# A Review of the Synthesis and Applications of Polymer-Nanoclay Composites
## 2 Synthesis
### In-Situ Polymerization Method  
The melt-blending method often leads to insufficient filler dispersion, which causes aggregation and intercalation, particularly at high filler contents [99]. Based on the silicate dispersion data [100], in-situ polymerization is more effective in the formation of composites, and can bypass the rigorous thermodynamic requirements associated with the polymer intercalation process [101] (Figure 4). Moreover, in-situ polymerization allows versatile molecular designs of the polymer matrix; it delivers an effective approach to the synthesis of different polymer/nanoclay composites with an expanded property range and enables the design of the interface between the nanoclays and the polymers by flexible tuning of the matrix composition and structure [102]. A number of studies focus on preparing novel polymer/nanoclay composites via the in situ polymerization method and demonstrate the benefits of this method in comparison with other types of synthesis methods [103] (Table 4). For instance, [PERSON] et al. [34] reported the synthesis of poly(2-ethyl-2-oxazoline)/nanoclay composites for the first time using in-situ polymerization. In their study, a ring-opening polymerization approach was designed, which triggered the delamination of clay layers in the polymer matrix and led to a composite formation. The results exhibited mixed exfoliated/intercalated layers and improved thermal stability compared to pure poly(2-ethyl-2-oxazoline). [PERSON] et al. [104] prepared a conductive composite containing PPy, silver and attapulgite clay using in-situ polymerization; the resulting composites with  
Figure 3: Melt-blending method scheme. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Nanoclay** & **Polymer** & **Clay Structure** & **Reference** \\ \hline Cloisite®30B & Nylon 6 & Intercalated & [93] \\ Na-MMT & Nylon 66 & Disordered & [94] \\ Na-MMT & Epoxy & Intercalated & [95] \\ Na-MMT & Polyamide & Exfoliated & [96] \\ MMT & Polypropylene & Exfoliated & [97] \\ MMT & Polyvinyl chloride & Exfoliated & [98] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Polymer/nanoclay prepared by the melt-blending method and dispersion states. MMT: montmorillonite. a beads-on-a-string morphology were obtained in 10 minutes. The in-situ polymerization method delivered well-dispersed clay fillers in a polymer matrix, which imparted an outstanding antibacterial property to the biodegradable composite material as well as an enhanced storage modulus. [PERSON] et al. [105] investigated the influence of the shape and area of the nanoclays used in the in-situ polymerization method. Their study demonstrated that needlelike clay promotes higher molar mass and better mechanical properties compared to laminar clay; they improved the in-situ polymerization process by using a non-isothermal temperature profile and an additional amount of co-catalyst. [PERSON] et al. [106] applied direct in-situ polymerization to synthesize poly(furfuryl alcohol)/MMT composites. The produced composites exhibited an intercalated and/or exfoliated structure, which promoted improved thermal stability and mechanical properties compared with pure polymer. [PERSON] et al. [107] synthesized several PMMA/MMT composites by in-situ polymerization and using a chloroform solution under probe sonication. The prepared composites exhibited mixed and intercalated morphologies, which contributed to promising properties for optical electronic devices. [PERSON] et al. [108] enhanced the thermal and mechanical properties of poly(MMA-co-BA)/Cloisite(r) 30B (BYK Additives & Instrument, Wesel, Germany) composites by using an ultrasound-assisted in-situ emulsion polymerization method. This innovative method provided higher thermal degradation resistance and mechanical strength than the composites synthesized using conventional techniques. The composite had a highly exfoliated and dispersed structure due to intense micro-convection induced by ultrasound and cavitation. Compared to the use of the melt-blending method, [PERSON] et al.