## 4 Conclusions  
The synthesis of well-defined arborescent copolymers consisting of linear chain segments grafted onto PBG cores by copper-catalyzed azide-alkyne Huisgen cycloaddition (CuAAC) chemistry was investigated. Well-defined linear polyglycidol, poly(ethylene oxide), and poly(2-trimethylsilylethyl acrylate) with terminal azide functionalities were synthesized by different polymerization techniques and chain end modification. Arborescent PBG with alkyne functionalities, either randomly distributed or at the chain ends, were derived from the corresponding carboxylic acid-functionalized substrates and prompargylamine by carbodiimide activation.  
Arborescent copolymers were synthesized by grafting either PGly, PEO, or P(HEA-TMS) chains onto the PBG cores through the CuAAC reaction. Successful CuAAC reactions were achieved with copper(II) sulfate and sodium ascorbate as catalyst, with grafting yields varying from 29% to 65%, depending on the PBG substrate and linear chain segments employed. Well-defined arborescent copolymers (\(M_{\rm w}/M_{\rm n}\leq 1.14\)) were obtained with the exception of two samples, G1 PBG-_eg_-PEO and G2 PBG-_eg_-PEO, characterized by \(M_{\rm w}/M_{\rm n}\) values of 1.30 and 1.23, respectively.  
The dynamic light scattering measurements revealed that even though the randomly grafted G1 and G2 arborescent copolymers with PHEA and PGly shells were dispersible in aqueous PBS solutions, they yielded either large aggregates or bimodal size distributions, while the analogous PEO copolymers were insoluble. Aggregation was arguably present even in the non-selective solvent DMF for most of the G1 copolymers, both randomly and end-grafted, presumably due to their open structure. In contrast, other copolymers with a more rigid PBG core (e.g., G2 PBG-_eg_-PEO, G3 PBG-_eg_-PGly, G3 PBG-_eg_-PEO) were characterized by a modest size increase in DMF relatively to their parent PBG substrates, comparable dimensions in DMF and in PBS, and unimodal CONTIN size distributions. These samples, therefore, appear to behave like unimolecular micelles based on both their average hydrodynamic diameters and the CONTIN size distributions, or if aggregation is present, it is not significantly higher in aqueous PBS solutions than in DMF. Further confirmation for the unimolecular nature of the micelles could be obtained by comparing the results of static light scattering measurements in DMF and in PBS solutions for these copolymers. This will be the topic of a future investigation. Similar trends in the aggregation behavior were observed for analogous arborescent copolymers obtained by carbodiimide coupling, in particular when comparing the solubility of randomly vs. terminally grafted copolymer systems [16]. The lower aqueous dispersibility of the randomly-grafted and the lower generation copolymers was explained by less efficient shielding of van der Waals interactions between the cores, due to a more diffuse interface between the hydrophobic core and the hydrophilic shell components.  
The following are available online at www.mdpi.com/2073-4360/9/10/540/s1.  
The authors thank the Natural Sciences and Engineering Research Council of Canada (NSERC) for supporting this work.  
[PERSON] and [PERSON] conceived and designed the experiments; [PERSON] performed the experiments; [PERSON] and [PERSON] analyzed the data; [PERSON] contributed reagents, materials and analysis tools; [PERSON] wrote and [PERSON] corrected the paper.  
The authors declare no conflict of interest.