Semiconducting polymers have been widely investigated due to their intriguing optoelectronic properties and their high crystallinity that provides a strong driving force for self-assembly. Although there are various reports of successful self-assembly of nanostructures using semiconducting polymers, direct in situ self-assembly of these polymers into two-dimensional (2D) nanostructures has proven difficult, despite their importance for optoelectronics applications. Here, we report the synthesis of a simple conjugated homopolymer by living cyclopolymerization of a 1,6-heptadiyne (having a fluorene moiety) and its efficient in situ formation of large-area 2D fluorescent semiconducting nanostructures. Using high-resolution imaging tools such as atomic force microscopy and transmission electron microscopy, we observed the solvent-dependent self-assembly behaviors of this homopolymer; the identical starting polymer formed 2D nanosheets with different shapes, such as rectangle, raft, and leaf, when dissolved in different solvents. Furthermore, super-resolution optical microscopy enabled the real-time imaging of the fluorescent 2D nanosheets, revealing their stable and uniform shapes, fluorescence, and solution dynamics. Notably, we propose an orthorhombic crystalline packing model to explain the direct formation of 2D nanostructures based on various diffraction patterns, providing important insight for their shape modulation during the self-assembly.

Typical multimechanophore polymers (MMPs) are comprised of numerous mechanophores (force-responsive moieties) distributed throughout the backbone of linear polymers. We have developed a new MMP design based on graft polymers with mechanophores linking each arm to the backbone. By utilizing maleimide–anthracene cycloadducts, polymeric species containing anthracene were released from the parent polymer, enabling facile quantification of mechanophore activation. With pulsed ultrasound experiments, we observed that mechanophore activation was dependent on the arm length (a faster rate with longer arms), and we observed that 85% of the polystyrene (PS) arms underwent scission (64% specifically at the mechanophore site) for a graft polymer with 23 kDa arms. Solid-state activation was also investigated with hand-grinding experiments. Fast reactions were observed, with up to 96% of PS arms undergoing scission and 70–75% of mechanophores being activated, for all arm lengths studied. Multimechanophore graft polymers provide important insight into the distribution of forces in topologically complex polymers and may enable the development of new mechanoresponsive materials.

Catalyst-transfer polymerization has revolutionized the field of polymer synthesis due to its living character, but for a given catalyst system, the polymer scope is rather narrow. Herein we report a highly efficient Suzuki−Miyaura catalyst-transfer polymerization (SCTP) that covers a wide range of monomers from electron-rich (donor, D) to electron-deficient (acceptor, A) (hetero)arenes by rationally designing boronate monomers and using commercially available Buchwald RuPhos and SPhos Pd G3 precatalysts. Initially, we optimized the controlled polymerization of 3,4-propylenedioxythiophene (ProDOT), benzotriazole (BTz), quinoxaline (QX), and 2,3-diphenylquinoxaline (QXPh) by introducing new boronates, such as 4,4,8,8-tetramethyl-1,3,6,2dioxazaborocane and its N-benzylated derivative, to modulate the reactivity and stability of the monomers. As a result, PProDOT, PBTz, PQX, and PQXPh were prepared with controlled molecular weight and narrow dispersity (Đ < 1.29) in excellent yield (>85%). A detailed investigation of the polymer structures using 1 H NMR and MALDI-TOF spectrometry supported the chain-growth mechanism and the high initiation efficiency of the SCTP method. In addition, the use of RuPhos−Pd showing excellent catalyst-transfer ability on both D/A monomers led to unprecedented controlled D−A statistical copolymerization, thereby modulating the HOMO energy level (from −5.11 to −4.80 eV) and band gap energy (from 1.68 to 1.91 eV) of the resulting copolymers. Moreover, to demonstrate the living nature of SCTP, various combinations of D−A and A−A block copolymers (PBTz-b-PProDOT, PQX-b-PProDOT, and PQX-b-PBTz) were successfully prepared by the sequential addition method. Finally, simple but powerful one-shot D−A block copolymerization was achieved by maximizing the rate difference between a fast-propagating pinacol boronate donor and a slow-propagating acceptor to afford well-defined poly(3hexylthiophene)-b-poly(benzotriazole).

Precise size control of semiconducting nanomaterials from polymers is crucial for optoelectronic applications, but the low solubility of conjugated polymers makes this challenging. Herein, we prepared length-controlled semiconducting one-dimensional (1D) nanoparticles by synchronous self-assembly during polymerization. First, we succeeded in unprecedented living polymerization of highly soluble conjugated poly­(3,4-dihexylthiophene). Then, block copolymerization of poly­(3,4-dihexylthiophene)-block-polythiophene spontaneously produced narrow-dispersed 1D nanoparticles with lengths from 15 to 282 nm according to the size of a crystalline polythiophene core. The key factors for high efficiency and length control are a highly solubilizing shell and slow polymerization of the core, thereby favoring nucleation elongation over isodesmic growth. Combining kinetics and high-resolution imaging analyses, we propose a unique mechanism called crystallization-driven in situ nanoparticlization of conjugated polymers (CD-INCP) where spontaneous nucleation creates seeds, followed by seeded growth in units of micelles. Also, we achieved “living” CD-INCP through a chain-extension experiment. We further simplified CD-INCP by adding both monomers together in one-shot copolymerization but still producing length-controlled nanoparticles.

Here we report a highly efficient living polymerization of challenging electron-rich or sterically hindered aryl isocyanides using an air-stable, but highly active, bisphosphinechelated nickel(II) complex. Initially, the living character was examined by screening various Ni(II) complexes, and we identified o-Tol(dppe)NiCl as an excellent initiator for the living polymerization of aryl isocyanides. On the basis of chain extension experiments and in situ 31 P NMR spectroscopy, we concluded that the high stability of the propagating species due to the tightly bound chelating ligand was crucial for successful living polymerizations. Not only reactive electron-poor aryl isocyanides but also more challenging electron-rich or sterically hindered aryl isocyanides underwent fast living polymerizations to give polymers having controlled M n with narrow dispersity. In addition, we confirmed that the electronic character of the monomer significantly affected the polymerization efficiency by comparing the polymerization of 4-octyloxyphenyl isocyanide and 3octyloxyphenyl isocyanide, which have the same substituents at different positions on the phenyl ring. Furthermore, ABCDE pentablock copolymer containing various substituents was efficiently synthesized in only 1 min.