# Microsphere Polymers in Molecular Imprinting: Current and Future Perspectives
## 3 Preparation of Molecularly Imprinted Microspheres
### Controlled/Living' Radical Precipitation Polymerisation (CRPP)
#### 3.2.2 Iniferter-induced 'Living' Radical Precipitation Polymerisation (ILRPP)  
Since 1982 [130], iniferter-induced 'living' radical polymerisation (ILRP) has drawn wide interest for its versatility in controlled macromolecular structure design. The controllable properties of ILRP are based on the use of an inferter agent (initiator-transfer agent-terminator, generally dithiocarbamates), which can act as either a dormant species (inferter) or an active species (propagating radical) with a non-reactive radical (dithiocarbamate radical) under suitable conditions (the latter acts as a capping agent for the propagating radicals) (Figure 3a). The obtained MIMs are generally end-capped with an inferter group, making them able to produce block polymers by inferter-induced chain-extension polymerisation [101; 131]. Iniferter-induced 'living' radical precipitation polymerisation (ILRPP) is the most recently developed CRPP by incorporating the ILRP system into precipitation polymerisation, which simply substitutes the conventional initiator (e.g., AIBN) with an inferter agent; an inferter is a compound that acts as an initiator, transfer agent and terminator at the same time during radical polymerisation [130] (Figure 3b). Being similar to conventional precipitation polymerisation, the processes of nucleation and particle growth also occur in ILRPP. The mechanism of particle formation in ILRPP is similar to that in ATRPP, where every part of the inferters in ILRPP is immediately converted into macroiniferters at the onset of polymerisation, which implies that the total yield of newly formed polymer chains throughout the particle growth stage ought to be unimportant. Like ATRPP, the polymer particles in the ILRPP grow by catching monomers straight from the solution via the process of surface-initiated controlled polymerisation. This shows that the controlled attributes of ATRPP have an impact on uniform particle growth and size. Moreover, the existence of 'living' inferter groups on MIM surfaces facilitates further surface modification [132]. [PERSON] et al. [101] first demonstrated ILRPP by using EGDMA as the functional monomer and benzyl dithiocarbamate (BDC) as the inferter agent in acetonitrile as the solvent. With this photoiniferter, UV light irradiation acts as the initiator of polymerisation at 37 \({}^{\circ}\)C (ambient temperature). Photo-ILRPP shows significant superiority among other thermal precipitation polymerisation reactions, as it can be conducted at relatively low temperatures that are suitable for the complexation of template-functional monomers. The factors that can affect ILRPP have also been studied [101]. As both the temperature and inferter concentration increase, the polymerisation rate also increases, indicated by an increased polymer yield. However, an increase in the inferter concentration also causes an increase in MIM particle size, and an increase in polymerisation temperature causes a decrease in particle size. This might be because an increase in the initiator concentration can increase the instantaneous concentration of the growing oligomeric radicals and lead to a larger final particle, while increasing the reaction temperature improves the solubility of the oligomer chains but also increases the decomposition rate of the initiator. Therefore, the particle size is inversely proportional to the reaction temperature, as smaller MIMs are formed at higher temperatures and larger ones are produced at lower temperatures [133]. It can be concluded that the particle sizes that are obtained via ILRPP can be efficiently controlled by adjusting the reaction conditions. [PERSON] et al. [101] also demonstrated the surface modification of MIMs via surface-initiated ILRPP by using NIPAAm. The incorporation of PNIPAAm onto the MIMs was observed by the increased weight and diameter of grafted polymer particles. The enhanced water dispersion stability of grafted MIMs was also shown in this study.