## 1 Introduction  
The properties of polymeric materials with tridimensional network structures produced by conventional free radical copolymerization with crosslinking (FRC) of vinyl and divinyl monomers make them relevant for many technological applications. The best performance in these applications is obtained when the materials possess homogeneous structures. Unfortunately, the FRC of vinyl/divinyl monomers usually leads to highly heterogeneous microstructures due to the inherent characteristics of this method, which include slow initiation, fast propagation, high termination rates, and large dispersities (D) of the molar mass of primary chains. Cyclization and compositional drift promote the formation of highly compact crosslinked regions mixed with looser ones, which add to the highly heterogeneous nature of polymer networks synthesized by this route [1]. The incorporation of reversible-deactivation radical polymerization (RDRP) controllers during the manufacture of polymer networks by FRC of vinyl/divinyl monomers is reported to reduce the heterogeneity of the materials [2]. Polymer networks with claimed reduced heterogeneity of crosslink density distribution have therefore been synthesized by nitroxide-mediated polymerization (NMP) [3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16], initiator-chain transfer-terminator (INIFERTER) polymerization [17; 18; 19; 20; 21], atom transfer radical polymerization (ATRP) [22; 23; 24; 25; 26; 27; 28; 29; 30; 31], and reversible addition-fragmentation chain transfer (RAFT) polymerization [32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45]. The first reports using NMP during the synthesis of polymer networks were pioneer reports focused on the synthesis of the materials [3; 4; 5; 6], measurement and control of the porosity of the materials [7; 8], synthesis in dispersed (mini-emulsion) [9; 10; 11; 12] or micro-suspension [13] conditions, generation of reliable kinetic data [14; 15], and a review on NMP which includes a comprehensive coverage of this topic [16]. The scope and progress are similar for the other chemistries (INIFERTER, RAFT and ATRP). The use of compressed fluids as solvents in polymer chemistry gained relevance in the 1990s and the first decade of this century. New developments continue in the present decade. Carbon dioxide at supercritical conditions (s\(\mathrm{cCO_{2}}\)) is the solvent most extensively used. The replacement of conventional polluting organic solvents by \(\mathrm{s\mathrm{cCO_{2}}}\) in organic synthesis is important from a non-polluting green chemistry perspective. There are many reports on the synthesis of polymers in \(\mathrm{s\mathrm{cCO_{2}}}\) as a continuous phase [46; 47; 48]. A few reviews on polymer chemistry in \(\mathrm{s\mathrm{cCO_{2}}}\) are available [47; 49; 50; 51; 52; 53]. A few years ago, we presented the first reports concerning the production of polymer networks using RDRP chemistries and carried out in \(\mathrm{s\mathrm{cCO_{2}}}\)[2; 54; 55]. The examples analyzed included the RAFT copolymerization of styrene (STY) and divinylbenzene (DVB) [54; 55], RAFT copolymerization of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) [2; 55], and RAFT copolymerization of hydroxyethyl methacrylate (HEMA) and EGDMA [55; 56; 57]. We have also modelled these copolymerizations [58].