehrung, S. Sun, E. A. Chamsaz, A. Joy, M. O. Oyewumi; Biocompatibility and in-vivo tolerability of a new class of photoresponsive alkoxyphenacyl based polycarbonates; J. Pharm. Sci. 2013, 102, 1650
- S. Sun, E. A. Chamsaz, A. Joy; Photoinduced polymer chain scission of alkoxyphenacyl based polycarbonates; ACS Macro Letters, 2012, 1, 1184