Surface-Initiated Initiators for Continuous Activator Regeneration (SI ICAR) ATRP of MMA from 2,2,6,6–tetramethylpiperidine–1–oxy (TEMPO) Oxidized Cellulose Nanofibers for the Preparations of PMMA Nanocomposites

An effective method of oxidation from paper pulps via 2,2,6,6-tetramethylpiperidine-1-oxy (TEMPO) compound to obtain TEMPO-oxidized cellulose nanofibers (TOCNs) was demonstrated. Following by acylation, TOCN having an atom transfer radical polymerization (ATRP) initiating site of bromoisobutyryl moiety (i.e., TOCN-Br) was successfully obtained. Through a facile and practical technique of surface-initiated initiators for continuous activator regeneration atom transfer radical polymerization (SI ICAR ATRP) of methyl methacrylate (MMA) from TOCN-Br, controllable grafting polymer chain lengths (Mn = ca. 10k-30k g/mol) with low polydispersity (PDI < 1.2) can be achieved to afford TOCN-g-Poly(methyl methacrylate) (PMMA) nanomaterials. These modifications were monitored by Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA), and water contact angle analysis. Eventually, TOCN-g-PMMA/PMMA composites were prepared using the solvent blending method. Compared to the pristine PMMA (Tg = 100 °C; tensile strength (σT) = 17.1 MPa), the composites possessed high transparency with enhanced thermal properties and high tensile strength (Tg = 110 °C and σT = 37.2 MPa in 1 wt% TOCN containing case) that were investigated by ultraviolet-visible spectroscopy (UV-Vis), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and tensile tests. We demonstrated that minor amounts of TOCN-g-PMMA nanofillers can provide high efficacy in improving the mechanical and thermal properties of PMMA matrix.