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• A bidentate H-bond donor and base successfully catalyzed ROPs without proton abstraction. • Produced PLAs possess broad molecular weight ranges and extremely narrow dispersities. • A strict HBD/base cocatalysis mechanism was validated by NMR titrations. Hydrogen bond donor (HBD) and organic base binary cocatalyst established a gold standard in organocatalytic ring-opening polymerizations (ROPs). In depth probe of the mechanisms revealed that proton abstraction of the acidic H on the HBDs by the bases do occur frequently. A truly simple HBD and Lewis base (LB) cocatalysis, however, was elusive. We proposed genuine HBD/LB cocatalyst for ROPs by introducing 3-amino-1,2,4-benzothiadiazine-1,1-dioxide (ABTD) as a bidentate H-bond donor and triethylamine (TEA) as a mild Lewis base. ROPs of lactide (LA) and trimethylene carbonate (TMC) in solutions at room temperature were success. The mild ROPs produced polylactide (PLA) of predictable molecular weights (from 1.6 to 26.7 kg mol−1) and extremely narrow dispersities (Đ 1.01 to 1.06). Furthermore, well-defined diblock copolymers PTMC-b-PLA were synthesized. NMR titration experiments verified exclusive H-bond donor activation of the monomer and TEA activation of the hydroxyl chain end without trace of proton abstraction. [ABSTRACT FROM AUTHOR]

Abstract Typical organocatalyst promoted ring-opening polymerization (ROP) by activation of monomer or polymer chain end via the acidic or basic mechanism. Dual activating of both the monomer and the propagating polymer chain end suggested an ideal strategy of widely tuneable catalysis of high efficiency. Stoichiometric Brønsted acid–base adduct was rarely employed in ROPs since general Brønsted acid and Brønsted base quench each other. We proposed that an acid–base adduct may work bifunctionally in catalysis. The cationic part of the acid–base adduct as H-bond donor activated the monomer, and the counter anion part as H-bond acceptor activated initiator/chain end. A series of guanidiniums, derived from commercially available Brønsted acids and guanidine, were employed as catalysts in ROPs of carbonate, lactide, and lactone. Guanidinium triazabicyclodecene hydrochloride exhibited outstanding catalytic performances in the respect of the rate and controlled in the ROPs of l -lactide, trimethylene carbonate, and δ-valerolactone with nearly full conversions, predicted molecular weights, as well as narrow dispersity of Đ = 1.07. These experimental results indicated that guanidinium is an efficient organocatalyst in controlled/living ring-opening polymerization. Graphical abstract Image 1 Highlights • Commercially available acids and guanidine at a ratio of 1:1 constituted simple and effective acid−base adduct catalysts. • Cation as H-bond donor activated monomer and anion as H-bond acceptor activated chain end. • Tunable anion in acid−base adducts realized controlled/living ring-opening polymerizations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polybenzoxazine anchored pyridyl moiety as organocatalyst was firstly proposed. • The polybenzoxazine was evaluated as nucleophilic catalyst in acylation reaction. • The catalyst was comparable to commercial PS-DMAP in catalysis and in recycles. Polybenzoxazine (PBz) anchored with an N -4′-pyridyl group on the backbone was prepared and characterized. Phenolic-type polybenzoxazine was selectively prepared by thermally initiated ring-opening polymerization of N -(4′-pyridyl)benzoxazine (Bz-Py). The loading of the catalytic moiety pyridyl on PBz-Py was 2.7 mmol g−1. The catalytic comparison of the prepared PBz-Py to commercial PS-DMAP in acylation reactions was investigated. The catalytic PBz-Py showed a broad scope of substrates of sterically hindered secondary and tertiary alcohols, aniline, quinoline, and steroid at room temperature within two hours by high yields up to 96%. Further extension to PBz-Py-catalyzed silylation and tritylation reactions resulted in high yields. The catalyst retained 85% activity after 4 recycles. The implementation of a 4-pyridyl group on the PBz backbone as a new type of polymeric catalyst showcased a general manifold to introduce catalytic moieties to designed polybenzoxazine catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • First example of polybenzoxazine installed pyridinium salt as efficient catalyst for CO 2 fixation. • The catalytic cycloadditions featured ambient pressure, high yields, and short reaction time. • A cooperated hydrogen-bonding mechanism was proposed and verified. Polybenzoxazine containing N-methylpyridinium iodide (PBz-[PyMe]I) was first utilized as an efficient catalyst for CO 2 fixation into cyclic carbonates. The polymer structure was determined as a phenolic-type polybenzoxazine characterized by FT-IR, 1H NMR. PBz-[PyMe]I shows a wide scope of substrates for the reaction of cycloaddition of CO 2 with epoxides including aliphatic epoxides, styrene oxide derivatives, glycidyl ethers, and spiro-epoxyoxindole at 120 °C within two hours, and obtains high yields up to 96%. The catalyst was recycled up to four times remaining 82% catalytic activity comparing to the first run. A combined hydrogen-bonding mechanism activated by both phenol and pyridinium salt was proposed and verified. The synthesis and application of PBz-[PyMe]I suggested the viability of other catalytic moieties could be introduced into polybenzoxazine. [ABSTRACT FROM AUTHOR]

• Pyridinium hydrohalides catalyzed ROPs of LLA in bulk at elevated temperatures. • Activations in bifunctional mechanism by H-bond donor and acceptor was elucidated. • Biosafety of PLA containing catalyst DMAP hydrochloride was assayed by MTT test. Polyesters produced by ring-opening polymerization (ROP) of cyclic monomers using organocatalysts were well developed in academia. Industrially viable ROPs were polymerizations at elevated temperatures in the bulk, thus desirable features of useful organocatalysts would be thermal stable, reasonably active in fast polymerization but mild enough to avoid transesterification. More importantly, the polyesters containing residue organocatalyst should met biosafety regulations. In these regards, series of pyridinium halides readily prepared by one step from mass-produced pyridines and hydrohalic acids were evaluated in ROPs of l -lactide (LLA), trimethylene carbonate (TMC), δ-valerolactone, and ε-caprolactone in the bulk. An optimal catalyst 4-(N,N -dimethylamino)pyridine hydrochloride (DMAP·HCl) was examined in the catalytic performances in ROPs of LLA, TMC, and diblock copolymerization affording PTMC- b -PLLA. Bulk ROP of LLA at 140 °C produced PLLAs by near quantitative conversions with precise molecular weights (M n,NMR = 3.3–16.6 kg mol−1) and narrow dispersities (Đ = 1.13–1.17). Kinetics data, chain extension experiments, and MALDI-ToF MS analysis all supported the controlled/living nature of the ROPs. A bifunctional activation mechanism in which pyridinium activated the monomer and halide activated the initiator/chain end was proposed and validated by 1H NMR and 13C NMR titrations. Poly (l -lactide) samples prepared by bulk ROPs of LLA that containing residue catalyst DMAP·HCl were tested by MTT assay in L929 mouse fibroblasts in vitro. High level of relative growth rate (RGR 93.6–96.8%) revealed favorable biosafety of the sample PLLAs. [ABSTRACT FROM AUTHOR]