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Zwitterionic catalysis is powerful in simultaneously activating electrophiles and nucleophiles in organic transformations; however, its potential in polymerizations remains untapped. Herein, a zwitterionic catalytic model for ring-opening polymerization (ROP) is introduced and a series quaternary ammonium carboxylate zwitterionic catalysts have been designed and evaluated in the ROPs of cyclic esters. Among the zwitterionic catalysts, L -carnitine, a commercially available and inexpensive natural product, showed the optimal catalytic performance. ROPs of L -lactide (L -LA), trimethylene carbonate, δ-valerolactone and ε-caprolactone were successful. PLLA was prepared with controlled molecular weight (1.4 to 21.2 kg mol−1) and narrow dispersion (Đ 1.02 to 1.21). The zwitterionic catalytic mechanism is proposed where quaternary ammonium and hydroxyl cooperatively activated the carbonyl of monomers, while the carboxylic anion activated the chain-end/initiator. NMR titrations validated the bifunctional activation mechanism. Organocatalysts of zwitterionic nature provide a new design tool for wider scope investigation of catalytic polymerizations. [ABSTRACT FROM AUTHOR]

The synthesis of catechol polymers often demands tedious protection and deprotection steps. In this work, the role of a guanidine base to subdue the catechol functions and promote the ring-opening polymerization (ROP) is suggested. Accordingly, guanidine, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), was employed to mediate ROP of N-carboxyanhydride (NCA) from a catechol initiator. MTBD played a dual-role in ROP of sarcosine-NCA (Sar-NCA) and masking the catechol initiator concurrently. Catechol-ended polysarcosine (PSar) was synthesized with a predicted molecular weight (Mn,SEC = 3.5 kg mol−1, Mn,NMR = 3.7 kg mol−1) and narrow dispersities (Đ < 1.11). This one base two-function strategy showed a new path for the synthesis of catechol functionalized polymers. [ABSTRACT FROM AUTHOR]

Polylactic acid or polylactide (PLA) is the leading commercialized bio‐based polyester widely used in biomedical apparatus and disposable food packaging materials, among others. Desirable features of green and environmentally friendly ring‐opening polymerization (ROP) of lactide (LA) by organocatalysts were bulk ROP at high temperature; the organocatalyst should be inexpensive, readily available, and biosafe in the produced PLA; and the ROPs should afford PLA of precisely controlled molecular weights with no transesterifications, nor epimerizations. An organocatalyst that met all these desirable merits has, to the best of our knowledge, not been reported to date. We proposed pyridinium saccharinate binary organocatalyst for industrially feasible ROPs of lactide, carbonates, and lactones. Pyridinium saccharinates of three commercial pyridines including 4‐dimethylaminopyridine (DMAP), 4‐pyrrolidinopyridine, and pyridine were prepared in one step by quantitative yields. An optimal DMAP saccharinate (DMAP ⋅ Sac) as the catalyst successfully promoted ROPs of l‐lactide (LLA) and δ‐valerolactone (VL) with benzyl alcohol (BnOH) as an initiator. The bifunctional DMAP ⋅ Sac coordinated to living polymer chain‐end with enolate oxygen to hydrogen of the hydroxyl, and to monomer with pyridinium N−H to oxygen of the carbonyl that successfully catalyzed efficient polymerization of LLA. High relative growth rate (RGR>90%) of the DMAP ⋅ Sac containing poly(l‐lactic acid) (PLLA) ensured the desirable biocompatibility and biosafety. [ABSTRACT FROM AUTHOR]

Catechol moiety offers a versatile platform in the preparation of functionalized polymers, but it is not usually compatible with catalysis in polymerizations. To address these challenges, we suggest employment of one Brønsted base in masking the activity of catechol moiety and to modulate the polymerization. Based on this strategy, the ring-opening polymerization (ROP) of sarcosine N-carboxyanhydrides (Sar-NCA) was carried out using dopamine hydrochloride as an initiator and triethylamine as a Brønsted base. PSar with predicted molecular weights (Mn,NMR=3.7 kg mol−1) and narrow dispersities (Đ<1.13) was prepared. Catechol initiator was successfully linked to PSar end as confirmed by MALDI-ToF MS. Subsequently, copolymerization of N-butyl glycine N-carboxyanhydrides (Bu-Gly-NCA) from the PSar in one-pot produced catechol end-functionalized amphiphilic polysarcosine-block-poly(N-butyl glycine) diblock copolypeptoids (cat-PSar-b-PGlyBu). Further, cat-PSar-b-PGlyBu enabled the aqueous dispersion of manganese oxide nanoparticles which was attributable to the anchor of the diblock copolymers onto the surface of the nanoparticles. The strategy for catechol masking and polymerization mediating by one Brønsted base offered a new avenue into the synthesis of catechol-ended block copolymers. [ABSTRACT FROM AUTHOR]

Amphiphilic block copolymers possess great potential as biomaterials in drug delivery and gene therapy. Herein, pseudopeptidic-type diblock copolymer of poly(2-oxazoline)- block-polypeptoid (POx- b-POI) is presented and synthesized. Poly[2-(3-butenyl)-2-oxazoline]- block-poly(sarcosine) (PBuOx- b-PSar) comprising hydrophobic POx segment bearing alkenyl side chain and hydrophilic POI segment of N-methyl glycine, viz., sarcosine, is prepared by ring-opening polymerization (ROP) through a one-pot and three-step route. Diphenyl phosphate initiates ROP of BuOx, and then the living chain end of PBuOx is quenched by ammonia to obtain PBuOx-ammonium phosphate in situ, the active ammonium group initiates ROP of sarcosine N-carboxy anhydride. PBuOx- b-PSar with controlled molecular weights (4.7-10.8 kg mol−1) and narrow dispersities ( ÐM 1.15-1.21) are characterized by 1H NMR, 13C NMR, and size-exclusion chromatography. Dynamic light scattering and transmission electron microscopy analysis reveal that PBuOx- b-PSar self-assembles into nanostructures of average diameter DH of 37-109 nm in aqueous solution. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test demonstrates the cytocompatibility (relative cell viability > 80%) of the PBuOx- b-PSar. In view of the self-assembly and biocompatibility, the readily prepared diblock copolymers may hopefully be used in biomedical applications. [ABSTRACT FROM AUTHOR]

The ring-opening polymerization of ɛ-caprolactone catalyzed by a novel lipaseCandidasp. 99-125 was achieved in organic solvents. ɛ-Caprolactone was found to be polymerized in quantitative yield in toluene at 80 °C for 5 days. The poly (ɛ-caprolactone) obtained had a number-average molecular weight of 14,120 (polydispersity index = 1.161). The effect of enzyme concentration, temperature, reaction time, reaction medium, and water content on monomer conversion and product molecular weight were investigated. Kinetic analysis showed that the enzyme displayed Michaelis–Menten kinetics and showed stronger affinity for ɛ-caprolactone (with aKmvalue of 6.1 mmol/L) than other reported lipases. [ABSTRACT FROM PUBLISHER]

ABSTRACT Cationic ring-opening polymerization of trimethylene carbonate using o-benzenedisulfonimide as a reusable catalyst under mild conditions was described. The polymerization proceeded homogeneously without decarboxylation and poly(trimethylene carbonates) (PTMCs) were synthesized with well-controlled molecular weights and narrow polydispersities ( Mw/ Mn = 1.12-1.18). The spectra of 1H-NMR, SEC, and MALDI-ToF MS clearly demonstrated the incorporation of the initiator residue into the polymer chains and the controlled/living nature of the polymerizations. Furthermore, the catalyst can be easily recovered, and its efficiency was fully retained. In addition, 1,3-propanediol, 1,1,1-trimethylolpropane, and pentaerythritol were successfully used as initiators to produce telechelic and star-shaped polycarbonates which were determined by intrinsic viscosity experiments. The number of arms estimated by the shrinking factors ( [ABSTRACT FROM AUTHOR]

Novel amphiphilic polypeptoid-polyester diblock copolymers based on poly(sarcosine) (PSar) and poly( ε-caprolactone) (PCL) are synthesized by a one-pot glovebox-free approach. In this method, sarcosine N-carboxy anhydride (Sar-NCA) is firstly polymerized in the presence of benzylamine under N2 flow, then the resulting poly(sarcosine) is used in situ as the macro­initiator for the ring-opening polymerization (ROP) of ε-caprolactone using tin(II) octanoate as a catalyst. The degree of poly­merization of each block is controlled by various feed ratios of monomer/initiator. The diblock copolymers with controlled molecular weight and narrow molecular weight distributions ( ĐM < 1.2) are characterized by 1H NMR, 13C NMR, and size-exclusion chromatography. The self-assembly behavior of PSar- b-PCL in water is investigated by dynamic light scattering (DLS) and transmission electron microscopy. DLS results reveal that the diblock copolymers associate into nanoparticles with average hydrodynamic diameters ( DH) around 100 nm in water, which may be used as drug delivery carriers. [ABSTRACT FROM AUTHOR]

ABSTRACT An organocatalytic approach to controlled/living ring-opening polymerizations (ROPs) of O-carboxyanhydrides (OCAs) using N-heterocyclic carbenes (NHCs) as nucleophilic catalysts has been investigated. NHCs with different structures were used in order to compare the catalytic performances in the ROP of OCA of l-lactic acid. 1H NMR, SEC, and MALDI-TOF MS measurements of the products clearly indicated a controlled/living manner of the polymerization. The controlled/living nature was further confirmed by kinetic and chain extension experiments. Additionally, polylol initiators were used to produce α,ω-dihydroxy telechelic, 3-, and 4-armed star-shaped polymers. Moreover, star-shaped diblock copolymer, bearing methyl and phenyl side groups, has been successfully synthesized with OCA/NHC system. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014. 52, 2306-2315 [ABSTRACT FROM AUTHOR]

ABSTRACT The ring-opening polymerization (ROP) of trimethylene carbonate (TMC) using imidodiphosphoric acid (IDPA) as the organocatalyst and benzyl alcohol (BnOH) as the initiator has been investigated. The polymerization proceeded without decarboxylation to afford poly(trimethylene carbonate) (PTMiC) with controlled molecular weight and narrow polydispersity. 1H NMR, SEC, and MALDI-TOF MS measurements of the obtained PTMC clearly indicated the quantitative incorporation of the initiator at the chain end. The controlled/living nature for the IDPA-catalyzed ROP of TMC was confirmed by the kinetic and chain extension experiments. A bifunctional activation mechanism was proposed for IDPA catalysis based on NMR and FTIR studies. Additionally, 1,3-propanediol, 1,1,1-trimethylolpropane, and pentaerythritol were used as di-ol, tri-, and tetra-ol initiators, producing the telechelic or star-shaped polycarbonates with narrow polydispersity indices. The well-defined diblock copolymers, poly(trimethylene carbonate)- block-poly(δ-valerolactone) and poly(trimethylene carbonate)- block-poly(ε-caprolactone), have been successfully synthesized by using the IDPA catalysis system. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1009-1019 [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A commercial DBuP was firstly evaluated as catalyst for ROP in bulk at 180 °C. • Polyesters of narrow dispersity and high molecular weight were obtained. • Diblock copolymers, end functionalized polyesters, and star polymers were prepared. • Cell viability of DBuP-catalyzed PCL meets biomedical requirements. Abstract Organocatalyzed ring-opening polymerization (ROP) of cyclic esters was developed into a stage that demanding translation of the academic success into commercially viable production. An industrial relevant development of the organocatalysis in ROPs required bulk polymerizations at high temperatures up to 180 °C. Organic phosphoric acid was one of the few organocatalysts workable under these conditions that devoid of otherwise commonly appeared transesterification, epimerization, and decarboxylation in the ROPs. A commercial dibutyl phosphate (DBuP), which was inexpensive and available by hundreds of tons as antistatic agent, was firstly evaluated as a catalyst. Well-defined polyesters catalyzed by DBuP were obtained with narrow dispersities (Đ m 1.08–1.31) and predicted molecular weights from 2.1 to 55 kg mol−1. Series of homopolymers, diblock copolymers and end-functionalized polymers of ε -caprolactone (CL), δ -valerolactone (VL), trimethylene carbonate (TMC), and l -lactide (LA) were synthesized. 1H NMR, 13C NMR, SEC, and MALDI–ToF MS analyses indicated that the obtained polyesters were exactly the designated ones. NMR titration experiments confirmed that the ROP proceeded a bifunctional activation mechanism. The cytotoxicity test using MTT assay showed biosafety of the polyesters. The experimental results suggested that dibutyl phosphate is a commercial organocatalyst widely useful in all major cyclic ester monomer toward commercial relevant ring-opening polymerizations. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Tunable H-bond donors were developed in HBD and Brønsted acid cocatalysis. • Well-defined homopolymers and diblock copolymers of VL and CL were prepared. • Cationic ROP mechanism by trifluoroacetic acid assisted by H-bond donor was proposed. Abstract H-bond donor (HBD) and base co-catalysis achieved great success in ring-opening polymerization (ROP). Parallel H-bond donor and Brønsted acid (HBD–BA) cocatalysis has been scarcely explored in ROPs. In developing the HBD–BA catalysis in to versatile toolbox for ring-opening polymerizations of wider scope and better control, tunable HBDs including boronate pinacol ester urea (BU), urea (U), and thiourea (TU) were evaluated in cooperation with trifluoroacetic acid (TFA) in HBD–BA catalytic mode. Each of the HBD–TFA co-catalyst promoted ROPs of δ-valerolactone (VL) and ε-caprolactone (CL) successfully. The catalytic performances of the HBD–TFA on the HBD part was in an order of BU > U > TU to their corresponding ROPs of VL and CL. The turnover frequencies of the catalyzed ROPs of VL and CL by BU–TFA was twice as that of TFA. The ROPs afforded homopolymers with predicted molecular weights (PVL, M n,NMR = 2.51–9.92 kg mol−1; PCL, M n,NMR = 2.51–11.1 kg mol−1) and narrow dispersities (PVL, Đ ≤ 1.16; PCL, Đ ≤ 1.18) by ratios of monomer to initiator from 20 to 100. The obtained polymers were analyzed by 1H NMR, 13C NMR, and MALDI-ToF MS, the results indicated the high chain-end fidelity. Chain extension experiments were conducted by a first ROP of VL/CL and second ROP of CL/VL with precise molecular weights (from 2.98 kg mol−1 to 6.15 kg mol−1) and narrow dispersities below 1.18. The kinetics plots showed a distinct first order relationship between ln([VL] 0 /[VL]) versus the reaction time, it indicated the controlled nature of the catalytic ROP. NMR titrations supported the proposed mechanism that HBD associated with TFA and promoted the cationic polymerization. [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]

Alcohol-initiated ring-opening polymerization (ROP) of cyclic esters for synthesizing polyesters was well established, but amine-initiated ROP of cyclic esters was rare. A challenge is slow initiation and fast propagation in the amine-initiated ROPs. To address the difficulties, an ionic H-bond donor (iHBD) and H-bond acceptor (HBA) binary organocatalysis in amine-initiated ROP of lactide (LA) was developed. Guanidinium hexahydro-2 H -pyrimido[1,2- a ] pyrimidin-1-ium [(HppH 2 ) + ] and tertiary amine sparteine (SP), cooperatively played the role of iHBD/HBA binary catalysts, efficiently promoted ROP of LA from amine initiators toward polylactide (PLA) and polysarcosine- block -polylactide diblock copolymer (PSar- b -PLA). Benzyl amine and N -methylbenzylamine initiated ROPs of LA under mild conditions produced PLAs with predictable molecular weights ( M n,NMR  = 2.9–17.1 kg mol −1 ) and narrow dispersities ( Ð M,SEC  = 1.13–1.23). Macroinitiator PSar copolymerized with LA under the iHBD/HBA catalysis, producing PSar- b -PLAs with controlled molecular weights ( M n,NMR  = 5.7–14.8 kg mol −1 ) and low dispersities ( Ð M,SEC  = 1.16–1.21). Kinetics and chain extension experiments confirmed that the amine-initiated ROP of LA in presence of (HppH 2 ) + BF 4 − /SP was in controlled/living manner. 1 H NMR, 13 C NMR, SEC, and MALDI-ToF MS analyses indicated that the obtained PLA was exclusively initiated from the corresponding amine with amide linkage. An iHBD/HBA binary activation mechanism was proposed. [ABSTRACT FROM AUTHOR]

H-bonding organocatalysis using (thio)urea/amine achieved massive success. H-bonding binding with Brønsted acid catalysis, especially in polymerizations, was scarcely explored. Here we disclosed 1,3- bis -(3,5- bis (trifluoromethyl)phenyl)thiourea (TU) as hydrogen bond donor (HBD), combined with trifluoroacetic acid (TFA) as a Brønsted acid (BA), promoted efficient controlled/living ring-opening polymerization (ROP) of δ-valerolactone (δ-VL) and ε-caprolactone (ε-CL) at room temperature. The ROPs of δ-VL and ε-CL with benzyl alcohol (BnOH) as the initiator yielded poly(δ-valerolactone) (PVL, M n, NMR = 1900–9900 g mol −1 , M w / M n = 1.28–1.34) and poly(ε-caprolactone) (PCL, M n, NMR = 2400–11,600 g mol −1 , M w / M n = 1.19–1.35) with predicted molecular weights and narrow dispersities. A plausible mechanism of the ROP promoted by associations of TU with TFA through double hydrogen bonding was suggested, in which stabilizing of the carboxylate anion and enhancing of the Brønsted acidity made the catalytic ROPs by TU–TFA viable. The quantitative incorporation of the initiator into the polymer chains was demonstrated by 1 H NMR and MALDI-ToF MS measurements. The controlled/living fashion of the polymerization was supported by the kinetics and chain extension experiments. Synthesis of well defined block copolymers of PVL- b -PCL and PCL- b -PVL verified again the ROPs were in controlled/living manner, and suggested the hydrogen bond donor binding with Brønsted acid catalysis to be a generally applicable method. [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]

• 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]

• TBAF was the first neutral Ionic pair initiator effect living AROPs of N -sulfonyl aziridines. • Mechanism of initiation by direct attack on the aziridine ring with fluoride and propagation by sulfonyl amidate anion was proposed. • Tetrabutylammonium halide (TBAX) was efficient initiator in anionic ring-opening polymerizations of N -sulfonyl aziridines Ionic pair tetrabutylammonium halide (TBAX) was efficient initiator in anionic ring-opening polymerizations (AROPs) of N- sulfonyl aziridines, in which the tetrabutylammonium fluoride (TBAF) was the optimal initiator effect controlled/living AROPs. TBAX initiated AROPs of 2-methyl- N -tosylaziridine (TsMAz) by relative activities on halide X in sequence of F > Cl > Br > I, which was corroborated to the nucleophilicities of the halides. Homopolymers and diblock copolymers of TsMAz and EsMAz were prepared. The AROPs possessed living nature by first order kinetics with fast polymerizations (0.5 to several hours), high conversions (90–99%), narrow dispersities (Đ < 1.16), and predicted molecular weights. Mechanism of initiation by direct attack on the aziridine ring with fluoride and propagation by sulfonyl amidate anion was proposed. This protocol provided new entry in design of catalyst/initiator of ionic pair for polymerizations, and developed synthetic toolbox for mild and efficient anionic ring-opening polymerizations. [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]

TBD catalyzed continuous flow ring-opening polymerizations of ε-caprolactone and δ-valerolactone were exemplified as the model investigation system of organocatalytic synthesis of polyesters in the simple PTFE tubular microreactor (MR). In contrast to the batch reactor (BR), significant benefits of utilizing continuous flow strategy were achieved including higher level control of molecular weights and molecular weight distributions as well as faster polymerizations ( k app (CL) = 0.00602 (MR) vs 0.00286 min −1 (BR); k app (VL) = 0.159 (MR) vs 0.079 min −1 (BR)). Furthermore, more easily and efficiently block copolymerizations were conducted in the integrated-microreactor by sequential introduction of monomers to well-defined poly(δ-valerolactone)- block -poly(ε-caprolactone) and poly(ε-caprolactone)- block -poly(δ-valerolactone). [ABSTRACT FROM AUTHOR]

Yttrium trisphenolates was developed as highly chemoselective catalyst toward thiol, primary and secondary hydroxyl. By utilizing yttrium trisphenolates, well-defined thiol-functionalized branched and linear poly(ε-caprolactone) were directly synthesized via ring-opening polymerization of ε-caprolactone in the presence of unprotected 3-mercaptopropane-1, 2-diol and 2-mercapto-1-ethanol as initiator respectively. The expected structures were characterized by 1 H NMR, MALDI TOF MS and SEC. High thiol fidelities (>70%) and yields (>90%) of products were obtained with controlled molecular weights. The resultant thiol-functionalized poly(ε-caprolactone) were used to stabilize silver nanoparticles through two-phase method. The red shift of the UV–vis absorption band of linear poly(ε-caprolactone) protected nanoparticles was observed comparing with the branched counterpart. Both two kinds of nanoparticles were well-dispersed with diameters around 2–3 nm according to TEM. [ABSTRACT FROM AUTHOR]

Abstract: The ring-opening polymerization (ROP) of trimethylene carbonate (TMC) catalyzed by phosphoramidic acid (PAA) and initiated with benzyl alcohol (BnOH) has been investigated. The polymerization conditions were optimized to afford well-defined polytrimethylene carbonates (PTMCs). The molecular weight of the obtained PTMC with the [TMC]0/[BnOH]0/[PAA]0 ratio of 40:1:1 was analyzed by 1H NMR, M n = 4180 g mol−1, showed good agreement with that estimated from the initial ratio, M n = 3830 g mol−1. The kinetics and chain extension experiments have been carried out to further justify the controlled/living nature of this polymerization. The 1H NMR, SEC, and MALDI-TOF MS measurements were applied to analyze the obtained PTMCs. [Copyright &y& Elsevier]