Synthesis and Self-Assembly of Well-Defined Star and Tadpole Homo-/Co-/Terpolymers George Polymeropoulos, † Panayiotis Bilalis, † Xueyan Feng, ‡ Edwin L. Thomas,* ,‡ Yves Gnanou, § and Nikos Hadjichristidis* ,† † Physical Sciences and Engineering Division, KAUST Catalysis Center, Polymer Synthesis Laboratory, King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia ‡ Department of Materials Science and Nano-Engineering, Rice University, Houston, Texas 77030, United States § Division of Physical Sciences & Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia * S Supporting Information ABSTRACT: Tadpole polymers are excellent candidates to explore how architecture can influence self-assembly because they combine two topologies in the same molecule (ring polymer as the head and linear polymer as the tail). In this work, we synthesize well-defined tadpole homo-/co-/terpol- ymers derived from the appropriate chemical modification reactions of the corresponding 3-miktoarm star homo-/co-/ terpolymers via anionic polymerization, high vacuum techniques, and chlorosilane chemistry in combination with the Glaser coupling reaction. The 3-miktoarm star homo-/ co-/terpolymers bear two arms with t-butyl dimethylsiloxypropyl functional end-groups, whereas after deprotection, the ω- hydroxyl chain-ends were modified to alkyne moieties. The dialkyne star polymers in the presence of Cu(I)Br and N,N,N′,N″,N″-pentamethyldiethylenetriamine were then transformed to well-defined tadpole homo-/co-/terpolymers. We employed strongly immiscible blocks to enable characterization using electron microscopy and X-ray scattering to explore how the molecular topology influences the self-assembled bulk-state microdomain morphologies. ■ INTRODUCTION The advent of “living” anionic polymerization 1 in the 1950’s enabled the synthesis of a broad portfolio of polymers with complex macromolecular architectures 2 such as star, 3-6 branched, 7-11 cyclic, 12-14 dendritic, 15,16 and graft 17-19 poly- mers and so forth. Considerable attention has been paid to the cyclic polymers because of their unique properties derived from the absence of chain-ends. It is well known that cyclic polymers possess smaller hydrodynamic volumes, higher glass transition temperatures, and lower intrinsic viscosities and consequently exhibit different properties compared to their linear/star analogues. 20 Among the two general strategies for synthesizing cyclic polymers, the ring expansion technique 21,22 affords the synthesis of high-purity, high molecular weight cyclic polymers but faces severe limitations concerning the variety of monomers that can be used, poor control over molecular weight, and broad polydispersity. On the other hand, the ring closure technique 23,24 is applicable to a great number of monomers and offers higher tolerance to different functional end-groups but has to overcome the entropic penalties associated with having the two chain-ends approach closely enough to bond. Despite the above-mentioned limitations, the ring closure strategy has been widely used for the synthesis of a plethora of ring polymers such as cyclic homopolymers, 25,26 cyclic diblock copolymers, 27,28 and cyclic triblock terpolymers. 29,30 Most importantly, via the ring closure methodology, the synthesis of even more complex cyclic-based macromolecular architectures such as tadpole, 31-33 dicyclic, 34,35 multicycle, 36,37 eight- shaped, 38,39 and spiro-bicyclic polymers 40,41 was feasible. The lack of experimental data on the self-assembly of tadpole co-/ terpolymers, arises from the inherent difficulties in synthesizing such chain architectures composed of blocks with large segment-segment interaction parameters and appropriate molecular weights to induce microphase separation. In our previous work, 29 the combination of anionic polymerization with the Glaser coupling reaction afforded the synthesis of well-defined cyclic triblock terpolymers consisting of poly- isoprene (PI), polystyrene (PS), and poly(2-vinylpyridine) (P2VP). It was found out that the Glaser coupling reaction between terminal alkynes in the presence of Cu(I)Br and N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA), under high dilution, promotes the formation of 1,3-diyne rings in high yield, without the presence of polycondensation Received: May 16, 2019 Revised: July 1, 2019 Published: July 17, 2019 Article pubs.acs.org/Macromolecules Cite This: Macromolecules 2019, 52, 5583-5589 © 2019 American Chemical Society 5583 DOI: 10.1021/acs.macromol.9b01013 Macromolecules 2019, 52, 5583-5589 Downloaded via UNIV OF CINCINNATI on April 3, 2020 at 02:06:35 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.