Synthesis of hydrophobically associative cellulose nanofibers by TEMPO-mediated oxidization

이예람,김진웅 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0

In recent years, cellulose materials have attracted significant attention because of their excellent structural stability as well as abundance in nature. This study synthesizes hydrophobically associative cellulose nanofibers by using combined ATRP and 2,2,6,6-tetramethylpiperidine-1-oxyl radical(TEMPO)-mediated oxidation. Specifically, cellulose nanocrystals are functionalized by partial esterification of superficial -OH groups with 2-bromoisobutyryl bromide to introduce initiation sites. Then, these initiation sites-functionalized cellulose nanocrystals are grafted with stearyl methacrylate and 2-methacryloxyethyl phosphorylcholine by ATRP. Finally, the TEMPO-mediated oxidation enables production of nanoscale cellulose nanofibers. We have found that the cellulose nanofibers can not only dramatically increases the viscosity of aqueous solution due to the hydrophobic attraction, but also display excellent tolerance to pH changes and salt addition due to the gel phase formation. We expect the cellulose nanofibers developed in this study would find great applicability as suspension rheology modifiers.

키틴과 셀룰로오스 나노파이버의 제조 및 특성과 고분자 필름에의 응용

임우주(Woo Ju Lim),강영정(Youngjeong Kang),김준호(Joon Ho Kim) 한국고분자학회 2020 폴리머 Vol.44 No.1

화학적 전처리와 초미세분쇄기 및 고압균질화기와 같은 기계적 처리를 이용한 피브릴화를 통해서 셀룰로오스 나노섬유(CNF)와 키틴 나노섬유를 제조하였다. 셀룰로오스와 키틴 모두 TEMPO에 의한 산화처리에 의해서 피브릴화가 촉진되었다. 제조된 나노섬유들을 함유하는 히드록시프로필 셀룰로오스(HPC) 수용액과 알긴산 나트륨(SA) 수용액으로부터 HPC 필름과 SA 필름을 각각 제조하였으며, 나노섬유 첨가량 변화가 각 필름의 인장 특성에 미치는 효과를 평가하였다. HPC 복합필름 및 SA 복합필름의 인장강도는 각각 소량의 CNF 및 키틴 나노섬유 첨가만으로도 크게 증가하였다. 강도 보강효과는 CNF가 키틴 나노섬유보다 컸으며, 필름의 광학적 투과도는 나노섬유 첨가량 증가에 비례하여 모두 감소하였으나 키틴 나노섬유에 비하여 CNF의 감소효과가 훨씬 작았다. Cellulose nanofiber (CNF) and chitin nanofiber were prepared by using chemical pretreatments and mechanical treatments such as ultrafine grinder and high-pressure homogenizer. The fibrillation was promoted by the 2,2,6,6-tetramethylpiperidin-1-oxyl radical (TEMPO) oxidation of cellulose and chitin, respectively. Hydroxypropyl cellulose (HPC) film and sodium alginate (SA) film including these nanofibers were cast using water as a solvent. The reinforcing effect of these nanofibers on the tensile properties of HPC film and SA film was investigated by changing the add-on amount of each nanofiber. The tensile strength of the HPC composite film and SA composite film increased remarkably by adding a small amount of CNF and chitin nanofiber, respectively. The film reinforcing effect of CNF was much higher than that of chitin nanofiber. The optical transparency of both films decreased with increasing content of nanofibers. The decreasing effect of CNF on the transparency of the film was much lower than that of chitin nanofiber.

Cellulose reinforced nylon-6 nanofibrous membrane: Fabrication strategies, physicochemical characterizations, wicking properties and biomimetic mineralization

Joshi, Mahesh Kumar,Tiwari, Arjun Prasad,Maharjan, Bikendra,Won, Ko Sung,Kim, Han Joo,Park, Chan Hee,Kim, Cheol Sang Elsevier 2016 Carbohydrate polymers Vol.147 No.-

<P><B>Abstract</B></P> <P>The aim of the present study is to develop a facile, efficient approach to reinforce nylon 6 (N6) nanofibers with cellulose chains as well as to study the effect that cellulose regeneration has on the physicochemical properties of the composite fibers. Here, a cellulose acetate (CA) solution (17wt%) was prepared in formic acid and was blended with N6 solution (20%, prepared in formic acid and acetic acid) in various proportions, and the blended solutions were then electrospun to produce hybrid N6/CA nanofibers. Cellulose was regenerated in-situ in the fiber via alkaline saponification of the CA content of the hybrid fiber, leading to cellulose-reinforced N6 (N6/CL) nanofibers. Electron microscopy studies suggest that the fiber diameter and hence pore size gradually decreases as the mass composition of CA increases in the electrospinning solution. Cellulose regeneration showed noticeable change in the polymorphic behavior of N6, as observed in the XRD and IR spectra. The strong interaction of the hydroxyl group of cellulose with amide group of N6, mainly via hydrogen bonding, has a pronounced effect on the polymorphic behavior of N6. The γ-phase was dominant in pristine N6 and N6/CA fibers while α- phase was dominant in the N6/CL fibers. The surface wettability, wicking properties, and the tensile stress were greatly improved for N6/CL fibers compared to the corresponding N6/CA hybrid fibers. Results of DSC/TGA revealed that N6/CL fibers were more thermally stable than pristine N6 and N6/CA nanofibers. Furthermore, regeneration of cellulose chain improved the ability to nucleate bioactive calcium phosphate crystals in a simulated body fluid solution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> N6/CL composite fibers were obtained via electrospinning and deacetylation. </LI> <LI> Fiber diameter and pore size controlled varying the composition of component polymers. </LI> <LI> N6/CL composite fiber were more thermally stable than pristine N6 and N6/CA fibers. </LI> <LI> Wicking rate was pronouncedly enhanced due to cellulose regeneration. </LI> <LI> Tensile properties and biomimetic mineralization were improved. </LI> </UL> </P>

Humidity Sensor of Coarse Cellulose Nanofiber-silver Nanoparticles (CNF-AgNPs) Deposited by All Printing Process

M. Jung(정민훈),H. Lee(이현아),D. S. Kim(김동수) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월

This paper presents an investigation on the humidity sensitivity of deposited cellulose-silver nanoparticles (AgNPs) using ink-jet printing between integrated electrodes (IDEs). The IDEs were fabricated on the glass using a Reverse-offset printer which has a soft double blanket. The Reverse-offset printing process is of great significance to exploit a simple, cost-effective, and environmentally friendly fabrication method of humidity sensors. Also, we have used coarse cellulose nanofiber (CNF) as a humidity sensor. Silver nanoparticles (AgNPs) as a humidity-sensitive layer were introduced onto cellulose surface via in situ reduction technique without disrupting cellulose structure. We have confirmed the coarse cellulose nanofiber silver nanoparticles (CNF-AgNPs) using UV–visible spectroscopy, transmission electron microscopy (TEM), and scattering electron microscopy (SEM) analysis revealed the successful deposition of silver nanoparticles onto coarse cellulose surface, which is referred as a CNF-AgNPs nanocomposite. The humidity sensitivity using CNF-AgNPs was obtained by measuring the resistance with different relative humidity at room temperature. The experimental results show the resistance increases linearly with increasing the relative humidity from 20 to 90% RH with highly sensitivity compared with coarse cellulose.

Preparation and Characterization of Cellulose Nanofibril/Polyvinyl Alcohol Composite Nanofibers by Electrospinning

Byung Dae Park,In Chul Um,Sun Young Lee,Alain Dufresne 한국목재공학회 2014 목재공학 Vol.42 No.2

This work undertook to prepare nanofibers of cellulose nanofibrils (CNF)/polyvinyl alcohol (PVA) composite by ele-ctrospinning, and characterize the electrospun composite nanofibers. Different contents of CNFs isolated from hardwood bleached kraft pulp (HW-BKP) by 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation were sus-pendedin aqueous polyvinyl alcohol (PVA) solution, and then electrospun into CNF/PVA composite nanofibers. The morphology and dimension of CNFs were characterized by transmission electron microscopy (TEM), which revealed that CNFs were fibrillated form with the diameter of about 7.07 ± 0.99 nm. Morphology of the electrospun nanofiber observed by field-emission scanning electron microscopy (FE-SEM) showed that uniform CNF/PVA composite nano-fiberswere manufactured at 1~3% CNF contents while many beads were observed at 5% CNF level. Both the viscosity of CNF/PVA solution and diameter of the electrospun nanofiber decreased with an increase in CNF content. The diam-eterand its distribution of the electrospun nanofibers helped explain the differences observed in their morphology. These results show that the electrospinning method was successful in preparing uniform CNF/PVA nanofibers, indicating a great potential for manufacturing consistent and reliable cellulose-based nanofibrils for scaffolds in future applications.

Characterization of Electrospun Nanofibers of Cellulose Nanowhisker/Polyvinyl Alcohol Composites

Mijung Cho,Byung Dae Park,John F. Kaclla 한국목재공학회 2012 목재공학 Vol.40 No.2

Cellulose nanowhisker (CNW) isolated from hardwood bleached kraft pulp (1-W-BKP) using sulfuric acid hydrolysis was suspended in polyvinyl alcohol (PVA) and electrospun into composites nanofibers. Transmission electron microscopy (TEM) revealed the CNW to be rod-like, approximately of 16.1 4.6 nm wide and 194 ± 61 nm long, providing an aspect ratio of about 12, with a particle size distribution range of 662.2 + 301.2 nm. Uniform and high quality CNW/PVA composite nanofibers were successfully manufactured by the electrospinning method. As the CNW loading increases, the viscosity of CNW/PVA solutions shows a minimum at 1% CNW level which subsequently results in the smallest diameter (193 nm) of electrospun nanofibers. The average diameter of the nanofibers increased up to 284 nm with increasing CNW loading. These results suggest that the electrospinning method provides a great potential of manufacturing consistent and reliable nanofibers from CNW/PVA solution for the formation of scaffolds with potentials in future application.

Antimicrobial activity of cellulose-based nanofibers with different Ag phases

Hyuk Jang, K.,Joon Yu, Y.,Ha Lee, Y.,Ok Kang, Y.,Ho Park, W. North-Holland 2014 Materials letters Vol.116 No.-

Cellulose acetate (CA) nanofibers containing Ag ions, CA (as-spun), were fabricated by electrospinning with 0.5 or 1wt% of silver nitrate (AgNO<SUB>3</SUB>). CA nanofibers containing Ag ions/nanoparticles (NPs), CA (UV), were prepared by UV irradiation of as-spun CA nanofibers. Also, cellulose nanofibers with Ag NPs, CA (UV+DA), were prepared by deacetylating the UV-irradiated CA nanofibers. The antimicrobial activities of Ag ions or NPs in nanofibrous matrices were examined against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. From conventional antimicrobial test for 18h, both Ag ions and Ag NPs in the CA or cellulose nanofibers exhibited strong antimicrobial activity against S. aureus. From kinetic antimicrobial test against E. coli for 30min, the CA (as-spun) showed faster bactericidal activity than the CA (UV) and CA (UV+DA) samples.

Cellulose Monoacetate/Tetraethyl Orthosilicate Hybrid Nanofibers for Electrochemical DNA Biosensors

Sinem Civan,Seval Aydin,Nilay Aladag Tanik,Yakup Aykut 한국섬유공학회 2021 Fibers and polymers Vol.22 No.4

Cellulose monoacetate/tetraethyl orthosilicate (CMA/TEOS) hybrid nanofibers were produced with differentratios via electrospinning and used for guanine oxidation analysis in the single strand deoxyribonucleic acid (ssDNA)molecules by electrochemical method. Nanofiber (NF) diameters for pure CMA dramatically decreased from between 2.4 μ-306 nm to between 958-42 nm with addition of hydrochloric acid (HCl) catalyzer into the electrospinning solution. UniformCMA nanofibers morphologies transform to more defect structures containing particular structures with the addition andincrease of TEOS content in CMA electrospinning solution. Also, nanofibers' diameters range became more fluctuated formand ultrafine nanofibers (diameters below 100 nm) existed more in the nanofiber mat. Even though the melting point wasseen at CMA nanofibers, melting points were not detectable in CMA/TEOS NFs since TEOS addition does not allow anappropriate crystallization. Thermal analysis results revealed that residual contents after TGA measurement in nitrogenatmosphere were gradually increased by increasing TEOS ratio in CMA/TEOS nanofibers. ssDNA molecules were immobilizedon the as-spun nanofibers and differential pulse voltammetry (DPV) measurements were carried out to investigate theguanine oxidation in ssDNA. Guanine oxidation signal intensities decreased with the initial addition of TEOS to CMAnanofibers and increases again by increasing TEOS content in CMA/TEOS hybrid nanofibers and then gradually decreasesagain with increasing TEOS content. The prepared CMA/TEOS hybrid nanofibers could be a promising candidate as anelectrode interface for genetic molecule detection via electrochemical methods.

Zein/Cellulose Acetate Hybrid Nanofibers: Electrospinning and Characterization

Shamshad Ali,김성훈,Zeeshan Khatri,오경화,김익수 한국고분자학회 2014 Macromolecular Research Vol.22 No.9

Protein based scaffolds are preferred for tissue engineering and other biomedical applications owing totheir unique properties. Zein, a hydrophobic protein, is a promising natural biodegradable polymer. However, electrospunstructures prepared from Zein have poor mechanical and wetting properties. Cellulose acetate (CA) is aneconomical, biodegradable polymer having good mechanical and water retention properties. The aim of presentstudy was to fabricate a novel material by electrospinning Zein/CA blends. A series of Zein/CA hybrid nanofiberswere electrospun and characterized. The attenuated total reflectance-Fourier transform infrared spectroscopy (ATRFTIR)spectrum showed the characteristic peaks of both Zein and CA, and was composition dependent. The X-rayphotoelectron spectrometry (XPS) curves of Zein/CA blends demonstrated a similar profile to that of pristine Zeinnanofibers. Thermogravimetric analyser (TGA) studies confirmed that the Zein/CA hybrid nanofibers have a higherdegradation temperature and better thermal stability than pristine Zein nanofibers. The glass transition temperature(Tg) of Zein/CA hybrid nanofibers was also increased in comparison to pure Zein nanofibers as revealed by differentialscanning calorimetry (DSC). Zein/CA hybrid nanofibers have hydrophilic surface character as revealed bywater contact angle (WCA) analysis. SEM imaging showed bead free morphology of the electrospun nanofibers. The average nanofiber diameter decreased for Zein/CA blends with increasing CA composition. The electrospunZein/CA hybrid nanofibers may be used for tissue engineering scaffolds and for other biomedical materials.

Electrospun polyvinylidene fluoride nanofibers with superhydrophilicity and improved biocompatibility

( Faheem Sheikh ),김헌 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

In this study, we had successfully prepared a colloidal solution consisting of polyvinylidene fluoride and cellulose acetate for obtaining nanofibers by electrospinning. The prepared nanofibers were characterized by SEM, FT-IR, TGA and XRD. These characterization techniques revealed that cellulose acetate can be easily introduced in polyvinylidene fluoride nanofibers using a colloidal solution, and this method favorably preserves the intact nature of cellulose acetate. The cell toxicity and cell attachment studies using NIH 3T3 fibroblasts indicated non-toxic behavior and good attachment of cells due to modification of cellulose acetate in polyvinylidene fluoride nanofibers.