Optically transparent nanocomposites reinforced with modified biocellulose nanofibers

Abstract

Abstract The objective of this study is to produce a class of optically transparent nanostructured biocomposites composed of surface‐modified bacterial cellulose (BC) nanofibers reinforced into poly(hydroxyethyl methacrylate) (PHEMA) hydrogel matrix. The surface of BC was first modified by fibrous heterogeneous acetylation to preserve the BC nanofibrillar morphology, followed by graft copolymerization with PHEMA hydrogel by free‐radical mechanisms using benzoyl‐peroxide as a radical initiator. A series of samples of grafted nanofiber having different degrees of acetylation and graft yields were produced and characterized using NMR, FTIR, and gravimetry. The maximum degree of acetylation obtained in this study was 2.3% and the maximum graft yield was 82.35 %.The modified nanofibers were thereafter reinforced into a polymeric matrix of PHEMA to form the final transparent biocomposite. The nanofiber‐network‐reinforced PHEMA polymer composite sample containing 1% (w/w) nanofiber transmitted over 80% of the light, while samples with less than 1% (w/w) nanofibrillar content exhibited higher light transmittances. The loss of transparency in the nanocomposite was small, despite the differences of refractive indices of BC and PHEMA. Increasing content of the BC nanofibers in the composite up to 1.4% (w/w) increased its water holding capacity up to 48.7% compared to the reference sample. This class of transparent nanostructured cellulose‐based hydrogel composite provides unique fluid handling capability of absorption and donation. These characteristics are essential for several applications as optically functional materials in addition to several biomedical applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012