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.

Cheng-Wei Tu,Chih-Feng Huang,Chi-Jung Chang,Jiawei Zhang,Tao Chen,Cheng-Han Yang,Shiao-Wei Kuo,Fang-Chang Tsai

doi:10.3390/polym11101631

Abstract

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.

Highlights

Polymers, unlike inorganic metals and ceramics, have special viscoelastic properties which are used in many commercial products over the world
A different cellulose chemical structure is obtained revealing that a portion of hydroxymethyl groups on the D–glucose repeating units of the cellulose was successfully converted to carboxyl groups through the TEMPO-oxidized reaction
The degree of oxidization (DO) of hydroxymethyl group and carboxylate content (CC) of TEMPO-oxidized cellulose nanofibers (TOCNs) are determined by conductometric titration method and approximated to 25.8% and 1.58 mmol/g, respectively

Summary

Introduction

Unlike inorganic metals and ceramics, have special viscoelastic properties which are used in many commercial products over the world. With the elevating specifications of industrial and general requirements, many pristine polymers are unable to match the new demands, like eco-friendliness with high thermal and mechanical properties. Different types of (nano)fillers were introduced into polymeric matrices, such as polymers with carbon-related fillers, metals, metal oxides, montmorillonite, organic, or inorganic fibril materials, to produce polymeric hybrid composites to meet the required properties of products. The polysaccharide chains aggregate in the presence of strong intermolecular hydrogen bonding to form large bundles with tens of micrometers in width. The strong hydrogen bonds between cellulose microfibers and hydrophilic properties make them hard to disperse in an organic solvent and form a strong enough interfacial force with polymer chains, which increases the difficulty in achieving a polymeric composite with a moderate uniformity. The increase of surface contact area and decrease of hydrophilicity are the keys to accessing homogeneous cellulose/polymer composites

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Conclusion