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MALDI‐TOF‐MS spectrum of PES initiated by ion pair 1 but quenched prematurely at 27 % conversion. One set of peaks with an intercept of 23 reveals the basic initiation pathway. Note that the shown chemical structures only represent one of several regiochemical possibilities.
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In typical cyclic polymer synthesis via ring‐closure, chain growth and cyclization events are competing with each other, thus affording cyclic polymers with uncontrolled molecular weight or ring size and high dispersity. Here we uncover a mechanism by which Lewis pair polymerization (LPP) operates on polar vinyl monomers that allows the control of...
Citations
The selective synthesis of ultrahigh-molar-mass (UHMM, >2 million Da) cyclic polymers is challenging as an exceptional degree of spatiotemporal control is required to overcome the possible undesired reactions that can compete with the desired intramolecular cyclization. Here we present a counterintuitive synthetic methodology for cyclic polymers, represented here by polythioesters, which proceeds via superbase-mediated ring-opening polymerization of gem-dimethylated thiopropiolactone, followed by macromolecular cyclization triggered by protic quenching. This proton-triggered linear-to-cyclic topological transformation enables selective, linear polymer-like access to desired cyclic polythioesters, including those with UHMM surpassing 2 MDa. In addition, this method eliminates the need for stringent conditions such as high dilution to prevent or suppress linear polymer contaminants and presents the opposite scenario in which protic-free conditions are required to prevent cyclic polymer formation, which is capitalized to produce cyclic polymers on demand. Furthermore, such UHMM cyclic polythioester exhibits not only much enhanced thermostability and mechanical toughness, but it can also be quantitatively recycled back to monomer under mild conditions due to its gem-disubstitution.
This review provides a comprehensive summary of organoboron-mediated free radical polymerization, Lewis pair polymerization, ionic polymerization, and polyhomologation, laying the groundwork for further establishment of polymerization methods.
It remains challenging to synthesize all‐(meth)acrylic triblock thermoplastic elastomers (TPEs), due to the drastically different reactivities between the acrylates and methacrylates and inevitable occurrence of side reactions during polymerization of acrylates. By taking advantage of the easy structural modulation features of N‐heterocyclic olefins (NHOs), we design and synthesize strong nucleophilic tetraphenylethylene‐based NHOs varying in the number (i.e. mono‐, dual‐ and tetra‐) of initiating functional groups. Its combination with bulky organoaluminum [iBuAl(BHT)2] (BHT = bis(2,6‐di‐tBu‐4‐methylphenoxy)) constructs Lewis pair (LP) to realize the living polymerization of both acrylates and methacrylates, furnishing polyacrylates with ultrahigh molecular weight (Mn up to 2174 kg‧mol‐1) within 4 min. Moreover, these NHO‐based LPs enable us not only realize the control over the polymers’ topology (i.e. linear and star), but also achieve triblock star copolymers in one‐step manner. Mechanical studies reveal that the star triblock TPEs exhibit better mechanical properties (elongation at break up to 1863% and tensile strength up to 19.1 MPa) in comparison with the linear analogs. Moreover, the presence of tetraphenylethylene group in the NHOs entitled the triblock TPEs with excellent AIE properties in both solution and solid state.
It remains challenging to synthesize all‐(meth)acrylic triblock thermoplastic elastomers (TPEs), due to the drastically different reactivities between the acrylates and methacrylates and inevitable occurrence of side reactions during polymerization of acrylates. By taking advantage of the easy structural modulation features of N‐heterocyclic olefins (NHOs), we design and synthesize strong nucleophilic tetraphenylethylene‐based NHOs varying in the number (i.e. mono‐, dual‐ and tetra−) of initiating functional groups. Its combination with bulky organoaluminum [ⁱBuAl(BHT)2] (BHT=bis(2,6‐di‐tBu‐4‐methylphenoxy)) constructs Lewis pair (LP) to realize the living polymerization of both acrylates and methacrylates, furnishing polyacrylates with ultrahigh molecular weight (Mn up to 2174 kg ⋅ mol⁻¹) within 4 min. Moreover, these NHO‐based LPs enable us to not only realize the control over the polymers’ topology (i.e. linear and star), but also achieve triblock star copolymers in one‐step manner. Mechanical studies reveal that the star triblock TPEs exhibit better mechanical properties (elongation at break up to 1863 % and tensile strength up to 19.1 MPa) in comparison with the linear analogs. Moreover, the presence of tetraphenylethylene group in the NHOs entitled the triblock TPEs with excellent AIE properties in both solution and solid state.
