Paper of the month: Copper catalyzed synthesis of conjugated copolymers using direct arylation polymerization

Pankow et al. report the first copper catalyzed synthesis of conjugated polymers via direct arylation polymerization.

C8PY00913A

Direct arylation polymerization is a useful methodology that allows for the preparation of conjugated polymers. One of the great advantages of this technique is that it eliminates the use of toxic and pyrophoric reagents typically utilized to prepare monomers for other polymerization methods (e.g. Stille, Suzuki, etc.). Importantly, the technique allows the preparation of polymers with undetectable levels of homo-coupling or branching defects leading to the defect free synthesis of a wide range of conjugated polymer architectures such as homopolymers, donor-acceptors copolymers and porous polymers. However, the vast majority of direct arylation polymerization methodologies rely on the use of noble metals such as palladium (Pd), which is a costly, low abundant, relatively toxic, and unsustainable metal. To circumvent this, Thompson and co-workers were inspired by the small molecule copper catalyzed aryl-aryl cross-coupling for various iodinated arenes and electron-deficient heterocycles. To transition from small molecules to conjugated polymers, the group judiciously optimized the reaction conditions including the concentration, the nature of the solvent, the ligand, the temperature and the base employed. Conjugated polymers were then prepared in very high yields (up to 97%) with Mn of up to 10 kDa. NMR spectroscopy was used to characterize the recovered polymer products and confirmed the absence (or minimization) of undesired couplings. This report is the first example of perfectly alternating donor-acceptor conjugated polymers using copper catalyzed direct arylation polymerization thus offering an initial step towards the replacement of toxic metals like Pd. Future work will hope to address milder reaction conditions, lower catalyst loading, and a broader scope.

Tips/comments directly from the authors:  

1. Fresh CuI is recommended. It is recommended to acquire a fresh bottle or a freshly purified stock of CuI and store it under inert gas in a freezer.

2. The strict exclusion of air and moisture is advisable, and so care should be taken to thoroughly sparge the reaction vessel with inert gas before and after the addition of reagents.

3. The selection of base is critical for the polymerization, and the base should be finely ground and dried using a vacuum oven before use. The base can be stored in a desiccator after drying, but should be dispensed quickly to limit contact with moisture

4. After addition of the CuI, the copper-phenanthroline catalyst appears to form instantly. However, stirring at room temperature for a several minutes before heating may help ensure complete coordination of the phenanthroline to copper

 

This article is FREE to read and download until 21st September 2018

 

Copper catalyzed synthesis of conjugated copolymers using direct arylation polymerization  Polym. Chem., 2018, 9, 4120-4124, DOI: 10.1039/C8PY00913A

 

About the Web Writer

AthinaDr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently a Global Marie Curie Fellow working alongside Professor Craig Hawker at the University of California, Santa Barbara (UCSB). In January 2019, she will join the ETH Materials Department as an Assistant Professor to establish her independent group.

 

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Paper of the month: Graft-modified cellulose nanocrystals as CO2-switchable Pickering emulsifiers

Glasing et al. report the use of graft-modified cellulose nanocrystals as stimuli-responsive Pickering stabilisers.

Renewable bio-based colloidal particles in emulsion-based products can be highly desirable as they can replace synthetic, small molecule surfactants. Pickering stabilisers or emulsifiers are solid particles that can be used as insoluble surfactants to stabilise emulsions. For such application, cellulose appears to be a good renewable biopolymer candidate owing to its abundance, sustainability and nontoxicity. Cellulose nanocrystals (CNCs) in particular exhibit little to no cytotoxicity and can thus represent a more sustainable and greener alternative to conventional surfactants. Cunningham and co-workers introduced new properties to cellulose nanocrystals by exploiting their graft modification with switchable poly((diethylamino)ethyl methacrylate) (PDEAMEA) and poly((dimethylamino)ethyl methacrylamide) (DMAPMAm). In this work, the use of well-defined graft modified CNCs with small amounts of grafted CO2-switchable PDMAPMAm and PDEAEMA as stimuli-responsive Pickering stabilisers for the reversible emulsification/demulsification of oil and water is thoroughly investigated. The obtained CNCs contained less than 25 wt% of grafted synthetic polymer and impressively resulted in stable Pickering emulsions with a shelf life up to one month without desulfating the CNCs or the introduction of ionic strength to the system. N2 and CO2 were used as environmentally benign triggers to stabilise the emulsions under N2 and break the emulsions under CO2. Importantly, the emulsification and demulsification were reversible and repeatable and the CNC-based Pickering emulsifier could be easily recovered, thus enabling it to be a potential candidate for oil harvesting applications. Such Pickering emulsifiers are not expected to have significant ecotoxicity compared to other conventional surfactants due to the CNCs and the polymer chains being too large in molecular weight to be bioavailable. The authors conclude that a higher fraction of hydrophobic copolymer in the grafts may further improve their system and enhance the adsorption of graft-modified CNC to the oil droplets and increase the emulsion stability.

C8PY00417J

 

Tips/comments directly from the authors:  

  1. It can be difficult to ‘switch off’ PDMAPMAm at room temperature using N2, meaning deprotonating the tertiary amine groups in water. To ensure sufficient wettability of CNC-g-P(DMAPMAm-co-S) with the oil phase when homogenizing, i.e. a high enough degree of deprotonation, the temperature of the CNC dispersion has to be slightly increased first (~40°C, although this depends by the chain length) before adding the oil phase and preparing the emulsion.

  1. For the synthesis of the materials (Polym. Chem., 2017, 8, 6000–6012), it is important that premade polymers are living and purified from unreacted monomer, BlocBuilder and dead polymer chains. Any nitrogen-containing impurity will artificially increase the nitrogen content obtained from elemental analysis and thus falsify the final value for the amount of grafted polymer, graft density and amino groups per 1 g of CNC. It is thus advisable to repeat the purification/elemental analysis until a constant N value is obtained.

  1. SEM analysis of the grafted CNC (ESI) can be very difficult unless the appropriate conditions are chosen. CNC needs to be coated with conductive material as the polymer and CNC are both non-conductive. The materials were coated with 3nm osmium particles using a standard 30 micron aperture probe at 300V. The current corresponded to 275 pA at 10kV. Low current and low voltage conditions need to be chosen in order to visualize the structures.

 

This paper is FREE to read and download until the 31st August!

 

Graft-modified cellulose nanocrystals as CO2-switchable Pickering emulsifiers, Polym. Chem., 2018, 9, 3864-3872

 

About the web writer
AthinaDr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently a Global Marie Curie Fellow working alongside Professor Craig Hawker at the University of California, Santa Barbara (UCSB). Please visit this link for more information.

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Paper of the month: Enzyme-driven biodegradable nanomotor based on tubular-shaped polymeric vesicles

Toebes et al. report an enzyme-driven biodegradable nanomotor that moves in the presence of fuel

The potential of nanomachines to mimic biological systems that can continuously move in and between cells to perform a function has attracted significant attention over the past decades. Although the autonomous movement, speed and functionality of various artificial nanomotors has improved over the years, it is interesting to note that the vast majority of them are based on catalytically active metals and harsh metal surfaces while requiring toxic fuel for propulsion. Wilson and co-workers are the first to report a biodegradable nanomotor which can autonomously move in the presence of fuel while carrying a load. To achieve this, Wilson’s group created poly(ethylene glycol)-b-poly(D,L-lactide) (PEG-PDLLA) polymerosomes with 5% wt% functional azide handles by employing ring opening polymerization. The spherical polymerosomes were then transformed to nanotubes by inducing osmotic pressure. The azide handles presented in periphery of the nanotubes were converted into COOH groups using strain-promoted alkyne-azide cycloaddition. Finally, catalase was coupled to the nanotubes surface via EDC coupling. Importantly, the catalytic conversion of H2O2 by the enzyme provided adequate propulsion to move the nanotubes forward. In addition, both hydrophobic and hydrophilic drugs could be simultaneously loaded in the tubes. Given the advantageous characteristics of tubular-shaped polymersomes, such as high-aspect-ratio and higher loading capacity, such materials can be potentially used as excellent nanocarriers for drug delivery.

Tips/comments directly from the authors:

  1. For the synthesis of PEG-PDLLA, keep the ratio of catalyst to initiator bellow 0.5 equivalents to obtain polymers with low PDI. Furthermore, the reaction is oxygen and water sensitive and should thus be carried out in inert atmosphere.
  2. The formation of polymersomes requires stable conditions, as small changes can affect the morphology and the polydispersity of the vesicles. Pre-cooled water is used for the shape transformation by dialysis while the dialysis is carried out in in the fridge at 4°C.
  3. Centrifugation of the nanotubes for functionalization reaction should not exceed 5000 rpm and should not be longer than 10 min to prevent aggregation and clogging of the spin filter and breakage of the tubes.
  4. It is recommended to use low concentration of nanomotors (< 109 particles/ml) when measuring their movement with the Nanosight LM10, as high oxygen production can lead to drift of the sample (dilute such that single motors are visualized).

 

Enzyme-driven biodegradable nanomotor based on tubular-shaped polymeric vesicles, Polym. Chem., 2018, 9, 3190-3194, DOI: 10.1039/C8PY00559A

 

This paper is free to read and download until 6 August!

 

About the webwriter

AthinaDr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently a Global Marie Curie Fellow working alongside Professor Craig Hawker at the University of California, Santa Barbara (UCSB). Please, visit http://hawkergroup.mrl.ucsb.edu/members/athina-anastasaki for more information.

 

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Future of Polyolefins 2019 Summit

 

Conference details:

Name:                          Future of Polyolefins 2019

Place and dates:          16th & 17th January 2019, Antwerp, Belgium

Telephone:                 +44 (0) 20 3 141 0606
E-mail:                         mahsan@acieu.net
Contact Name:             Mohammad Ahsan

Conference Fee:          £1,595 + vat (if applicable)

15% discount code:     CFPe7MKT

Link: http://www.wplgroup.com/aci/event/polyolefins-conference/

Agenda Link: https://www.wplgroup.com/aci/cfpe7-agenda_mkt/

With the new European directive on plastic waste & circular economy targets, and the investments wave on new production plants, the polyolefins industry is facing changes in the near future. It will not only need to adapt to them, but also work as a whole, with all actors from the value chain involved, to live up to expectations and thrive.

All these changes, and other pressing matters in the industry, will be addressed at ACI’s 7th edition of the Future of Polyolefins Summit, taking place in Antwerp, Belgium, on the 16th & 17th January 2019.

Over the two days, the participants will discuss the different factors influencing the polyolefins industry, and of course the impact of the Circular Economy.

The conference will also discuss how to maintain performance whilst aiming for recyclability & degradability of materials; lightweighting; design & application for polyolefin based packaging; converting technologies; as well as recycling & reusing polyolefins.

This new edition will bring together senior executives from petrochemical companies, plastic converters, technology providers, chemical intermediate suppliers, researchers, as well as other influential stakeholders from the value chain.

Join us in Antwerp for two days of exchanging perspectives, learning and excellent networking opportunities with your peers.
 

Key Topics Include

  • Factors Influencing Pricing on Feedstock & Polyolefins
  • The Circular Economy Impact
  • Polyolefins Market: Current Outlook & Predictions
  • Polyolefin Production: Performance Retention & Recyclability
  • Converting Technologies
  • Maximising Degradability of Polyolefins
  • Managing the ever increasing Amount of Plastic in a Sustainable Way
  • Optimising Lightweighting
  • Design & Application in Polyolefins Packaging Production
  • Recycling & Reusing Polyolefin based Products

For more information & registration, contact

Mohammad Ahsan
on +44 (0) 20 3 141 0606
or
mahsan@acieu.net

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Paper of the month: Discrete oligodimethylsiloxane–oligomethylene di- and triblock co-oligomers: synthesis, self-assembly and molecular organisation

Genabeek et al. explore the self-assembly behaviour and impact of crystallinity in uniform block co-oligomers comprised of oligodimethylsiloxane and oligomethylene blocks.

A long lasting challenge in polymer chemistry is to design new block copolymer combinations that allow a decrease of feature sizes and to propose models that describe the molecular organization within the microphase-segregated structures. A recently developed way to achieve this is through a new class of low molecular weight, discrete block copolymers (dispersity of 1). In this contribution, Meijer, Palmans and co-workers designed and synthesized a new class of discrete-length block co-oligomers comprising of oligodimethylsiloxane (oDMS) and oligomethylene (oM). By employing differential scanning calorimetry and small-angle X-ray scattering it was shown that all block co-oligomers exhibit microphase separation into well-ordered lamellar morphologies, driven by the crystallization of the oM blocks. Pre-melting order-order transitions were found for a number of block co-oligomers, resulting in an alternation of the oM crystal packing and in changes of the overall microphase-segregated structure. Importantly, uniform microphase-segregated domains were discovered and among them, one of the smallest domain spacing ever reported (dLAM=5.8 nm), highlighting that the combination of small feature sizes and structural perfection is unique for this type of materials. The authors also elegantly proposed models to describe the molecular organisation within the microphase-segregated structures. This was achieved by evaluating the changes in the lamellar thickness upon alternation of the block co-oligomer architecture. Such type of materials are of critical importance to fundamentally understand the molecular structure and the self-assembly of polymeric materials.

DOI: 10.1039/c8py00355f

 

Tips/comments directly from the authors: 

  1. The large difference between the affinities of oDMS hydride and oDMS with a silanol endgroup toward silica remains a useful tool to separate traces of starting material from the product during the oDMS synthesis. Secondly, the large difference in solubility of short (< 11 repeat units) and long (> 11 repeat units) siloxane oligomers was used frequently to purify the materials.
  1. During the synthesis of the oM blocks, we routinely used a two-stage protection and deprotection protocol of the cyclic ethylene acetal via a dialkyl acetal intermediate.
    Thus, stages involving the free aldehyde could be conducted at room temperature, minimizing the risk of degradation of the aldehyde functionality, which otherwise might led to inseparable side-products (e.g., the result of unwanted condensation reactions).
  1. To ensure good solubility of the oM blocks, a molecular design containing at least one double bond per 30 carbon atoms is advised.
  1. Crystallisation kinetics in oDMS–oM and related systems generally are very fast. In a select number of cases we clearly noticed the benefits of very slow (< 0.1 °C min-1) cooling from the melt in order to decrease the number of defects/increase the size of the crystalline domains in the phase-segregated systems.

 

This article is free to read and download until 26 June

 

Discrete oligodimethylsiloxane–oligomethylene di- and triblock co-oligomers: synthesis, self-assembly and molecular organisation, Polym. Chem., 2018, 9, 2746-2758, DOI: 10.1039/c8py00355f

 

 

About the webwriter 

Dr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is Athinacurrently a Global Marie Curie Fellow working alongside Professor Craig Hawker at the University of California, Santa Barbara (UCSB). Please, visit this link for more information.

 

 

 

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Polymer Chemistry welcomes new Associate Editors Tanja Junkers and Jeremiah Johnson

We are delighted to welcome Professor Tanja Junkers (Monash University) and Professor Jeremiah A. Johnson (MIT) as Associate Editors for Polymer Chemistry!

 

Tanja JunkersProfessor Tanja Junkers studied chemistry and graduated with a PhD in physical chemistry from Göttingen University. In January 2018 she became full professor at Monash University in Melbourne, she remains guest professor at Hasselt University and her group is currently active at both locations.

Her main research interests are precision polymer synthesis, use of continuous flow chemistry approaches, light-induced chemistries, polymer surface modification and investigations on kinetics and mechanisms of radical reactions. To find out more about her research read some of her recent publications below!

Visible light-induced iniferter polymerization of methacrylates enhanced by continuous flow
Maarten Rubens,  Phanumat Latsrisaeng  and  Tanja Junkers
Polym. Chem., 2017,8, 6496-6505

RAFT multiblock reactor telescoping: from monomers to tetrablock copolymers in a continuous multistage reactor cascade
Evelien Baeten,  Joris J. Haven  and  Tanja Junkers
Polym. Chem., 2017,8, 3815-3824

 

 

Jeremiah Johnson
Professor Jeremiah Johnson is now an Associate Professor in the Department of Chemistry at MIT. He was previously an Editorial Board member for Polymer Chemistry.

His research focuses on researching molecular design in three primary areas: nano-scale materials synthesis, macro-scale materials synthesis, and development of new chemical methods for modifying interfaces between bulk and nanoscale objects (surface chemistry). The tools of traditional organic and organometallic synthesis, synthetic polymer chemistry, photochemistry, surface science, and biopolymer engineering are combined to realize the design of target materials. To find out more about his research read some of his publications below!

Improving photo-controlled living radical polymerization from trithiocarbonates through the use of continuous-flow techniques
Mao Chen  and  Jeremiah A. Johnson
Chem. Commun., 2015,51, 6742-6745

Tailoring the structure of polymer networks with iniferter-mediated photo-growth
Awaneesh Singh,  Olga Kuksenok,  Jeremiah A. Johnson  and  Anna C. Balazs
Polym. Chem., 2016,7, 2955-2964

 

As Polymer Chemistry Associate Editors, Tanja and Jeremiah will be handling submissions to the journal. Why not submit your next paper to their Editorial Office?

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Paper of the month: Luminescent color tuning with polymer films composed of boron diiminate conjugated copolymers by changing the connection points to comonomers

Yamaguchi et al. report the first example that allows to tune the luminescence properties with aggregation-induced emission-active conjugated polymers without changing the chemical components.

The development of “element-block polymers” (defined as a minimum functional unit composed of heteroatoms) and the exploration of controlled methods for their electronic properties is crucial to design new tactics for advanced optical materials. Chujo, Tanaka and co-workers significantly contributed to this direction by developing a new concept for controlling the solid-state luminescence properties of polymers without changing the chemical components. This was achieved by synthesizing a series of alternative copolymers composed of boron diiminate with variable connection points to the comonomer units. The optical measurements revealed that the polymers possessed aggregation-induced emission (AIE) properties originating from boron diiminate. Importantly, the emission colour was varied from green to orange by altering the connection points in the film samples. Careful mechanistic studies suggested that the electron-donating and accepting abilities of the boron diiminate unit can be switched by selecting the connection points. As a result, the chain transfer character in the emission properties of the polymers was changed. Further theoretical investigations proposed that boron diiminate acts as a strong electron-acceptor in the excited state when the comonomers were connected to either one or both of the phenyl groups on the nitrogen atoms. On the contrary, when the comonomers were linked at the phenyl groups on the carbon atoms, a much weaker electron-donating property was induced. These findings pave the way for the design of advanced polymeric materials with precision function tunability without changing the chemical components.

Luminescent color tuning with polymer films composed of boron diiminate conjugated copolymers by changing the connection points to comonomers

 

Tips/comments directly from the authors:  

  1. Conventional conjugated polymers can show emission only in solution, meanwhile these polymers can present intense emission even in the film. Solid-state luminescent properties were originated from AIE ability of the boron complex.
  2. Usually, drastic changes in chemical structures are essential for colour regulation of conjugated polymers. In this boron complex, originating from significant localization of highest occupied molecular orbitals in the boron complex, optical properties can be readily modulated by altering connecting points. Therefore, various types of luminescent materials can be obtained with the same chemical components.
  3. The monomers and polymers can be obtained through the several synthetic steps without special techniques. The intermediates and products showed high stability under ambient conditions. The purification for the polymers was simply performed with re-precipitation, and pure materials having good film-formability were successfully obtained.

Luminescent color tuning with polymer films composed of boron diiminate conjugated copolymers by changing the connection points to comonomers, Polym. Chem., 2018, 9, 1942-1946, DOI: 10.1039/C8PY00283E

This paper is free to read until 30 May

About the web writer

AthinaDr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently a Global Marie Curie Fellow working alongside Professor Craig Hawker at the University of California, Santa Barbara (UCSB). Please, visit this link for more information.

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Paper of the month: Cu(0)-RDRP of acrylates based on p-type organic semiconductors

Sauvé et al. report the synthesis of p-type organic semiconductors via Cu(0)-RDRP

Cu(0)-RDRP of acrylates based on p-type organic semiconductors

p-type organic semiconductor polymers can find a use in organic electronics, including organic light-emitting diodes (OLEDs), solar cells, and organic thin-film transistors. These materials offer unique characteristics over inorganic semiconductors such as flexibility and light weight. To maximize their potential, reversible deactivation radical polymerization (RDRP) methodologies are often used with traditional atom transfer radical polymerization and reversible addition/fragmentation chain transfer polymerization dominating in this area. To this end, Hudson and co-workers exploited Cu(0)-RDRP as an effective method for preparing functional acrylate-based polymers with p-type organic semiconductors as side chains. Impressively, all polymers were obtained in high yields (~ 90 %) with low dispersity and high end group functionality while the polymerizations displayed first order kinetics. Both low and high molecular weight polymers could be prepared in a facile manner and the choice of solvent seemed to be crucial to maintain good control over the molecular weight distributions. It should be highlighted that the described technique represents the most simple, low-cost and efficient way to synthesize these materials with improved end group functionality and yields over previous methods. The optical, electrochemical and thermal properties of each of these p-type materials were also carefully investigated with cyclic voltammetry and thermogravimetric analysis revealing the potential for further studies in optoelectronic applications. The Hudson group will now focus on the synthesis of more complex materials, including multiblock copolymers, and subsequently utilize them for optoelectronics.

Tips/comments directly from the authors:  

  1. The Cu(0) wire should be prepared immediately before use for best activity, as substantial reductions in polymerization rate are observed when the wire is cleaned and stored.
  2. Reducing the relative amount of Cu(0) wire when attempting the synthesis of high molecular weight polymers reduces the polymerization rate, but provides improved control over the polydispersity of the products.
  3. For long-term storage all monomers should be stored in the freezer (–10 ºC), but are stable on the bench top under air for 1-2 days.
  4. Yields of pure monomers 5a-c are substantially improved when purification is conducted quickly (<5 min) on a short silica column to minimize decomposition; the same urgency is not required for 5d.

Cu(0)-RDRP of acrylates based on p-type organic semiconductors, Polym. Chem., 2018, 9, 1397-1403, DOI: 10.1039/C8PY00295A

This article is free to read until 30 April

About the webwriter

AthinaDr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently a Global Marie Curie Fellow working alongside Professor Craig Hawker at the University of California, Santa Barbara (UCSB). Please, visit this site for more information.

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Outstanding Reviewers for Polymer Chemistry in 2017

We would like to highlight the Outstanding Reviewers for Polymer Chemistry in 2017, as selected by the editorial team, for their significant contribution to the journal. The reviewers have been chosen based on the number, timeliness and quality of the reports completed over the last 12 months.

We would like to say a big thank you to those individuals listed here as well as to all of the reviewers that have supported the journal. Each Outstanding Reviewer will receive a certificate to give recognition for their significant contribution.

Dr Athina Anastasaki University of California, Santa Barbara
Dr C. Remzi Becer, Queen Mary University of London, ORCID: 0000-0003-0968-6662
Dr Cyrille Boyer, University of New South Wales, ORCID: 0000-0002-4564-4702
Professor Yuanli Cai, Soochow University, ORCID: 0000-0001-5473-485X 
Professor Dr Gaojian Chen, Soochow University, ORCID: 0000-0002-5877-3159
Dr Sophie M Guillaume, CNRS – Université de Rennes, ORCID: 0000-0003-2917-8657 
Dr Dominik Konkolewicz, Miami University, ORCID: 0000-0002-3828-5481 
Dr Elango Kumarasamy, Columbia University
Dr Zachariah Page, University of California, Santa Barbara, ORCID: 0000-0002-1013-5422
Dr Per Zetterlund, University of New South Wales, ORCID: 0000-0003-3149-4464

We would also like to thank the Polymer Chemistry board and the polymer research community for their continued support of the journal, as authors, reviewers and readers.

If you would like to become a reviewer for our journal, just email us with details of your research interests and an up-to-date CV or résumé.  You can find more details in our author and reviewer resource centre

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Paper of the month: Self-stabilized, hydrophobic or PEGylated paclitaxel polymer prodrug nanoparticles for cancer therapy

Bao et al. report the synthesis of self-stabilized hydrophobic or PEGylated paclitaxel polymer prodrug nanoparticles through controlled radical polymerization approaches.

Paclitaxel (Ptx) is one of the most widely used chemotherapeutic agents for the treatment of a broad range of human tumors. Polymer prodrugs are often employed to solve a number of issues associated with its limited water solubility, the absence of ionisable groups to enable Ptx salt formation and the short colloidal stability of its formulations. In a way analogous to polymer synthesis, the “grafting from” approach, also referred to here as “drug-initiated” consists of the controlled growth of a polymer from a drug. However, this approach is limited by the poor colloidal stability of hydrophobic drug-polymer nanocarriers and the lack of the direct synthesis of PEGylated prodrugs. Nicolas and co-workers managed to tackle these issues by developing a global method which enables the facile derivatization of Ptx followed by the subsequent reversible deactivation radical polymerization to design surfactant-free, Ptx-polymer prodrug nanocarriers with contrasting properties. In particular, nitroxide-mediated polymerization (NMP) and reversible addition-fragmentation chain transfer polymerization were elegantly selected to grow short polyisoprene or poly[(oligo(ethylene glycol) methyl ether methacrylate)] chains from Ptx in a controlled fashion. This allowed for the formation of either self-stabilized, all-hydrophobic Ptx-polymer prodrug nanoparticles or their PEGylated counterparts. Importantly, these prodrug nanocarriers exhibited high cytotoxicity on three different cancer cell lines, with chain length-cytotoxicity dependency and IC50 values comparable to those of the parent drug. This versatile approach demonstrates the robustness and the broad use of the drug-initiated method for the simple design of efficient polymer prodrug nanoparticles consisting of polymers of opposite nature, thus opening new perspectives in the nanomedicine field.

Self-stabilized, hydrophobic or PEGylated paclitaxel polymer prodrug nanoparticles for cancer therapy

Tips/comments directly from the authors:  

  1. The drug-initiated NMP of isoprene from Ptx is a very simple yet efficient method to prepare surfactant-free, stable polymer prodrug nanoparticles with high drug payload, without any protection/deprotection chemistry.
  2. When using the AMA-SG1 alkoxyamine for Ptx derivatization, the resulting Ptx-AMA-SG1 alkoxyamine is obtained as a mixture of diastereomers (this is related to the two chiral centers of the alkoxyamine). The signals from the NMR spectrum should be carefully assigned. Alternatively, the diastereomers can also be separated by column chromatography with a less polar eluent.
  3. Mn of PEGMA-based prodrugs are higher than those of PI-based prodrugs because shorter POEGMA chains hardly precipitate compared to PI with similar Mn. Dialysis was not attempted because of potential hydrolytic cleavage between the drug and the polymer (especially with the diglycolate linker)

Self-stabilized, hydrophobic or PEGylated paclitaxel polymer prodrug nanoparticles for cancer therapy, Polym. Chem., 2018, 9, 687-698, DOI: 10.1039/C7PY01918A

This article is free to read until 16 April 2018

About the webwriter

AthinaDr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently a Global Marie Curie Fellow working alongside Professor Craig Hawker at the University of California, Santa Barbara (UCSB). Please, visit this site for more information.

 

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