Archive for the ‘Paper of the Month’ Category

Paper of the Month: Geared photochemistry: an interdependent heterogeneous near-infrared catalytic system using up-conversion glass and g-CN for CuAAC chemistry

Kocaarslan et al. employ a heterogeneous near-infrared catalytic system using up-conversion glass (UCG) and g-CN to synthesize (macro)molecules via click chemistry.

 

 

The efficiency and accessibility of “click” chemistry, and more specifically the copper-catalyzed azide-alkyne cycloaddition reaction (CuAAC), have been valorized in synthetic macromolecular chemistry via a plethora of approaches. In this synthetic arena, photochemical process have been shown to efficiently achieve the in situ reduction of air-stable copper(II) species to the active copper(I) species catalyzing CuAAC.

Expanding the scope of current CuAAC photocatalysis, Yagci and coworkers developed a “geared photochemistry” approach for NIR induced CuAAC click chemistry using a dual-heterogeneous photocatalyst that generates light emission in upconversion materials combined with graphitic carbon nitride (g-CN). To achieve this, it is shown that Tm3+ and Yb3+ ion-doped zinc-tellurite glass that absorbs laser irradiation at 975 nm and is capable of emitting blue light at 475 nm, can photocatalytically activate g-CN via an internal light emitting process. For the CuAAC process, this visible light excitation of g-CN in the presence of CuCl2/PMDETA was proven to generate active copper(Ι) species able to catalyze a CuAAC click reaction between various azide and alkyne compounds. This system was proven efficient in click reactions between macromolecular chains such as azide functional polystyrene (PS-N3) and alkyne functional poly(ε-caprolactone) (PCL-alkyne) yielding block copolymers with structurally different segments. In the same vein, photoinduced crosslinking could also be achieved upon irradiation of multifunctional click components (such as bisphenol A di(3-azido-2-hydroxy propan-1-ol) ether and 1-(prop-2-yn-1-yloxy)-2,2-bis((prop-2-yn-1yloxy)methyl) butane) with a 875 nm laser in the presence of mesoporous graphitic carbon nitride (mpg-CN) and CuCl2/PMDETA under open air conditions within 2 hours. Importantly, the heterogeneous catalyst prepared via the combination of graphitic carbon and UCG could be successfully used several times enhancing the applicability of the system.

The interdependent heterogeneous system using UCG in conjunction with g-CN under NIR light presented in this study, offers a highly efficient click methodology for (macro)molecules in synthetic (polymer) chemistry.

 

Tips/comments directly from the authors:

  • Our group’s research activities focus on the development of new photoinitiating systems for macromolecular synthesis. In this line, many photoinitiators acting at wide wavelength range of the electromagnetic spectrum were developed. “Geared photochemistry”, introduced for the first time in this paper, reflects the light-triggered reaction sequence that interdependently proceeds .  In this approach, up-conversion glass absorbs light at NIR region and convert it to visible light. Upon absorption of the emitted visible light graphitic carbon nitride (mpg-CN) in the reaction media creates electron and hole pairs. The copper (II) complex, which has no absorbance at these two wavelengths, is reduced from copper II to copper I by the released electrons. After all this gear-like system, copper I ions catalyze the click reaction between azide and alkyne compounds to form a triazole ring. We are happy to publish this work in an important journal in polymer science, Polymer Chemistry.
  • This approach will open new horizons not only for click chemistry, but also for many synthesis procedures involving electron transfer reactions. It should be considered that the change of absorbance with upconversion glasses is important for many light-activated photocatalysts.

 

Citation to the paper: Geared photochemistry: an interdependent heterogeneous near-infrared catalytic system using up-conversion glass and g-CN for CuAAC chemistry, Polym. Chem., 2022,13, 6393-6399, DOI: 10.1039/D2PY01075E

 

Link to the paper:

https://pubs.rsc.org/en/content/articlelanding/2022/py/d2py01075e

 

Kelly Velonia is saddened to hear about the passing of Prof. Yusuf Yagci, an exceptional scientist and person. Condolences to his family and loved ones. The polymer community will certainly miss him.

 

 

Dr. Kelly Velonia is an Advisory Board Member and a Web Writer for Polymer Chemistry. She joined the Department of Materials Science and Technology at the University of Crete in 2007. Research in her group focuses on the synthesis and applications of bioconjugates and biopolymers. You can follow Kelly on twitter @KellyVelonia


 

 

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Paper of the month: Using precision polymer chemistry for plastics traceability and governance

Johnson et al. propose that a synergy between chemical sciences and law research needs to be deployed to address the plastic pollution challenge through tracing technologies.

Among the major challenges faced by societies worldwide is the reduction of plastic pollution which has risen to be one of the largest environmental issues of the planet. A key barrier to improving plastic management is the inability to trace plastics along supply and value chains.

Addressing this issue, Johnson, Barner-Kowollik and colleagues with equal first authors Chambers and Holloway highlight how valorization of state-of-the-art chemistry could help eradicate plastic anonymity and propose that plastic management can become efficient once production of traceable plastics is implemented and incorporated into the legal frameworks for plastics governance.

To embed information into plastics and access it throughout its lifetime, both the inherent chemical composition of the macromolecules and chemical labelling can be exploited. Spectroscopic identification can fingerprint polymer chemistry but tracing a specific polymer to the producer would require introducing unique labels in the plastic material, with little information depth. Alternatively, information can be introduced through physically labelling the surface of a material. Both approaches carry information that can be readily affected by degradation over time. Chemical labeling with sequence-defined polymers on the other hand can be used to embed all necessary information within the material without being compromised by degradation. Barner-Kowollik and coworkers highlight state-of-the-art synthetic routes toward sequence-defined polymers, review the approaches to decode them and provide a set of criteria to be fulfilled by advanced read-out methodologies in order to successfully integrate such advanced plastics into recycling facilities.

Critical improvements to regulation policies need to be implemented to leverage on advanced plastics and especially sequence-defined polymers traceability. The authors propose that five key areas need to be addressed in law and policy: design or eco-design standards to reduce the environmental impacts of products and services along their entire lifecycle, consumer behavior to reduce consumption and encourage eco-friendlier choices, recycling systems to compensate the high cost of collecting, sorting and recycling materials, extended-producer responsibility schemes to respond to plastic waste, and combatting illegal waste streams that breache domestic or international laws.

This perspective is a critical overview on how chemistry, law and social sciences should advance, coordinate and collaborate in order to address the issue of plastic pollution in the most efficient manner.

 

Tips/comments directly from the authors:

  1. It’s been an amazing journey for our team of chemists to work with colleagues from the faculty of law. It took many conversations, lots of explanations and the willingness on both sides to learn about law and chemistry, respectively. The process was enormously rewarding for the entire team, who continues to work together on developing plastic tracers in a joint effort between law and chemistry.
  2. We highly recommend to all chemistry colleagues to research out into the humanities and social sciences for collaboration opportunities. These research fields have equal importance to the natural sciences and engineering, deliver enormous value and help chemists to put an entirely different perspective onto their own research. We believe the chemistry community should be at the absolute forefront of engaging with the social sciences and humanities.
  3. We are very proud of Polymer Chemistry (RSC) for opening the journal to law research that speaks to chemical problems and being a trailblazer for true transdisciplinary research.

 

Citation to the paper: Using precision polymer chemistry for plastics traceability and governance, Polym. Chem., 2022, 13, 6082-6090.

Link to the paper: https://pubs.rsc.org/en/content/articlelanding/2022/py/d2py01180h

 

Follow Christopher Barner-Kowollik on Twitter @BarnerKowollik and the QUT Centre for Materials Science @QUTmaterials to keep up to date with their latest research

 

Dr. Kelly Velonia is an Advisory Board Member and a Web Writer for Polymer Chemistry. She joined the Department of Materials Science and Technology at the University of Crete in 2007. Research in her group focuses on the synthesis and applications of bioconjugates and biopolymersYou can follow Kelly on twitter @KellyVelonia


 

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Paper of the month: Redox-triggerable firefly luciferin-bioinspired hydrogels as injectable and cell-encapsulating matrices

Jin et al. employ redox activated macromers to achieve precise control over the gelation onset and kinetics of a redox-triggerable, firefly luciferin-inspired hydrogel platform.

Stimuli-responsive hydrogels are porous crosslinked networks which have recently attracted tremendous interest thanks to their unique response to external stimuli allowing to tune their properties on demand. In particular, chemically-responsive hydrogels that can be actuated via mild redox reactions are quite promising for biomedical applications once biocompatible and non-cytotoxic. Despite the remarkable progress in the field, lack of precise triggering of the gelation onset and control over the rate of the gelation process of responsive hydrogels restricts a range of applications. In their current contribution, Paez and coworkers report on a novel firefly luciferin-inspired hydrogel platform endowed with redox-triggering ability and tunability of its mechanical and biological properties. To achieve this goal, protected macromers (PEG-Cys(SR)) which can be activated in the presence of a mild reductant were used as hydrogel polymeric precursors. This design allowed to in situ trigger gel formation and achieve a high degree of control. Importantly, the gelation onset and rate could be fine-tuned via altering the molecular characteristics of the precursors (e.g., structure of the protecting group, reductant type) and/or the environmental parameters of the deprotection reaction (e.g., pH, temperature). Specifically, gelation could be achieved in times spanning from seconds (CBT–Cys(SEt) / TCEP) to hours (CBT–Cys(StBu)/DTT) using precursors with good long-term stability upon storage in physiologically-relevant aqueous conditions. Furthermore, high stem cell viability was observed after 1–3 days of encapsulation in biofunctionalized CBT–Cys(SR) hydrogels. The authors anticipate that the precise control over the gelation onset and kinetics of this this redox-triggerable system, will facilitate its use for drug delivery and tissue engineering as well as inks for extrusion-based printing of soft constructs for regenerative medicine.

 

Tips/comments directly from the authors:

  •  We engineered macromers at the molecular level to achieve highly controlled gelation onset and kinetics. In the rheological characterization, it is recommended to prepare the hydrogel formulation by mixing polymer precursors solution and reductant solution in equal volume. This enables better mixing of the components and ensures good reproducibility of the rheological measurements. Two polymer precursor solutions can be mixed in advance (first half of the total volume) before adding the reductant (second half of the total volume) and loading to the rheometer.

 

  • We evaluated the cytocompatibility of the redox-triggerable hydrogels and found excellent cell viability after 1-3 days culture. Before doing 3D cell encapsulation, it is recommended to perform a preliminary experiment of gel preparation under same conditions but in the absence of cell suspension to estimate the gelation time. Cell suspension can be replaced by cell culture medium.

 

Citation to the paper: Redox-triggerable firefly luciferin-bioinspired hydrogels as injectable and cell-encapsulating matrices, Polym. Chem., 2022, 13, 5116-5126, DOI: 10.1039/D2PY00481J

Link to the paper:

https://pubs.rsc.org/en/content/articlehtml/2022/py/d2py00481j

 

The Paez laboratory at the University of Twente:

Twitter account: @PaezLab

ResearchGate account: https://www.researchgate.net/profile/Julieta-Paez

 

 

Dr. Kelly Velonia is an Advisory Board Member and a Web Writer for Polymer Chemistry. She joined the Department of Materials Science and Technology at the University of Crete in 2007. Research in her group focuses on the synthesis and applications of bioconjugates and biopolymersYou can follow Kelly on twitter @KellyVelonia


 

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Paper of the month: Microfluidic-supported synthesis of anisotropic polyvinyl methacrylate nanoparticles via interfacial agents

Visaveliya et al. combine microfluidics with bulk batch synthesis to fabricate complex (non-spherical) anisotropic polyvinyl methacrylate (PVMA) nanoparticles (NPs) in a single step.

Τhe properties of polymer nanoparticles are dictated by both structure-property and structure-function relationships however, the importance of particle shape is generally overlooked due to the inherent difficulty to synthesize anisotropic nanoparticles in a single step. Anisotropic colloids are currently produced via multi-step synthesis platforms restrict scaling-up and evaluating as an alternative to the well-established spherical colloidal particles.

To address this issue, Eisele and collaborators developed a single-step, microfluidic-supported synthesis for anisotropic polyvinyl methacrylate (PVMA) nanoparticles that takes advantage of the homogeneous conditions given by microfluidics for the initial emulsification process and of the inhomogeneous conditions provided by bulk batch synthesis for the thermal polymerization. Α monomer with two active polymerization sites (vinyl methacrylate) was used and the impact of interfacial agents including a molecular surfactant (sodium dodecyl sulfate, SDS), anionic polyelectrolytes (poly(sodium 4-styrene sulfonate), PSSS and poly(4-styrene sulfonic acid) ammonium salt, PSSA), a cationic polyelectrolyte (poly(diallyldimethylammonium chloride), PDADMAC), and the non-ionic polymer (polyvinylpyrrolidone,PVP) on the shape and size of the produced nanoparticles was systematically evaluated. A direct effect of the identity and the concentration on the shape of the produced nanoparticles was observed and led to a plethora of structures varying from isotropic spherical structures (SDS) to anisotropic elongated (PSSS, PSSA) and flower-like structures (low PVP concentrations) or irregularly shaped assemblies (PDADMAC, high PVP concentrations).

In summary, this study provides a general framework to guide investigations on colloidal polymerization towards predicting nanoparticle shapes below the critical 200 nm regime.

 

Microfluidic-supported synthesis of anisotropic polyvinyl methacrylate nanoparticles via interfacial agents, Polym. Chem., 2022,13, 4625-4633

Link to the paper: https://pubs.rsc.org/en/content/articlelanding/2022/py/d1py01729b

 

Dr. Kelly Velonia is an Advisory Board Member and a Web Writer for Polymer Chemistry. She joined the Department of Materials Science and Technology in 2007. Research in her group focuses on the synthesis and applications of bioconjugates and biopolymers

You can follow Kelly on twitter @KellyVelonia


 

 

 

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Paper of the month: Donor modification of thermally activated delayed fluorescence photosensitizers for organocatalyzed atom transfer radical polymerization

Polgar et al. use donor-modified thermally activated delayed fluorescence (TADF) emitters as photocatalysts for O-ATRP.

O-ATRP has emerged as an attractive alternative to conventional metal-catalyzed ATRP that uses organic compounds that catalyze polymerization under light irradiation instead of the well-studied metal catalysts. Specifically, O-ATRP using thermally activated delayed fluorescence (TADF) emitters as photocatalysts takes advantage of the unique ability of TADFs to interconvert singlet and triplet excited states and has been more recently implemented in diverse fields including organic electronics, photocatalysis, biological imaging, and chemical sensing. TADF emitters mostly contain a twisted donor–π–acceptor (D–π–A) motif which results in a prolonged excited state lifetime and facilitates singlet and triplet energy and electron transfer. Nevertheless, the coexistence of both electron donors and acceptors in photoredox catalysis results in unwanted excited state side reactivity that limits initiator efficiency and might also deactivate the catalyst.

To address this issue, Hudson and collaborators use donor-modified TADF emitters as photocatalysts for O-ATRP. More specifically, TADF photosensitizers based on 9,10-dihydro-9,9-dimethylacridine/2,4,6-triphenylpyrimidine conjugates exhibiting strong visible absorption, large excited state reduction potentials, and long-lived triplet excited states were employed to evaluate catalyst structure–activity relationships. The stability of the radical cation was found to be determining for controlled polymerization, however, significant differences were observed among donor-modified catalysts which were also related to variation in the rates of photoinduced electron transfer (PET). Time-resolved photoluminescence studies of the catalysts supported initiation by electron transfer from both singlet and triplet states while, the functionalized donors possessed the higher driving forces for PET. Through this study, the donor-modified TADF photocatalyst PymDMDMA -bearing a methoxyphenyl substituent- was identified to yield methacrylic polymers with Đ below 1.3 at low catalyst loadings (50 ppm) while also being able to catalyze the controlled synthesis of block copolymers in contrast to the unmodified TADF.

This study explores the ability to design more efficient catalysts by merely altering the types of donors, acceptors and their derivatives and proposes that more efficient catalysts can be designed through theoretical modeling.

Tips/comments directly from the authors:

  • ppm-levels of catalyst are sufficient for the synthesis of polymers with well-defined size, composition, and topology by O-ATRP, potentially obviating the need for post-polymerization purification.
  • Donor-acceptor fluorophores can exhibit thermally activated delayed fluorescence (TADF), a phenomenon that prolongs the excited state lifetime. The ability to control the lifetime and excited-state reduction potential of TADF emitters makes them versatile photocatalysts for O-ATRP, particularly at low catalyst loadings.
  • A donor-modification strategy was used in this study to mitigate deleterious excited-state side-reactivity associated with the electron-rich donors used in TADF. Rational design of modifying groups can not only enhance the photostability of these dyes, but also provide an extra dimension of control over the excited state reduction potentials and rates of electron transfer in O-ATRP.

 

Donor modification of thermally activated delayed fluorescence photosensitizers for organocatalyzed atom transfer radical polymerization, Polym. Chem., 2022, 13, 3892-3903. 

 

Link to the paper: https://pubs.rsc.org/en/content/articlelanding/2022/py/d2py00470d

 

Dr. Kelly Velonia is an Advisory Board Member and a Web Writer for Polymer Chemistry. She joined the Department of Materials Science and Technology in 2007. Research in her group focuses on the synthesis and applications of bioconjugates and biopolymers.


 

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Paper of the month: Supramolecularly cross-linked nanoassemblies of self-immolative polyurethane from recycled plastic waste: high encapsulation stability and the triggered release of guest molecules

Santra et al. use recycled plastic-waste derived monomers to synthesize a redox-responsive self-immolative amphiphilic polyurethane nanoassembly.

 

 

Polymeric nanoparticles have undeniably found numerous applications in fields ranging from medicine to nanoelectronics. Despite the significant progress in the area, there is an increasing demand in chemotherapeutics to construct polymeric nanoassemblies able to encapsulate and deliver cargo on-demand. Most polymeric nanocarriers suffer from uncontrolled disassembly leading to premature, non-specific guest release while often; guests need to be covalently entrapped to achieve high encapsulation stability.

To address these issues, Molla and collaborators developed a strategy that allows upcycling plastic waste to synthesize a redox-responsive, self-immolative amphiphilic polyurethane that assembles into robust, tightly packed nanoassemblies with high encapsulation efficiency and stability. More specifically the upcycled-plastic nanocontainers were equipped with aromatic moieties enhancing their stability, disulfide bonds offering redox response and tertiary amines inducing charge tunability. Triethylene glycol monomethyl ether units were periodically incorporated on the polymer to enhance hydrophilic interactions with water. Computational studies supported that the high encapsulation stability observed in these polyurethane nanocarriers stems from supramolecular cross-linking via π–π stacking and H-bonding interactions. Notably, in a redox environment 70 % of guest release was obtained from the self-immolative polyurethane nanocarriers while significantly reduced release was observed in polymers lacking the disulfide linker and polymers lacking the aromatic component.  The high encapsulation stability was supported by the low leakage coefficient measured in FRET experiments. Pleasingly, zeta potential measurements revealed the generation of nanoassemblies with positive surface charge at a tumor extracellular matrix relevant pH was attributed to the tertiary amine component.

In summary, a plastic waste derived monomer was used as a basis to create robust self-immolative polyurethane nanocarriers with promising biomaterial characteristics such as biocompatibility, triggered release, and environment-specific charge modulation.

Mijanur Rahaman Molla et al., Supramolecularly cross-linked nanoassemblies of self-immolative polyurethane from recycled plastic waste: high encapsulation stability and the triggered release of guest molecules, Polym. Chem., 2022, 13, 3294-3303.

Link to the paper: https://pubs.rsc.org/en/content/articlelanding/2022/PY/D2PY00341D

 

 

 

Dr. Kelly Velonia is an Advisory Board Member and a Web Writer for Polymer Chemistry. She joined the Department of Materials Science and Technology in 2007. Research in her group focuses on the synthesis and applications of bioconjugates and biopolymers.

You can follow Kelly on twitter @KellyVelonia


 

 

 

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Paper of the month: ‘Design rules for performing water-sensitive ring-opening polymerizations in an aqueous dispersion’

Harrier et al. highlight the encapsulation methodology as a readily available, efficient methodology to perform ROPs in aqueous dispersions.

 

Ring opening polymerizations (ROP) are widely used to synthesize a variety of biodegradable polymers typically under the strict limitations requiring anhydrous media and inert atmosphere (usually dictating the use of complex setups such as Schlenk lines or glove boxes). These practical limitations limit the polymeric material accessible by ROP.
To address this limitation, Guironnet and collaborators implemented a droplet microfluidic encapsulation strategy and systematically investigated both the process and the formulation parameters that govern the stability of the formed micro-droplets. The identification of these parameters together with the addition of amphiphilic block copolymers (PEG-PVL, PEG-PCL, and Pluronic) and a hydrophobe (hexadecane) allowed to control the viscosity, surface tension, and hydrophobicity of the formed droplets. As a result, the conditions in which the ROP catalyst was efficiently shielded in the aqueous dispersion could be identified and used to achieve higher monomer conversion and higher molecular weight polymers in the polymerization of valerolactone and caprolactone. By changing the amphiphilic block copolymer composition, ROP reaction time could also be further improved. To highlight the strength of this approach, these design rules were also used to tune the viscosity and surface tension of the droplets during ROP of propylene oxide catalyzed by an organic Lewis-Pair catalyst system (i.e. a phosphazene base and triethyl borane), leading to the synthesis of polyether particles dispersed in water.

 

In summary this study highlights the power and versatility of the encapsulation methodology applied with an off-the-shelf droplet-based microfluidic device and establish the fundamental guiding principles to encapsulate water-sensitive polymerization catalysts to efficiently synthesize spherical polymer particles dispersed in water.

 

Design rules for performing water-sensitive ring-opening polymerizations in an aqueous dispersion, Polym. Chem., 2022, 13, 2459-2468

Link to the paper: https://pubs.rsc.org/en/content/articlelanding/2022/py/d2py00069e#cit11

 

Dr. Kelly Velonia is an Advisory Board Member and a Web Writer for Polymer Chemistry. She joined the Department of Materials Science and Technology in 2007. Research in her group focuses on the synthesis and applications of bioconjugates and biopolymers.


 

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Paper of the month: Reconsidering terms for mechanisms of polymer growth: the “step-growth” and “chain-growth” dilemma

An international group of polymer scientists from the International Union of Pure and Applied Chemistry (IUPAC) Subcommittee on Polymer Terminology (SPT) convey concerns with the basic terms typically used for classifying methods of polymer synthesis and initiate a dialogue with the broader polymer community to resolve terminology shortcomings.

In 1994 the IUPAC SPT highlighted long-standing problems with the widely used terms “step-growth polymerization” and “chain-growth polymerization,” which describe two discrete mechanisms of polymer growth, and depreciated their use since they do not describe the fundamental differences in the growth of polymers by these methods and are often confusing. To address this, the 1994 SPT members recommended the terms polycondensation and polyaddition for the two variants of “step-growth polymerization”, and similarly chain polymerization and condensative chain polymerization for the two variants of “chain-growth polymerization”. However, these terms have not been widely adopted by the community, and have also created confusion.

In this contribution, current IUPAC SPT members provide detailed descriptions of these two processes and outline concerns associated with the terms “step-growth,” “chain-growth,” and related terms. By discussing in detail the historical development of these terms and analyzing their use in current textbooks, the authors underline the lack of consensus in the terminology used within the polymer community. Interestingly, they demonstrate how the similarity of these terms leads to further confusion when translating into languages other than English. Finally, examples of polymerizations that cannot be classified under the umbrella of the existing definitions and have no designated terminology are discussed.

In 2019, IUPAC recognized the need to resolve these polymer terminology shortcomings and approved a project aimed to propose new terminologies. The authors, as members of the IUPAC SPT task group studying this issue, aim to clarify the naming of polymerisation processes and invite all members of the community to contribute by emailing to polymer.terminology@iupac.org.

Tips/comments directly from the authors:

  • We, the subcommittee of polymer nomenclature (SPT), want to raise attention to a long-standing dilemma in the terms that many of us use every day: “step-growth” and “chain-growth” polymerization.
  • A number of terms have been used over the past century to describe these two fundamental mechanisms of polymer growth, and many prominent polymer chemists have noted their shortcomings in textbooks.
  • We detail here the history of the terms, current usage in textbooks, and our specific concerns.
  • In particular, we invite feedback from the broader polymer community, including from students, lecturers, researchers, and anyone who uses polymer science regularly.

 

Reconsidering terms for mechanisms of polymer growth: the “step-growth” and “chain-growth” dilemma, Polym. Chem., 2022, 13, 2262-2270.

Link to the paper: https://pubs.rsc.org/en/content/articlelanding/2022/py/d2py00086e

You can follow the authors on twitter: @IUPACPolymer

 

Dr. Kelly Velonia is an Advisory Board Member and a Web Writer for Polymer Chemistry. She joined the Department of Materials Science and Technology in 2007. Research in her group focuses on the synthesis and applications of bioconjugates and biopolymers.

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Paper of the month: The difference between photo-iniferter and conventional RAFT polymerization: high livingness enables the straightforward synthesis of multiblock copolymers

Lehnen et al. highlight the role of reversible deactivation as a key difference between photo-iniferter and conventional RAFT polymerization.

The use of light has become increasingly widespread in diverse polymerization approaches including reversible-addition fragmentation chain-transfer (RAFT) strategies. Among these, the photo-iniferter (PI)-RAFT polymerization in which light directly activates the chain transfer agent (CTA), has been shown to overcome several of the restrictions of conventional RAFT resulting in increased chain end fidelity. In this context, reversible deactivation is accepted to determine the fate of the growing radical via pathways that need to be understood to offer the means to further push the limits of PI-RAFT polymerization.  

To address this, Hartlieb and collaborators studied the PI-RAFT using an acrylamide (N-acryloyl morpholine) and a xanthate ((2-((ethoxycarbonothioyl)thio)propionic acid)). This monomer-CTA pair combination was selected on the basis of the low chain transfer capabilities (Ctr < 1) expected to result in high dispersities (>1.5). When targeting different degrees of polymerization (DP), the control over the molecular weight distribution was not found to significantly increase. However, control could be achieved through slow monomer addition that results in increasing the numbers of activation-deactivation events per monomer addition. Importantly, the high livingness associated with PI-RAFT proved to be invaluable in chain extension experiments since it was found to enable the straightforward, easy and rapid synthesis of very high molecular weight multiblock copolymers with up to 20 blocks and a high number of repeating units per block (DP = 25-100) with impressive precision.  

In summary this study highlights the role of reversible deactivation and employs the high livingness of PI-RAFT to demonstrate its enormous potential for the synthesis of polymeric materials and more specifically segmented macromolecules.

Tips/comments directly from the authors:

  • We want to emphasize how fast and easy polymerization reactions can be performed using this technique as the shown xanthate is an extremely powerful iniferter
  • The shown multiblocks were produced in a very straight forward way; no rigorously clean or inert conditions or specialized equipment.
  • The photo-iniferter process is older than RAFT polymerization but its full potential isn’t used yet.  

 

The difference between photo-iniferter and conventional RAFT polymerization: high livingness enables the straightforward synthesis of multiblock copolymers, Polym. Chem., 2022, 13, 1537-1546

Link to the paper: https://pubs.rsc.org/en/content/articlelanding/2022/py/d1py01530c

Link to Dr Matthias Hartlieb’s group website: https://www.uni-potsdam.de/polybio

You can follow Dr Matthias Hartlieb on Twitter: @PolyBioPotsdam

 

Dr. Kelly Velonia is an Advisory Board Member and a Web Writer for Polymer Chemistry. She joined the Department of Materials Science and Technology in 2007. Research in her group focuses on the synthesis and applications of bioconjugates and biopolymers.

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Paper of the month: Iron-containing poly(ionic liquid) membranes: a heterogeneous Fenton reaction and enhanced anti-fouling ability

Guan et al. develop iron-containing poly(ionic liquid) (Fe-PIL) membranes with anti-fouling properties enhanced by a heterogeneous Fenton reaction.

The life span of membranes used in various separation technologies is often limited by fouling causing decreased performance and large economic costs. Recently, poly(ionic liquid)s (PILs) have been employed to prepare membranes with a large range of applications due to their unique material properties including excellent stability, processability and flexibility. Although PIL membranes are less prone to fouling and easier to clean due to their charged nature, the problem of irreversible pollutant deposition can limit their efficiency.  

To address this, Zhang and collaborators developed iron-containing PIL (Fe-PIL) membranes and used them as catalysts for heterogenous Fenton reaction. Poly(4-vinylpyridine)-b-polysulfone-b-poly(4-vinylpyridine) (PSF-b-P4VP) blend membranes were synthesized via Cu(0)-RDRP. The pore size and hydrophilicity of the membranes fabricated via NIPS, were found to depend on the block ratio of the polymer. A quaternization reaction followed by coordination with Fe(II) bromide was employed to generate the Fe-PILs on the surface of the polysulfone blends.  The membranes were shown to possess low surface roughness, increased hydrophilicity, anti-fouling properties and scalability. The dispersibility of the catalyst and the catalytic efficiency in heterogeneous Fenton reactions were shown to be excellent in a broad pH range from acidic to neutral and basic conditions. More importantly, the Fe-PIL membranes exhibited superior synergistic performance with filtration in the dynamic heterogeneous Fenton reaction and excellent reusability as they could be maintained well after five cycles.

In summary this study combines PIL membrane technology with dynamic heterogeneous catalysis (Fenton reaction) to create reusable PILs that address the issue of membrane fouling.

 

Iron-containing poly(ionic liquid) membranes: a heterogeneous Fenton reaction and enhanced anti-fouling ability, Polym. Chem., 2022,13, 130-138

Link to the paper: https://pubs.rsc.org/en/content/articlelanding/2022/py/d1py01345a

 

Dr. Kelly Velonia is an Advisory Board Member and a Web Writer for Polymer Chemistry. She joined the Department of Materials Science and Technology in 2007. Research in her group focuses on the synthesis and applications of bioconjugates and biopolymers.

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