Complex Arborescent Copolymer Architectures by Self-assembly Aklilu Worku Mario Gauthier 04 May 2016

Outline INTRODUCTION What is an arborescent copolymer and how it is made? Why arborescent? What has been and is being done? Objectives Polyion Complex Synthesis & Metal Loading Arborescent Copolymer Complex Structures Conclusions Acknowlegements 2

Introduction 3

What is an Arborescent Polymer? 4 Teertstra, S.J.; Gauthier, M. Prog. Polym. Sci. 2004, 29, Gauthier, M.; Li, J.; Dockendorff, J. Macromolecules 2003, 36, G1PS-g-P2VP (G2) Linear PS 1) Functionalization G1PS G0PS 2) P2VP 2) PS 2) PS Arborescent Polymer: Semicontrolled dendritic (treelike branched) polymer structure (Gauthier, M.; Möller, M.)

Metallic nanoparticles are being investigated for different applications, e.g. imaging, microelectronics, catalysis, drug delivery systems, cell therapy, etc. Dendritic (e.g. arborescent) polymers are potentially useful as templates for the synthesis of metallic nanoparticles High molecular weights attained in a few reaction steps while maintaining a molar mass dispersity (Ð = M w /M n ≤ 1.1) The composition, branching functionality and size (generation number) of arborescent polymers can be easily tailored Unimolecular micelles: More stable as templates for loading polar compounds, such as metallic salts, than micelles formed by the self-assembly of linear block copolymers, since they have no critical micelle concentration Why Arborescent? 5

What has been and is being done? 6 Dockendorff, J.M. Ph.D. Thesis, University of Waterloo, Waterloo, G1PS-g-(P2VP25-b-PS20) R h = 34 nm Ring-like metal organization G2PS-g-(P2VP15-b-PS11) R h = 54 nm Raspberry-like G3PS-g-(P2VP14-b-PS11) R h = 82 nm Cylinder-in-sphere But as the generation number increases, the grafting yield in the template synthesis decreases How to improve? As templates for the preparation of metallic nanoparticles Catalysis Contrast agents and cell hyperthermia Drug encapsulation and release

7 Objectives

Polyion Complex Synthesis & Metal Loading 8 HAuCl 4 G0PS-g-P2VP PAA-b-PS NaBH 4 Metal Loading PAA & P2VP interaction  Electrostatic (weak acid-weak base) interactions and hydrogen bonding contribute to the self-assembly

Arborescent Polymer Synthesis 9

NMR and GPC Analysis of Arborescent Copolymer NMR Analysis of Arborescent CopolymerGPC Analysis of Arborescent Polystyrene 10

Arborescent Copolymer Complex Structures 11

G2 Arborescent Copolymer Complex Structures G1PS-g-P2VP30K (G1PS-g-P2VP30K)-g-(PAA10-b-PS205) (1:2 mass ratio) PAA-b-PS Number-weighed DLS diameter distribution curves Size polydispersity PDI ≤ 0.15 One population observed in intensity, volume and number diameter distributions Size increase from the substrate to the complex, larger increase for longer PS segments 12

Effect of PS Chain Length on Morphology of G2 Complex Systems a b cd Shorter PS chains lead to aggregation after loading Complexes with inter- mediate PS chain lengths (205, 260) display ring- like metal organization, matching what has been seen previously in our lab when using anionic grafting to synthesize the templates G1PS-g-P2VP30K complexes with PAA10-b-PS a) 85, b) 205, c) 260, d) 305 loaded with 0.5 eq of HAuCl 4 in toluene 13

Effect of PS Chain Length on Size of Au Nanoparticles (G2 Systems) a) G1PS-g-P2VP30K-g-PAA17-b-PS195 b) G1PS-g-P2VP30K-g-PAA17-b-PS250 c) G1PS-g- P2VP30K-g-PAA17-b-PS395 loaded with 0.5 eq of HAuCl 4 and reduced with NaBH ± 2.9 nm, 7.1 ± 1.7 nm, 6.0 ± 1.4 nm Au NPs obtained inside the complexes in (a), (b) and (c), respectively Longer PS chain prevent Ostwald ripening a b c 14

UV-Vis Absorption Analysis a b (G1PS-g-P2VP30K)-g-(PAA10-b-PS392) complex loaded with 0.5 eq of HAuCl 4 in toluene with 10% ethanol at 0.8 mg/mL: (a) TEM image before reduction and (b) AFM phase image after reduction. UV-Vis absorption spectra The morphology of the complex seems to change after reduction Characteristic red wavelength shift (322 nm to 540 nm) observed after reduction 15

AFM height (a) and phase (b) and TEM (c) images for G2PS-g-P2VP13K in THF (scale bar = 100 nm) a bc 16 G3 Arborescent Copolymer Structures In all cases spherical topology observed

AFM height (left) and phase (right) images for G2PS-g-P2VP13K complexed with PAA10-b-PS260 (scale bar = 100 nm) 17 Size increases and raspberry-like morphology observed, matching the previous work G3 Arborescent Copolymer Complex Structures

DLS Analysis of G3 Arborescent Copolymer System PDI ≤ 0.08 One population observed in intensity, volume and number distributions Size increases from the substrate to the complex Description DLSAFMTEM Size(d- nm) G2PS53± ± G2PS-P2VP13K91± ± ±5 75.3±3 PAA10-PS ± ± G2PS-P2VP13K- PAA10-PS ± ± ±584±7 18 DLS Number distribution

Effect of PS Chain Length on G3 Complex System Sample DLS Size(d-nm) G2PS-g-P2VP13K 91± ±0.01 G2PS-g-P2VP13K)-g-(PAA13-b- PS156) 109± ± 0.01 G2PS-g-P2VP13K)-g-(PAA13-b- PS305) 119 ± ± 0.02 G2PS-g-P2VP13K)-g-(PAA13-b- PS395) 121 ± ± 0.03 DLS number size distribution for G3 arborescent complex systems with different PS chain lengths PDI ≤ 0.08 One population observed in intensity, volume and number distributions Size increase from the substrate to the complex, larger increases for longer PS chains 19

c (G2PS-g-P2VP13K)-g-(PAA10-b-PS260) loaded with 0.5eq of HAuCl 4 Metal Loading Raspberry-like morphology observed after loading, that also matches previous work 20

Effect of Solvent on Morphology on G3 Complex Systems bca 21 (G2PS-g-P2VP13K)-g-(PAA10-b-PS260) loaded with 0.5 eq of HAuCl 4 in a) toluene with 2% methanol, b) THF with 25% cyclohexane, and c) chloroform (scale bar = 100 nm) The metal organization in the complex appears to depend on the type of solvent used; Toluene with 2% methanol: uniformly distributed with dimple at the center THF with 25% cyclohexane : more concentrated at the center Chloroform: single or two connected ring-like organization

Conclusions 22  Increase in size observed upon complexation of the arborescent substrates with the block copolymers, yielding self-assembled structures with a single, narrow size population  This method offers a simple but effective way to prepare polymeric templates with  100% coupling yield  HAuCl 4 was successfully loaded in the micelles and subsequent reduction of the (G1PS-g-P2VP30K)-g-(PAA-b-PS) complex yielded aggregation-free gold nanoparticles with a size ranging from 6 to 17 nm inside the polyion complexes.  The PS chain length appears to affect the size of the Au NPs in the G2 system: smaller size for longer PS segments  Nanomorphologies observed that were similar to the systems previously obtained in our laboratory by anionic block copolymer grafting

Acknowledgements University of Waterloo Natural Sciences and Engineering Research Council of Canada (NSERC) Prof. Xiaosong Wang 23

Thank You 24