Nanocomposite Films of Laponite/PEG-Grafted Polymers and Polymer Brushes with Nonfouling Properties

We explore the suitability of nanocomposite thin films based on laponite nanomaterial and grafted antiadhesive polymers as transparent nonfouling surfaces. For this purpose, two polymers were chosen: a linear poly(ethylene glycol) (PEG) silane, 2-[methoxy(polyethyleneoxy)propyl]-trimethoxysilane), and thermoresponsive poly(oligo ethylene glycol)-methyl ether-methacrylate (POEGMA) brushes. PEG silane was grafted on the laponite nanoparticles in solution yielding homogeneous and transparent thin films via a dip coating procedure on glass and silicon substrates. POEGMA was grafted on laponite-(3-Aminopropyl)trimethoxysilane (APTMS) nanocomposite films that were processed similarly to PEG-silane using atom transfer radical polymerization (ATRP). Film characterization with, among others, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM) attests to successful grafting of the polymers to the laponite nanoparticles. In particular, evidence of basal plane expansion of laponite with increasing silane concentration are obtained using XRD, while patent morphological changes are revealed with AFM. The results are discussed in terms of the different grafting sites on laponite and compared with literature. While LP-PEG-silane is easily applied to a surface from a precursor solution via a dip coating procedure LP-APTMS-OEGMA requires lots more chemicals, a thorough control of reaction parameters, and longer reaction time in order to generate films with the desirable properties. We therefore also addressed the antifouling properties of the films. These were tested together with control samples of bare glass and laponite thin films for 30 days in an algae container. More tests were conducted with fibroblast cell cultures. Our preliminary results show that grafting of PEG containing polymers and polymer brushes alters the properties of the laponite films from fouling to nonfouling surfaces. As a first estimate, the adhesion of particles (diatoms, algae, etc.) to surfaces is reduced by approximately 85% in the case of LP-PEG-silane and up to 92% in the case of LP-APTMS-POEGMA, in comparison to the control surfaces. Furthermore, practically no cell adhesion on such surfaces could be observed.