Synthesis, Thermal Properties, and Morphologies of Amphiphilic Brush Block Copolymers with Tacticity-Controlled Polyether Main Chain

Influence of Tacticity on the Self-Assembly of Poly(ethylene glycol)-b-poly(lactic acid) Block Copolymers

Lactide, possessing two stereocenters and thus three distinct configurations (DD, DL, and LL), serves as a captivating building block for polymers and self-assembly. Notably, polylactide (PLA) exhibits stereocomplexation, displaying heightened interactions between different configurations compared with interactions within the same configuration. This characteristic renders PLA an intriguing subject for investigating self-assembly behavior. In this study, 22 PEG-b-PLA polymers were synthesized and self-assembled, with analysis conducted through NMR and cryo-TEM techniques. A range of morphologies, including vesicles, diamond-shaped lamellae, and branched networks, were achieved by manipulating the tacticities. Enhanced comprehension of self-assembly interactions holds promise for advancing molecular recognition, self-replication, and asymmetric catalysis.

Stereoselective Polymerization of 3,6-Disubstituted N-Vinylcarbazoles

Poly(N-vinylcarbazole) (PNVC-H) is a valuable nonconjugated photoconductive polymer, but the free radical polymerization conditions typically used for its synthesis do not control polymer stereochemistry and are not tolerant to many substituted N-vinylcarbazoles. Here, we report the stereoselective cationic polymerization of a series of 3,6-disubtituted N-vinylcarbazole derivatives using a chiral scandium-bis(oxazoline) Lewis acid catalyst. The combination of asymmetric ion-pairing catalysis and inherent monomer stereoelectronics facilitated stereoselective polymerization at room temperature, which enabled the polymerization of less soluble 3,6-disubstituted-N-vinylcarbazole derivatives. Isotactic halogen-substituted PNVCs demonstrated self-assembly in solution through halogen-halogen bonding, which was not observed in their atactic counterparts. Initial spectral characterization displayed a wide range of excitation-emission profiles for substituted PNVCs, which demonstrate the promise of these materials as a new class of nonconjugated photoconductive polymers for optoelectronic applications. Overall, these results showcase a diverse class of isotactic poly(N-vinylcarbazoles), highlight the benefits of identifying alternative stereocontrol mechanisms for polymerization, and expand the suite of accessible nonconjugated hole-transport materials.

Anionic ring-opening polymerization of functional epoxide monomers in the solid state

Despite recent advancements in mechanochemical polymerization, understanding the unique mechanochemical reactivity during the ball milling polymerization process still requires extensive investigations. Herein, solid-state anionic ring-opening polymerization is used to synthesize polyethers from various functional epoxide monomers. The critical parameters of the monomers are investigated to elucidate the unique reactivity of ball milling polymerization. The controllable syntheses of the desired polyethers are characterized via NMR, GPC, and MALDI-ToF analyses. Interestingly, bulky monomers exhibit faster conversions in the solid-state in clear contrast to that observed for solution polymerization. Particularly, a close linear correlation is observed between the conversion of the ball milling polymerization and melting point of the functional epoxide monomers, indicating melting point as a critical predictor of mechanochemical polymerization reactivity. This study provides insights into the efficient design and understanding of mechanochemical polymerization.

Crystalline CO2 -Based Aliphatic Polycarbonates with Long Alkyl Chains

Carbon dioxide (CO₂ ) is an easily available, renewable carbon source and can be utilized as a comonomer in the catalytic ring-opening polymerization of epoxides to generate aliphatic polycarbonates. Dodecyl glycidyl ether (DDGE) is copolymerized with CO₂ and propylene oxide (PO) to obtain aliphatic poly(dodecyl glycidyl ether carbonate) and poly(propylene carbonate-co-dodecyl glycidyl ether carbonate) copolymers, respectively. The polymerization proceeds at 30 °C and high CO₂ pressure utilizing the established binary catalytic system (R,R)-Co(salen)Cl/[PPN]Cl. The copolymers with varying DDGE:PO ratios are characterized via NMR, FT-IR spectroscopy, and SEC, exhibiting high molecular weights between 11 400 and 37 900 g mol^-1 with dispersities (Р= M _w /M _n ) in the range of 1.37-1.61. Copolymers with T _g s of -11 °C or T _m s from 5 to 15 °C and thermal decomposition >200 °C depending on the comonomer ratio, are obtained as determined by differential scanning calorimetry/TGA.

Synthesis of μ-ABC Tricyclic Miktoarm Star Polymer via Intramolecular Click Cyclization

Cyclic polymers exhibit unique physical and chemical properties because of the restricted chain mobility and absence of chain ends. Although many types of homopolymers and diblock copolymers possessing cyclic architectures have been synthesized to date, there are relatively few reports of cyclic triblock terpolymers because of their synthetic difficulties. In this study, a novel synthetic approach for μ-ABC tricyclic miktoarm star polymers involving t-Bu-P₄-catalyzed ring-opening polymerization (ROP) of glycidyl ethers and intramolecular copper-catalyzed azido-alkyne cycloaddition (CuAAC) was developed. First, the t-Bu-P₄-catalyzed ROP of decyl glycidyl ether, dec-9-enyl glycidyl ether, and 2-(2-(2-methoxyethoxy) ethoxy) ethyl glycidyl ether with the aid of functional initiators and terminators was employed for the preparation of a clickable linear triblock terpolymer precursor possessing three azido and three ethynyl groups at the selected positions. Next, the intramolecular CuAAC of the linear precursor successfully produced the well-defined tricyclic triblock terpolymer with narrow dispersity in a reasonable yield. The present strategy is useful for synthesizing model polymers for studying the topological effects on the triblock terpolymer self-assembly.

Polymerization of long chain alkyl glycidyl ethers: a platform for micellar gels with tailor-made melting points

Controlled polymerization of long-chain alkyl glycidyl ethers (AlkGE) under anionic ring opening conditions is enabled by the addition of 18-crown-6. Capitalizing on this strategy, highly amphiphilic block copolymers are prepared that form hydrogels with adjustable melting points.