## 1 Introduction
Both the dehydration and the aggregation processes were found to be kinetically controlled, with the enthalpy and the transition temperature dependent on the scanning rate and the polymer concentration [21]. The reversibility of the process was observed by looking at the dissolution of the aggregates upon cooling. Measurements made at low scan rates on the cooling scan showed the coexistence of two different processes, namely, the disruption of the intra-chain hydrogen bonds created upon the collapse of the chains, and the dissolution of the aggregates [24]. The shape of the cooling peak was therefore dependent upon the aggregation state reached by the polymer, i.e., small dispersed clusters in diluted solutions, large precipitate clusters, or hydrogels in concentrated solutions [21]. In contrast to the studies carried out on classical coil-to-globule thermoresponsive polymers, an extensive calorimetric investigation of the transition is often missing for polymers possessing a globule-to-aggregate transition, and, for example, is absent in the field of thermoresponsive polymers capable of self-folding into unimer micelles. One interesting example showing the potentialities of calorimetry in this field was reported by [PERSON] et al. [13], who published a paper with the synthesis, morphologic, and calorimetric characterization of the phase transition for telechelic PNIPAM modified with a perfluorinated end-group. The polymer was capable of assembling at room temperature into small micelles with a hydrodynamic diameter (\(D_{\rm{h}}\)) of 24 nm and possessed an LCST phase transition, forming larger aggregates above the cloud point temperature. The transition studied ended up being completely reversible and much sharper with respect to the non-reversible larger peak obtained with the azide-terminated precursor, suggesting that cooperative effects in the transition were provided by the presence of the hydrophobic fluorinated groups in the chain. However, no more specific mechanistic hypotheses on the aggregation process were reported in the paper. Thermoresisive polymers containing poly (ethylene glycol) (PEG) groups have gained increasing interest in the last two decades due to the high biocompatibility offered by PEG. (Meth)acrylates containing PEG side chains have been frequently used as basic monomers to form thermoresponsive poly(oligo(ethylene glycol) methyl ether methacrylate (POEGMA)-based polymers). At first glance, this class of polymers undergoes a fully reversible transition, in contrast to PNIPAM [25], but there are no in-depth calorimetric studies in the literature that support this assumption. Indeed, when micro-calorimetry was used to study the transition of POEGMA grafted on cellulose nanocrystals, this was shown to involve hysteresis upon cooling [26]. Examples of amphiphilic random copolymers possessing an LCST-type transition are obtained by the copolymerization of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) and fluorinated monomers [15; 27; 28; 29], including pentafluorostyrene (PFS). The latter system has been shown to possess a well-tunable \(T_{\rm{cp}}\)[30] and is also capable of self-assembling or self-folding even below this temperature in small micellar structures (down to 10 nm in diameter) [31; 32]. An alternative route to obtaining an amphiphilic homopolymer based on PFS would be to exploit the facile substitution of the fluorine atom in the para position of the pentafluorostyrene monomer [33] to introduce a hydrophilic oligo(ethylene glycol) segment capable in principle of providing thermoresponsive behavior. Amphiphilic PFS-based copolymers, containing triethylene glycol grafts, have been studied for their anti(bio)fouling activities, but are not water-soluble [34; 35; 36; 37; 38; 39]. In this paper, we report on the synthesis of amphiphilic PFS-based homopolymers p(EFS)x derived from the atom transfer radical polymerization (ATRP) of a pentafluorostyrene monomer substituted in the para position with an oligo(ethylene glycol)chain (\(M_{\rm{n}}\) = 300 g/mol).