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Synthesis of discrete guanylated antimicrobial oligomers through reversible addition fragmentation chain transfer (RAFT) polymerization followed by flash chromatography is described.

Using ridge regression, the propagation rate coefficients for radical polymerization are correlated with basic molecular properties.

A novel method for creating a semiconducting nanoparticles of the donor–acceptor conjugated polymer p(IDT-NDI) containing indacenodithienothiophene (IDT) and naphthalene diimide (NDI) units is presented.

Rate coefficients for secondary radical propagation, backbiting and tertiary radical monomer addition for ethylhexyl acrylate have been determined.

Automated continuous flow is used as high-throughput method with high accuracy.

The dataset used to generate IUPAC benchmark Arrhenius parameters for propagation rate coefficients in radical polymerization is extended and reanalyzed, taking into account systematic interlaboratory variation.

The influence of dispersity in the molecular weight distributions in the core forming block for block copolymer (BCP) self-assembly is analyzed via an automated flow synthesis approach.

We integrate continuous flow organocatalysed ring-opening polymerisation with a core-grafting strategy to rapidly and readily prepare multifunctional, processable polyesters. Their potential use in materials applications is subsequently highlighted.

Continuous flow chemistry offers an exceptionally high degree of operational flexibility to handle photochemical transformations.

Controlling monomer sequence and dispersity in synthetic macromolecules is a major goal in polymer science as both parameters determine materials’ properties and functions. However, synthetic approaches that can simultaneously control both sequence and dispersity remain experimentally unattainable. Here we report a simple, one pot and rapid synthesis of sequence-controlled multiblocks with on-demand control over dispersity while maintaining a high livingness, and good agreement between theoretical and experimental molecular weights and quantitative yields. Key to our approach is the regulation in the activity of the chain transfer agent during a controlled radical polymerization that enables the preparation of multiblocks with gradually ascending (Ɖ = 1.16 → 1.60), descending (Ɖ = 1.66 → 1.22), alternating low and high dispersity values (Ɖ = 1.17 → 1.61 → 1.24 → 1.70 → 1.26) or any combination thereof. We further demonstrate the potential of our methodology through the synthesis of highly ordered pentablock, octablock and decablock copolymers, which yield multiblocks with concurrent control over both sequence and dispersity. Synthetic approaches that can simultaneously control both polymer sequence and dispersity are difficult to achieve. Now, a switchable RAFT agent that regulates chain transfer activity during controlled radical polymerization has been shown to enable the one-pot synthesis of sequence-controlled multiblocks with on-demand control over dispersity while maintaining high livingness.

Using a log-log regression, the propagation rate coefficients for radical polymerization are correlated with basic molecular properties. These are either available from literature, or from simple and non-time-consuming calculations. Parameters under consideration are molecular weights, boiling points or dipolar moments. The model brings acrylates and methacrylates with linear and branched structures, and monomers that are known to be influenced strongly by H-bonding in line with each other, allowing to fit all data in a single approach. The model also successfully correlates monomers such as styrene and acrylonitrile successfully. Both absolute rate coefficients, as well as Arrhenius activation parameters can be described with high accuracy. With the presented model it is thus possible to describe practically all monomers for which kinetic data is available simultaneously and to carry out predictions for monomers for which no experimental data exist.

Linear monodisperse 18- and 20-mer acrylates are obtained via consecutive synthesis of two sequence-defined acrylate 9- and 10-mers, followed by disulfide coupling utilizing reversible addition−fragmentation chain transfer (RAFT) end group chemistry. The sequence-defined oligoacrylates are accessed via consecutive single (SUMI) and multiple (MUMI) unit monomer insertions through RAFT polymerization, using the extensive acrylate monomer library as functional building blocks. Aminolysis of the trithiocarbonate macro-RAFT end group and in situ oxidation of the thiols to form a disulfide bridge lead to the formation of 18- and 20-mer acrylates. In this approach, one or multiple acrylate building blocks can be inserted in each step by chain extension to form a stable carbon−carbon backbone. Isolation of the targeted monodisperse oligomers, from the statistical mixtures obtained at first, is performed by flash column chromatography with high efficiency. It is shown that the SUMI and MUMI strategy, when combined with flash column chromatography separation, is highly efficient and allows to construct monodisperse materials of very considerable length starting from cheap and very versatile building blocks. Funding from the Fonds Wetenschappelijk Onderzoek and Hasselt University is kindly acknowledged.

Micelle dispersions purification is made available via inline flow dialysis in which micelles are separated from the organic solvent used to dissolve the block copolymers in the micelle formation step. Purification was performed using simple and cost-effective dialysis units employing cellulose membranes. The proposed setup allows us to remove THF from a micelle dispersion within a few hours almost entirely in a looped flow system, without significantly changing the micelle size. Purification is found to be independent of the exact flow rates and only on the circulation time through the dialysis units. The system is not only able to reduce the concentration of the organic solvent, but also water-soluble monomers can be removed. Further, the integration of the method into a full synthesis line to produce encapsulated micelles directly from block copolymer solutions is demonstrated with a throughput of 1.2 g of micelles per hour.

Size exclusion chromatography (SEC) based on direct homopolymer calibration is the preferred method for molecular weight determination in macromolecular synthesis. However, using the same method and calibration in block copolymer (BCP) characterization can lead to an apparent molecular weight reduction when in fact the opposite has taken place. This leads to a situation where researchers often have enough difficulties in interpreting their data, creating false conclusions and deeming successful experiments unsuccessful or vice versa. Here, a selection of block copolymers from the literature is discussed for which such an incoherent change in the retention time has been observed. These examples represent four categories of BCPs for which unexpected SEC results can occur. We discuss the importance of a critical evaluation of SEC and the reasons for the deviating behavior and highlight the danger of the common practice to use elugrams to prove or disprove successful chain extensions in synthesis. Next to a critical evaluation of the various cases, we give recommendations for which other detection and characterization methods may enable accurate block copolymer characterization.

Many attempts to mimic the structure of biopolymers via precision polymer synthesis with reversible deactivation radical polymerization (RDRP) techniques have been made. For peptides and proteins and their building blocks in particular, a broad variety of mimics have previously been suggested. However, general consistency in the design of these materials has been lacking. In this work, the foundations of a consistent acrylamide monomer library that mimics essential amino acids has been laid, defining mimics as the reaction product of acryloyl chloride and the decarboxylized respective amino acid. Five of these monomers were then selected as model monomers, each representing one of the the five major groups of amino acids. The model monomers were synthesized in flow procedures directly from acrylic acid and subjected to reversible addition fragmentation chain transfer (RAFT) polymerizations. 2-Hydroxyethyl acrylamide, N-isobutylacrylamide, N-methylacrylamide and isopropyl 4 – acrylamidobutanoate (mimicking serine, valine, glycine and glutamic acid) were polymerized via a general thermal RAFT approach resulting in high monomer conversions and good molecular weight control after short reaction times of 5 to 15 minutes. For the mimic of arginine, 1,3-di-boc-guanidinobutyl acrylamide, photoRAFT at room temperature was required to reach consistent polymerization conditions, then also resulting in well-defined materials.

Functional acrylamides are valuable intermediates for organic synthesis and building blocks in many industrial areas, like polymer synthesis, fine chemicals and pharmaceutics. The conventional batch reaction copes with some safety issues, due to the intrinsic reactivity and careful handling of the reagents. Moreover, the hazardous solvents used and the energy consumed have an enormous environmental impact. The development of an efficient and robust continuous flow process, allowing a safe and on-demand synthesis of acrylamides with high yield leads the way to a more sustainable chemistry. Two alternative synthesis routes for the preparation of N-phenyl acrylamide, but applicable as a continuous production process, are presented: both based on the Schotten-Baumann reaction, one starting from 3-chloropropanoyl chloride and the other starting from acrylic acid. The latter reaction, with a laboratory throughput of 16.5 g·h−1, low operation temperatures and the use of less hazardous chemicals, provides an efficient and sustainable alternative synthesis route of the desired acrylamides, minimizing side-products and enabling a safe and convenient scale-up.

Summary Dispersity (Ɖ) can significantly affect polymer properties and is a key parameter in materials design. Here, we report a straightforward and versatile batch method based on reversible addition-fragmentation chain transfer (RAFT) polymerization to tailor the molecular weight distributions for a wide range of monomer classes, including acrylates, acrylamides, methacrylates, and styrene. In addition, our methodology is compatible with more challenging monomers, such as methacrylic acid, methyl vinyl ketone, and vinyl acetate. Control over Ɖ is achieved by mixing two RAFT agents with sufficiently different chain-transfer activities in various ratios, affording polymers with monomodal molecular weight distributions over a broad dispersity range (Ɖ ∼ 1.09–2.10). Our experimental findings were supported by simulations through the use of deterministic kinetic modeling, and our method was further demonstrated for the preparation of well-defined block co-polymers, regardless of the initial homopolymer dispersity.

Discovery of the intricate structure of self-assembled DNA has spurred an enormous research interest and inspired attempts to harness the properties of this fascinating biopolymer in synthetic analogs. Transferring the complementary hydrogen bonding characteristic of DNA and RNA nucleobases to synthetic polymers gives access to selective, dynamic behavior for unique materials properties. Adenine (A), thymine (T), uracil (U), cytosine (C) and guanine (G) derivatives of acrylic monomers were synthesized and used in reversible addition–fragmentation chain transfer (RAFT) single monomer addition. Consecutive RAFT reactions with intermediate purification via flash chromatography enabled the preparation of multiple-hydrogen bond sequence-defined (MHB SD) oligomers. Optimized flash conditions were established by separating different insertion products of an oligomer mixture with 0–5 uracil-based monomer repeating units. These separation conditions were applied in successive RAFT polymerizations resulting in three MHB SD tetramers with sequences AAAA, ACAC and finally ACTG, the latter of which contains all four distinct DNA nucleobase derivatives. This approach offers complete freedom of the desired short nucleobase sequence where the selective hydrogen bonding is appealing for applications ranging from biosensors to polymer–DNA conjugates, adhesives or self-healing materials.

Polymerization-induced self-assembly (PISA), which allows scalable synthesis of nano-objects, has drawn significant research attention in the past decade. However, the initiation methods in most of the current reported PISA are still restricted to thermal or photo processes. Sonolysis of a water molecule by high frequency ultrasound to generate a hydroxyl radical and to initiate polymerization has the potential to be a new “initiator-free” synthesis technique. Despite ultrasound-initiated polymerization-induced self-assembly (sono-PISA) being reported, only spherical micelle morphology was achieved. We demonstrate here the first room temperature synthesis of diblock copolymer nano-objects with different morphologies using ultrasound (990 kHz) initiated reversible addition–fragmentation chain transfer PISA (sono-RAFT-PISA) in an aqueous system. It was found that the morphologies of the block copolymer nano-objects prepared by sono-RAFT-PISA were different from those prepared by conventional thermal-PISA. Furthermore, the impacts of ultrasound and presence of a cross-linker on the nano-object morphology were investigated. It was observed that the stability of worm-like micelles will be affected by ultrasound but could be strengthened via core-cross-linking (CCL). Overall, the externally-regulatable, easily scalable and sustainable “green” features of ultrasound have the potential to promote the application of sono-PISA for the fabrication of nano-objects.

A method for encryption and safe transmission of data in the shape of molecular weight distributions (MWD) is presented. Relatively simple individual distributions serve as the key to encode information by mixing those in known amounts to an overlapped MWD. Increasing molecular weights are used to denote the position of these individual sub-distributions, and the relative quantity per sub-distribution is used to store data. The concept is demonstrated by a series of messages, whereby two-letter codes can be transmitted per overall MWD. In the final step, the encryption safety is confirmed. Due to the inherent differences in SEC calibrations, samples sent from Australia to Belgium could only be deconvoluted when the recipient of the message owned the physical sub-distributions, which then act as the encryption key.

Low dispersity poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)]-1,4-phenylenevinylene (MDMO-PPV) with well-defined end-groups is made available by performing the anionic polymerization in a continuous tubular reactor under flash chemistry conditions. The anionic polymerization was carried out via the sulfinyl (Vanderzande) precursor route, following a protocol previously established. Flash flow chemistry allowed now to not only control the microstructure, but also the disperisty of the PPV efficiently. Further, this is the first time that premature termination of PPV anionic polymerization could be observed. Only at ultra-low reaction times in the order of tens of miliseconds products can be observed that have not reached full monomer conversion, redering this type of polymerization one of the fastest polymerizations known. Due to the efficient mixing in the tubular reactors, dispersities of 1.2 could be reached at such low residence times, which is unachievable in conventinal batch-wise chemistry. In a second step, a block copolymer was formed of the precursor PPV and tert-butyl acrylate (tBuA), which is further converted into an amphiphilic block copolymer of PPV with poly(acrylic acid) (PAA). Self-assembly of the PPV-b-PAA block copolymer in a continuous tubular reactor resulted in micelles with a number average diameter of 170 nm.

Muconic acid (MA) is a high value-added dicarboxylic acid with conjugated double bonds, presenting three isomeric forms, i.e., cis,cis-MA, cis,trans-MA and trans,trans-MA. Its production is garnering increased interest owing to its potential as a starting material for the synthesis of value-added products as well as by being a versatile monomer for the production of specialty polymers. This review presents a systematic overview of production and synthesis routes to MA isomers as well as the routes for its final valorization. The production of MA through chemical pathways and the progress developed in the biotechnological pathways will be discussed. Traditional and new processes for achieving successful isomerization into the value-added trans,trans form of MA are also discussed and compared, with their constraints and possible solutions. The valorization of the three different isomers of MA into value-added chemicals such as adipic or terephthalic acids and MA polymers are summarized. Finally, the review concludes with a thorough summary, a practical insights section and an outlook. This work thus offers new perspectives and guidelines to tackle the challenges in MA chemistry, especially when aiming to combine an efficient biotechnological production of MA with its valorization.

Continuous-flow simplified electrochemically mediated atom transfer radical polymerization (seATRP) was achieved for the first time without supporting electrolytes (self-supported) using a novel sonicated tubular microreactor. Polymerizations of different acrylic monomers were carried out under different applied currents. The reaction was fast with 75% conversion achieved at ambient temperature in less than 27 minutes. Results also showed good evolution of molecular weight and maintained narrow molecular weight distribution. The reaction rate can be further manipulated by tuning the applied current. Sonication under proper conditions was found to be able to significantly improve both reaction rate and controllability. Self-supported reactions also enable more environmentally friendly and cost-effective operations. ispartof: CHEMICAL SCIENCE vol:13 issue:42 pages:12326-12331 ispartof: location:England status: published

Diffusion-ordered NMR spectroscopy (DOSY) allows for accurate molecular weight calibration and determination that can be corrected for solvent influences. Polystyrene and poly(ethylene glycol) standards have been used to calibrate DOSY diffusion data for a variety of solvents, showing a high correlation of data when the bulk viscosity of the solvent is accounted for following the Stokes-Einstein equation. In this way, a type of universal calibration is introduced that allows for determinations of average molecular weight that are at least as accurate as those of traditional size-exclusion chromatography (SEC), if not better. Further, we demonstrate that DOSY calibrations can be used between laboratories, hence removing the need for individual calibration of setups as currently done.

Antoine Buchard and Tanja Junkers introduce the Polymer Chemistry themed collection on Sustainable Polymers.

The first steps towards top-down morphology control in micellar self-assembly are introduced. Kinetically stable micelles are formed from block copolymers (BCPs) using continuous flow techniques by turbulent mixing of water with a THF solution of polymers. In this way, particle shape and size can be altered from spheres to ellipsoids solely via tuning of mixing parameters from a single BCP.

Flowreactorsbecomemoreand moreautomatedby enablingon-linereactionmonitoringand adjustingthe processparame-ters. On-linemonitoringof chemicalprocessesis a valuabletoolto steerprocesses,leadingto preciseengineeringof macro-molecularmaterials.Detailedinformationaboutspecificprod-uct patterns,end-groupfunctionalityor materialcompositioncan be obtainedby couplinga flowreactorto a massspectrometer(e.g. ESI-MS).In this work,we studythe depro-tectionof maleimidesand its subsequentphotoenolfunctional-izationto synthesizecomplexmacromoleculesusinga photoflow reactorcoupledto an ESI-MS.Usinga trappingagent(TA),furanis efficientlyremovedfromthe maleimideDielsAlderadductwithinjustminutesat 175°C andquantitativelyconvertedinto an unreactivespeciesthat doesnot interferewith furtherreactionsof the maleimide.The photoenolreactionwaslikewiseshownto be highlyeffectiveto proceedinmicroreactors,reachingquantitativeconversionof trifunctionalmoleculesin as little as 2 min N.Z. acknowledges the European Union Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 665501 with the research Foundation Flanders (FWO). C.B.-K. acknowledges the Australian Research Council (ARC) for a Laureate Fellowship enabling his photochemical research program, as well as the Queensland University of Technology (QUT) for continued financial support.

Functional precision polymers based on monodisperse oligo(N-substituted acrylamide)s and oligo(2-substituted-α-hydroxy acid)s have been synthesized. The discrete sequences originate from a direct translation of side-chain functionality sequences of a peptide with well-studied properties. The peptide was previously selected to solubilize the photosensitizer meta-tetra(hydroxyphenyl)chlorin. The resulting peptidomimetic formulation additives preserve the drug solubilization and release characteristics of the parent peptide. In some cases, superior properties are obtained, reaching up to 40 % higher payloads and 27-times faster initial drug release.

The authors are grateful for funding from the Fonds Wetenschappelijk Onderzoek in the form of a project grant and an FWO-SB grant of M.R. Further support via the Karlsruhe Nano Micro Facility (KNMF) is kindly acknowledged. The K-Alpha+ instrument was financially supported by the Federal Ministry of Economics and Technology on the basis of a decision by the German Bundestag. The authors wish to thank Mrs. Emely Bopp (IFG, KIT) for performing some ToF-SIMS experiments.

The synthesis of polymer nanoparticles for potential drug delivery applications via photoinduced electron transfer-reversible addition-fragmentation chain transfer aqueous dispersion polymerizations employing Eosin Y/triethanol amine as catalytic system is described. A scalable synthesis procedure for the polymerization of poly(dimethyl acrylamide)-b-(poly(diaceteone-stat-dimethyl acrylamide)) is reported under visible light (lambda(max) = 530 nm). A variety of solid contents and block lengths for the solvophilic and solvophobic blocks are investigated, expanding the compositional space of worms, jellyfish, and vesicles using flow chemistry. A simple two-step process using a coupled flow reactor setup is used without the need for intermediate purification.

Magnetic force microscopy (MFM) has become a widely used tool for the characterization of magnetic properties. However, the magnetic signal can be overlapped by additional forces acting on the tip such as electrostatic forces. In this work the possibility to reduce capacitive coupling effects between tip and substrate is discussed in relation to the thickness of a dielectric layer introduced in the system. Single superparamagnetic iron oxide nanoparticles (SPIONs) are used as a model system, because their magnetic signal is contrariwise to the signal due to capacitive coupling so that it is possible to distinguish between magnetic and electric force contributions. Introducing a dielectric layer between substrate and nanoparticle the capacitive coupling can be tuned and minimized for thick layers. Using the theory of capacitive coupling and the magnetic point dipole-dipole model we could theoretically explain and experimentally prove the phase signal for single superparamagnetic nanoparticles as a function of the layer thickness of the dielectric layer. Tuning the capacitive coupling by variation of the dielectric layer thickness between nanoparticle and substrate allows the distinction between the electric and the magnetic contributions to the MFM signal. The theory also predicts decreasing topographic effects in MFM signals due to surface roughness of dielectric films with increasing film thickness. The authors acknowledge the financial support by the ELSTATIK-Foundation Gunter and Sylvia Luttgens through the project ESEMA and DAAD through the project MPFL.

To be applicable to in vivo measuring, molecularly imprinted polymer (MIP) based sensors need to have high reproducibility, require miniaturization, and must be free of toxic materials (such as hea...

A novel continuous flow system for automated high-throughput screening, autonomous optimization, and enhanced process control of polymerizations was developed. The computer-controlled platform comprises a flow reactor coupled to size exclusion chromatography (SEC). Molecular weight distributions are measured online and used by a machine-learning algorithm to self-optimize reactions towards a programmed molecular weight by dynamically varying reaction parameters (i.e. residence time, monomer concentration, and control agent/initiator concentration). The autonomous platform allows targeting of molecular weights in a reproducible manner with unprecedented accuracy (

The development of practical routes that enable the synthesis of unimolecular non-natural macromolecules on multi-gram scales remains a key challenge in polymer chemistry. Herein, we present a continuous flow setup employing the light-induced chemistry based on photocaged dienes as a controlled ligation system to establish a new platform for scalable monodisperse macromolecular synthesis. 800mg of sequence-defined linear chains with 8 repeating units were obtained in a sequential protecting group based 2-step process. The current study demonstrates that photoflow synthesis is a viable approach to generate large quantities of monodisperse oligomers.

The properties of polymeric materials are dependent on their chemical architecture and overall molecular weight distribution (MWD). Despite a plethora of research on controlled and living polymerization techniques to obtain narrow molecular weight distributions, there are only comparatively few direct methods to tune and manipulate the final shape and characteristics of a MWD. These methods are limited by restrictions in predicting the final MWDs, by tedious and intensive sample preparation or both. Using a predictive framework, we demonstrate how artificial MWDs can be conveniently synthesized with high accuracy and with minimal human intervention.