Covalently grafted carbon nanotube on bacterial cellulose composite for flexible touch screen application

doi:10.1016/j.matlet.2013.05.126

Materials Letters

Volume 107, 15 September 2013, Pages 247-250

https://doi.org/10.1016/j.matlet.2013.05.126 Get rights and content

Highlights

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Chemically modified bacterial cellulose by carbon nanotube.
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Polarization induced by carbon nanotube.
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Touch screen application on Green substrate.

Abstract

Carbon nanotube was successfully grafted on hydroxyl group of bacterial cellulose molecule by conventional synthetic method. The purpose of incorporated carbon nanotube on bacterial cellulose was to enhance the polarization effect on its composite. The appearant peak from Fourier transform infrared at 1730 and 1350 cm⁻¹ exhibited that chemically modified bacterial cellulose by insertion of carbon nanotube was observed. Scanning electron microscope revealed that the structure of composite was designed as 3 stacks of grafted carbon on bacterial cellulose encapsulated on both sides by resin. In addition, significant enhancement on dielectric properties can be remarkably observed, suggesting bacterial cellulose composite exhibited superiority on polarization effect and it may initially be developed as electroactive macterials.

Introduction

Due to the growing environmental awareness and concerns over reliable availability of petrochemicals in the future, the polymer industry and academia have been pressed to design and produce polymers and composites based on renewable natural resources. In the past decades, the push towards flexible electronic device based on “Green composite materials” has been evident. Achievement of this new promising concept can easily lead to flexible displays and optoelectronics, as well as more novel ideas such as smart textiles, photovoltaic cells, and building lighting. Among the flexible electronic displays, organic light emitting diode (OLED) [1] is a versatile platform system that has attracted worldwide attention. OLED has been traditionally fabricated on rigid glass sheet substrates. Although flexible polymer substrates have been expected as potential alternatives in replacing the glass substrate, the use of conventional polymer substrates has been limited by their coefficient of thermal expansion (CTE). Okahisa [2]and Choi et al. [3] suggested that the CTE of the substrate should be restricted to 20 ppm/K at most, as the thermal expansion of the substrate can lead to the destruction of functional materials of the OLED circuit during the temperature fluctuation in OLED assembly and mounting processes. To overcome the CTE limitation of the flexible polymer substrate, our previous works have focused on the exploitation of the composite of nano-sized cellulose and polymeric matrices [4]. Bacterial cellulose, which is a nano-sized extracellular product of the bacteria strain Acetobacter xylinum, has the CTE of as low as 0.1 ppm/K. The incorporation of bacterial cellulose into polymeric matrix can be expected to yield a composite film with much decreased CTE to be less than 20 ppm/K. In addition, bacterial cellulose has the typical thickness and width of 10 and 50 nm. Its nano-entity will allow the fabrication of optically transparent OLED substrate as any element with size smaller than one-tenth of visible light wavelength is free of visible light-scattering. Moreover, up to the present time, in order to prolong the service lifetime of electronic device, this bacterial cellulose composite was further developed for water vapor transmission barrier [5] and surface smoothness [6], respectively.

Recently, on the other hand, small amount of carbon nanotube (CNT) incorporated on cellulose composite has been pioneered to re-discover as a smart material that can be utilized for sensors and actuators, so-called electro-active paper (EAPap). It commonly offered numerous advantages including lightweight, dryness, large deformation as well as minimal on power consumption. Due to this achievement on electro-active properties on cellulose modified by carbon-based material, not only elastic modulus and mechanical properties can be improved, but also, it can open to the wide vision on the development of successfully transparent and flexible cellulose composite with additional feature of touch screen characteristic. However, as the structure of cellulose was strongly evident as nano-fibril network. The important idea is to insert carbon nanotube in the air gap among cellulose chain and it may covalently be grafted at OH position in cellulose structure for not only electro-active but also mechanical properties if this cellulose will be further developed in industrial commercialization. Therefore, in this research work, we wish to extend our study on bacterial cellulose composite. Small amount of carbon nanotube was preliminary investigated by covalently grafted on bacterial cellulose composite for electro-mechanical properties purpose [7], [8]. The actuator properties were evaluated by investigating on preliminary experiment on piezoelectric properties. This bacterial cellulose will exhibit excellent properties on “Touch Screen” feature in the near future.

Section snippets

Materials, instruments and methods

Materials: Bacterial cellulose was extracted from commercially available Nata de coco (Uno Foods product), an indigenous Filipino-originated dessert of which the main component was reported as bacterial cellulose. The characterization of transparent and flexible feature of bacterial cellulose from Nata de coco were carried out in our previous article [9]; and its characteristics matched those of bacterial cellulose extracted from the culture of A. xylinum. Polyurethane based resin was purchased

Results and discussion

Carbon nanotube (CNT) grafted on bacterial cellulose preparation and characterizations: Bacterial cellulose was successfully exacted from Nata de Coco product. SEM investigation were used to study the size of bacterial cellulose. It can be seen that bacterial cellulose nanofibrils were about 50–100 nm in width and numerous micrometers long. The orientation of exacted bacterial cellulose exhibited three dimensional network structure, with air interstices in between. This is probably due to the

Conclusion

Small amount (less than 0.05 wt%) of carbon nanotube was successfully grafted on hydroxyl group of bacterial cellulose and it was further developed as sandwich-like structure of nanocomposite. The insertion of carbon nanotube did not provide the change on bacterial cellulose morphology. The excellence on engineering properties including transparent and thermal resistance satisfied the criteria of optoelectronic substrate. In addition, it can be found that small piezoelectric coefficient can be

Acknowledgment

The author would like to sincerely thank the financial support from the National Research Council Thailand (NRCT), Grant number GRB_BSS_66_56_63_08. We also extent our appreciation to Polymer Processing and Nanomaterials research unit, Chulalongkorn University for partially fund.

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Optically transparent wood-cellulose nanocomposite as a base substrate for flexible organic light-emitting diode displays
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Prog Polym Sci
(2008)
S. Ummartyotin
Development of transparent bacterial cellulose nanocomposite film as substrate for flexible organic light emitting diode (OLED) display
Ind Crops Prod
(2012)
S. Ummartyotin
Si–O barrier technology for bacterial cellulose nanocomposite flexible displays
Carbohydr Polym
(2011)
S. Ummartyotin
The role of ferrofluid on surface smoothness of bacterial cellulose nanocomposite flexible display
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There are more references available in the full text version of this article.

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Covalently grafted carbon nanotube on bacterial cellulose composite for flexible touch screen application

Highlights

Abstract

Introduction

Section snippets

Materials, instruments and methods

Results and discussion

Conclusion

Acknowledgment

Compos Sci Technol

Prog Polym Sci

Ind Crops Prod

Carbohydr Polym

Chem Eng J