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DOSY measurements demonstrated the changes in volume upon the self-assembly of poly-1 (Figures 3a). The diffusion Figure 3. (a) DOSY spectra of poly-1 (1.0 mmol L™') and poly-2 (0.5 mmol L~') at 293 K in chloroform-d, and (b) volume-average size distribution measured by dynamic light scattering of poly-1 (2.4 mmol L”’) and poly-2 (0.93 mmol L~’) at 293 K in chloroform.

Figure 3 DOSY measurements demonstrated the changes in volume upon the self-assembly of poly-1 (Figures 3a). The diffusion Figure 3. (a) DOSY spectra of poly-1 (1.0 mmol L™') and poly-2 (0.5 mmol L~') at 293 K in chloroform-d, and (b) volume-average size distribution measured by dynamic light scattering of poly-1 (2.4 mmol L”’) and poly-2 (0.93 mmol L~’) at 293 K in chloroform.

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tar-shaped polymers are a novel class of macromolecules with more than three linear polymeric chains radiating from a central core.'° They represent higher-order architectures with unique properties’ ’ compared to the linear counterparts due to their spatially defined yet compact three- dimensional structure. Therefore, star-shaped polymers have attracted significant attention and have been used in drug delivery,” gene delivery,” imaging,’ catalysis,”’'* and theology,'”'® as well as for their thermal properties.'’ These functions are associated with their star-shaped structures and the properties of their side chains; therefore, establishing the desired functions requires a variation of the side chain and the structures. Although a diverse range of star-shaped polymers have been prepared by various covalent synthetic methods, including arm-first,'® core-first,'? and coupling onto~° methods, controlling the number and structures of the side chains can be difficult, which limits the variability of star- shaped polymers.” Johnson et al. successfully developed a coordination-driven self-assembly of ligand-terminated polymer chains that allowed control of the number of chains and the resulting geometries which determined the properties of the polymer.”’ Although these self-assembly strategies for generating star-shaped supramolecular polymers have become powerful tools to fabricate large and elaborate organizations, there are few examples of the self-assembly directed synthesis of star-shaped polymers that result in well-defined star-shaped geometries.
tar-shaped polymers are a novel class of macromolecules with more than three linear polymeric chains radiating from a central core.'° They represent higher-order architectures with unique properties’ ’ compared to the linear counterparts due to their spatially defined yet compact three- dimensional structure. Therefore, star-shaped polymers have attracted significant attention and have been used in drug delivery,” gene delivery,” imaging,’ catalysis,”’'* and theology,'”'® as well as for their thermal properties.'’ These functions are associated with their star-shaped structures and the properties of their side chains; therefore, establishing the desired functions requires a variation of the side chain and the structures. Although a diverse range of star-shaped polymers have been prepared by various covalent synthetic methods, including arm-first,'® core-first,'? and coupling onto~° methods, controlling the number and structures of the side chains can be difficult, which limits the variability of star- shaped polymers.” Johnson et al. successfully developed a coordination-driven self-assembly of ligand-terminated polymer chains that allowed control of the number of chains and the resulting geometries which determined the properties of the polymer.”’ Although these self-assembly strategies for generating star-shaped supramolecular polymers have become powerful tools to fabricate large and elaborate organizations, there are few examples of the self-assembly directed synthesis of star-shaped polymers that result in well-defined star-shaped geometries.
“Reagents and conditions: (i) DMAP, imidazole, TBSCl, DMF, 65%; (ii) n-BuLi, I,, Et,O, 77%; (iii) 5-(4-(pinacolatoboryl) phenyl)-2,2’- bipyridine, Cs,CO3, AsPh3, [Pd(PPh;),]Cl, 1,4-dioxane-water (25:1), 81%; (iv) TBAE, THE, 88%; (v) DMAP, HOBt, DCC, 4- (butyltrithiocarbonylmethy)benzoic acid, DMF, 80%; vi) AIBN, styrene, 75%, vii) AgBF,, CHC]; 99%; viii) AgBF,, CHCl, 99%.
“Reagents and conditions: (i) DMAP, imidazole, TBSCl, DMF, 65%; (ii) n-BuLi, I,, Et,O, 77%; (iii) 5-(4-(pinacolatoboryl) phenyl)-2,2’- bipyridine, Cs,CO3, AsPh3, [Pd(PPh;),]Cl, 1,4-dioxane-water (25:1), 81%; (iv) TBAE, THE, 88%; (v) DMAP, HOBt, DCC, 4- (butyltrithiocarbonylmethy)benzoic acid, DMF, 80%; vi) AIBN, styrene, 75%, vii) AgBF,, CHC]; 99%; viii) AgBF,, CHCl, 99%.
Scheme 1. Schematic Representation of the Coordination- Driven Self-Assembly of Poly-1 and Guest G1 Scheme 2. Synthesis of poly-1 and poly-2°
Scheme 1. Schematic Representation of the Coordination- Driven Self-Assembly of Poly-1 and Guest G1 Scheme 2. Synthesis of poly-1 and poly-2°
The coordination-driven self-assembly of 1 in the absence of a polymer chain was assessed in the presence of two equivalents of silver tetrafluoroborate in chloroform-d,. The changes in the chemical shifts of the 2,2’-bipyridyl protons confirmed the silver coordination to the bipyridyl units (Figure S17a,b).°° The formation of 2 was confirmed by a guest encapsulation experiment. When a rigid guest G1 was added into a solution of 2, the acetoxyl protons appeared at shifts higher than —1 ppm, with a large complexation-induced upfield shift (CIS) of —3.7 ppm (Figure 2a—c). Accordingly, Figure 2. Partial 'H NMR spectra of (a) 2 (1.2 mmol L7’), (b) 2 (1.2 mmol L~') with 20 equiv of G1, (c) G1, (d) poly-2 (1.9 mmol L™'), and (e) poly-2 (1.9 mmol L™!) with 40 equiv of G1 at 293 K in chloforom-d,.""
The coordination-driven self-assembly of 1 in the absence of a polymer chain was assessed in the presence of two equivalents of silver tetrafluoroborate in chloroform-d,. The changes in the chemical shifts of the 2,2’-bipyridyl protons confirmed the silver coordination to the bipyridyl units (Figure S17a,b).°° The formation of 2 was confirmed by a guest encapsulation experiment. When a rigid guest G1 was added into a solution of 2, the acetoxyl protons appeared at shifts higher than —1 ppm, with a large complexation-induced upfield shift (CIS) of —3.7 ppm (Figure 2a—c). Accordingly, Figure 2. Partial 'H NMR spectra of (a) 2 (1.2 mmol L7’), (b) 2 (1.2 mmol L~') with 20 equiv of G1, (c) G1, (d) poly-2 (1.9 mmol L™'), and (e) poly-2 (1.9 mmol L™!) with 40 equiv of G1 at 293 K in chloforom-d,.""
Figure 1. (a) SEC chromatogram of poly-1 (eluent: chloroform) and (b) plot of the molecular weight and polydispersity index vs conversion. number-average molecular weight of the polymer was found to be 10100 g mol™ from the molecular weight distribution curve based on polystyrene standards (Figure la). All the isolated polymers showed narrow molecular weight distribu- tions, with M,/M, < 1.10, confirming the controlled chain- growth nature of the polymerization (Figure 1b).
Figure 1. (a) SEC chromatogram of poly-1 (eluent: chloroform) and (b) plot of the molecular weight and polydispersity index vs conversion. number-average molecular weight of the polymer was found to be 10100 g mol™ from the molecular weight distribution curve based on polystyrene standards (Figure la). All the isolated polymers showed narrow molecular weight distribu- tions, with M,/M, < 1.10, confirming the controlled chain- growth nature of the polymerization (Figure 1b).
Figure 4. (a) Specific viscosities of poly-1 (open circles) and poly-2 (filled circles) and (b) reduced viscosities of poly-1 and poly-2 at 298 K in 1,2-dichloroethane.
Figure 4. (a) Specific viscosities of poly-1 (open circles) and poly-2 (filled circles) and (b) reduced viscosities of poly-1 and poly-2 at 298 K in 1,2-dichloroethane.
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