Hydrophilic Graft Polymerization of Polymeric Surfaces with Unique Micro-Spherical Topography

Polymeric coatings with predefined micro-spherical morphologies have an advantage of high surface area which is beneficial for many applications such as materials with high sorption capacity, nanoreactors and resins for heterogeneous catalysis. Strategies for fabrication of stable, non-leachable spherical polymers on solid surfaces is still a challenging task. A promising way for achieving grafted spherical coating on surfaces was recently discovered by our group.⁽¹⁾ A one-step generation of micro-scale spherical poly(ethylene glycol) brushes on water treatment membrane surfaces was achieved by using UV-initiated graft-polymerization process of poly(ethylene glycol) methacrylate (PEGMA, Figure 1A) onto different polymeric surfaces. The surfaces were characterized chemically by ATR-FTIR and visually by SEM (Figures 1B-1C), grafting yield estimated by gravitational analysis, and wettability by water drop contact angle. Spherical particles were observed on the surfaces, with clear preference to hydrophobic templates in hydrophilic solutions. Moreover, when comparing the grafting of PEGMA to other methacrylate monomers, the grafted PEGMA gave the highest grafting yield and much better resistance against leaching by long washing steps. The spherical shape of the coating was found to be related to the polymerized monomers according to the critical micelle concentration (CMC); Spheres were present bellow the CMC of the monomers. The understanding of the molecular mechanisms of evolution of such micro-spherical structures on polymeric surfaces is expected to pave the way for designing stable polymer brushes with nano- and micro-structures.

Figure 1 - (A) Poly(ethylene glycol) methacrylate monomer (PEGMA). Polyether sulfone surfaces grafted with PEGMA of Number Average Molecular Weight of (B) 360 and (C) 500 gram/mole.

(1) S. Belfer, R. Fainchtain, Y. Purinson, O. Kedem, Journal of Membrane Science 172 (2000), p. 113–124