Elsevier

Materials Letters

Volume 137, 15 December 2014, Pages 106-109
Materials Letters

Facile preparation of conductive composite hydrogels based on sodium alginate and graphite

https://doi.org/10.1016/j.matlet.2014.08.137Get rights and content

Highlights

  • SA/graphite conductive composite hydrogels were prepared by a facile method.

  • Incorporation of graphite into SA hydrogel matrix can influence its structure.

  • The composite hydrogels showed excellent swelling and conductive performance.

Abstract

Conductive composite hydrogels based on sodium alginate (SA) and graphite were obtained by a facile method of dispersing homogeneously conductive graphite into SA hydrogel matrix formed by in situ release of Ca2+ from Ca-EDTA, which avoids the multistep reactions and tedious purification compared to the previous work. The SA/graphite composite hydrogels exhibit reticulate and layer-type structure. The equilibrium swelling ratio of the composite hydrogels decreased with higher graphite content, although the swelling kinetics with various graphite contents was similar. The conductivity of the composite hydrogels could be tuned by adjusting f ([Ca2+]/[COO in alginate]) and the content of graphite, which reaches up to 10−3 S/cm.

Introduction

Conductive hydrogel is one kind of intelligent hydrogels in response to the electrical stimuli that combines the properties of hydrogels with the conductive components, which have significant applications in biosensor and bioelectronic devices. Conductive hybrid polymer hydrogels based on polyaniline [1], [2] and polypyrrole [3] have been attracting the interest of many researchers, however, the most obvious and intractable problems for polymeric conductive hydrogels are probably the complicated synthesis procedures and poor mechanical toughness [4]. In order to improve the strength properties, carbon conducting materials such as graphite, carbon black and carbon nanotubes were added into hydrogels formed by polyacrylamide [5] and chitosan [6] to obtain the carbon conductive composite hydrogels. These composite hydrogels can be strength-enhanced, however, the preparation process is complicated via the methods of free radical polymerization and electrodepositing. Therefore, it is significant to develop a facile method via blending carbon conducting substances with polymeric hydrogels directly to obtain the conductive composite hydrogels.

Sodium alginate (SA), an anionic polyelectrolyte extracted from seaweeds [7], is the commonly used natural macromolecule as promising material for its excellent biocompatibility, biodegradation and nontoxicity. SA is a linear polysaccharide consisting of (1→4) linked β-d-mannuronate (M) and α-l-guluronate (G) residues arranged in a non-regular block pattern [8]. It is easy to form hydrogels by chelating with calcium and other divalent metal ions owing to the numerous hydroxyl groups and the large free volume between the molecular chains [9], [10]. In this work, SA/graphite conductive composite hydrogels were fabricated by a facile method of dispersing homogeneously conductive graphite into SA hydrogel matrix formed by in situ release of Ca2+ from calcium chelate.

Section snippets

Experimental

SA (viscosity: 250–300 cps; G/M=0.5) and glucolactone (GDL) were received from Sigma-Aldrich. Ethylene diamine tetraacetic acid (EDTA) and graphite micropowders were purchased from Jiangsu Chemical Regent Co. Ltd., China. Sodium hydroxide was obtained from Tianjin Science and Technology Ltd. Calcium chloride and hydrochloric acid were purchased from Guangzhou Industrial Company. All the reagents were of analytical grade and used as received.

A structure parameter, f, is defined as [Ca2+]/[COO in

Results and discussions

Raman spectra of SA hydrogel and SA/graphite composite hydrogel are shown in Fig.1. Peaks at 1324 cm−1 and 1584 cm−1 could be obviously seen in SA/graphite composite hydrogel (Fig.1b). The peak at 1324 cm−1 is usually associated with the vibrations of carbon atoms with dangling bonds for the in-plane terminations of disordered graphite and is labeled as the D-band; the peak at 1584 cm−1 (G-band) (corresponding to the E2g mode) is closely related to the vibration in all sp2 bonded carbon atoms in a

Conclusion

Conductive composite hydrogels based on SA and graphite were fabricated by a facile method of dispersing homogeneously conductive graphite into SA hydrogel matrix formed by in situ release of Ca2+ from Ca-EDTA. The composite hydrogel shows controllable conductivity and reticulate structure with layered construction. Swelling behaviors of the composite hydrogels at various graphite contents were similar and the equilibrium SR decreased at higher graphite content. The conductivity of the

Acknowledgment

This work was supported by the National Natural Science Foundation of China (No. 31200457), the Fundamental Research Funds for the Central Universities (2013ZZ0072).

Cited by (15)

  • A dual-crosslinked self-healing and antibacterial nanocellulose hydrogel for monitoring of human motions

    2022, Materials and Design
    Citation Excerpt :

    When the hydrogel is cut off and then healed, the LED achieves a conversion from extinction to illumination. The ionic conductivity of the NC-B-PVA hydrogel, tested using the four-probe method, has an average value of 0.469 S cm−1, remarkably higher than that of the sodium alginate/graphite conductive hybrid hydrogel (10−3 S cm−1) [36] and the phytic acid/poly(N‐isopropylacrylamide) hydrogel (8 × 10−3 S cm−1). [37] Fig. 1e shows the self-healing process of the NC-B-PVA hydrogel.

  • Acid-catalyzed in-situ cross-linking of polyol on sodium alginate to improve its strength and hydrophobic properties

    2022, Materials and Design
    Citation Excerpt :

    The wet spinning process of alginate fiber is a green and environmentally friendly spinning process, then the various functional applications of alginate fiber have been explored by scholars [11,12]. In previous studies, most of the alginate fibers were obtained by chelating with metal ions [13–15]. However, because of the loosely cross-linked structure, the fiber has shortcomings such as low strength, high brittleness, and poor toughness, which limits its further application in various fields.

  • Enhanced delivery efficiency and sustained release of biopharmaceuticals by complexation-based gel encapsulated coated microneedles: rhIFNα-1b example

    2021, Asian Journal of Pharmaceutical Sciences
    Citation Excerpt :

    The BSA (isoelectric point 4.7) would be trapped by the undegraded SA gel, and resulting in the decreased cumulative release of BSA. In the subsequent penetration and pharmacokinetic studies, the drug in GEC-MNs was completely released due to the acidic environment and enzymes in the skin [38]. Considering the previous in vitro release in terms of the significant slow-release effect of in situ gel composed of SA: (GDL/EDTA-Ca) = 10:1 (v/v), the skin permeability study was conducted.

  • Alginate fiber toughened gels similar to skin intelligence as ionic sensors

    2020, Carbohydrate Polymers
    Citation Excerpt :

    The properties qualified this compound for wide applications in the food, medicine, and biosensor fields (Li, Zhao, Xu, Zhang, & Chen, 2011; Tai, Mulle, Ventura, & Lubineau, n.d.; Ziv et al., 2014). In previous research, most alginate hydrogels with excellent mechanical properties were obtained by chelation of sodium alginate with metal ions (Kalyani, Smitha, Sridhar, & Krishnaiah, 2006; Qu, Chen, Qian, Xiao, & He, 2014; Xu, Jiang, Lu, Wu, & Yuan, 2006). However, some constructional factors might be also crucial to improve mechanical properties of hydrogels like fibrous tissues.

View all citing articles on Scopus
View full text