Abstract
One of the main factors responsible for the mechanical and physical properties of nanocomposites is
the effectiveness of the interfacial region to transfer loads and mechanical vibrations between the nanoreinforcements
and the matrix. Surface functionalization has been the preferred approach to engineer the
interfaces in polymer nanocomposites in order to maximize their potential in structural and functional
applications. In this study, amine-functionalized cellulose nanofibrils (mCNF-G1) were synthesized via
silylation of the hydroxyl groups on the CNF surface using 3-aminopropyltrimethoxysilane (APTMS). To
further increase the amine density (mCNF-G2), dendritic polyamidoamine (PAMAM) was grafted onto
mCNF-G1 by the Michael addition of methacrylate onto mCNF-G1, followed by the transamidation of
the ester groups of methacrylate using ethylenediamine. Compared to native CNF-reinforced, poly(llactide)
(PLLA) nanocomposites, amine-functionalized CNF exhibited significantly improved dispersion
and interfacial properties within the PLLA matrix due to the grafting of PLLA chains via aminolysis. It is
also a more effective nucleating agent, with 15% mCNF-G1 leading to a crystallinity of 32.5%, compared
to 0.1 and 8.7% for neat PLLA and native CNF-reinforced composites. We have demonstrated that APTMSfunctionalized
CNF (mCNF-G1) significantly improved the tensile strength compared to native CNF, with
10% mCNF-G1 being the most effective (i.e., >100% increase in tensile strength). However, we also found
that excessive amines on the CNF surface (i.e., mCNF-G2) resulted in decreased tensile strength and
modulus due to PLLA degradation via aminolysis. These results demonstrate the potential of optimized
amine-functionalized CNF for future renewable material applications
