Chitosan/ Polyvinyl Pyrrolidone/Nano-layer Graphene ...

1 downloads 0 Views 1MB Size Report
Mar 9, 2014 - Chitosan/ Polyvinyl Pyrrolidone/Nano-layer Graphene Oxide Biocompatible Films for Food. Packaging. N. Mahmoudia, F. Ostadhosseina, ...
Proceedings of the 5th International Conference on Nanostructures (ICNS5) 6-9 March 2014, Kish Island, Iran

Chitosan/ Polyvinyl Pyrrolidone/Nano-layer Graphene Oxide Biocompatible Films for Food Packaging N. Mahmoudia, F. Ostadhosseina, A. Simchia,b* a

Department of Materials Science and Engineering, Sharif University of Technology, Tehran, 11365-9466, Iran Institute for Nanoscience and Nanotechnology, Sharif University of Technology, Tehran, 89694- 14588, Iran *[email protected]

b

Abstract: Chitosan (CS)/polyvinyl pyrrolidone (PVP)/graphene oxide (GO) films were prepared by solvent casting methods. Microstructural studies showed parallel arrangement of GO layers inside the films indicating selforganization during drying. The self-organization of GO inhibited transport of water molecules and thus decreasing its permeability. The presence of GO also increased the thermal stability of the films and the glass transition temperature of the polymer matrix (Tg) was shifted to higher temperatures. Additionally, results showed that increasing the PVP content improved the permeability and transparency of the films. Therefore, physical properties of the composite films could be tuned by the addition of GO sheets and CS/PVP ratio for food packaging applications.

Keywords: Chitosan; PolyVinyl Pyrrolidone; Graphene Oxide; Biocomposite; Food packaging Introduction Investigation of the physical and structural properties of biofilms usable in biomedical applications and food packaging has been of interest for a decade. Chitosan (CS) is one of the most studied biopolymers for various applications due to its biocompatibility, antimicrobial properties, high film forming ability, and low permeability [1-3]. However, CS suffers from water solubility and degradation by UV radiation that limit its applications [4]. To tackle these barriers, polyvinyl pyrrolidone (PVP) can be utilized as PVP is a biocompatible, nontoxic, hydrophilic and transparent synthetic polymer with high film forming properties [58]. In contrast to wide usage of PVP in medical, food packaging and cosmetics [9-10], it is fragile a polymer [4]. Blends of CS/PVP have been of interest for a decade as their properties can be tuned for targeted applications [4,8,11]. However, transparency and permeability of the films cannot be engineered simultaneously due to different properties of CS and PVP. Additionally, the mechanical stiffness of CS/PVP films does not fulfill demands of many biomedical applications. Therefore, reinforcement of the polymer matrix with stiffer particles has recently attracted the focus of many studies [5,7,11]. Graphene (GR) and graphene Oxide (GO) exhibit outstanding physical and mechanical properties [12-15]; hence, they have been used in polymer-matrix composites frequently [12,15]. Particularly, GO sheets are potentially attractive as fillers in composites because the presence of functional groups on GO as well as its high surface energy that increase the affinity of GO-polymer bonding [14,15]. In the present work, we studied the effect of PVP addition on the physical properties of CS films containing 1wt.% GO sheets. The composite of CS/PVP/GO films were fabricated by facile solvent-casting methods. The structure and physical properties of the films were investigated by various analytical techniques. The role of

PVP and GO on the permeability and transparency of CS is discussed.

Materials and method CS (Mw=190-310 kDa, degree of deacetylation: ~ 85%) and PVP (K-40, average molecular weight: Mw=40 kDa) were supplied by Sigma-Aldrich Co (USA). Graphite powder was purchased from CHEER Carbone Materials (China). All other reagents used in the synthesis of GO were purchased from Merck Co. (Germany) with analytical grades. The modified Hummer’s method [16] was used to synthesize GO sheets. Solvent casting methods were utilized to prepare CS/PVP/GO films. Aqueous solutions of CS and PVP with concentration of 1 wt.% in acetic acid/distilled water (1% v/v) were prepared. These solutions were mixed at different CS to PVP ratios and finally 1wt.% GO was added. The mixture were then stirred for 3 hrs at 45°C and poured into Petri dishes to dry gently. Microstructure of the prepared films was studied by SEM (KYKY, EM 3200, China). To determine the opacity of the films, UV-Vis (spectrophotometer 6705, Jenway, UK) was utilized. The absorption intensity at 600 nm divided by the film thickness was considered as the opacity [17]. Water permeability was determined in accordance to ASTM E 96-92. Changes in the weight of the films versus time were recorded and related to the permeability. Fourier transform infrared spectrometery (FTIR, ABB Bomem, MB-100, Canada) and differential scanning calorimetry (DSC, Q100, TA Instruments, USA) were used to characterize the structural bonding and thermal stability of the biofilms. Atomic Force Microscopy (AFM) (AutoProbe CP-Research, Veeco, USA) was also conducted to characterize the GO sheets.

Results and Discussion AFM image of GO sheets is shown in Fig. 1a. The thickness of the sheets is about 1 nm with 3 micrometer

Proceedings of the 5th International Conference on Nanostructures (ICNS5) 6-9 March 2014, Kish Island, Iran

length. Fig. 1b shows the distribution of GO sheets in the polymer matrix. The GO nanolayers are arranged in an approximately ordered configuration. It seems that the alignment of GO sheets occurred during drying due to the

2.9 µm

through itself. On the other hand, the addition of GO to the pristine PVP/CS sheets significantly decreased the permeability at different PVP contents. The high aspect ratio of the GO sheets also operate as a barrier against water vapor diffusion through the film which results in a lower permeability. To study the thermal stability of the composite films, DSC was performed (Fig. 3). Endothermic peaks were detected that corresponded to the glass transition temperatures (T g) of the polymers. By increasing the PVP content, Tg was shifted to higher temepratures and the reaction became more endeothermic (Table 3).

Fig. 1. (a) AFM image of GO sheets.(b) Fracture surface of CS/25%PVP/1%GO film shows allignment of GO nanolayers (SEM image).

slow rate of solvent evaporation. FTIR spectrum of biocomposites at different PVP concentration are shown in Fig. 2a. The characteristic absorption peaks of CS are located at 1073, 1595 and 1649 cm-1 which correspond to the stretching vibration of C-O, the deformation bending of N-H and the stretching vibration of both C=O and the C-N of amide group, respectively. The peak detected at 3400 cm-1 is assigned to the intermolecular hydrogen bonding between hydroxyl and amine groups in CS. The PVP absorption peaks are seen at 1285, 1458 and 1663 cm-1. The hydrogen bonding between the protonated groups of CS such as OH-C6, OH-C3 and NH2-C2, and the deporonated functional group of C=O in PVP is noticable [4,5,11]. Fig. 2a also shows that increasing of the PVP content is accompanied by a red shift in the main characteristic peaks [4]. This observation can be attributed to formation of stronger hydrogen bonds between CS and PVP functional groups [4,5]. The absorption spectrum of the films at different PVP concentrations are shown in Fig. 2b. As reported in Table 1, the opacity number of the films decreased (higher transparency) by increasing the PVP content. Table 2 reports the water vapor permeability of prepared films with and without GO sheets. The effect of PVP on the improved water permeability of CS/GO is noticeable. This can be attributed to the high intrinsic permeability of PVP which facilitates the diffusion of water molecules

Fig. 2: (a) FTIR and (b) UV-Vis spectrum of CS/PVP/1wt% GO composite films. Table 1: Opacity of CS/PVP films containing 1% GO at different PVP concentrations PVP concentration

Film thickness )µm± standard deviation(

Absorption at 600 nm

Opacity

0

30±8.94

0.213

7.1

25

22±4.47

0.153

6.95

50

30±8.16

0.127

4.23

75

24±5.47

0.097

4.04

100

27 ± 5

0.113

4.18

Proceedings of the 5th International Conference on Nanostructures (ICNS5) 6-9 March 2014, Kish Island, Iran

[4]

[5]

[6]

Fig. 3. Effect of PVP on the thermal properties of composite films.

[7]

Table 2. Water permeability of films PVP concentration

Water permeability (g.mm/m2.h.kPa) Without GO

[8]

With 1% GO

0

3.21±0.37

3.08±0.21 (A0)

25

4.51 ± 0.24

4.28±0.19 (B0)

50

5.34 ± 0.61

5.01±0.42 (C0)

75

7.12 ± 0.93

6.57± 0.82 (D0)

100

8.36 ± 1.32

7.98±1.24 (E0)

[9]

[10]

Table 3. The effect of PVP on thermal properties of films PVP concentration 0

Tg (°C) 61.41 56.08 57.86 59.38 65.38

25 50 75 100

Peak Temperature (°C) 104.96 101.25 109.29 110.09 114.96

Heat Flow (J/g) 244.3 363.0 346.6 470.0 307.4

[11]

[12]

Conclusions Biocompatible CS/PVP/GO films were prepared by solvent casting methods with tunable optical properties and permeability for possible application in food packaging. The effect of PVP concentration was investigated. Aligned nanosheets of GO were distributed in the polymer matrix. The permeability increased with increasing PVP content but decreased by the addition of 1% GO. The thermal stability of the films was also improved by GO sheets.

References [1]

[2]

[3]

R. Jayakumar, M. Prabaharan, P. Sudheesh Kumar, S. Nair, and H. Tamura, "Biomaterials based on chitin and chitosan in wound dressing applications," Biotechnology advances, vol. 29, pp. 322-337, 2011. P. Dutta, S. Tripathi, G. Mehrotra, and J. Dutta, "Perspectives for chitosan based antimicrobial films in food applications," Food Chemistry, vol. 114, pp. 1173-1182, 2009. N. Peelman, P. Ragaert, B. De Meulenaer, D. Adons, R. Peeters, L. Cardon, et al., "Review: Application of

[13]

[14]

[15]

[16]

[17]

bioplastics for food packaging," Trends in Food Science & Technology, 2013. J. T. Yeh, C. L. Chen, K. Huang, Y. Nien, J. Chen, and P. Huang, "Synthesis, characterization, and application of PVP/chitosan blended polymers," Journal of applied polymer science, vol. 101, pp. 885891, 2006. L. Zhang, X. Bai, H. Tian, L. Zhong, C. Ma, Y. Zhou, et al., "Synthesis of antibacterial film CTS/PVP/TiO 2/Ag for drinking water system," Carbohydrate Polymers, vol. 89, pp. 1060-1066, 2012. B. Sun, Y. Long, H. Zhang, M. Li, J. Duvail, X. Jiang, et al., "Advances in Three-Dimensional Nanofibrous Macrostructures via Electrospinning," Progress in Polymer Science, 2013. D. Archana, B. K. Singh, J. Dutta, and P. Dutta, "InVivo Evaluation of chitosan-PVP-titanium dioxide nanocomposite as wound dressing material," Carbohydrate Polymers, 2013. J. Li, S. Zivanovic, P. Davidson, and K. Kit, "Characterization and comparison of chitosan/PVP and chitosan/PEO blend films," Carbohydrate Polymers, vol. 79, pp. 786-791, 2010. W. Nie, D. Yu, C. Branford-White, X. Shen, and L. Zhu, "Electrospun zein‐PVP fibre composite and its potential medical application," Materials Research Innovations, vol. 16, pp. 14-18, 2012. A. Bernal, I. Kuritka, and P. Saha, "Preparation and characterization of poly (vinyl alcohol)‐poly (vinyl pyrrolidone) blend: A biomaterial with latent medical applications," Journal of applied polymer science, vol. 127, pp. 3560-3568, 2013. M. Zeng, H. Xiao, X. Zhang, X. Sun, C. Qi, and B. Wang, "A Novel Chitosan/Polyvinyl Pyrrolidone (CS/PVP) Three-Dimensional Composite and Its Mechanism of Strength Improvement," Journal of Macromolecular Science, Part B, vol. 50, pp. 14131422, 2011. P. Mukhopadhyay and R. K. Gupta, "Trends and frontiers in graphene-based polymer nanocomposites," Plastics Engineering, vol. 67, pp. 32-42, 2011. Y. J. Shin, Y. Wang, H. Huang, G. Kalon, A. T. S. Wee, Z. Shen, et al., "Surface-energy engineering of graphene," Langmuir, vol. 26, pp. 3798-3802, 2010. D. R. Dreyer, S. Park, C. W. Bielawski, and R. S. Ruoff, "The chemistry of graphene oxide," Chemical Society Reviews, vol. 39, pp. 228-240, 2010. M. Fang, K. Wang, H. Lu, Y. Yang, and S. Nutt, "Covalent polymer functionalization of graphene nanosheets and mechanical properties of composites," Journal of Materials Chemistry, vol. 19, pp. 70987105, 2009. S. H. Ajili, N. G. Ebrahimi, and M. Soleimani, "Polyurethane/polycaprolactane blend with shape memory effect as a proposed material for cardiovascular implants," Acta Biomaterialia, vol. 5, pp. 1519-1530, 2009. M. Abdollahi, M. Albofitile, R. Behrooz, M. Rezaei, and R. Miraki, "Reducing water sensitivity of alginate bio-nanocomposite film using cellulose nanoparticles," International journal of biological macromolecules, 2012.