**1. Introduction**

People's dependence on energy from fossil fuels is now getting higher, so energy resource supply is day by day decreasing. One of the alternative energy sources that is potential to overcome that problem is fuel cell [1]. A fuel cell is an electrochemical device that converts chemical energy into electrical energy continuously. The use of fuel cells is expected to reduce people's reliance on fossil fuels and reduce the damage to the atmosphere due to emissions [2]. Therefore, fuel cell is a promising alternative energy that is environmentally friendly.

The main component of the fuel cell is polymer electrolyte membrane (PEM) [2]. Since the role of polymer electrolyte membrane in fuel cell performance is very important, the study of technological development of polymer electrolyte

membrane is needed [3]. Currently, the electrolyte membrane that most widely used in industry is Nafion 117 membrane or Perfluoro sulfonic acid [1]. As a polymer electrolyte membrane in Direct Methanol Fuel Cell (DMFC), the Nafion 117 membrane has very good ability to deliver proton with good chemical stability, but it has a weakness of methanol cross over which is signed by the high methanol permeability and low operating temperature (60–120°C) [1]. Another drawback is its poisonous nature due to the elemental fluorine content and its high price. Therefore, several studies have been conducted to obtain membranes that environmentally friendly and have better capabilities than Nafion 117 membrane at an economical cost [4].

Chitosan is one alternative polymer matrix that is potential for replacing the Nafion 117 membrane. Chitosan is an environmentally friendly biopolymer, produced by utilizing marine waste such as shrimp, crabs, lobsters, and fish shells. Chitosan is easily generated through deacetylation process of chitin by strong alkali or prepared from fungal cell walls via fermentation technology [5]. Chitosan is inexpensive, hydrophilic, has a functional group in the backbone that can be modified according to the desired characteristics and has low methanol permeability [6]. Chitosan has a free amine group that can be protonated and has a hydroxy group, so it can be categorized as natural polycation. These two groups make it possible to modify chitosan to produce the desired physical and chemical properties [7]. However, according to [8], chitosan membrane still has low proton conductivity that is 1.74 × 10−2 S/cm, so this value is lower than the proton conductivity of Nafion 117 membrane that is 5.66 × 10−2 S/cm.

To improve the performance of chitosan-based membrane matrix, some efforts have been done to modify chitosan by combining with other such as silica based materials [8, 9]. Silica based materials are chosen for several reasons. They can reduce hydrophilicity degree of the chitosan main chain that is hydrophilic due to the presence of free amino acid groups and hydroxides on its carbon atom [9]. Silica materials can absorb methanol on the surface of chitosan membrane so that most of the methanol does not pass through the membrane. The addition of inorganic additives such as zeolites and montmorillonites which able to act as molecular filters will provide tetrahedral silica that can cover the pores in the membrane so that the transfer of methanol through the membrane is very small [8, 10]. It is reported that silica addition into the polymer matrix can reduce crystallinity of the polymer and increase mechanical strengths such as water resistance, stretch strength, and tensile strength [11]. The ability of silica to combine with chitosan is very limited because of the different hydrophilicity properties of the two materials. Therefore, silica in the form of nanoparticles was developed to create strong composites.

Tetraethylorthosilicate (TEOS) or Si(OC2H5)4 is a source of silica materials which is widely used because it is easy to do purification, the reaction rate is slow and it can be controlled [12]. TEOS is even easily converted into nanosilica particles by reacting with water. The hydrolysis reaction occurs in the sol–gel process. TEOS is commonly used as a crosslinking agent in inorganic polymers synthesis because of its ability to form Si-O-Si chains. The sol–gel method has been extensively developed in the surface modification of silica particles because it will form a more reactive silica precursor with the formation of Si-OH groups [13]. The weakness is that silica is insoluble in chitosan solution, so the dope solution formed from nanosilica and chitosan is not homogeneous [14] because physical mixing causes nanosilica dispersion in the chitosan matrix to be less homogeneous and weak interface interactions of the two material surfaces.

To improve the compatibility of silica particles and chitosan, it is needed a coupling agent [15]. The addition of 10% of GPTMS (3-glycidyloxypropyl

**181**

*Characterization of Chitosan Membrane Modified with Silane-Coupled Nanosilica for Polymer…*

Therefore, in this study, the addition of silane (GPTMS) is done as a coupling agent on the chitosan-nanosilica membrane. This coupling agent is selected because it has epoxy groups that can react with a free amine group in chitosan, so nanosilica can also be bounded strongly with chitosan (12, 15). Nanosilica is chosen because of its small size and wide surface so that making it possible to penetrate the polymer

The use of GPTMS as a coupling agent and nanosilica particles (from TEOS) as fillers in the chitosan matrix for polymer electrolyte membrane makes this study different from previous studies. The use of GPTMS as a coupling agent on nanosilica particles was carried out by [17]. Silica precursors used were silica fume and the investigation carried out was nanosilica variations on chitosan and did not investigate silane variation effect on membranes. The membranes produced for biopolymer applications which have high thermal resistance. Chitosan modified with silica (TEOS) and GPTMS has been coated on a cotton fabrics in [18] results clear transparent thin layer on cotton surface. While [19] has combined chitosan with silica and GPTMS for tissue engineering application. For dehydration of ethanol application, chitosan-silica study has been performed by [20, 21]. For fuel cell application, chitosan have been combined with silica-based material [5, 8, 10, 22, 23]. The result of [5, 10] used GPTMS-montmorillonite as filler in chitosan membrane, while research [8] used GPTMS-modified zeolite, [22] used sulfonated polyaniline/ silica and [23] used silica/ sulfonated poly-

The materials are tetraethyl orthosilicate (TEOS 99%, ρ = 0.94 L/kg Merck), absolute ethanol (C2H5OH 99–100%, ρ = 0.79 L/kg Merck), ammonia (NH3 25%, ρ = 0.90 L/kg Merck), aqua demineralization, chitosan from CV Ocean Fresh Bandung (deacetylation degree = 82.7%, solubility in 1% acetic acid ≥99%, molecular weight = 8.78 kDa), acetic acid (CH3COOH 100%, ρ = 1.05 L/kg Merck), methanol (CH3OH 99.9%, ρ = 0.79 L/kg Merck), dimethyl formamide (DMF HCON(CH3)2 99.80%, ρ = 0.94 L/kg Merck) and silane (3-glycidyloxypropyl trimethoxysilane)

Nanosilica synthesis from TEOS by sol–gel method was adopted from [8]. A total of 2.27 mL of TEOS was dissolved in 46 mL absolute ethanol at a speed of 600 rpm at room temperature for 15 minutes. Then ammonia was added dropwise until pH 10. After 1 hour, 1 mL distilled water was then added dropwise into the solution. The stirring process was continued for 6 hours. Then the solution was allowed to stand for 24 hours during the aging process. After the aging process, the obtained gel was then roasted at a temperature of 80°C for 24 hours. The crystals were crushed into powder in further calcined for 2 hours at the temperature of

/s and proton conductivity of 1.31 × 10−2 S/cm [8]. The

trimethoxysilane) on chitosan/zeolite-β membrane produces methanol perme-

electrolyte membrane investigation of SPAEK-C with 10% GPTMS addition produces proton conductivity of (1.5 ± 0.1) × 10−2 S/cm and methanol permeability

*DOI: http://dx.doi.org/10.5772/intechopen.95580*

/s [12, 16].

ether-ether ketone as filler in chitosan.

**2. Experiments and characterization**

(GPTMS C9H20O5Si ≥ 98%, ρ = 1.07 L/kg Sigma-Aldrich).

600°C. The resulting crystals were sieved at 230 mesh.

ability of 2.20 × 10−7 cm2

of 2.99 × 10−7 cm2

matrix easily.

**2.1 Materials**

**2.2 Nanosilica preparation**

*Characterization of Chitosan Membrane Modified with Silane-Coupled Nanosilica for Polymer… DOI: http://dx.doi.org/10.5772/intechopen.95580*

trimethoxysilane) on chitosan/zeolite-β membrane produces methanol permeability of 2.20 × 10−7 cm2 /s and proton conductivity of 1.31 × 10−2 S/cm [8]. The electrolyte membrane investigation of SPAEK-C with 10% GPTMS addition produces proton conductivity of (1.5 ± 0.1) × 10−2 S/cm and methanol permeability of 2.99 × 10−7 cm2 /s [12, 16].

Therefore, in this study, the addition of silane (GPTMS) is done as a coupling agent on the chitosan-nanosilica membrane. This coupling agent is selected because it has epoxy groups that can react with a free amine group in chitosan, so nanosilica can also be bounded strongly with chitosan (12, 15). Nanosilica is chosen because of its small size and wide surface so that making it possible to penetrate the polymer matrix easily.

The use of GPTMS as a coupling agent and nanosilica particles (from TEOS) as fillers in the chitosan matrix for polymer electrolyte membrane makes this study different from previous studies. The use of GPTMS as a coupling agent on nanosilica particles was carried out by [17]. Silica precursors used were silica fume and the investigation carried out was nanosilica variations on chitosan and did not investigate silane variation effect on membranes. The membranes produced for biopolymer applications which have high thermal resistance. Chitosan modified with silica (TEOS) and GPTMS has been coated on a cotton fabrics in [18] results clear transparent thin layer on cotton surface. While [19] has combined chitosan with silica and GPTMS for tissue engineering application. For dehydration of ethanol application, chitosan-silica study has been performed by [20, 21]. For fuel cell application, chitosan have been combined with silica-based material [5, 8, 10, 22, 23]. The result of [5, 10] used GPTMS-montmorillonite as filler in chitosan membrane, while research [8] used GPTMS-modified zeolite, [22] used sulfonated polyaniline/ silica and [23] used silica/ sulfonated polyether-ether ketone as filler in chitosan.
