*3.2.4 Functional groups analysis of chitosan-nanosilica membrane with silane addition*

**Figure 5** shows FT-IR spectra of nanosilica and chitosan-nanosilica membrane with silane addition. The FT-IR spectrum of chitosan on the membrane is characterized by the presence of ─CN groups (amide groups) in all variations of the chitosan-nanosilica membrane with the addition of silane at the wavenumbers 1627.92 cm−1 and 1635.64 cm−1 [38]. The wavenumbers shift in the FTIR spectrum of chitosan indicates an interaction between the amide group in the chitosan matrix and the polysiloxane network in the nanosilica addition of silane through hydrogen bonds. The absorption around the wave number 1060–1084 cm−1 indicates the ─CO group (ketone group) [38]. The ─CO group (ketone group) which is a characteristic of the polysaccharide appears at the wave number 1080.14 cm−1. The -CH bonds in -NHCOCH3 appear at wave numbers 2854.65 cm−1 and 1404.18 cm−1 [39, 40]. This absorption in assigned to the –+ N–H bonds, indicating that the chitosan could be interacting with another groups by coulombic forces [40].

In FT-IR spectrum of nanoslilca in **Figure 5**, the main functional group analysis results is the emergence of Si–O–Si groups on nanosilica and chitosannanosilica membrane with silane addition. Absorption around wave numbers 1100–1200 cm−1 and 460–480 cm−1 indicates the presence of the Si–O–Si group (siloxane group) [39]. This absorption band (Si-O-Si groups) did not appear in the chitosan membrane spectra but appear in chitosan-nanosilica membrane. This sharp increase in absorption band intensity indicates the presence of stretching vibrations of Si–O–Si (siloxane group) which is getting stronger. According to [24], it indicates that some of the siloxane groups (Si–O–Si) of polysiloxane network in silane addition and nanosilica have interacted strongly with chitosan matrix. Absorption band at wave number 894.97 cm−1 indicates the presence of the Si–OH groups (silanol groups) [38]. The Si–OH groups (silanol groups) show hydrogen bonds existence between silanol groups in nanosilica-silane with amide groups in the chitosan matrix. It is also seen in **Figure 5** that there are absorption bands around wave number 3400–3500 cm−1 which indicate the –OH (hydroxyl)

#### **Figure 5.**

*Chitin and Chitosan - Physicochemical Properties and Industrial Applications*

methanol does not pass through the membrane.

that is 5.8887 × 10−7 cm2

equal to 6.5229 × 10−7 cm2

leaks and avoids methanol cross over.

The decrease in methanol membrane permeability as shown in **Figure 4(b)** from the composition of nanosilica:silane 1:0 to 1:1 is caused by properties adhesion and interface interaction (hydrogen bonds) of chitosan-nanosilica with the silane addition is stronger [15] than chitosan-nanosilica membranes without silane addition (1:0). According to [29], the decrease in hydrophilicity in this case is due to the silane nature which is able to balance the hydrophilic and hydrophobic nature of an organic or inorganic material. The addition of nanosilica which has been carried out by silane can close pores on the chitosan membrane through strong interactions between amines in chitosan with polysiloxane in nanosilica so that most of the

Chitosan-nanosilica membrane with silane addition in nanosilica:silane variation 1:1.5 and 1:2 there is an increase in methanol permeability value

/s respectively. This is due to

/s. This is also

/s. The addition of silane chitosan nanosilica mem-

/s and 5.9341 × 10−7 cm2

the composition of silane addition cannot interact perfectly with chitosan matrix so the adhesion force decreases and the chitosan matrix interaction with silane nanosilica addition is weak. The highest methanol permeability value was obtained on the chitosan-nanosilica membrane without silane is

brane that has good performance in methanol permeability value followed by high proton conductivity value is the chitosan-nanosilica membrane addition

supported by the proton conductivity value obtained by 7.8988 × 10−4 S/cm. Chitosan-nanosilica membrane with silane addition nanosilica variation: silane 1:0.5 has the lowest methanol permeability value when compared to Nafion 117 membrane that is 1.01 × 10−6 S/cm [16]. For DMFC applications, it is expected that membranes with small methanol permeability. Small permeability prevents

**Figure 4(c)** explains that the highest membrane selectivity is obtained on the chitosan-nanosilica membrane with silane addition in nanosilica:silane variation 1:0.5. Membrane selectivity is a parameter that connects proton conductivity with methanol permeability. For DMFC applications, the desired membrane is a membrane with high conductivity and low methanol permeability, so the determination of membrane selectivity uses Eq. (7) [8]. Through this membrane selectivity determination, the facts show that the chitosan-nanosilica membrane with 1:0.5 silane addition is the membrane with the best performance as PEM for DMFC applications. Membrane selectivity aims to evaluate membrane performance capability based on high proton conductivity values and low methanol permeability values. The membrane selectivity is influenced by modulus young value as mechanical properties of the membrane. It can be explained that the higher membrane selectivity, the higher modulus young so that the membrane physical properties are in harmony with the membrane chemical properties as polymer electrolyte membrane (PEM). The results of membrane synthesis in this study are supported by high modulus young values, high proton conductivity values and low methanol

When compared to Nafion 117, chitosan-nanosilica membrane with silane addition in nanosilica:silane variation 1:0.5 has lower membrane selectivity value. It shows that chitosan-nanosilica membrane with silane nanosilica variation: silane 1:0.5 addition has the ability under Nafion 117, but this membrane can still be used as PEM for DMFC applications, it means that the membrane can deliver protons even though it runs slowly but it can reduce the entry of methanol fuel through the membrane supported by methanol permeability obtained that is smaller than

of nanosilica:silane 1:0.5 variation which is 5.8434 × 10−7 cm2

**188**

permeability.

Nafion 117 membrane.

*FT-IR spectra of chitosan-nanosilica membranes with variation of silane addition. (a) Chitosan; (b)Nanosilica; (c) chitosan membrane with nanosilica:silane = 1:0; (d) 1:0,25; (e) 1:0,05; (f) 1:1; (g) 1:1,5; (h) 1:2.*

groups presence. A sharp intensity increase occurs in the vibration stretching –OH (hydroxyl group). According to [39], it indicates that some hydroxyl groups (–OH) on the chitosan matrix have interacted strongly with the polysiloxane network in nanosilica-silane through hydrogen bonds. Another important absorption band is at 1644–1637 cm−1 which indicates the bending vibration H-O-H indicates the vibration of water molecules bound to the inorganic framework.

Variation of nanosilica:silane membrane at 1:0.50 is the best membrane that has the highest value of membrane selectivity and has the best mechanical properties. FT-IR spectra of the chitosan-nanosilica membrane with silane addition in nanosilica:silane membrane at 1:0.50 as in **Figure 5** shows that absorption band at wavenumber 3448.72 cm−1 is stretching vibration absorption –OH groups more sharply when compared with other variation. It shows that the hydrogen bonds between the chitosan matrixes with this silane addition on nanosilica more easily formed than the nanosilica without silane addition. The amine group on the chitosan is easier to form hydrogen bonds with epoxy groups on the silane. Besides, there are new absorption wavenumbers around 900–912 cm−1 which indicate the presence of epoxy groups (-C2H3O) in silane [15, 21], and from 2900 to 2960 cm−1 indicating –CH2 groups of silane compound [4] in. It can be seen in **Figure 8** that absorption at wavenumber 902.69 cm−1 indicates epoxy groups presence of organofunctional group silane compound and absorption at wavenumber 2924.09 cm−1 that indicates the stretching vibration –CH2 groups. Absorption at wavenumber 2924.09 cm−1 is absorption of the bridge group –CH2 alkyl silane compound and it is not from chitosan.

#### *3.2.5 Morphology analysis of chitosan-nanosilica membrane with silane addition*

**Figure 6** shows membrane morphology of chitosan, chitosan-nanosilica without silane addition (variation 1:0) and chitosan-nanosilica with silane addition. **Figure 6(a)** shows a homogenous surface of chitosan membrane, while in **Figure 6(b-d)** show heterogeneous surface of chitosan matrix containing nanosilica particles. Besides, there is fairly large agglomeration in **Figure 6(b)** as chitosan-nanosilica without silane. It suggests that the interaction between the chitosan matrix with nanosilica is poor without silane as coupling agent. Good interaction will produce homogeneous surface morphology [21].

**Figure 6(c)** shows membrane morphology of chitosan-nanosilica membrane with silane addition variation 1:0.50 (the best membrane) that shows good interaction between chitosan and nanosilica with silane addition. This is due to the occurrence of attachment between nanosilica and silane as coupling agents with relatively small amounts so that they can spread evenly with chitosan matrix, eventually being able to cover the pores of membrane well. Excessive agglomeration occurs in chitosan-nanosilica membranes with nanosilica:silane 1:2.0 composition (**Figure 6(d)**) due to excessive amounts of silane that interfere effective attachment process, so that the morphology resulting membrane appears to be lumps and not homogenous. But, other techniques are necessary to support this facts. A good alternative is X-ray photoelectron spectroscopy (XPS), specifically high-resolution XPS of C, O, N, and Si.

#### *3.2.6 Membrane topographic analysis using AFM*

Membrane topographic analysis using AFM quantitatively is shown in **Table 1**. Topographic analysis with backward amplitude results in surface morphology of surface roughness (Sa) and root mean square (RMS) roughness or Sq, as well as the highest surface height (Hmax) and lowest surface (Hmin) as in [41–45] studies. In

**191**

**Figure 6.**

**Table 1.**

between chitosan and nanosilica.

*nanosilica:silane = 1:0, (c) 1:0.5, and (d) 1:2.0.*

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

**Table 1** the surface roughness parameter values on chitosan-nanosilica membrane without silane showing the value of Sa, Sq, Hmax, and Hmin have the lowest value. The addition of 50% GPTMS silane or in composition 1:0.5 as the coupling agent raises the value of the surface roughness parameter even at this point reaching the highest value. These peaks indicate the optimum interaction with the 50% silane addition to chitosan-nanosilica. It proves that silane addition as the coupling agent between chitosan and nanosilica at the optimum amount raises the value of average roughness or Sa and root mean square roughness Sq, as well as the highest surface height (Hmax) and lowest surface (Hmin) and then decreases at next addition. The next point is the addition of 100% silane or in composition of 1:2.0 the surface roughness parameter shows a decrease that is, the excess silane causes reduced interaction

*Results of quantitative AFM analysis on chitosan-nanosilica membranes with Silane addition.*

*Morphology surface (5000 magnification) by SEM of (a) chitosan; (b) chitosan-nanosilica membrane with* 

**Chitosan-nanosilica Membranes Sa mean (nm) Sq mean (nm) Hmax (nm) Hmin (nm)** Nanosilica:silane = 1:0 0.956 1.327 43.000 −28.000 Nanosilica:silane 1 = 1:0.5 2.308 3.713 121.667 −83.333 Nanosilica:silane 1 = 1:2.0 1.473 1.857 82.667 −66.333

The qualitative results of membrane topography are shown in **Figure 7**. The AFM analysis provides topographic information of chitosan-nanosilica composite membranes with GPTMS (silane) addition as coupling agent in two-dimensional

*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*

#### **Figure 6.**

*Chitin and Chitosan - Physicochemical Properties and Industrial Applications*

vibration of water molecules bound to the inorganic framework.

groups presence. A sharp intensity increase occurs in the vibration stretching –OH (hydroxyl group). According to [39], it indicates that some hydroxyl groups (–OH) on the chitosan matrix have interacted strongly with the polysiloxane network in nanosilica-silane through hydrogen bonds. Another important absorption band is at 1644–1637 cm−1 which indicates the bending vibration H-O-H indicates the

Variation of nanosilica:silane membrane at 1:0.50 is the best membrane that has the highest value of membrane selectivity and has the best mechanical properties. FT-IR spectra of the chitosan-nanosilica membrane with silane addition in nanosilica:silane membrane at 1:0.50 as in **Figure 5** shows that absorption band at wavenumber 3448.72 cm−1 is stretching vibration absorption –OH groups more sharply when compared with other variation. It shows that the hydrogen bonds between the chitosan matrixes with this silane addition on nanosilica more easily formed than the nanosilica without silane addition. The amine group on the chitosan is easier to form hydrogen bonds with epoxy groups on the silane. Besides, there are new absorption wavenumbers around 900–912 cm−1 which indicate the presence of epoxy groups (-C2H3O) in silane [15, 21], and from 2900 to 2960 cm−1 indicating –CH2 groups of silane compound [4] in. It can be seen in **Figure 8** that absorption at wavenumber 902.69 cm−1 indicates epoxy groups presence of organofunctional group silane compound and absorption at wavenumber 2924.09 cm−1 that indicates the stretching vibration –CH2 groups. Absorption at wavenumber 2924.09 cm−1 is absorption of the bridge group –CH2 alkyl silane compound and it is not from

*3.2.5 Morphology analysis of chitosan-nanosilica membrane with silane addition*

interaction will produce homogeneous surface morphology [21].

**Figure 6** shows membrane morphology of chitosan, chitosan-nanosilica without silane addition (variation 1:0) and chitosan-nanosilica with silane addition. **Figure 6(a)** shows a homogenous surface of chitosan membrane, while in **Figure 6(b-d)** show heterogeneous surface of chitosan matrix containing nanosilica particles. Besides, there is fairly large agglomeration in **Figure 6(b)** as chitosan-nanosilica without silane. It suggests that the interaction between the chitosan matrix with nanosilica is poor without silane as coupling agent. Good

**Figure 6(c)** shows membrane morphology of chitosan-nanosilica membrane with silane addition variation 1:0.50 (the best membrane) that shows good interaction between chitosan and nanosilica with silane addition. This is due to the occurrence of attachment between nanosilica and silane as coupling agents with relatively small amounts so that they can spread evenly with chitosan matrix, eventually being able to cover the pores of membrane well. Excessive agglomeration occurs in chitosan-nanosilica membranes with nanosilica:silane 1:2.0 composition (**Figure 6(d)**) due to excessive amounts of silane that interfere effective attachment process, so that the morphology resulting membrane appears to be lumps and not homogenous. But, other techniques are necessary to support this facts. A good alternative is X-ray photoelectron spectroscopy (XPS), specifically high-resolution

Membrane topographic analysis using AFM quantitatively is shown in **Table 1**. Topographic analysis with backward amplitude results in surface morphology of surface roughness (Sa) and root mean square (RMS) roughness or Sq, as well as the highest surface height (Hmax) and lowest surface (Hmin) as in [41–45] studies. In

**190**

XPS of C, O, N, and Si.

*3.2.6 Membrane topographic analysis using AFM*

chitosan.

*Morphology surface (5000 magnification) by SEM of (a) chitosan; (b) chitosan-nanosilica membrane with nanosilica:silane = 1:0, (c) 1:0.5, and (d) 1:2.0.*


#### **Table 1.**

*Results of quantitative AFM analysis on chitosan-nanosilica membranes with Silane addition.*

**Table 1** the surface roughness parameter values on chitosan-nanosilica membrane without silane showing the value of Sa, Sq, Hmax, and Hmin have the lowest value. The addition of 50% GPTMS silane or in composition 1:0.5 as the coupling agent raises the value of the surface roughness parameter even at this point reaching the highest value. These peaks indicate the optimum interaction with the 50% silane addition to chitosan-nanosilica. It proves that silane addition as the coupling agent between chitosan and nanosilica at the optimum amount raises the value of average roughness or Sa and root mean square roughness Sq, as well as the highest surface height (Hmax) and lowest surface (Hmin) and then decreases at next addition. The next point is the addition of 100% silane or in composition of 1:2.0 the surface roughness parameter shows a decrease that is, the excess silane causes reduced interaction between chitosan and nanosilica.

The qualitative results of membrane topography are shown in **Figure 7**. The AFM analysis provides topographic information of chitosan-nanosilica composite membranes with GPTMS (silane) addition as coupling agent in two-dimensional

**Figure 7.**

*The AFM analysis of chitosan-nanosilica composite membranes with GPTMS silane coupling agent addition in (a) two-dimensional (2D) and (b) three-dimensional (3D), variation nanosilica:silane (1) 1:0, (2) 1:0.5 and (3) 1:2.0.*

(2D) (**Figure 7a(1–3)**) and three-dimensional (3D) (**Figure 7b(1–3)**) appearance. The analysis results using AFM shows that chitosan-nanosilica membrane without silane (chitosan-nanosilica:silane ratio = 1:0) shows that membrane topography tends to be regular and evenly distributed. It shows that the membrane still carries typical state of chitosan and nanosilica whose topography is not yet affected by other materials. It means between the two materials, chitosan and nanosilica, maximum interaction has not yet occurred. This result is in accordance with morphological analysis result with SEM which shows rough surface. In chitosannanosilica membranes with 50% silane addition to nanosilica, or the composition of chitosan-nanosilica = 1:0.5 indicates significant change in topography surface. The membrane surface forms irregular bumps (hills and valleys) caused by the certain amount of nanosilica composition that interacts well with chitosan on the membrane. On 100% silane addition or chitosan-nanosilica: of 1:2.0, bumps on membrane topography are no longer occurred, but the surface tends to be evenly distributed and more homogeneous, indicating prominent characteristics of each chitosan and nanosilica. The presence of nanosilica fillers interact with chitosan through hydrogen bonds as proven by FTIR analysis. The interaction will be maximized when the coupling agent is added in the form of silane at an optimum amount. In the presence of some silanes, the chitosan matrix will begin to be affected by the presence of silane-coupled nanosilica fillers to produce the formation of a certain number of hills and valleys at AFM analysis in line with capabilities of the existing filler and coupling agent. **Figure 7** shows a rough topography with fairly wide distribution of hills and valleys. The number of irregular areas is due to the presence of nanosilica hydrophobic fillers that interact with chitosan by the addition of an optimum amount silane as coupling agent. Rugged topography with many hills and valleys spread evenly over almost all surfaces that are found on the membrane with 50% silane addition. In this membrane, the chitosan and nanosilica matrices are no longer dominant, because the added nanosilica filler has interacted well with chitosan due to the GPTMS as coupling agent.

**193**

**Figure 8.**

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

The interaction that occurs between the chitosan matrixes with nanosilica fillers in the presence of silane as coupling agent forms a unified and strong membrane. As a result, membrane topography is fused between two components, shown in more uniform color in **Figure 7**. The 3D images on the composition of chitosannanosilica:silane = 1:0.5 resulting from AFM analysis does not show any differences in the regions or parts of chitosan and nanosilica. The surfaces of both valleys and hills are joined in such a way that they show that the two materials interact very well. This phenomenon is supported by research [46] who makes a composite membrane from an organic matrix in the form of chitosan and alumina as an inorganic filler. The results of AFM analysis in [46] study shows that the chitosan/ alumina composite membrane shows rough topography with membrane surface covered with granules show that chitosan has interacted strongly with alumina. Identical with [46] study, chitosan subtle areas are covered by nanosilica material so that the membrane topography in 3D shows the presence of hills and valleys that are evenly distributed to all surfaces. AFM analysis in [20] study also supports the facts and results of the AFM analysis in this study. As [20] research on chitosannanosilica supports mixed matrix membranes and the results of AFM analysis show that the incorporation of nanosilica and silane increases the membranes surface rippling which, as FTIR results shows, are attributed to strong bonds formed

The thermal stability of the chitosan-nanosilica hybrid membrane is evaluated by thermo gravimetric analysis with TGA. The thermograms are shown in **Figure 8** and the change in mass percentage on each thermogram stage is presented in **Tables 2** and **3**. In TGA analysis, sample changes are marked by deviations from the horizontal line. As shown in **Figure 8** and **Table 2**, all membranes show three stages of weight-loss as area of change in mass percentage on TGA

The first weight loss at around 35–150°C (**Table 2**) is attributed to the loss of water molecules present in hybrid membrane [10, 47] with mass reduction 12–14%. The difference in temperature range and the percentage of sample weight-loss is

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

between nanosilica particles and chitosan matrix.

*TGA thermograms of chitosan-nanosilica membrane with silane addition.*

*3.2.7 Thermal analysis using TGA*

thermogram of membrane samples.

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

The interaction that occurs between the chitosan matrixes with nanosilica fillers in the presence of silane as coupling agent forms a unified and strong membrane. As a result, membrane topography is fused between two components, shown in more uniform color in **Figure 7**. The 3D images on the composition of chitosannanosilica:silane = 1:0.5 resulting from AFM analysis does not show any differences in the regions or parts of chitosan and nanosilica. The surfaces of both valleys and hills are joined in such a way that they show that the two materials interact very well. This phenomenon is supported by research [46] who makes a composite membrane from an organic matrix in the form of chitosan and alumina as an inorganic filler. The results of AFM analysis in [46] study shows that the chitosan/ alumina composite membrane shows rough topography with membrane surface covered with granules show that chitosan has interacted strongly with alumina. Identical with [46] study, chitosan subtle areas are covered by nanosilica material so that the membrane topography in 3D shows the presence of hills and valleys that are evenly distributed to all surfaces. AFM analysis in [20] study also supports the facts and results of the AFM analysis in this study. As [20] research on chitosannanosilica supports mixed matrix membranes and the results of AFM analysis show that the incorporation of nanosilica and silane increases the membranes surface rippling which, as FTIR results shows, are attributed to strong bonds formed between nanosilica particles and chitosan matrix.

#### *3.2.7 Thermal analysis using TGA*

*Chitin and Chitosan - Physicochemical Properties and Industrial Applications*

(2D) (**Figure 7a(1–3)**) and three-dimensional (3D) (**Figure 7b(1–3)**) appearance. The analysis results using AFM shows that chitosan-nanosilica membrane without silane (chitosan-nanosilica:silane ratio = 1:0) shows that membrane topography tends to be regular and evenly distributed. It shows that the membrane still carries typical state of chitosan and nanosilica whose topography is not yet affected by other materials. It means between the two materials, chitosan and nanosilica, maximum interaction has not yet occurred. This result is in accordance with morphological analysis result with SEM which shows rough surface. In chitosannanosilica membranes with 50% silane addition to nanosilica, or the composition of chitosan-nanosilica = 1:0.5 indicates significant change in topography surface. The membrane surface forms irregular bumps (hills and valleys) caused by the certain amount of nanosilica composition that interacts well with chitosan on the membrane. On 100% silane addition or chitosan-nanosilica: of 1:2.0, bumps on membrane topography are no longer occurred, but the surface tends to be evenly distributed and more homogeneous, indicating prominent characteristics of each chitosan and nanosilica. The presence of nanosilica fillers interact with chitosan through hydrogen bonds as proven by FTIR analysis. The interaction will be maximized when the coupling agent is added in the form of silane at an optimum amount. In the presence of some silanes, the chitosan matrix will begin to be affected by the presence of silane-coupled nanosilica fillers to produce the formation of a certain number of hills and valleys at AFM analysis in line with capabilities of the existing filler and coupling agent. **Figure 7** shows a rough topography with fairly wide distribution of hills and valleys. The number of irregular areas is due to the presence of nanosilica hydrophobic fillers that interact with chitosan by the addition of an optimum amount silane as coupling agent. Rugged topography with many hills and valleys spread evenly over almost all surfaces that are found on the membrane with 50% silane addition. In this membrane, the chitosan and nanosilica matrices are no longer dominant, because the added nanosilica filler has interacted

*The AFM analysis of chitosan-nanosilica composite membranes with GPTMS silane coupling agent addition in (a) two-dimensional (2D) and (b) three-dimensional (3D), variation nanosilica:silane (1) 1:0, (2) 1:0.5 and* 

**192**

**Figure 7.**

*(3) 1:2.0.*

well with chitosan due to the GPTMS as coupling agent.

The thermal stability of the chitosan-nanosilica hybrid membrane is evaluated by thermo gravimetric analysis with TGA. The thermograms are shown in **Figure 8** and the change in mass percentage on each thermogram stage is presented in **Tables 2** and **3**. In TGA analysis, sample changes are marked by deviations from the horizontal line. As shown in **Figure 8** and **Table 2**, all membranes show three stages of weight-loss as area of change in mass percentage on TGA thermogram of membrane samples.

The first weight loss at around 35–150°C (**Table 2**) is attributed to the loss of water molecules present in hybrid membrane [10, 47] with mass reduction 12–14%. The difference in temperature range and the percentage of sample weight-loss is

**Figure 8.** *TGA thermograms of chitosan-nanosilica membrane with silane addition.*


**Table 2.**

*The area of change (stages) in mass percentage reduction on TGA thermogram of membrane samples.*


#### **Table 3.**

*Chitosan-nanosilica:silane membrane thermal degradation.*

not significant indicates that the water content in samples are not significantly different. Mass reduction in chitosan-nanosilica membrane samples with silane coupling agent is higher when compared to sample without silane. This shows that chitosan-nanosilica with silane is more hygroscopic.

The second weight-loss in **Table 2** appearing at around 150–335°C indicates the decomposition of chitosan polymer chain in hybrid membrane [10]. This chain decomposition is related to the loss of side groups as acetyl groups (as shown in **Figure 1**) in chitosan because the acetyl groups has a weak phi bond so it breaks easily first. The temperature range and the percentage of sample weight-loss is significantly different. The temperature range and the percentage of mass reduction in two samples with silane as coupling agent shows a large range. The second stage temperature range in the sample with silane shows a widened temperature region. This is due to the presence of the silane as coupling agent interact with the acetyl groups thus preventing the release of the acetyl groups. As a result, a large number of these groups release at higher temperatures.

The third weight-loss stage is observed near 335–450°C is due to unstable parts of the polymeric matrix whereas it is occurring due to complete decomposition of the backbone of polymeric matrix [48] and residual organic groups [8]. The temperature range and the percentage of sample weight-loss in this stage is significantly different. The temperature range in third stage in two samples with silane as coupling agent shows a large range while the percentage of mass reduction is a small range. The incorporation of silane has improved the interaction of nanosilica and chitosan by introducing more functional groups with hydrogen bond formation as **Figure 1** and FTIR results. Hydrogen bond between hydroxyl groups (–OH) in silane-coupled nanosilica interacts with the amine group (–NH2) ether group (C–O–C) of chitosan that could form a good interface interaction [32]. This all makes it difficult for chitosan chain to degrade so that the degradation temperature range is greater and the remaining mass is less. In addition, chitosan membrane samples with silane-coupled nanosilica have higher component heterogeneity than chitosan-nanosilica without silane. High heterogeneity of polymer components causing a longer range of degradation and decomposition temperature. Therefore, it can be understood that **Table 3** shows that nanosilica:silane 1 = 1:0.5 have the

**195**

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

highest thermal degradation. This result is in line with the results of FTIR and AFM analysis which finds that the composition nanosilica:silane 1 = 1:0.5 provides the best hydrogen bond interaction. This result is in accordance with [17] which state that the proper addition of modified nanosilica with silane enhanced the thermal performance by acting as superior insulator and mass transport barrier to the

The influence of silane as coupling agent on the chitosan-nanosilica membrane causes homogeneity and prevents agglomeration between nanosilica and chitosan. The higher silane compositions added, it decrease the water uptake, increases proton conductivity, decreases methanol permeability, and increases selectivity of the membrane. The best membrane performance is on the variation of nanosilica: silane 1:0.50 which has water uptake of 37.52%, tensile strength of 11.8 MPa, proton conductivity of 7.8988 x 10−4 S/cm at 25°C, methanol permeability of 5.8434 x

high thermal stability of 452.94°C with mass residue 44%. Based on the results of membrane selectivity analysis, the best and most suitable chitosan membrane for electrolyte polymer applications is the chitosan membrane with the addition of nanosilica:silane = 1:0.5; 1:0.25; 1:1; 1:0; 1:1.5 and 1:2.0 (w/w). This is based on the order of membrane selectivity values from the highest to the lowest. The results of FT-IR, SEM and AFM analysis on membranes show that optimum silane addition provides the best interaction between chitosan matrix and silane-coupled nanosilica so that they have higher thermal resistance. When compared to Nafion 117 membrane, this membrane has lower proton conductivity value, but the advantages are it more environmentally friendly, has lower methanol permeability, higher temperatures stability and of course more economical in terms of cost. Further efforts are needed to increase the proton conductivity of this chitosan membrane for DMFC

This research is supported by the Direktorat Riset dan Pengabdian Masyarakat (DRPM) under Kementerian Riset, Teknologi dan Perguruan Tinggi Republik Indonesia (Indonesian Ministry of Research, Technology and Higher Education/ Ristekdikti) through Pekerti Scheme Funding (Skim Penelitian Kerjasama Antar Perguruan Tinggi) in 2016. The authors are grateful to Chemistry Department of Institut Teknologi Sepuluh Nopember (ITS), Instrumentation and Analytical Science Laboratory of ITS and also Material Chemistry and Energy Laboratory of

S s/cm3

. This membrane has

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

**4. Conclusions**

10−7 cm2

applications.

**Acknowledgements**

ITS for cooperation.

volatile products generated during decomposition.

/s, and membrane selectivity of 13.5174 x 102

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

highest thermal degradation. This result is in line with the results of FTIR and AFM analysis which finds that the composition nanosilica:silane 1 = 1:0.5 provides the best hydrogen bond interaction. This result is in accordance with [17] which state that the proper addition of modified nanosilica with silane enhanced the thermal performance by acting as superior insulator and mass transport barrier to the volatile products generated during decomposition.
