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The recent advances in polymerization of lactide (LA) from organic salts enriched the toolbox to prepare well‐defined materials. Herein we report the use of crown ether (CE) as an additive to polymerize the L‐LA when initiated by 12‐hydroxydodecanoic acid (HDA) activated by one equivalent of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU). While both size and structure of the ether additive play an important role on the overall rate of reaction, the CE decomplexation is crucial to outpace transfer reactions and also permit the process to be moderately conducted under air atmosphere by an efficient water trapping process. [ABSTRACT FROM AUTHOR]

The exponential increase in the use of plastic demands that biosourced and biodegradable polymers such as poly( l -lactide)s (PLLA)s be considered to replace some petroleum based polymers in a range of applications. In order to produce PLLA in the greenest manner, i.e. by ring-opening polymerization (ROP) of l -lactide using an organocatalyst in solvent free conditions at high temperature (in bulk) has proven to be a significant challenge. Indeed, the high required temperature (180 °C) has led to poorly controlled polymerizations as a result of transesterification reactions of the PLLA backbone, racemization of the lactide monomers as well as the degradation and thus deactivation of the organocatalyst. We report herein the efforts made over the past 20 years in order to conduct the ROP of l -lactide in bulk by using organic molecules and the problems encountered by the scientific community in addressing this challenge to date. [ABSTRACT FROM AUTHOR]

Catalystsare commonly used in polymer synthesis. Traditionally,catalysts used to be metallic compounds but some studies have pointedout their toxicity for human health and environment, and the removalof metal impurities from synthetic polymer is quite expensive. Organocatalystshave been intensively synthesized and are now widely used in ring-openingpolymerization (ROP) reactions to address these issues. However, formost of them, there is not any evidence of their safety. The presentstudy attempts to assess whether well-established organo-based ROPcatalysts used for the preparation of FDA-approved polyesters maypresent a certain level of cytotoxicity. In vitro toxicity is evaluatedusing a methyl-thiazol-tetrazoliumcytotoxicity assay on two cell models (FHs74Int and HepaRG). Amongthe investigated organocatalysts, only functionalized thiourea showsan important cytotoxicity on both cell models. 4-Dimethylaminopyridine(DMAP), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), and meta-(trimethylammonio)phenolate betaine (m-BE) showcytotoxicity against HepaRG cell line only at a high concentration. [ABSTRACT FROM AUTHOR]

Abstract: Environmental concerns along with the need to develop aliphatic polycarbonate materials free of any toxic compounds have driven scientists to implement macromolecular engineering processes by replacing potentially toxic and carcinogenic metal-based catalysts traditionally used for the ring-opening polymerization of cyclic carbonates by organic compounds. This issue is of particular importance as aliphatic polycarbonates are gaining increasing credibility for biomedical applications owing to their biocompatibility and bioresorbability. This review provides a complete account of the various metal-free catalysts that has been developed so far as well as comprehensive investigations on the related polymerization mechanisms. [Copyright &y& Elsevier]

Wereport the use of an organic catalyst system capable of switchingbetween active and dormant propagating states during the ROP of cyclicmonomers. While the ROP of both ε-caprolactone and trimethylenecarbonate proceeds under nitrogen, the simple addition of CO2results in a dormant “off” state. Cycling betweenatmospheres provides the ability to regulate the molecular weightsof the resulting polymers without appreciable loss of catalytic activityfor several “on/off” cycles. [ABSTRACT FROM AUTHOR]

Abstract: Several methods for polymerizing 4-methyl-2-oxetanone (β-butyrolactone, BL) were developed allowing the controlled synthesis of polymers with molar masses up to 100kDa. Although new catalytic systems have been described for the living anionic polymerization of BL, no detailed studies have been published on the influence of the monomer purity on the polymerization reaction. In the present study, nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) are used for assessing monomer purity. These techniques indicate that an additional reaction of BL with an oxidizing agent such as potassium permanganate produces a monomer of higher purity as demonstrated by the higher rate of BL polymerization and improved control over the polymerization process that is initiated with either tetrabutylammonium acetate or carboxylic acid/phosphazene base (P1-t-Bu, P2-t-Bu and P4-t-Bu) systems. [Copyright &y& Elsevier]

The oxyanionic ring‐opening polymerization of propylene oxide (PO) from an exogenous alcohol activated with benign (complexed) metal‐alkali carboxylates is described. The equimolar mixture of potassium acetate (KOAc) and 18‐crown‐6 ether (18C6) is demonstrated to be the complex of choice for preparing poly(propylene oxide) (PPO) in a controlled manner. In the presence of 18C6/KOAc, hydrogen‐bonded alcohols act as soft nucleophiles promoting the PO SN2 process at room temperature and in solvent‐free conditions while drastically limiting the occurrence of parasitic hydrogen abstraction generally observed during the anionic ROP of PO. The resulting PPO displays predictable and unprecedented molar masses (up to 20 kg mol−1) with low dispersities (ĐM < 1.1), rendering the 18C6/KOAc complex the most performing activator for the oxyanionic polymerization of PO reported to date. Preliminary studies on the preparation of block and statistical copolyethers are also reported. [ABSTRACT FROM AUTHOR]

Abstract: Tandem mass spectrometry is increasingly applied to polymer ions in the context of in-depth structural characterization. In particular, the well-known collision-induced dissociation (CID) methodology is nowadays advantageously used to characterize end-groups and to distinguish isomeric polymer ions. When applied to sodium-cationized polyesters, CID was demonstrated to mainly involve charge remote fragmentation processes and consecutive as well as competitive dissociation pathways. In the present report, an experimental and theoretical study of collision induced dissociation of isomeric sodium cationized polylactide was investigated. The investigated polymers were designed to obtain oligomers only differentiated on the basis of regioisomeric end-groups, using ortho-, meta-, and para-methylbenzyl alcohols as initiators. The CID spectra revealed the presence of competitive charge driven and charge remote fragmentations. In particular, the charge induced fragmentations allowed the minute distinction between the three isomeric end-groups. The intermediacy of an ion/neutral complex was proposed to account for the observed decomposition and some theoretical calculations were performed to support the proposal. [Copyright &y& Elsevier]

Abstract: 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) organic catalyst has generated a tremendous impact in the metal-free ring-opening polymerization of (di)lactones. Interestingly, its extraction after use has never been studied so far and a simple deactivation by addition of benzoic acid to generate the corresponding salt has always been supposed to kill its activity. This study reveals and highlights the importance of the work-up to remove or at least drastically limit the presence of the benzoic acid/DBU salt from poly(l-lactide). Three different extraction methods allowed us to conclude that a two-step work-up gathering liquid/liquid extractions and a drop by drop precipitation is highly required to keep the enantiomerically pure lactic acid polymer safe. If not perfectly extracted the benzoic acid/DBU salt has been proved to degrade the materials during a melt process even during a differential scanning calorimetry experiment. [Copyright &y& Elsevier]

We describe the organocatalytic depolymerization of poly(ethylene terephthalate) (PET), using a commercially available guanidine catalyst, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). Postconsumer PET beverage bottles were used and processed with 1.0 mol % (0.7 wt %) of TBD and excess amount of ethylene glycol (EG) at 190 °C for 3.5 hours under atmospheric pressure to give bis(2-hydroxyethyl) terephthalate (BHET) in 78% isolated yield. The catalyst efficiency was comparable to other metal acetate/alkoxide catalysts that are commonly used for depolymerization of PET. The BHET content in the glycolysis product was subject to the reagent loading. This catalyst influenced the rate of the depolymerization as well as the effective process temperature. We also demonstrated the recycling of the catalyst and the excess EG for more than 5 cycles. Computational and experimental studies showed that both TBD and EG activate PET through hydrogen bond formation/activation to facilitate this reaction. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]

Regioregular poly(3-hexylthiophene) has been successfully incorporated into various poly( N, N-dimethylamino-2-ethyl methacrylate)-based block copolymers, i.e., P3HT- b-PDMAEMA, via Grignard metathesis (GRIM) method and atom transfer radical polymerization (ATRP) reactions. The structure of the diblock copolymers was fully confirmed by FT-IR, H NMR spectroscopy, gel permeation chromatography (GPC), and ultraviolet-visible spectroscopy (UV-vis). The recovered copolymers could be treated by protonation of the pending tertiary amine functions and depending on the relative content in PDMAEMA, the copolymers could be solubilized in more polar solvents where P3HT alone proved to be totally insoluble. [ABSTRACT FROM AUTHOR]

Abstract: New brush-like copolymers have been synthesized using functional polymethacrylate backbones bearing pendant sugars. Ring-opening polymerization (ROP) of l-lactide and ε-caprolactone have been performed using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) carbohydrate residues on the polymethacrylate chains. The latter have been first synthesized by copolymerization of three methacrylate monomers including methyl methacrylate (MMA), α-methoxy, ω-methacrylate poly(ethylene oxide) (MAPEO), and 1,2:3,4-di-O-isopropylidene-6-O-methacryloyl-d-galactopyranose (MAIGP) by atom transfer radical polymerization (ATRP) in toluene at 80°C using CuBr ligated with 1,1,4,7,10,10 hexamethyltriethylenetetramine (HMTETA) as catalytic complex. The protected sugars have been selectively deprotected using an aqueous solution of formic acid. The molecular characterization of those copolymers was performed by 1H-NMR spectroscopy, FT-IR spectroscopy and gel permeation chromatography (GPC) analysis. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we describe the design and characterization of regioregular poly(3-hexylthiophene)-poly(ε-caprolactone) di- and tri-block copolymers (RRP3HT-b-PCL and PCL-b-RRP3HT-b-PCL). The well-controlled synthesis of (di)hydroxyl-terminated RRP3HT makes possible to design block copolymer structures with a narrow molecular weight distribution. The microscopic morphology is investigated by atomic force microscopy, which reveals self-assembled fibrillar structures with the RRP3HT nanoribbons separated by narrow domains of insulating PCL. The charge transport properties are characterized in thin films field-effect transistors, and comparison between the devices performances is carried out in view of the nanoscale morphology within the transistor channel. [Copyright &y& Elsevier]

Abstract: Biodegradable polymers represent a class of extremely useful materials for many biomedical and pharmaceutical applications, as exemplified by drug delivery systems, which in recent years have taken advantage of (bio)degradable polymeric matrices. However, before being selected for any biomedical application, a biodegradable polymer requires careful investigation of its interactions and compatibility within the human body. To date, polyesters, both natural and synthetic, constitute the most fully developed class of degradable biomaterials. Poly(ε-caprolactone) (PCL) and polylactides (PLAs), recognized as biocompatible and biodegradable polyesters, are very promising for controlled drug delivery devices. Bacterial polyesters and malic acid-based polymers (poly(malic acid), PMLA and derivatives) are poly(β-hydroxyacid)-type polyesters that represent excellent alternatives for temporary therapeutic applications. Although these polyesters can be produced by polycondensation, high molecular weight structures have, until now, been produced almost exclusively by ring-opening polymerization (ROP) of the corresponding cyclic monomers. The ability of aluminum alkoxides (AlR x (OR′)3− x ) and tin(II) bis(2-ethylhexanoate) (Sn(Oct)2) to control the ROP of (di)lactones in terms of molecular parameters has opened the way to a wide range of molecular structures and topologies. Beyond the mechanistic and thermodynamic aspects of ROP of (di)lactones using organometallic compounds, this review is focused on new non-organometallic N-heterocyclic carbenes recently reported as catalysts for the controlled ROP of cyclic esters. Interestingly, the use of these simple organic molecules as catalysts or promoters in asymmetric polymer synthesis has provided organocatalytic alternatives to traditional organometallic reagents. [Copyright &y& Elsevier]

[Display omitted] • RGD-NanoStar micellar nanoassemblies loaded with Doxorubicin against osteosarcoma. • Impact of RGD on nanoparticles surface for osteosarcoma chemotherapy. • Dox released from RGD-NanoStar reach the nucleus unlike untargeted NanoStar. • Preserving Doxorubicin from degradation occurring under physiological conditions. • Sustained and prolonged Dox release from RGD-NanoStar@Dox. We developed cyclic RGD-tagged polymeric micellar nanoassemblies for sustained delivery of Doxorubicin (Dox) endowed with significant cytotoxic effect against MG63, SAOS-2, and U2-OS osteosarcoma cells without compromising the viability of healthy osteoblasts (hFOBs). Targeted polymeric micellar nanoassemblies (RGD-NanoStar@Dox) enabled Dox to reach the nucleus of MG63, SAOS-2, and U2-OS cells causing the same cytotoxic effect as free Dox, unlike untargeted micellar nanoassemblies (NanoStar@Dox) which failed to reach the nucleus and resulted ineffective, demonstrating the crucial role of cyclic RGD peptide in driving cellular uptake and accumulation mechanisms in osteosarcoma cells. Micellar nanoassemblies were obtained by nanoformulation of three-armed star PLA-PEG copolymers properly synthetized with and without decoration with the cyclic-RGDyK peptide (Arg-Gly-Asp-D-Tyr-Lys). The optimal RGD-NanoStar@Dox nanoformulation obtained by nanoprecipitation method (8 % drug loading; 35 % encapsulation efficiency) provided a prolonged and sustained drug release with a rate significantly lower than the free drug under the same experimental conditions. Moreover, the nanosystem preserved Dox from the natural degradation occurring under physiological conditions (i.e., dimerization and consequent precipitation) serving as a slow-release "drug reservoir" ensuring an extended biological activity over the time. [ABSTRACT FROM AUTHOR]

Control of stereoregularity is inherent to precision polymerization chemistry for the development of functional materials. A prototypal example of this strategy is the ring-opening polymerization (ROP) of racemic lactide (rac-LA), a bio-sourced monomer. Despite significant advances in organocatalysis, stereoselective ROP of rac-LA employing chiral organocatalysts remains unexplored. Here we tackle that challenge by resorting to Takemoto's catalyst, a chiral aminothiourea, in the presence of a phosphazene base. This chiral binary organocatalytic system allows for fast, chemo- and stereoselective ROP of rac-LA at room temperature, yielding highly isotactic, semi-crystalline and metal-free polylactide, with a melting temperature as high as 187 °C. [ABSTRACT FROM AUTHOR]

Alternating copolymers are distinctly unique in comparison with other copolymers. Herein, an in-depth investigation of the oxyanionic ring-opening copolymerization of propylene oxide (PO) and allyl glycidyl ether (AGE) from benzyl alcohol (BnOH) activated with potassium acetate (KOAc) complexed by 18-crown-6 ether (18C6) is described. We demonstrate that the 18C6/KOAc complex is an efficient and benign catalytic system to promote copolymerization of both oxirane monomers, leading to well-defined polyethers with varied comonomer content and low dispersity values (ƉM < 1.20). Kinetic analysis confirmed the controlled nature of the (co)polymerization process, and the determination of reactivity ratios revealed a quasi-alternating copolymerization profile, according to the Fineman-Ross method. The comparison between the quasi-alternating-type PO/AGE copolymerization and block or gradient copolymerization revealed significant differences, to confirm the different sequence incorporation in the different topological copolymers. These results highlight the great potential of 18C6/KOAc-mediated copolymerization process for the controlled sythesis of a series of copolymer topologies. all: To meet the rising demand for sustainable and simple polymer syntheses, organocatalytic polymerizations are a powerful tool. Here, the authors report the quasi-alternating polymerization of oxirane monomers at room temperature and in solvent-free conditions catalyzed by potassium acetate complexed by 18-crown-6 ether, leading to well-defined polyethers with varied comonomer content and low dispersity values. [ABSTRACT FROM AUTHOR]

Synthetic polymers occupy a unique place in the field of ion mobility mass spectrometry (IMS–MS). Indeed, due to their intrinsic dispersity, they have the asset to offer a broad range of homologous ions with different lengths that can be detected in several charge states. In addition, the gas-phase structure of polymer ions mostly depends on their ability to screen the adducted charges. Several works dealing with linear, cyclic, and star-shaped polymers have already shown that the gas-phase structure of polymer ions heavily relies on the polymer architecture, i.e. the primary structure. In the present work, we move a step further by evaluating whether a relationship exists between the primary and secondary structures of synthetic homo and copolymers. The IMS–MS experiments will be further complemented by MD simulations. To highlight the effectiveness of IMS separation, we selected isomeric homo and copolymers made of lactide (LA) and propiolactone (PL) units. In this way, the mass analysis becomes useless since isomeric comonomer sequences can coexist for any given chain length. An UPLC method was implemented in the workflow to successfully separate all PL–LA comonomer sequences before infusion in the IMS–MS instrument. The analysis of doubly charged copolymers showed that the comonomer sequence has an impact on the IMS response. However, this only holds for copolymer ions with precise sizes and charge states, and this is therefore not a rule of thumb. [ABSTRACT FROM AUTHOR]

Organocatalysis offers a number of prospects in the polymer community and presents advantages over metal based and bio‐organic methods. The use of organic molecules for performing chemical reactions is not a new concept, and any research into organocatalytic reactions builds on a respected history. Compared to the organocatalysis of large lactones, which began in the early 2000s, the examples presented here will demonstrate that few metal‐free initiating systems had been applied to β‐lactones well before the beginning of the current millennium. These metal‐free initiating systems present indisputable advantages over metal‐based processes. In the following paper, ring‐opening polymerizations (ROPs) of various β‐lactones for the preparation of poly(hydroxyalkanoate)s will be presented, as will the types of mechanisms involved, that is, zwitterionic and anionic, and cationic or supramolecular‐based ROPs. The advantages and drawbacks of the different technics will be discussed in the domain, which, for us, is important in the overall production of bioplastics. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 657–672 Metal‐free initiating systems present indisputable advantages in the ring‐opening polymerizations of various β‐lactones for the preparation of poly(hydroxyalkanoate)s. These have been presented in the following highlight focusing on the types of mechanisms involved as well as the advantages and drawbacks of the different techniques. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Hypothesis Since the emergence of the molecular-kinetic theory and the hydrodynamic approach, it is generally accepted that the displacement of the contact line is controlled by the viscous or frictional channel of energy dissipation for respectively high-viscosity and low-viscosity liquids. However, how the dissipation switches from one channel to another is still unknown. We therefore hypothesized that, by progressively changing the viscosity of a liquid, a better understanding of the underlying mechanism driving this wetting dynamic transition would be obtained. Experiments Performing capillary rise experiments of polydimethylsiloxane on a poly(ethylene terephthalate) fiber at different temperatures, i.e. at different liquid viscosities, we characterized the transition between the viscous and frictional regimes. The fiber surface topography was also characterized and its effect on the wetting dynamics was quantified. Findings The wetting dynamics switched from one regime to the other in a very short viscosity interval. Besides, the wetting behavior in the transition region is sensitive to the fiber surface topography. The presence or the absence of a liquid rim ahead of the contact line actually determines the dominant channel of dissipation. [ABSTRACT FROM AUTHOR]

Controlled Oxyanionic Polymerization of Propylene Oxide: Unlocking the Molecular-Weight Limitation by a Soft Nucleophilic Catalysis In its presence, alcohols act as soft nucleophiles promoting a perfectly controlled oxyanionic polymerization at room temperature and in bulk leading to polymers displaying predictable and unprecedented molar masses. B Front Cover b : Article 2200424 by Olivier Coulembier and co-workers reveals that an equimolar mixture of potassium acetate and 18-crown-6 ether is highly effective for controlling the polymerization of propylene oxide. [Extracted from the article]

Poly(3-hexylthiophene)s end-functionalized with π-extended porphyrins have been synthesized in a one-pot procedure. The polymers show a broad absorption profile extending to 700 nm and a fibrillar microstructure, which can be tuned through judicious selection of the porphyrin molar ratio. [ABSTRACT FROM AUTHOR]

The ionic nucleophilic character of ammonium betaine catalysts allows for controlling the ROP of L-LA for DP as high as 750 with very narrow dispersity values (≤1.18). Compared to ionic nucleophilic and hydrogen-bonding based catalysts for ROP, meta-betaine combines the positive aspects of both processes in terms of kinetics and selectivity. The versatility of ammonium betaines was evidenced by varying the nature of the initiating alcohol and monomer used. [ABSTRACT FROM AUTHOR]

Abstract: Novel synthetic transfection vectors with linear triblock and star-shaped diblock copolymer architectures have been synthesized by atom transfer radical polymerization (ATRP). Based on 2-(dimethylamino)ethyl methacrylate (DMAEMA) and copolymerization with poly(ethyleneglycol) α-methoxy, ω-methacrylate (MAPEG), the synthesis was realized using CuBr ligated with 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) as catalytic complex and either ethyl 2-bromoisobutyrate (EBiB) or bis(α-bromoisobutyryl) N-methyl diethanolamine (DEA) or tris(α-bromoisobutyryl) triethanolamine (TEA) as (multifunctional)initiator. The polymers were characterized by GPC and NMR. The solution properties of these homopolymers and palm-tree-like copolymers were investigated by viscometry either in pure water or in buffered aqueous solutions. Interestingly, all the synthesized polymers show polyelectrolyte effect in Millipore water (25°C) and in Hepes (20mM) buffer solution (pH 7.4, NaCl 155mM, 25°C). Fitting of these viscometric data according to either Fuoss or Fedors equation allows for calculating the intrinsic viscosity of the polymers. These results are compared with dynamic light scattering (DLS) experiments to determine absolute masses. Finally, DEA based palm-tree-like copolymer is investigated to AFM measurement and micelles were observed at pH 8. [Copyright &y& Elsevier]

Polylactide is one of the most versatile biopolymers, but its slow crystallization limits its temperature usage range. Hence finding ways to enhance it is crucial to widen its applications. Linear and cyclic poly (L -lactide) (l -PLLA and c -PLLA) of similarly low molecular weights (MW) were synthesized by ring-opening polymerization of L -lactide, and ring-expansion methodology, respectively. Two types of blends were prepared by solution mixing: (a) l -PLLA/ c -PLLA, at extreme compositions (rich in linear or in cyclic chains), and (b) blends of each of these low MW materials with a commercial high MW linear PLA. The crystallization of the different blends was evaluated by polarized light optical microscopy and differential scanning calorimetry. It was found, for the first time, that in the l -PLLA rich blends, small amounts of c -PLLA (i. e., 5 and 10 wt%) increase the nucleation density, nucleation rate (1/τ 0), spherulitic growth rate (G), and overall crystallization rate (1/τ 50%), when compared to neat l -PLLA, due to a synergistic effect (i. e., nucleation plus plasticization). In contrast, the opposite effect was found in the c -PLLA rich blends. The addition of small amounts of l -PLLA to a matrix of c -PLLA chains causes a decrease in the nucleation density, 1/τ 0 , G , and 1/τ 50% values, due to threading effects between cyclic and linear chains. Small amounts of l -PLLA and c -PLLA enhance the crystallization ability of a commercial high MW linear PLA without affecting its melting temperature. The l -PLLA only acts as a plasticizer for the PLA matrix, whereas c -PLLA has a synergistic effect in accelerating the crystallization of PLA that goes beyond simple plasticization. The addition of small amounts of c -PLLA affects not only PLA crystal growth but also its nucleation due to the unique cyclic chains topology. [Display omitted] [ABSTRACT FROM AUTHOR]

The synthesis of well‐defined propargyl‐functional aliphatic polycarbonates is achieved via the organocatalytic ring‐opening polymerization of prop‐2‐yn‐1‐yl 2‐oxo‐1,3,6‐dioxazocane‐6‐carboxylate (P‐8NC) using a wide variety of commercially available or readily made, shelf‐stable organocatalysts. The resulting homopolymers show low dispersities and end‐group fidelity, with the versatility of the system being demonstrated by the synthesis of telechelic copolymers and block copolymers with molar mass up to 40 kDa. [ABSTRACT FROM AUTHOR]

Rationale: Since their discovery, cyclic polymers have attracted great interest because of their unique properties. Today, the preparation of these macrocyclic structures still remains a challenge for polymer chemists, and most of the preparation pathways lead to an inescapable contamination by linear by‐products. As the properties of the polymers are closely related to their structure, it is of prime importance to be able to assess the architectural purity of a sample. Methods: In this work, the suitability of ion mobility spectrometry‐mass spectrometry (IMS‐MS) for the quantification of two isomers was investigated. A cyclic poly(L‐lactide) was prepared through photodimerization of its linear homologue. Since IMS‐MS can be used to differentiate cyclic polymer ions from their linear analogues because of their more compact three‐dimensional conformation, the present work envisaged the use of IMS‐MS for the quantification of residual linear polymers within the cyclic polymer sample. Results: Using the standard addition method to plot calibration curves, the fraction of linear contaminants in the sample was determined. By doing so, unrealistically high values of contamination were measured. Conclusions: These results were explained by an ionization efficiency issue. This work underlines some intrinsic limitations when using IMS‐MS in the context of the relative quantification of isomers having different ionization efficiencies. Nevertheless, the linear‐to‐cyclic ratio can be roughly estimated by this method. [ABSTRACT FROM AUTHOR]

Poly(l-lactide) end-functionalized by an imidazolium ring was synthesized by ring-opening polymerization of l-lactide from a hydroxylated ionic liquid. When challenged with CNTs in solution, this polyester exhibited significant binding ability towards the nanotube surface with respect to ω-pyrene poly(l-lactide). [ABSTRACT FROM AUTHOR]

The desire for sustainability drives interest in the production of chemicals from carbon dioxide. The synthesis of poly(trimethylene carbonate), PTMC, by copolymerization of carbon dioxide and oxetane using organocatalysis affords a green route to this important polymer but has proven to be a very challenging process. Herein we report that the application of iodine, in combination with organic superbases provides a highly active system for the direct synthesis of PTMC from CO2 with very high levels of carbonate linkage (95% in selectivity). Mechanistic studies reveal the in situ formation of trimethylene carbonate which eventually polymerizes through an active chain-end process from an I2-oxetane adduct. [ABSTRACT FROM AUTHOR]

The development of sustainable synthetic approaches to biodegradable and biocompatible polymeric materials represents a key challenge in polymer chemistry. A novel solvent-free and organocatalyzed ring-opening (co)polymerization (ORO(c)P) method utilizing benzoic acid(BA) as simple thermostable carboxylic acid-type catalyst is proposed to not only produce structurally well-defined aliphatic homopolyesters derived from l-lactide (l-LA) and ε-caprolactone (CL), but also and, unexpectedly, statistical copolyesters based on the two monomer units. RO(c)P reactions were conducted in bulk in a temperature range of 155–180 °C, in presence of alcohols as initiators. A triblock copolymer, namely, PLLA-b-PCL-b-PLLA, was also synthesized, attesting to the “controlled/living” character of this BA-OROP process. A bifunctional mechanism is proposed to operate, involving activation of both the monomer and the propagating hydroxyl by H-bonding. Very importantly, the BA organocatalyst could be readily recycled by simple sublimation and could be reused in further organocatalytic cycles. [ABSTRACT FROM AUTHOR]

Ring closure click chemistry methods have been used to produce cyclic c-PLLA and c-PDLA of a number-average molecular weight close to 10 kg/mol. The effects of stereochemistry of the polymer chains and their topology on their structure, nucleation, and crystallization were studied in detail employing wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), polarized light optical microscopy (PLOM), and standard and advanced differential scanning calorimetry (DSC). The crystal structures of linear and cyclic PLAs are identical to each other, and no differences in superstructural morphology could be detected. Cyclic PLA chains are able to nucleate much faster and to produce a higher number of nuclei in comparison to linear analogues, either upon cooling from the melt or upon heating from the glassy state. In the samples prepared in this work, a small fraction of linear or higher molecular weight cycles were detected (according to SEC analyses). The presence of such "impurities" retards spherulitic growth rates of c-PLAs, making them nearly the same as those of l-PLAs. On the other hand, the overall crystallization rate determined by DSC was much larger for c-PLAs, as a consequence of the enhanced nucleation that occurs in cyclic chains. The equilibrium melting temperatures of cyclic chains were determined and found to be 5 °C higher in comparison with values for l-PLAs. This result is a consequence of the lower entropy of cyclic chains in the melt. Self-nucleation studies demonstrated that c-PLAs have a shorter crystalline memory than linear analogues, as a result of their lower entanglement density. Successive self-nucleation and annealing (SSA) experiments reveal the remarkable ability of cyclic molecules to thicken, even to the point of crystallization with extended collapsed ring conformations. In general terms, stereochemistry had less influence on the results obtained in comparison with the dominating effect of chain topology. [ABSTRACT FROM AUTHOR]

One of the main issues when using traveling wave ion mobility spectrometry (TWIMS) for the determination of collisional cross-section (CCS) concerns the need for a robust calibration procedure built from referent ions of known CCS. Here, we implement synthetic polymer ions as CCS calibrants in positive ion mode. Based on their intrinsic polydispersities, polymers offer in a single sample the opportunity to generate, upon electrospray ionization, numerous ions covering a broad mass range and a large CCS window for different charge states at a time. In addition, the key advantage of polymer ions as CCS calibrants lies in the robustness of their gas-phase structure with respect to the instrumental conditions, making them less prone to collisional-induced unfolding (CIU) than protein ions. In this paper, we present a CCS calibration procedure using sodium cationized polylactide and polyethylene glycol, PLA and PEG, as calibrants with reference CCS determined on a home-made drift tube. Our calibration procedure is further validated by testing the polymer calibration to determine CCS of numerous different ions for which CCS are reported in the literature. [ABSTRACT FROM AUTHOR]

The preparation of stereoregular isotactic P( l -BnMA) and PLLA by ring-opening polymerization (ROP) of 5-( S )-[(benzyloxycarbonyl)methyl]-1,3-dioxolane-2,4-dione ( l -malOCA) and ( S )-5-methyl-1,3-dioxolane-2,4-dione ( l -lacOCA) is reported. The polymerization process was shown to be well controlled using two easily accessible single organocatalyst/initiator systems, pyridine/ l -benzyl(Bn)malate and pyridine/lactic acid (Py·LA) ion pair adducts respectively. The obtained biodegradable polymers displayed narrow dispersity ( Đ M ) and excellent molar mass control. All ROP reactions were conducted at ambient temperature. The stereoregularity and thermal properties of the materials were thoroughly studied, demonstrating the retention of high levels of isotactic enrichment. [ABSTRACT FROM AUTHOR]

Polyesteramides (PEAs) are considered intriguing materials due to the combination of the favorable degradable capacity of aliphatic polyesters given by the hydrolizable ester groups and the desirable thermal and mechanical behavior of polyamides given by the amide groups. Between polyamides and polyester families, poly(ε-caprolactam) and poly( l -lactide) stand out due to their commercial value and outstanding properties. Nevertheless, to date these two monomers have not been co-polymerized due to their different reactivities. In this work, we report for the first time, up to our knowledge, the synthesis of poly(ε-caprolactam- co - l -lactide) copolymers with different compositions. Two different catalysts: (a) Brønsted acid ionic liquid 1-(4-sulfobutyl)-3-methylimidazolium hydrogen sulfate (BAIL) and (b) Brønsted base P 4 - t -Bu have been explored. In the presence of Brønsted acid the l -lactide reactivity is higher than the ε-caprolactam while in the presence of Brønsted base the opposite behavior is observed. Using Kelen-Tudos method the monomer reactivity ratios are calculated and obtained as r CLa = 0.39 and r LA = 1.6 and r CLa = 2.2 and r LA = 0.1 using BAIL and P 4 - t -Bu, respectively. These differences in the monomer reactivity ratios give us the possibility to create copolymers with different chain microstructure depending on the employed catalyst between 2 and 9 kDa. Thus, using P 4 - t -Bu random copolymers can be obtained at high l -lactide concentration and blocky character copolymers at high ε-caprolactam concentration. Meanwhile, using BAIL catalyst random like copolymers are obtained at high ε-caprolactam contents and blocky character at high l -lactide contents. [ABSTRACT FROM AUTHOR]

Different P3HT chain lengths have been synthesized, functionalized at both chain ends with aldehyde moieties and finally cyclized following the McMurry reaction in a pseudo high dilution process. The confirmation of the high yielded intramolecular coupling came from the decrease of the hydrodynamic radius observed by SEC, correlated to the conservation of the mass distribution by MALDI-ToF and by the very low content of residual linear precursor estimated by NMR. Different aggregation behaviors between linear and cyclic and between short and long systems have been pointed out by DSC and UV-vis absorption spectroscopy. We estimate that long cyclic structures present similar aggregation behavior than long linear ones mainly due to the folding of those chains. [ABSTRACT FROM AUTHOR]

The preparation of cyclic macromolecules has always represented a challenging task for polymer science, mainly because of difficulties in connecting chain extremities together. Initiated by the pioneering studies of Jacobson and Stockmayer, preparative pathways to cyclic polymers have been considerably improved within the last two decades thanks to the advent of both controlled polymerizations and efficient coupling reactions in organic chemistry. This Review aims to provide a critical up-to-date overview and illustrate the considerable efforts that have been made in the past few years to improve the availability of macrocycles for industrial and academic investigations through the use of the ring-closure approach. Particular attention is paid to methods for the preparation of monocycles over more complex architectures, since the latter are usually derived from the former. [ABSTRACT FROM AUTHOR]

Die Synthese cyclischer Makromoleküle war – vor allem bedingt durch die schwierige Verknüpfung der Kettenenden – schon immer eine anspruchsvolle Aufgabe in den Polymerwissenschaften. Beginnend mit den wegweisenden Arbeiten von Jacobson und Stockmayer wurden die Herstellungsmethoden für cyclische Polymere in den vergangenen zwanzig Jahren dank der Einführung kontrollierter Polymerisationsmechanismen und effizienter Kupplungsreaktionen in die organischen Chemie erheblich verbessert. Dieser Aufsatz bietet einen kritischen aktuellen Überblick und veranschaulicht die beträchtlichen Leistungen in den letzten Jahren, mit denen die Verfügbarkeit von Makrocyclen für Untersuchungen in Industrie und Forschung durch Ringschlussmethoden verbessert wurde. Einen Schwerpunkt bilden dabei die Herstellungsmethoden für Monocyclen, aus denen normalerweise wiederum kompliziertere Strukturen erhalten werden. Der Kreis schließt sich: Die Herstellung cyclischer Makromoleküle ist anspruchsvoll. Auf diesem Gebiet wurden jedoch in den letzten Jahren enorme Leistungen vollbracht, die mittels Ringschlussmethoden synthetisierte Makrocyclen für die Industrie und Forschung besser verfügbar gemacht haben. Einen Schwerpunkt dieses Aufsatzes bilden Methoden zur Synthese von Monocyclen, aus denen sich wiederum kompliziertere Strukturen erhalten lassen. [ABSTRACT FROM AUTHOR]

The synthesis of symmetric cyclo poly(ε-caprolactone)- block-poly( l( d)-lactide) ( c(PCL- b-PL(D)LA)) by combining ring-opening polymerization of ε-caprolactone and lactides and subsequent click chemistry reaction of the linear precursors containing antagonist functionalities is presented. The two blocks can sequentially crystallize and self-assemble into double crystalline spherulitic superstructures. The cyclic chain topology significantly affects both the nucleation and the crystallization of each constituent, as gathered from a comparison of the behavior of linear precursors and cyclic block copolymers. The stereochemistry of the PLA block does not have a significant effect on the nonisothermal crystallization of both linear and cyclo PCL- b-PDLA and PCL- b-PLLA copolymers. [ABSTRACT FROM AUTHOR]

This work deals with the synthesis and characterization of new diblock copolymers based on π-conjugated and depolymerizable units. These diblock copolymers are based on a regioregular poly(3-hexylthiophene) sequence associated with a sacrificial block, namely polyphthalaldehyde. The conjugated polymer was obtained by Grignard metathesis polymerization and end-capped by an alkynyl group while the depolymerizable segment was synthesized by an anionic cyclopolymerization from an azide moiety. Diblock copolymers with different molecular weights were then successfully synthesized via an alkyne-azide coupling reaction. Under specific conditions, these copolymers self-assemble intofibrillar nanostructures in thin films. The elimination of polyphthalaldehyde was carried out by thermal treatment, generating nanoporous poly(3-hexylthiophene) films. The use of a dry treatment to remove the polyphthalaldehyde block strongly reduces the morphological damages that would occur with a "wet" processing route. These nanoporous poly(3-hexylthiophene) films could be useful for controlling the morphology of the heterojunction in organic photovoltaic devices after successful filling with an electron-acceptor material. [ABSTRACT FROM AUTHOR]

Conjugated poly(3-hexylthiophene) copolymer derivatives containing 10% appended porphyrin moieties are prepared using a supramolecular approach toward applications in organic electro­nics. The self-assembled polythiophene-porphyrin copolymers are synthesized by coordination of the porphyrinato central zinc ions to the imidazole-functionalized polythiophene side chains. Evidence for the self-assembly process is provided by 1H NMR spectroscopy, single crystal X-ray diffraction, and optical absorption studies on model compounds. The polythiophene-porphyrin copolymers show an extended absorption window in the region of 420-650 nm due to the contribution of the porphyrin. Photoluminescence studies indicate concentration-dependent energy transfer from P3HT to the porphyrin. Preliminary photovoltaic studies are performed by combining the polythiophene-porphyrin copolymers with PC61BM in the photo­active layer of bulk heterojunction organic solar cells. [ABSTRACT FROM AUTHOR]

To date, the controlled preparation of cyclic polymers is mainly achieved using click ligation strategies. The light-induced Diels-Alder click coupling has recently been shown to function as an attractive catalyst-free alternative to the copper-catalyzed alkyne-azide cycloaddition. However, the need for a light emitting system limits its applicability. To overcome this drawback, a sunlight-induced Diels-Alder reaction as an efficient route for the preparation of cyclic aliphatic polyesters in high yields and purity based on the same chemistry is demonstrated in the present contribution. The versatility and robustness of the proposed strategy against divergent atmospheric conditions is demonstrated. In light of the simplicity of the strategy presented here, it is suggested that the sunlight-induced Diels-Alder click-cyclization is a world-wide transposable process. [ABSTRACT FROM AUTHOR]

Identifyingsolvent- and catalyst-free conditions for polymerizationsof engineering thermoplastics is of increasing interest due to newpolymer processing technologies such as 3-D printing. We report theselective formation of linear poly(aryl ether sulfone)s (PESs) fromthe polycondensation of trimethylsilyl-protected bisphenol A (TMS-BPA)with nitro-substituted diaryl fluorides without added solvent or catalyst.DFT calculations show that nitro groups strategically placed in the ortho-position to the fluoride leaving group form a stableMeisenheimer complex during polyether synthesis. This strategy representsa route to linear PESs that employs anionic conditions, destabilizingpropagating phenoxide chain ends preventing backbiting while simultaneouslystabilizing the Meisenheimer complex intermediate. Thermodynamic overkinetic control in the polycondensation minimizes cyclic PES formationand promotes the formation of pure linear PESs. [ABSTRACT FROM AUTHOR]

We report herein a detailed study of the use of porphyrins fused to imidazolium salts as precursors of N-heterocyclic carbene ligands 1 M. Rhodium(I) complexes 6 M- 9 M were prepared by using 1 M ligands with different metal cations in the inner core of the porphyrin (M=NiII, ZnII, MnIII, AlIII, 2H). The electronic properties of the corresponding N-heterocyclic carbene ligands were investigated by monitoring the spectroscopic changes occurring in the cod and CO ancillary ligands of [( 1 M)Rh(cod)Cl] and [( 1 M)Rh(CO)2Cl] complexes (cod=1,5-cyclooctadiene). Porphyrin-NHC ligands 1 M with a trivalent metal cation such as MnIII and AlIII are overall poorer electron donors than porphyrin-NHC ligands with no metal cation or incorporating a divalent metal cation such as NiII and ZnII. Imidazolium salts 3 M (M=Ni, Zn, Mn, 2H) have also been used as NHC precursors to catalyze the ring-opening polymerization of L-lactide. The results clearly show that the inner metal of the porphyrin has an important effect on the reactivity of the outer carbene. [ABSTRACT FROM AUTHOR]

A joint experimental and theoretical study of singlet exciton diffusion in spin-coated poly(3-hexylthiophene) (P3HT) films and its dependence on molecular weight is presented. The results show that exciton diffusion is fast along the co-facial π- π aggregates of polymer chromophores and about 100 times slower in the lateral direction between aggregates. Exciton hopping between aggregates is found to show a subtle dependence on interchain coupling, aggregate size, and Boltzmann statistics. Additionally, a clear correlation is observed between the effective exciton diffusion coefficient, the degree of aggregation of chromophores, and exciton delocalization along the polymer chain, which suggests that exciton diffusion length can be enhanced by tailored synthesis and processing conditions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Assessment of end-group functionality in ATRP of NiPAm. [•] Synthesis of well-defined “smart” amphiphilic block copolymers. [•] Relevance of side reactions and diffusional limitations in ATRP of NiPAm. [ABSTRACT FROM AUTHOR]

Review: 165 refs. [ABSTRACT FROM AUTHOR]