Functional Heterochain Polymers Constructed by Alkyne Multicomponent Polymerizations

Chain-Growth Sulfur(VI) Fluoride Exchange Polycondensation: Molecular Weight Control and Synthesis of Degradable Polysulfates

Sulfur(VI) fluoride exchange (SuFEx) click chemistry has offered a facile and reliable approach to produce polysulfates and polysulfonates. However, the current SuFEx polymerization methods lack precise control of target molecular weight and dispersity. Herein, we report the first chain-growth SuFEx polycondensation process by exploiting the unique reactivity and selectivity of S-F bonds under SuFEx catalysis. Given the higher reactivity of iminosulfur oxydifluoride versus fluorosulfate, the chain-growth SuFEx polycondensation is realized by using an iminosulfur oxydifluoride-containing compound as the reactive chain initiator and deactivated AB-type aryl silyl ether-fluorosulfates bearing an electron-withdrawing group as monomers. When 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was utilized as the polymerization catalyst, precise control over the polymer molecular weight and polydispersity was achieved. The resulting polymers possess great thermal stability but are easily degradable under mild acidic and basic conditions.

In Situ Generation of Heterocyclic Polymers by Triple-Bond Based Polymerizations

Stemming from unique ring structures, heterocyclic polymers exhibit distinguished electrical, mechanical, and photophysical properties and have been widely used in a variety of important applications. Along with the technological significance are the challenges in their synthesis. Traditional synthetic strategies toward heterocyclic polymers often require the direct attachment of heterocycles to polymer backbones, which are generally limited by the lack of suitable and low-cost heterocyclic monomers, tedious reaction process, difficulties in incorporation of multiple substitutents, etc. Alternatively, in situ construction of heterocyclic polymers via triple-bond based polymerization offers promising prospects. This review summarized the recent progress on polymerizations of triple-bond based monomers including alkynes, nitriles, and isonitriles that can in situ generate heterocyclic polymers. The properties and advanced applications of the derived heterocyclic polymers will also be discussed. Finally, the future perspectives and challenges in this field will be addressed.

Synthesis of Conjugated Polymers via Transition Metal Catalysed C-H Bond Activation

Transition metal catalysed C-H bond activation chemistry has emerged as an exciting and promising approach in organic synthesis. This allows us to synthesize a wider range of functional molecules and conjugated polymers in a more convenient and more atom economical way. The formation of C-C bonds in the construction of pi-conjugated systems, particularly for conjugated polymers, has benefited much from the advances in C-H bond activation chemistry. Compared to conventional transition-metal catalysed cross-coupling polymerization such as Suzuki and Stille cross-coupling, pre-functionalization of aromatic monomers, such as halogenation, borylation and stannylation, is no longer required for direct arylation polymerization (DArP), which involve C-H/C-X cross-coupling, and oxidative direct arylation polymerization (Ox-DArP), which involves C-H/C-H cross-coupling protocols driven by the activation of monomers' C(sp² )-H bonds. Furthermore, poly(annulation) via C-H bond activation chemistry leads to the formation of unique pi-conjugated moieties as part of the polymeric backbone. This review thus summarises advances to date in the synthesis of conjugated polymers utilizing transition metal catalysed C-H bond activation chemistry. A variety of conjugated polymers via DArP including poly(thiophene), thieno[3,4-c]pyrrole-4,6-dione)-containing, fluorenyl-containing, benzothiadiazole-containing and diketopyrrolopyrrole-containing copolymers, were summarized. Conjugated polymers obtained through Ox-DArP were outlined and compared. Furthermore, poly(annulation) using transition metal catalysed C-H bond activation chemistry was also reviewed. In the last part of this review, difficulties and perspective to make use of transition metal catalysed C-H activation polymerization to prepare conjugated polymers were discussed and commented.

Multicomponent Spiropolymerization of Diisocyanides, Diethyl Acetylenedicarboxylate, and Halogenated Quinones

Multicomponent spiropolymerization (MCSP) provides an efficient synthetic tool for the construction of spiropolymers based on nonspiro monomers. In this study, a method of MCSP using diisocyanides 1, diethyl acetylenedicarboxylate 2, and halogenated quinones 3 is developed for the in situ construction of bis-spiropolymers with high molecular weights (M_w up to 29 200) and good yields (up to 87.7%) under mild reaction conditions. The structure of the obtained bis-spiropolymers is confirmed by gel permeation chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance analysis. Halogenated bis-spiropolymers show good thermal stability, good solubility, and film-forming ability. The photosensitizer rhodamine B is used as a doping agent to induce the photodegradation of the polymer P1a3c into small-molecule segments, which results in the slow release of halogenated spiro-groups under irradiation with simulated sunlight. This finding reveals that P1a3c has the potential to be applied in pesticides. Therefore, this MCSP is a novel method for preparing halogen-containing bis-spiropolymers, which accelerates the development of multifunctional polymer materials.

Merging of cationic RAFT and radical RAFT polymerizations with ring-opening polymerizations for the synthesis of asymmetric ABCD type tetrablock copolymers in one pot

A new bifunctional and switchable RAFT agent and a mechanism switching strategy were proposed to control the cationic RAFT polymerization, radical RAFT polymerization and ring-opening polymerization of vinyl and cyclic ester monomers and to produce block copolymers.