# A Review of the Synthesis and Applications of Polymer-Nanoclay Composites
## 2 Synthesis
### In-Situ Polymerization Method
#### 2.3.2 Controlled Radical-Mediated Photopolymerization (P-CRP)  
The use of light to mediate controlled radical polymerization has emerged as a powerful strategy for novel polymer/nanoclay composite fabrication. Generally, controlled radical-mediated photopolymerization (P-CRP) can be divided into two different categories, namely intramolecular photochemical processes and photoredox processes [126]. There are a number of synthesis subcategories based on perspectives of the specific reagents, catalysts, and reaction mechanisms [127]. The P-CRP method utilizes low-cost and ubiquitous light sources as external regulators to prepare polymer/nanoclay composites. The method offers various potential advantages in applications such as photo-responsive gel design, particle preparation, surface fabrication, and continuous flow technology [127]. It enables the preparation of polymer/nanoclay composites with well-controlled molecular weights and topology, and provides rapid polymerization rates at relatively low temperatures [42]. Thus, the P-CRP method has attracted growing interest in recent years. A number of updated reviews have been published to discuss the P-CRP method with a focus on reagents, catalysts, applications, reaction mechanisms, polymer backbones and light sources [126; 127; 128; 129; 130; 131; 132].  
[PERSON] et al. [133] prepared exfoliated poly(glycidyl methacrylate)/nanoclay composites via P-CRP using thiolated-bentonite as a chain transfer agent. The synthesized composites exhibited superior thermal and mechanical properties. In the following year, the group applied the similar P-CRP method to synthesize poly(glycidyl methacrylate)/nanoclay composites. The results depicted a highly exfoliated structure and the modified nanoclay performed as a hydrogen donor for benzophenone [134]. [PERSON] et al. [135] prepared polymer/nanoclay composites by intercalating triacrylated siloxane in cetyltrimethylammonium bromide-modified MMT layers prior to performing thiol-ene polymerization reactions by exposure to a light source. [PERSON] et al. [38] developed a novel in-situ photo-induced SI-ATRP method to prepare intercalated poly(propargyl methacrylate)/nanoclay composites using click chemistry. [PERSON] et al. [136] implemented the P-CRP process using a wide range of wavelengths (350-750 nm) to design a finely responsive polymerization system. Their study demonstrated \"one-pot\" selective regulation of P-CRP by simply altering the irradiation wavelength. [PERSON] et al. [137] prepared various stereo-polymers using an advanced photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) process. This method delivered excellent control of tacticity, dispersity, molecular weight and dispersity compared with the thermal polymerization system. [PERSON] et al. [138] developed a simple flow reactor for P-CRP processes, which enabled the process to generate trifluoracorbanes (TTCs) along with significant enhancements in scalability and reaction rates compared with batch reactions. The study also demonstrated the \"on/off\" photo-switchability of the P-CRP process under various flow conditions. The P-CRP method delivered a promising synthesis approach for polymer/nanoclay composites with spatiotemporal control and unprecedented levels of functionality using light as an external stimulus.