Facile procedures capable of simultaneously conferring hydrophilicity and tailored topography to surfaces of hydrophobic supports, such as polycarbonate (PC), are very attractive but rare. In this work, we describe a simple methodology to wrinkle PC surfaces after a process of (a) contacting with a photopolymerizable vinylic solution, (b) UV curing of such solutions, and (c) detachment of the formed polymer network, upon swelling in ethanol. The influence of different parameters such as contact lag time between the PC surface and the polymerizable solution, the monomer concentration and type of solvents, as well as the cross-linking degree on the formation of wrinkles, has been studied. The dimensions of the wrinkles can be tailored to some extent by altering the different parameters. Surface chemistry has been analyzed by contact angle measurements and by confocal Raman microscopy. The results are consistent with a chemical alteration of the surface and the formation of an outer hydrogel layer, which is interpenetrated into the PC structure. A mechanism of monomer diffusion and PC swelling that produces surface instabilities and wrinkling is proposed.
We
report a straightforward procedure to simultaneously functionalize
hydrophobic PC supports with vinylpyrrolidone (VP)-based hydrogels
with both variable ionic load as well as surface topography, forming
wrinkles. The strategy involves three consecutive steps: first, a
contact of the polymeric support (PC) with a photopolymerizable solution
comprising vinylic monomers is established. Second, UV-light exposure
curing of the solution and finally, the third step involes the swelling
of the hydrogel network that finally provokes its surface detachment.
Interestingly, a wrinkled hybrid PC/hydrogel interface remains after
this detachment. Several experimental parameters permitted us to finely
control the wrinkle characteristics such as amplitude and period.
The experimental parameters that can be varied, herein we will focus
on the variation of the elapsed time (i.e., time of contact between
the support and the photosensitive monomer mixture, or the solvent
(type and amount) included in the monomer mixture. Equally, the nature
of the additional ionic methacrylate monomers (M) employed plays a
key role on the final topography. According to confocal raman microscopy
results, we evidenced that a monomer diffusion into the PC substrate
before the UV irradiation step modifies the interfacial (hydrogel/substrate)
chemical composition and leads upon UV irradiation to the formation
of a thin hydrogel surface layer. The surface chemical composition
and structural characteristics were demonstrated to significantly
change the surface interaction with different cell lines, affecting
cell adhesion, proliferation, or transplantation.
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