Facile Route to Transparent, Strong, and Thermally Stable

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Article

A facile route to transparent, strong, and thermally stable nanocellulose/ polymer nanocomposites from an aqueous Pickering emulsion Shuji Fujisawa, Eiji Togawa, and Katsushi Kuroda Biomacromolecules, Just Accepted Manuscript • DOI: 10.1021/acs.biomac.6b01615 • Publication Date (Web): 13 Dec 2016 Downloaded from http://pubs.acs.org on December 13, 2016

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A facile route to transparent, strong, and thermally

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stable nanocellulose/polymer nanocomposites from

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an aqueous Pickering emulsion

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Shuji Fujisawa,* Eiji Togawa, and Katsushi Kuroda

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Forestry and Forest Products Research Institute, Tsukuba 305-8687, Japan

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KEYWORDS Pickering emulsion, cellulose nanofibril, TEMPO-mediated oxidation, Polymer

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composite

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ABSTRACT Cellulose nanofibril (CNF) is a promising nanofiller for polymer nanocomposite

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materials, and a critical challenge in designing these materials is organization of the

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nanostructure using a facile process. Here, we report a facile aqueous preparation process for

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nanostructured polystyrene (PS)/CNF composites, via the formation of a CNF-stabilized

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Pickering emulsion. PS nanoparticles, with a narrow size distribution, were synthesized by free

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radical polymerization in water, using CNF as a stabilizer. The nanoparticles were easily

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collected by filtration and the resulting material had a composite structure of PS nanoparticles

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embedded in a CNF framework. The PS/CNF nanocomposite showed high optical transparency,

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strength, and thermal dimensional stability. Thus, this technique provides a simple and

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environmentally-friendly method for the preparation of novel CNF/polymer nanocomposite

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materials.

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INTRODUCTION

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A key element in the design of high-performance polymer nanocomposites is organization of

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the nanostructure to overcome the high surface energy of the nanofillers. Several strategies for

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engineering composite structures using a variety of nanofillers have been reported, such as

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efficient mechanical exfoliation, layer-by-layer deposition, and self-assembly templating.1-8

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Some of the most-studied nanofillers are carbon nanotubes,9-11 graphenes,12-14 and nanoclays.15-17

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A well-organized nanoscale structure could tailor macroscale material properties, such as the

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optical, mechanical, and thermal properties.

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Cellulose nanofibril (CNF) is a promising building block for nanocomposite materials.18 CNF,

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which provides structural support to plant bodies in nature, possesses high strength (2‒6

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GPa),19,20 high elastic moduli (130‒150 GPa),21-23 and low thermal expansion coefficients (4‒6

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ppm K‒1).24,25 Taking advantage of these unique properties, great effort has been made

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developing the use of CNF as a reinforcing filler in polymer nanocomposite materials.26,27

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However, during the development of these composites, incompatibility with hydrophobic

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polymers often becomes a critical issue. Generally, to achieve homogeneous distribution of CNF

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in hydrophobic polymer matrices, melt compounding at high temperatures or solution casting

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using organic solvents is necessary. In other words, to overcome the high interfacial energies that

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exist, nanocomposite preparation requires a lot of energy and careful processing, which hinders

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its commercial viability.

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Here, we report on a facile and scalable method for the preparation of a nanostructured

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PS/CNF composite, using an aqueous polymerization process. Surface-carboxylated CNF, with a

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width of ~3 nm, was prepared using TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)-mediated

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oxidation of wood cellulose.28 The PS/CNF composite was successfully prepared by


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polymerizing a styrene monomer via a formation of an aqueous Pickering emulsion, using CNF

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as a stabilizer. This approach has recently appeared elsewhere using partially delignified wood as

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a stabilizer for PS, and the resulting composite showed improved mechanical properties.29 In this

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study, we demonstrate that ultrafine CNF prepared by TEMPO-mediated oxidation can construct

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an organized PS nanoparticle/CNF structure, and acts as a reinforcing nanofiller in the resulting

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composite material.

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EXPERIMENTAL SECTION

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Materials. A softwood bleached kraft pulp was kindly provided by Nippon Paper Industries

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Co. Ltd. in a never-dried state. TEMPO, a 2M sodium hypochlorite solution, sodium bromide,

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styrene, 2,2'- azobis(2,4-dimethylvaleronitrile) (ADVN), tetrahydrofuran (THF), and other

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chemicals were obtained from Wako Chemical Co. Ltd. and used as received. PS with a Mw of

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324 000 was purchased from Sigma Aldrich for use as a reference.

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Preparation of CNF aqueous dispersion. CNF was prepared from softwood bleached kraft

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pulp by TEMPO-mediated oxidation.28 The pulp (1 g) was oxidized with TEMPO (0.1 mmol),

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sodium bromide (1 mmol), and sodium hypochlorite (10 mmol) in water (100 mL) at pH 10. The

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oxidized pulp was washed thoroughly with distilled water by filtration, then suspended in water

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at a concentration of 0.1 % w/v. CNFs were dispersed in water using a double-cylinder-type

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homogenizer (Physcotron, Microtec Nition, Japan) at 7,500 rpm for 1 min and an ultrasonic

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homogenizer (VP-300N, TAITEC) for 4 min. The unfibrillated fraction (˂ 5%) was then

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removed by centrifugation at 10,000g for 30 min. The carboxylate content of CNF was

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determined to be 1.7 mmol g−1 by electric conductivity titration. The introduction of the carboxyl

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groups was also confirmed by evaluating the chemical structure of the CNF using solid-state 13C


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cross-polarization/ magic-angle spinning (CP/MAS) nuclear magnetic resonance (NMR). The

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CNF with a uniform width of 3 nm and average length of ~400 nm was successfully prepared,

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and formed transparent dispersion in water (Figure S1 in the Supporting Information). The

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concentration of the CNF dispersion was adjusted to 1.0 % w/w using an evaporator at 40 ºC

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under reduced pressure.

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Preparation of CNF-stabilized Pickering emulsion. Styrene (1 mL) was added to the CNF

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aqueous dispersion (9 mL) and the styrene/water emulsion, stabilized by CNFs, was formed by

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ultrasonication (60 W, 20 KHz) in an ice bath.

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Preparation of PS/CNF composite. The PS/CNF composite was prepared by polymerizing

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the styrene monomer inside the emulsion. ADVN was used as an initiator at a concentration of

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0.01 mol L‒1 (0.3 % w/w) based on styrene monomer. Styrene containing the initiator (1 mL)

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was added to the CNF dispersion (9 mL) and emulsified by ultrasonication as described above.

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In order to polymerize the styrene, the suspension was gently stirred at 200 rpm in a water bath

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kept at 70 ºC. After the polymerization reaction, methanol (20 mL) and 0.1 M HCl (0.1 mL) was

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added to the system and white the precipitate formed was thoroughly washed with methanol by

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filtration through a 0.1-µm pore size PTFE membrane. The obtained precipitate was vacuum

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dried at 40 ºC for more than a week. Transparent PS/CNF composite films, ~200 µm thick, were

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formed by pressing the composite samples at 160 ºC and 3 MPa for 30 sec.

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Size distribution measurement of Pickering emulsion. The emulsion size distribution was

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determined using a laser diffraction particle size analyzer (λ = 405 nm; SALD-7500nano,

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Shimadzu). The emulsion was dispersed in water and analyzed using a flow cell unit.


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C NMR analysis. Solid-state

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C CP/MAS NMR analysis was carried out using an NMR

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spectrometer (CMX Infinity 300, Chemagnetics). The spectra were obtained using a 1.2-ms

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contact time and 3.0 s repetition time. The samples were loaded into a 4-mm zirconia rotor and

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spun at 10,000 Hz during the measurements.

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SEC-MALLS analysis. The molecular weight of PS was determined by size-exclusion

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chromatography using a multi-angle laser light scattering (SEC-MALLS) detector (DAWN

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HELEOS II, Wyatt Technology) with THF as an eluent. The SEC-MALLS system consisted of a

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degasser (DGU-20A, Shimadzu), a high-pressure pump (LC-20AD, Shimadzu), a stainless steel

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inline filter with a 0.1 µm poly(tetrafluoroethylene) (PTFE) membrane (Millipore), an auto-

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sampler (SIL-20A HT, Shimadzu), a column oven (CTO-10AS VP, Shimadzu), a SEC column

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(KF-806M, Shodex), a MALLS detector, and a refractive index detector (Optilab rEX, Wyatt

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Technology). The SEC conditions were as follows: flow rate 0.5 mL min−1, injection volume 50

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µL, sample concentration 0.3 % w/v, and column temperature 40 ºC. A value of 0.180 mLg−1

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was used for the refractive index increment value (dn/dc) of PS. A PS standard (Mw 30,000,

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Mw/Mn 1.06; Pressure Chemical Co.) was used for the MALLS calibration.

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SEM analysis. A field-emission scanning electron microscope (FE-SEM) (S-4800, Hitachi)

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was used to analyze the surface structure of PS/CNF composite. Secondary electron images were

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obtained at an acceleration voltage of 1 kV with about 5 nm osmium coating by an osmium

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coater (Neo Osmium Coater, Meiwafosis) at 5 mA for 5 s.

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UV-vis spectroscopy. Transmittance spectra of the composite films were monitored using an ultraviolet–visible light spectrophotometer (UV-2400PC, Shimadzu).


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Tensile testing. Tensile properties of the PS/CNF composite film were investigated using a

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tensile tester (EZ Graph, Shimadzu) equipped with a 500-N load cell. The specimens were tested

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with a span of 10 mm at a crosshead speed of 1 mm min‒1.

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Thermomechanical analysis (TMA). Thermal dimensional stability of the films was

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evaluated using a thermomechanical analyzer (TMA-60, Shimadzu). The linear coefficient of

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thermal expansion (CTE) of the film was determined using a 0.03 N load cell under a nitrogen

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atmosphere from 30 to 150 ºC at 5 ºC min‒1.

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RESULTS AND DISCUSSION

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CNF-stabilized Pickering emulsion. The CNF-stabilized Pickering emulsion was successfully

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formed by ultrasonication of the styrene/CNF aqueous dispersion mixture, and the emulsions

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were individually dispersed in water (Figure 1). In the absence of CNF, a phase separation

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occurred spontaneously and reduced the interfacial energy of the styrene/water system (Figure 1a

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left). Therefore, CNFs stabilized the oil in water (o/w) emulsion by adsorption at the

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styrene/water interface, as previously reported CNF-stabilized Pickering emulsions.30-34

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Cellulose has natural amphiphilic properties and it is likely that the hydrophobic surface of the

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CNFs preferentially attracted the styrene phase.31,35,36 The repulsive forces between the

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emulsions arise primarily from osmotic pressure caused by the carboxyl groups introduced by

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the TEMPO-mediated oxidation.32,37 The density of the surface carboxylate groups on the CNFs

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was calculated to be as high as 1.7 groups nm−2.38 Therefore, the Pickering emulsion showed

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remarkable coalescence stability by exposing the carboxyl groups on the surfaces.


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Figure 1. CNF-stabilized Pickering emulsion formed at a 10/90 ratio (o/w). (a) Photograph of

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styrene/water mixture with (right) and without (left) CNF, (b) optical microphotographs, (c) size

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distribution.

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The Pickering emulsion showed a monomodal size distribution (Figure 1b and c). The larger

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emulsion particles became smaller with increasing sonication time and when sonicated for longer

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than 1 min the size leveled off at a median diameter of ~9.0 µm (Figure S2). The emulsion

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showed good stability. The size distribution of the emulsion remained unchanged for over a

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week (Figure S3), and no appreciable creaming was observed. In some previous studies, o/w

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emulsions stabilized by cellulose nanocrystals rapidly form a creaming layer, due to the density

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difference between the oil and water phases.30-32 The long-term stability in this study is likely

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due to both the stronger repulsive forces between the emulsions and the increased viscosity of

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the aqueous phase, caused by the ultrafine CNFs.39 The increased viscosity could cause

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decreased velocity of creaming (or sedimentation). In this way, hydrophobic styrene was

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successfully encapsulated in the CNF and homogeneously dispersed in the aqueous phase.

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PS/CNF composite. The PS/CNF composite was prepared by polymerizing the encapsulated

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styrene monomer at 70 ºC using ADVN as an initiator. Figure 2a and b compare the dispersion

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before and after polymerization. The size of the emulsion particles decreased significantly during

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the polymerization process and a stable dispersion of smaller particles was obtained. We initially


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Figure 2. Photographs and optical micrographs of CNF-stabilized emulsion containing an

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initiator (a) before and (b) after polymerization for 8 h.

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assumed that microparticles, reflecting the size of the Pickering emulsion (~10 µm), would result

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from the polymerization. However, it was found that the polymerization produced

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monodispersed nanoparticles of ~150 nm in diameter (Figure 3). In Figure S4, it can be seen that

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the PS nanoparticles were squeezed out of the CNF-stabilized emulsion, reducing the emulsion

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diameter. In general, Pickering emulsions could be used as templates for preparation of

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microparticles.40,41 However, the CNF-stabilized Pickering emulsion in this study is not so robust

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for the polymerization that the PS nanoparticles came out of the emulsion. This behavior seems

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complex, but can be understood as a dispersion polymerization-like process. Dispersion

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polymerization is a useful technique for synthesizing monodispersed polymer particles in the

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region of about 0.1‒10 µm, by conducting the reaction in a poor solvent for the polymer.42-44 The

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polymerization proceeds in the solvent and/or monomer and as a result, the polymer particles are

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precipitated in the medium. In this study, PS nanoparticles were precipitated in the aqueous

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medium in the same way and each individual particle was stabilized by CNF networks.

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Therefore, a unique film structure, where the PS nanoparticles were confined by the CNF

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framework, was easily obtained by filtration and subsequent drying.


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Figure 3. (a) Photograph, (b‒e) SEM images, and (f) Schematic illustration of PS/CNF

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composite with 12 % w/w CNF before melt pressing. (b,c) film surface, (d) edge, and (e) side

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surface.

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The composite was composed purely of PS and CNF, demonstrated by solid-state

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C

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CP/MAS NMR analysis (Figure S5). The CNF content in the composite film was calculated to

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be 12 % w/w based on the conversion of styrene (83 %), which was also confirmed by

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comparing the peak areas of PS (~146 ppm ) and CNF (~105 ppm) in solid-state

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NMR spectra. Mw of PS was as high as 1 560 000, with a polydispersity (Mw/Mn) of 1.59 (Figure

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4). The yields of the PS were more than 80 % and the PS showed high Mw values when the

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initiator amount was 0.01−0.05 mmol/mL against styrene monomer (Figure S6). The Mw value is

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one order higher than that of commercially used PS which is synthesized by bulk polymerization

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(typical Mw: ~150 000‒400 000,45 see Figure S7). Interestingly, when this polymerization was

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conducted without forming the micron-sized Pickering emulsions by ultrasonication, the

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obtained PS showed lower M w and higher M w/Mn values, likely due to a heterogeneous

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polymerization (Figure S8). Moreover, the Mw is about 10 times higher than that of partially

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d e l i g n i f i e d

w o o d - s t a b i l i z e d

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C CP/MAS

e m u l s i o n


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Figure 4. Molecular mass distribution of PS. (a) Elution pattern and Mw plots, and (b) double

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logarithmic plots of radius of gyration (Rg, z) vs Mw for PS.

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polymerization (Mw : 124 000),29 likely due to the formation of uniform Pickering emulsion in

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this study. Therefore, the Pickering emulsion acted as a microreactor and enhanced heat transfer

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due to the higher volume-to-surface ratio, which could contribute to the efficient polymerization

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of encapsulated styrene.46 The slope of the conformation plot for PS was 0.59 (Figure 4b), which

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corresponds to the conformation of linear flexible polymers in good solvents.47 There was no

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convincing evidence of covalent bond formation between PS and CNFs in the NMR spectrum

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and the SEC-MALLS result showed that only pure PS chains were detected at high yield

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(~100 %). Therefore, pure PS without branching was synthesized through the polymerization

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process.


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Figure 5. (a) Photograph of PS/CNF composite film with 12 % w/w CNF after melt pressing, (b)

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UV-Vis transmittance spectra, (c) stress-strain curves and (d) thermal expansion behavior of

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PS/CNF composite and PS films.

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Transparent PS/CNF composite film was simply formed by subsequent melt pressing (see

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Figure 5a and S8). The film showed high optical transparency with a transmittance of 88 % at

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600 nm, as high as that of PS films (90%) (Figure 5b). Moreover, the transmittance is

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comparable to that of a PS/CNF nanocomposite film prepared by solvent casting from N,N-

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dimethylformamide (89 %).48 Therefore, in this study, high optical transparency was achieved

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using the organic solvent-free process.


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Figure 5c shows the stress‒strain curves of the films. Incorporation of CNF improved the

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mechanical strength of PS. Young’s modulus, ultimate strength, and strain to failure of the

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composite film was 3.4 ± 0.1 GPa, 50.1 ± 2.6 MPa, and 1.5 ± 0.1 %, respectively (Table S1).

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These improvements are more marked than those of PS/CNF nanocomposite film prepared by

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solvent casting.48 Although the modulus and strength increased, the improvement is not so

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significant for the CNF content. Moreover, the nanocomposite became brittle, which is likely due

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to the insufficient attractive interfacial interaction between the hydrophilic CNF and hydrophobic

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PS, as discussed in our previous study.48 This problem could be solved by selective surface

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modification of the CNF.38 Ben Elmabrouk et al. have reported on preparation of poly(styrene-

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co-hexylacrylate)/cellulose whiskers nanocomposites via miniemulsion polymerization, and the

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obtained nanocomposite showed better mechanical properties even with less than 5 wt % of the

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whisker loadings.49 In the work, they added a low amount of reactive silane to stabilize the

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miniemulsion. In contrast, the PS/CNF composite in this study did not require any other

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stabilizers, and the obtained composite showed good mechanical properties due to the

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reinforcement by the CNF. Moreover, the composite showed better thermal dimensional stability

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(Figure 5d). The CTE of the composite was 56.7 ppm K‒1, below the glass transition region of

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PS (Tg: ~100 ºC), while that of PS was 143 ppm K‒1. The CTE above Tg significantly decreased

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from > 7000 to 151 ppm K‒1 with the addition of CNF, which is mainly due to the strong

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hydrogen bonding network between the nanofibrils.50 The Tg of the PS seems not to have been

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significantly changed in the presence of CNFs as previously reported.48 In this way, the

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mechanical properties and thermal dimensional stability of PS film were effectively improved

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due to the homogeneous distribution of CNF throughout the material.


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CONCLUSIONS

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A nanostructured PS nanoparticle/CNF composite was successfully prepared using a facile

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aqueous process. The process involved the encapsulation of a styrene monomer in a CNF-

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stabilized Pickering emulsion and subsequent polymerization. The PS/CNF composite was easily

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collected by filtration and subsequent melt pressing allowed the preparation of a transparent

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PS/CNF composite film. The film showed good mechanical properties and thermal dimensional

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stability due to the reinforcement by the homogeneously distributed CNFs. This material could

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be extended to nanotechnology application such as flexible electronic devices and solar cells

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combining transparency and thermostable properties. Moreover, this novel CNF/nanoparticle

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structure could be useful for optical applications or as a template for porous materials. Therefore,

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this technique paves the way toward novel green nanocomposite production using a facile and

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scalable process.

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ASSOCIATED CONTENT

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Supporting Information

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Photographs and size distributions of CNF aqueous dispersion and CNF-stabilized Pickering

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emulsions, SEM images of the emulsion, molecular mass distribution of PS, solid-state CP MAS

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charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

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Corresponding Author

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*Phone: +81 29 829 8270. Fax: +81 29 874 3720. E-mail: [email protected]

C NMR spectrum, and tensile properties of the composite. This material is available free of


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Notes

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The authors declare no competing financial interest.

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ACKNOWLEDGMENT

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This research was supported by Grants-in-Aid for Scientific Research (Grant number

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JP15H06848) from the Japan Society for the Promotion of Science (JSPS).

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REFERENCES

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(1)

252 253

Kovtyukhova, N. I.; Ollivier, P. J.; Martin, B. R.; Mallouk, T. E.; Chizhik, S. A.; Buzaneva, E. V.; Gorchinskiy, A. D., Chem. Mater. 1999, 11, 771-778.

(2)

Podsiadlo, P.; Kaushik, A. K.; Arruda, E. M.; Waas, A. M.; Shim, B. S.; Xu, J.;

254

Nandivada, H.; Pumplin, B. G.; Lahann, J.; Ramamoorthy, A.; Kotov, N. A., Science

255

2007, 318, 80-83.

256

(3)

257 258

Mater. 2002, 1, 190-194. (4)

259 260

(5)

(6)

Ogasawara, W.; Shenton, W.; Davis, S. A.; Mann, S., Chem. Mater. 2000, 12, 28352837.

(7)

265 266

Khan, M. K.; Giese, M.; Yu, M.; Kelly, J. A.; Hamad, W. Y.; MacLachlan, M. J., Angew. Chem. Int. Ed. 2013, 52, 8921-8924.

263 264

Olek, M.; Ostrander, J.; Jurga, S.; Mohwald, H.; Kotov, N.; Kempa, K.; Giersig, M., Nano Lett. 2004, 4, 1889-1895.

261 262

Mamedov, A. A.; Kotov, N. A.; Prato, M.; Guldi, D. M.; Wicksted, J. P.; Hirsch, A., Nat.

Walther, A.; Bjurhager, I.; Malho, J. M.; Pere, J.; Ruokolainen, J.; Berglund, L. A.; Ikkala, O., Nano Lett. 2010, 10, 2742-2748.

(8)

Zhu, J.; Zhang, H. N.; Kotov, N. A., ACS nano 2013, 7, 4818-4829.


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(9)

Coleman, J. N.; Khan, U.; Blau, W. J.; Gun’ko, Y. K., Carbon 2006, 44, 1624-1652.

268

(10)

Byrne, M. T.; Gun'ko, Y. K., Adv. Mater. 2010, 22, 1672-1688.

269

(11)

Moniruzzaman, M.; Winey, K. I., Macromolecules 2006, 39, 5194‒5205.

270

(12)

Ramanathan, T.; Abdala, A. A.; Stankovich, S.; Dikin, D. A.; Herrera-Alonso, M.; Piner,

271

R. D.; Adamson, D. H.; Schniepp, H. C.; Chen, X.; Ruoff, R. S.; Nguyen, S. T.; Aksay, I.

272

A.; Prud'Homme, R. K.; Brinson, L. C., Nat. Nanotechnol. 2008, 3, 327-331.

273

(13)

274 275

Rafiee, M. A.; Rafiee, J.; Wang, Z.; Song, H. H.; Yu, Z. Z.; Koratkar, N., ACS nano 2009, 3, 3884-3890.

(14)

276

Liang, J.; Huang, Y.; Zhang, L.; Wang, Y.; Ma, Y.; Guo, T.; Chen, Y., Adv Funct. Mater. 2009, 19, 2297-2302.

277

(15)

Okada, A.; Usuki, A., Macromol. Mater. Eng. 2006, 291, 1449-1476.

278

(16)

Giannelis, E. P., Adv. Mater. 1996, 8, 29-35.

279

(17)

Pavlidou, S.; Papaspyrides, C. D., Prog. Polym. Sci. 2008, 33, 1119-1198.

280

(18)

Berglund, L. A.; Peijs, T., MRS Bull. 2010, 35, 201-207.

281

(19)

Saito, T.; Kuramae, R.; Wohlert, J.; Berglund, L. A.; Isogai, A., Biomacromolecules

282

2013, 14, 248-253.

283

(20)

Wu, X. W.; Moon, R. J.; Martini, A., Cellulose 2014, 21, 2233-2245.

284

(21)

Sakurada, I.; Nukushina, Y.; Ito, T., J. Polym. Sci. 1962, 57, 651-660.

285

(22)

Sturcova, A.; Davies, G. R.; Eichhorn, S. J., Biomacromolecules 2005, 6, 1055-1061.

286

(23)

Iwamoto, S.; Kai, W.; Isogai, A.; Iwata, T., Biomacromolecules 2009, 10, 2571-2576.

287

(24)

Hori, R.; Wada, M., Cellulose 2005, 12, 479-484.

288

(25)

Diaz, J. A.; Wu, X. W.; Martini, A.; Youngblood, J. P.; Moon, R. J., Biomacromolecules

289

2013, 14, 2900-2908.


15

Biomacromolecules

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 18

290

(26)

Samir, M. A. S. A.; Alloin, F.; Dufresne, A., Biomacromolecules 2005, 6, 612-626.

291

(27)

Eichhorn, S. J.; Dufresne, A.; Aranguren, M.; Marcovich, N. E.; Capadona, J. R.; Rowan,

292

S. J.; Weder, C.; Thielemans, W.; Roman, M.; Renneckar, S.; Gindl, W.; Veigel, S.;

293

Keckes, J.; Yano, H.; Abe, K.; Nogi, M.; Nakagaito, A. N.; Mangalam, A.; Simonsen, J.;

294

Benight, A. S.; Bismarck, A.; Berglund, L. A.; Peijs, T., J. Mater. Sci. 2010, 45, 1-33.

295

(28)

296 297

Saito, T.; Nishiyama, Y.; Putaux, J. L.; Vignon, M.; Isogai, A., Biomacromolecules 2006, 7, 1687-1691.

(29)

Ballner, D.; Herzele, S.; Keckes, J.; Edler, M.; Griesser, T.; Saake, B.; Liebner, F.;

298

Potthast, A.; Paulik, C.; Gindl-Altmutter, W., ACS Appl. Mater. Interaces 2016, 8,

299

13520-13525.

300

(30)

Kalashnikova, I.; Bizot, H.; Cathala, B.; Capron, I., Langmuir 2011, 27, 7471-7479.

301

(31)

Kalashnikova, I.; Bizot, H.; Cathala, B.; Capron, I., Biomacromolecules 2012, 13, 267-

302 303

275. (32)

Gestranius, M.; Stenius, P.; Kontturi, E.; Sjöblom, J.; Tammelin, T., Colloids and

304

Surfaces,

305

doi:10.1016/j.colsurfa.2016.04.025.

306

(33)

307 308

(34)

and

Engineering

Aspects

2016,

in

press,

Blaker, J. J.; Lee, K. Y.; Li, X. X.; Menner, A.; Bismarck, A., Green Chem. 2009, 11,

Hu, Z.; Ballinger, S.; Pelton, R.; Cranston, E. D., J. Colloid Interface Sci. 2015, 439, 139148.

(35)

311 312

Physicochemical

1321-1326.

309 310

A:

Glasser, W. G.; Atalla, R. H.; Blackwell, J.; Brown, R. M.; Burchard, W.; French, A. D.; Klemm, D. O.; Nishiyama, Y., Cellulose 2012, 19, 589-598.

(36)

Alqus, R.; Eichhorn, S. J.; Bryce, R. A., Biomacromolecules 2015, 16, 1771-1783.


16

Page 17 of 18

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Biomacromolecules

313

(37)

Isogai, A.; Saito, T.; Fukuzumi, H., Nanoscale 2011, 3, 71-85.

314

(38)

Fujisawa, S.; Saito, T.; Kimura, S.; Iwata, T.; Isogai, A., Biomacromolecules 2013, 14,

315

1541-1546.

316

(39)

Tanaka, R.; Saito, T.; Hondo, H.; Isogai, A., Biomacromolecules 2015, 16, 2127-2131.

317

(40)

Kim, S. D.; Zhang, W. L.; Choi, H. J., J. Mater. Chem. C 2014, 2, 7541-7546.

318

(41)

Kim, Y. J.; Liu, Y. D.; Seo, Y.; Choi, H. J., Langmuir 2013, 29, 4959-4965.

319

(42)

Lok, K. P.; Ober, C. K., Can. J. Chem. 1985, 63, 209-216.

320

(43)

Tseng, C. M.; Lu, Y. Y.; Elaasser, M. S.; Vanderhoff, J. W., J. Polym. Sci., Part A:

321 322

Polym. Chem. 1986, 24, 2995-3007. (44)

323

Ober, C. K.; Lok, K. P.; Hair, M. L., J. Polym. Sci., Part C: Pom.l Lett. 1985, 23, 103108.

324

(45)

Polymer Reaction Engineering. Blackwell Science Publ: Oxford, 2007; p 1-367.

325

(46)

Mason, B. P.; Price, K. E.; Steinbacher, J. L.; Bogdan, A. R.; McQuade, D. T., Chem.

326

Rev. 2007, 107, 2300-2318.

327

(47)

Wyatt, P. J., Anal. Chim. Acta 1993, 272, 1-40.

328

(48)

Fujisawa, S.; Ikeuchi, T.; Takeuchi, M.; Saito, T.; Isogai, A., Biomacromolecules 2012,

329 330

13, 2188-2194. (49)

331 332

Ben Elmabrouk, A.; Thielemans, W.; Dufresne, A.; Boufi, S., J. Appl. Polym. Sci. 2009, 114, 2946-2955.

(50)

Iwamoto, S.; Nakagaito, A. N.; Yano, H.; Nogi, M., Appl. Phys. A 2005, 81, 1109-1112.


17

Biomacromolecules

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Facile Route to Transparent, Strong, and Thermally Stable

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