*3.2.1 Water uptake of chitosan-nanosilica membrane with silane addition*

The water uptake determines how much water is absorbed by the membrane, so the PEM membrane must be able to hold water because the proton will be transported along the water channel created in the membrane polymer matrix. Thus, the high water uptake is favorable for PEM high-performance to facilitate great numbers of protons hopping and diffusion through the membrane [5, 14]. **Figure 2** shows all chitosan-nanosilica membranes with silane addition in this research potentially can be used as a DMFC membrane because it has water uptake value <50% as mentioned by [33]. The water on the membrane serves as proton transport medium and needed as the mobile phase to facilitate proton conductivity but if is it too high it will damage the membrane easily and lower their mechanical properties [33]. In **Figure 2**, it appears that silane addition to nanosilica has an impact on water uptake, which is an increase in water uptake on nanosilica:silane variations of 1:0, 1:0.25 to 1:0.5, but decrease on nanosilica:silane variations of 1:1 to 1:2. The most optimum membrane is variation nanosilica:silane 1:0.50 with water uptake is 37.52%, while chitosan-nanosilica membrane without silane reaches 32.16% water uptake.

The addition of silane to nanosilica increases the active Si-OH groups as shown in **Figure 1** (silane-coupled nanosilica) which will cause increased water absorption of the membrane. The addition of more silane that is silane 1:1 to 1:2 addition causes excess silane to interact with silica. Silane itself is hydrophobic so that if it is added to hydrophobic nanosilica [23] it will increase water absorption to chitosan membrane. This fact is following the results of the [14] study that pure chitosan

**185**

**Figure 1.**

**Figure 2.**

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

membrane has 40.66% water uptake and increases along with nanosilica increase addition and water uptake increase along with silane addition in line with the results of [12] study. Nafion 117 has 18,3% in water uptake [12], so the water uptake

*3.2.2 Mechanical properties of chitosan-nanosilica membrane with silane addition*

**Figure 3** explains the relations between silane addition in chitosan-nanosilica membrane and their mechanical properties, that is tensile strength, break and elasticity (modulus young) elongation. The tensile strength value of nanosilica:silane variations of 1:0 to 1:0.5 increases with the increasing silane composition that is 4.7, 5.1, 11.8 MPa respectively. It shows that the coupling agent presence causes strong interaction through hydrogen bonding between chitosan and nanosilica so that the tensile strength of the resulting membrane also increases. However, there

membranes produced in this study have bigger than Nafion 117.

*The relationship between water swelling value (%) and nanosilica:silane composition (w:w).*

*Illustration of nanosilica-silane and chitosan interaction in membrane.*

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

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

*Chitin and Chitosan - Physicochemical Properties and Industrial Applications*

put on the tip and detected by the device at certain distance.

The membrane (1x1 cm2

**3. Results and discussions**

by the device.

**matrix**

via oxane bonds [32].

**silane-coupled nanosilica**

reaches 32.16% water uptake.

The membrane surface morphology was observed using SEM FEI Inspect S50.

Membrane topography was observed in three dimensions and two dimensions using AFM Bruker N8 Neos 5.5 IF367. The membrane was taken several parts then

Thermal stability analysis using TGA Mettler Star SW 10.00 was carried out on the selected membrane specimens that had the best and worst properties therefore it represented all variations. Thermal stability analysis data was recorded in nitrogen atmosphere at every 10°C/minute heating rate at 30–500°C temperatures.

**3.1 Synthesis of silane-coupled Nanosilica and its incorporation into chitosan** 

**Figure 1** illustrates the interaction model between chitosan, nanosilica, and silane in membranes. At the final stage of silylation process that is epoxy groups deformation (ring-opening) on silane organofunctional group end chain, silane form two hydroxyl groups (–OH) which interacts with the amine group (–NH2) and and hydroxyl groups (-OH) in chitosan to form hydrogen bonds that could form a good interface interaction of chitosan and silane-coupled nanosilica network. Thus forming groups Si–OH via hydrogen bonds [5, 10] and siloxane groups (Si–O–Si)

**3.2 The results characterization of chitosan membrane modified with** 

*3.2.1 Water uptake of chitosan-nanosilica membrane with silane addition*

The water uptake determines how much water is absorbed by the membrane,

The addition of silane to nanosilica increases the active Si-OH groups as shown in **Figure 1** (silane-coupled nanosilica) which will cause increased water absorption of the membrane. The addition of more silane that is silane 1:1 to 1:2 addition causes excess silane to interact with silica. Silane itself is hydrophobic so that if it is added to hydrophobic nanosilica [23] it will increase water absorption to chitosan membrane. This fact is following the results of the [14] study that pure chitosan

so the PEM membrane must be able to hold water because the proton will be transported along the water channel created in the membrane polymer matrix. Thus, the high water uptake is favorable for PEM high-performance to facilitate great numbers of protons hopping and diffusion through the membrane [5, 14]. **Figure 2** shows all chitosan-nanosilica membranes with silane addition in this research potentially can be used as a DMFC membrane because it has water uptake value <50% as mentioned by [33]. The water on the membrane serves as proton transport medium and needed as the mobile phase to facilitate proton conductivity but if is it too high it will damage the membrane easily and lower their mechanical properties [33]. In **Figure 2**, it appears that silane addition to nanosilica has an impact on water uptake, which is an increase in water uptake on nanosilica:silane variations of 1:0, 1:0.25 to 1:0.5, but decrease on nanosilica:silane variations of 1:1 to 1:2. The most optimum membrane is variation nanosilica:silane 1:0.50 with water uptake is 37.52%, while chitosan-nanosilica membrane without silane

) was firstly coated using gold so that it could be detected

**184**

*Illustration of nanosilica-silane and chitosan interaction in membrane.*

#### **Figure 2.**

*The relationship between water swelling value (%) and nanosilica:silane composition (w:w).*

membrane has 40.66% water uptake and increases along with nanosilica increase addition and water uptake increase along with silane addition in line with the results of [12] study. Nafion 117 has 18,3% in water uptake [12], so the water uptake membranes produced in this study have bigger than Nafion 117.

#### *3.2.2 Mechanical properties of chitosan-nanosilica membrane with silane addition*

**Figure 3** explains the relations between silane addition in chitosan-nanosilica membrane and their mechanical properties, that is tensile strength, break and elasticity (modulus young) elongation. The tensile strength value of nanosilica:silane variations of 1:0 to 1:0.5 increases with the increasing silane composition that is 4.7, 5.1, 11.8 MPa respectively. It shows that the coupling agent presence causes strong interaction through hydrogen bonding between chitosan and nanosilica so that the tensile strength of the resulting membrane also increases. However, there

**Figure 3.**

*The relationship of silane addition in chitosan-nanosilica membrane to their mechanical properties.*

is a decrease in the silane variation of 1:1 to 1:2 (excess) that is 8.7, 5.4, and 4.1 MPa respectively. This happens because excess silane causes an imbalance in the interaction between silane and nanosilica. The effect of silane addition to nanosilica gives various levels of elongation at break on the membrane that are 6.07, 13.67, 6.1, 4.1, 7.88, and 2.18% respectively. Membrane elasticity is determined by the magnitude of modulus young. The fact is that silane addition can increase modulus young value of nanosilica:silane variation membrane 1:0.25 to 1:1, and decrease significantly in 1:1.5, then increase again in silane addition variation 1:2.

A membrane is said to be good and has the best mechanical performance seen from the high tensile strength values and low elongation at break values [22, 34], so modulus young values which expected is high. In this research chitosan-nanosilica membrane with nanosilica:silane is 1:0.5 reach optimum mechanical properties. Silane addition to nanosilica increases physical interaction between nanosilica and chitosan. Hydrogen bonds formed between hydroxyl groups in polysiloxane with amine and ether groups in chitosan as described in **Figure 1**. Strong interaction between nanosilica and chitosan causes high physical and mechanical strength including tensile strength, elongation and modulus young.
