New biodegradable materials produced by ring opening polymerisation of poly(L-lactide) on porous silicon substrates

In this paper, we describe for the first time the preparation of biodegradable inorganic/organic hybrid materials by grafting poly(L-lactide) (PLLA) from porous silicon (pSi) films and microparticles. To graft a PLLA layer from pSi, tin(II) 2-ethylhexanoate catalysed ring opening polymerisation was performed using pSi surface-bound hydroxyl groups as initiators. Chemical surface characterisation by means of diffuse reflectance infrared spectroscopy, X-ray photoelectron spectroscopy and water contact angle measurements confirmed the presence of the PLLA film. Furthermore, atomic force microscopy demonstrated the formation of PLLA nanobrushes on the pSi surface. We also ascertained by interferometric reflectance spectroscopy that the PLLA layer successfully slowed down the corrosion of the porous silicon layer in aqueous medium. Finally, thermal gravimetric analysis showed weight loss transitions that closely resemble the expected decomposition peak for low molecular weight PLLA. We believe that biodegradable hybrid materials like the ones presented here will find uses in tissue engineering and drug delivery, for example in applications where complex degradation profiles are required that cannot be achieved with one type of material alone.