# Styrene-Based Copolymer for Polymer Membrane Modifications
## 3 Results and Discussion
### FTIR-ATR Analysis of Blend Membranes  
PVDF is known to exhibit polymorphism. [PERSON] and [PERSON] reported [PERSON] and [PERSON] (1999) that it may be present in four different well-known crystalline structures; the orthorhombic \(\alpha\), \(\beta\), and \(\delta\) phases, and the monoclinic \(\gamma\) phase. The FTIR-ATR fingerprint regions of the top surface of 100% PVDF, 100% styrene-acrylonitrile membranes, and the blend membranes are shown in Figure 6a. In the case of the 100% PVDF membrane, the peaks at 762 cm\({}^{-1}\) (skeletal bending), 615 cm\({}^{-1}\) (CF\({}_{2}\) bending), and 798 cm\({}^{-1}\) (-CH\({}_{2}\) rocking) represent the typical \(\alpha\)-phase with 511 cm\({}^{-1}\) (CF\({}_{2}\) bending) and 840 cm\({}^{-1}\) (-CH\({}_{2}\) rocking) as typical \(\beta\)-phase peaks. The peaks at 1178 cm\({}^{-1}\) and 1275 cm\({}^{-1}\) show the in-plane stretching of C-F bonds [PERSON] and [PERSON] (1999). According to [PERSON] _et al._[PERSON] _et al._ (2016), this signifies the change in composition of that particular phase. The \(\alpha\)-phase, trans di-substituted alkene peak of 975 cm\({}^{-1}\) and 798 cm\({}^{-1}\) for the 100% PVDF membranes are significantly reduced in the styrene-acrylonitrile blend membranes. The presence of acrylonitrile (-CN) group in the blend membranes was confirmed by the presence of a minor peak at 2237 cm\({}^{-1}\). The peaks at 760 cm\({}^{-1}\) and 513 cm\({}^{-1}\) are the shifted peaks previously observed at 762 cm\({}^{-1}\) and 511 cm\({}^{-1}\), respectively, which represent the peaks of the  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Membrane** & **Td** & **Res. wt. \%** & **Td** & **Td** & **Res. wt. \%** & \(\Delta\)**Td** & \(\Delta\)**Res** \\  & **(Start) \({}^{\circ}\)C** & **(Start)** & **(Peak) \({}^{\circ}\)C** & **(Final) \({}^{\circ}\)C** & **(Finish)** & & **wt. \%** \\ \hline
100\% PVDF & 417.5 & 97.5 & 477.5 & 495 & 30.4 & 77.5 & 67.1 \\
10\% styrene-acrylonitrile & 368 & 97.2 & 467 & 493 & 36.4 & 125 & 60.8 \\
20\% styrene-acrylonitrile & 355 & 97 & 460 & 491.5 & 38 & 136.5 & 59.0 \\
60\% styrene-acrylonitrile & 350 & 96.1 & 469 & 480 & 18.5 & 130 & 77.6 \\
100\% styrene-acrylonitrile & 340 & 95.5 & 405 & 430 & 3.5 & 90 & 92.0 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Degradation temperatures of PVDF blend membranes.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Membrane** & **Melting Pt. (Tm)**, \({}^{\circ}\)**C** & \(\Delta\)_Hf, Jyg_ & **PVDF Content** & \(\Delta\)_Hf, PVDF, Jyg_ \\ \hline
100\% PVDF & 171.40 & 60.77 & 1.00 & 60.77 \\
10\% styrene-acrylonitrile & 172.5 & 37.60 & 0.90 & 41.77 \\
60\% styrene-acrylonitrile & 169 & 10.93 & 0.40 & 27.31 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Melting point (Tm), melting enthalpy (\(\Delta\)_Hf_) of membranes obtained from a differential scanning calorimeter (DSC).  
\(\alpha\)-phase and the \(\beta\)-phase of (-CH\({}_{2}\) rocking) the 100% styrene-acrylonitrile. The peak at 700 cm\({}^{-1}\) represents a mono-substituted benzene, which is the characteristic peak of styrene present in the styrene-acrylonitrile blend membranes. However, the bending vibration band of the benzene ring plane had split into two independent peaks at respectively 760 and 790 cm\({}^{-1}\) for 60% styrene-acrylonitrile and 10% styrene-acrylonitrile membranes.