posted on 2018-11-05, 00:00authored bySihao Xu, Jonathan Yeow, Cyrille Boyer
We
report a facile benchtop process for the synthesis of cross-linked
polymeric nanoparticles by exploiting wavelength-selective photochemistry
to perform orthogonal photoinduced polymerization-induced self-assembly
(Photo-PISA) and photo-crosslinking processes. We first established
that the water-soluble photocatalyst, zinc meso-tetra(N-methyl-4-pyridyl) porphine tetrachloride (ZnTMPyP) could activate
the aqueous PET-RAFT dispersion polymerization of hydroxypropyl methacrylate
(HPMA). This photo-PISA process could be conducted under low energy
red light (λmax = 595 nm, 10.2 mW/cm2)
and without deoxygenation due to the action of the singlet oxygen
quencher, biotin (vitamin B7), which allowed for the synthesis
of a range of nanoparticle morphologies (spheres, worms, and vesicles)
directly in 96-well plates. To perform wavelength selective nanoparticle
cross-linking, we added the photoresponsive monomer, 7-[4-(trifluoromethyl)coumarin]
methacrylamide (TCMAm) as a comonomer without inhibiting the evolution
of the nanoparticle morphology. Importantly, under red light, exclusive
activation of the photo-PISA process occurs, with no evidence of TCMAm
dimerization under these conditions. Subsequent switching to a UV
source (λmax = 365 nm, 10.2 mW/cm2) resulted
in rapid cross-linking of the polymer chains, allowing for retention
of the nanoparticle morphology in organic solvents. This facile synthesis
of cross-linked spheres, worms, and vesicles demonstrates the utility
of orthogonal light-mediated chemistry for performing decoupled wavelength
selective chemical processes.