Paper of the month: Development of the first panchromatic BODIPY-based one-component iodonium salts for initiating the photopolymerization processes

Ortyl et al. develop and implement new BODIPY-based derivatives as panchromatic, single-component polymerization photoinitiators.

Light is undeniably a fundamental tool for diverse chemical transformations in organic and polymer chemistry. Photopolymerization processes in particular, have gained widespread interest as they provide powerful, green methodologies for a variety of processes dealing with (bio)materials production, especially those involving 3D printing processes. In this aspect, due to their initiation efficiency, single-component photoinitiators are of particular interest. However, most known cationic photoinitiators have poor matching of their absorption characteristics with the emission characteristics of industrial UV light sources, the so-called medium pressure lamps and UV-LED and Vis-LED diodes.

To address this, Ortyl and collaborators developed and tested in 3D printing applications new BODIPY derivatives and more specifically iodonium salts based on a 4,4-difluoro-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indecene (B-1) chromophore. The new tosylate, hexafluorophosphate, hexafluoroantimonate, and triflate iodonium B-1 salts were found initiate cationic photopolymerization  with the hexafluoroantimonate derivative showing the highest reactivity. All derivatives were found to efficiently initiate the polymerization of a variety of monomers (such as epoxides, ethers, glycidyls and oxetanes) as well as of hybrid monomers (such as divinyl/triacrylate and diepoxide/triacrylate). Importantly, diodes of wide spectrum could be used as light source in a wavelength range from 365 to 520 nm.  The applicability of the novel BODIPY derivative photoinitiators was demonstrated with 3D printing of epoxy and acrylic resins with good resolution. Moreover, the B-1 chromophore could also be used as a olorimetric sensor of the degree of photopolymerization.

In summary, BODIPY-based derivatives were developed as panchromatic, single-component polymerization photoinitiators.  

 

Tips/comments directly from the authors:

  • Newly developed cationic photoinitiators based on the BODIPY chromophore effectively initiate various photopolymerization processes.
  • The choice of the appropriate concentration of new photoinitiators, current intensity, type of diode, and monomers enable to obtain polymers with a high degree of polymerization (conversions up to even 95%).
  • We described the application of the new BODIPy-based photoinitiators for photo-cured 3D printing. But the newly developed photoinitiators can be successfully used in other applications, such as temporary photo-cured coloured fillings for milk teeth for children.

 

Development of the first panchromatic BODIPY-based one-component iodonium salts for initiating the photopolymerization processes, Polym. Chem., 2021, 12, 6873-6893.

Link to the paper: https://pubs.rsc.org/en/content/articlehtml/2021/py/d1py01263k

You can follow Professor Ortyl on Twitter: @JoannaOrtyl

 

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.

 

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Paper of the month: Aqueous ROPISA of α-amino acid N-carboxyanhydrides: polypeptide block secondary structure controls nanoparticle shape anisotropy

Bonduelle et al. prove that ROPISA can be used to concomitantly yield well-defined amphiphilic copolypeptide chains and self-assembled nanostructures in a rapid, facile, and straightforward manner.

Synthetic polypeptides are among the most versatile building blocks to guide the formation of self-assembled nanomaterials through biomimetic structuring since they merge advantageous features of both synthetic polymers and proteins. Recent advances in ring-opening polymerization methodologies offer the unique ability to precisely design polypeptides fitting a particular function. In this context, application of polymerization-induced self-assembly (PISA) – i.e. in situ growth of a living amphiphilic polymer chain during its self-assembly into nanostructures- offers unprecedented possibilities for the synthesis of functional peptide-based nanomaterials. 

To address this possibility, Bonduelle, Lecommandoux and collaborators comprehensively studied the recently reported aqueous ROPISA process of N-carboxyanhydrides in the presence of α-amino-poly(ethylene oxide) initiators. A library of polypeptides was prepared from two NCA monomers derived from benzyl-L-glutamate (BLG-NCA) and L-Leucine (Leu-NCA) and a hydrophilic PEG5kDa-NH2 macroinitiator by varying the degree of polymerization. This combined one-pot synthesis and self-assembly was found to produce well-defined amphiphilic copolypeptide chains with narrow molar mass dispersity (Đ) values (between 1.12 and 1.17), controllable number-averaged molar mass Mn and good reaction yields. Importantly, in contrast to previous studies where nanomaterial morphology was essentially defined by the hydrophobic to hydrophilic ratio, the anisotropic rod-like nanostructure morphologies were dictated by the chemical nature of the NCA monomer and the secondary structure of the resulting polypeptides. In addition, ROPISA was found to provide control over the diameter of the produced rod-like self-assembled nanostructures. The β-sheet forming PLeu polypeptides were found to strongly favor the formation of long rods with high aspect ratio, as compared to α-helical PBLG polypeptides.

In summary, ROPISA provides a rapid, facile, and straightforward methodology for the synthesis of rigid polypeptide-based nanomaterials at high solid content with tunable anisotropy.  These new results strengthen the potential of using ROPISA to obtain polypeptides with N-carboxyanhydrides and open new avenues towards the design of functional nanomaterials.

  

Tips/comments directly from the authors:

  • The polymerization of NCAs via ROPISA can easily be contaminated by homopolymers that originate from the hydrolysis of a monomer to an amino acid that then initiates the polymerization process. Salt concentration and temperature are important parameters to control this secondary reaction.
  • The agitation of the reaction medium is a key factor in the ROPISA process: insufficient stirring makes the synthesis too inhomogeneous and does not provide good results. At high solid contents (above 10%) and in some experiments, hydrogels are obtained, a phenomenon we are currently studying.
  • Other molar mass of poly(ethylene glycol) can be used: we have performed ROPISA with PEG2k or PEG10k with the two monomers described. We obtain in most cases anisotropic nano-objects.

 

Citation to the paper: Aqueous ROPISA of α-amino acid N-carboxyanhydrides: polypeptide block secondary structure controls nanoparticle shape anisotropy, Polym. Chem., 2021,12, 6242-6251

Link to the paper: https://pubs.rsc.org/en/content/articlelanding/2021/py/d1py00995h

 

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.

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Introducing the Polymer Chemistry Emerging Investigators Series

For many years Polymer Chemistry has showcased special collections dedicated to work carried out by researchers in the earlier stages of their research careers in our Emerging Investigator collections, most recently in our 2020 Emerging Investigators collection.

We hope that the polymer chemistry community has found these issues to be valuable, both in the high quality of the articles and in drawing attention to newer voices in the community. The journal editors and Editorial Board consider these to have been highly successful.

In light of disruption to research programmes worldwide, we have taken the opportunity to reassess the format of this initiative, and we are now excited to announce the launch of the Polymer Chemistry Emerging Investigators Series.

 

What is changing?

In place of a dedicated journal issue, Emerging Investigators papers will be published throughout the year. We anticipate the following benefits to this change:

  • No fixed submission deadlines allowing more flexibility for authors
  • Continual exposure of exciting work from early-career members of the community
  • Greater emphasis and focus on individual authors and research groups

We hope for this to offer a better service to our authors and readers well into the future.

 

What is not changing?

While we will no longer dedicate a specific journal issue to our Emerging Investigators, all other aspects of this initiative will remain the same. This includes:

  • Eligibility criteria (see below)
  • A dedicated web page for published articles alongside our other collections
  • Rigour and speed in peer review
  • An overall objective to showcase the full diversity of cutting-edge research carried out from polymer chemists in the early stages of their independent careers worldwide

 

What happens now?

The Polymer Chemistry Editorial Office will contact nominated Emerging Investigators throughout the year.

Regarding eligibility, contributors must:

  • Publish research within the journal scope
  • Currently be an independent research leader
  • Have not been featured as an Emerging Investigator in a previous Polymer Chemistry Emerging Investigators article
  • Have either no more than 12 years of post-PhD research experience in the year of submission when taking into account any career breaks

 

Do you fit the criteria above, and wish to be featured as an Emerging Investigator in the journal? Get in touch with us at polymers-rsc@rsc.org

 

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Paper of the month: Fully amorphous atactic and isotactic block copolymers and their self-assembly into nano- and microscopic vesicles

Wehr et al. introduced chirality into aqueous block copolymer (BCP) self-assemblies in a study discriminating the effect of tacticity from that of crystallinity.

Amphiphilic block copolymers (BCPs) bearing mostly atactic hydrophobic polymers on the main chain have long served as building blocks to produce nanocompartments with diverse morphologies and a variety of (bio)technological applications. More recently, the use of isotactic hydrophobic blocks has attracted significant interest since the effect of stereoregularity of the main chain of BCPs on the formation and morphology of aqueous self-assemblies has not yet been elucidated. Recent studies on isotactic hydrophobic blocks are based on crystallisation-driven self-assembly (CDSA) not allowing to unravel the differences between atactic and isotactic BCPs and associate them with morphological changes in BCP assemblies. CDSA additionally prevents higher complexity and applicability since the formed crystalline membranes generally lack flexibility and fluidity or require handling in temperatures above their melting or glass transition temperatures (Tg) to form well-controlled self-assemblies.

To discriminate the effect of tacticity from that of crystallinity in aqueous self-assemblies of amphiphilic BCPs, Gaitzsch, Meier and collaborators synthesized poly(butylene oxide)-block-poly(glycidol) (PBO-b-PG) BCPs, differing solely in their tacticities (R/S, R and S). Despite the differences in their stereochemistry, all polymers displayed similar thermal and structural behaviour, proving that stereoregularity did not induce crystallinity or formation of secondary structures in bulk or in solution. However, the nanoscopic polymersomes (i.e. small unilamellar vesicles, SUVs) composed of the different BCPs expressed stability differences when studying self-assembly into homogenous phases of SUVs. Interestingly, only the atactic BCPs formed microscopic giant unilamellar vesicles (GUVs) which were stable over several hours while GUVs composed of isotactic BCPs ruptured within minutes after formation. The ability of atactic PBO-b-PG to form microreactors was highlighted by reconstituting the membrane protein OmpF in the GUV membrane via microfluidics and performing an enzyme reaction inside its lumen.

This study differentiates for the first time the effect of tacticity from that of crystallinity in aqueous self-assemblies of amphiphilic BCPs and is expected pave the way in designing versatile vesicles with fluid membranes composed of atactic or isotactic BCPs. Studies of the interplay of membrane chirality with transmembrane proteins or guests in nano- and micro- compartments are now within reach. 

 

Tips/comments directly from the authors:

  • Kinetic measurements of the polymerisations of racemic and enantiopure monomers revealed that both enantiomers reacted in the same speed. Hence in case of synthesising the atactic polymer, an ideal statistical distribution of m and r diads is achieved.
  • The microfluidic technique applied in here was essential to form the GUVs. Other approaches to form GUVs were not successful due to the instability of the self-assemblies especially of the stereoregular polymers.
  • We essentially took commercially available but expensive enantiopure monomers to generate highly stereoregular polymers, which formed less stable (i.e. inferior) self-assemblies than the cheaply accessible atactic polymers. However, it allowed us to falsify the common believe that a higher order in polymers always leads to better defined structures or a higher stability.

 

Citation to the paper: Fully amorphous atactic and isotactic block copolymers and their self-assembly into nano- and microscopic vesicles, Polym. Chem., 2021,12, 5377-5389.

Link to the paper: https://pubs.rsc.org/en/content/articlelanding/2021/py/d1py00952d

 

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.

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Call for papers: Tailoring Dispersity and Shape of Molecular Weight Distributions

 

We are delighted to announce a call for papers for our latest themed collection on “Tailoring dispersity and shape of molecular weight distributions” Guest Edited by Athina Anastasaki (ETH Zurich) and Brett Fors (Cornell University).

 

This special issue will cover new synthetic or engineering methods to tailor polymer dispersity or the shape of molecular weight distributions. This includes discrete or nearly monodispersed materials and the properties thereof. Submissions where the effect of varying either the dispersity or the shape of molecular weight distributions are also encouraged and can be illustrated in any type of property of applications.

 

You can access the online collection here to look at the first few contributions to this collection.

 

Manuscripts should be submitted via the Royal Society of Chemistry’s online submission service available at https://mc.manuscriptcentral.com/py. Please add a “note to the editor” in the submission form when you submit your manuscript to say that this is a submission for the themed collection. The Editorial Office reserves the right to check suitability of submissions in relation to the scope of the collection.

 

All manuscripts will be subject to the journal’s usual peer review process. Accepted manuscripts will be added to the online collection as soon as they are online and they will be published in a regular issue of Polymer Chemistry.

If you have any questions about the journal or the collection, then please do contact the Editorial Office at polymers-rsc@rsc.org.

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Paper of the month: On-demand shape transformation of polymer vesicles via site-specific isomerization of hydrazone photoswitches in monodisperse hydrophobic oligomers

Wang et al. synthesized amphiphilic block copolymers bearing photoswitches and evaluated the effect of the photoswitch number and position on solution self-assembly.

Diverse applications of amphiphilic block copolymers (BCPs) stem from their ability to self-assemble into nanostructures with well-defined architectures the shape of which has been shown to bear significant effect on BCP nanostructure properties and applications. In this aspect, photo-triggered polymer vesicles (polymersomes) have been extensively investigated for on-demand cargo delivery as light-triggered conformational changes of the BCPs offer macroscopic actuation of the nanocarriers and enable reversible mass transport through the vesicular membrane without permanent disruption. However, the effect of the number and location of the photoswitches in the BCP on their conformational change has been challenging to study.

To address this, Kim and collaborators synthesized amphiphilic block copolymers composed of hydrophilic polyethylene glycol (PEG) blocks and discrete oligo(phenyllactic acid) (OPLA) blocks containing hydrazone-based photoswitches at specific positions. The photoswitches were selected on the basis of their ability to undergo EZ isomerization upon light irradiation causing a conformational change on the hydrophobic block. As a result, vesicles formed via cosolvent self-assembly were shown to undergo a reversible shape transformation upon irradiation with UV or visible light. Importantly, the location and number of photoswitches per polymer was shown to have a significant effect. When the hydrazone-based photoswitch was embedded in the middle of the hydrophobic OPLA chains a dramatic membrane deformation was observed causing reversible shape transformation from polymeric vesicles to urchin-like structures. In contrast, when the hydrazone-based photoswitches were embedded at the junction of the hydrophilic and the hydrophobic block, the self-assembled nanocarriers did not undergo shape transformation when irradiating with different light sources. This indicates that the position of the switch in the hydrophobic moiety of the BCP is a decisive factor determining the shape transformation of the nanoparticles driven by the light-induced configurational change of the hydrazone-based photoswitches. It was further shown that when the number of photoswitches embedded in the OPLA chains was increased, the extent of shape transformation was significantly enhanced.

This study offers new insights on the design and development of BCPs for the fabrication of polymersomes tailored for a wide range of potential applications involving on-demand release of cargo molecules.

Citation to the paper: On-demand shape transformation of polymer vesicles via site-specific isomerization of hydrazone photoswitches in monodisperse hydrophobic oligomers, Polym. Chem., 2021,12, 5027-5036.

Link to the paper: https://pubs.rsc.org/en/content/articlelanding/2021/py/d1py00981h

 

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.

 

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

We are very pleased to announce that Professor Athina Anastasaki has joined Polymer Chemistry as an Associate Editor

Profile picture of Athina AnastasakiAthina Anastasaki completed her PhD studies at the University of Warwick under the supervision of Professor Dave Haddleton and received the Jon Weaver Award for the best PhD thesis in Polymer Chemistry in the United Kingdom. She then commenced a Monash-Warwick post-doctoral appointment between Monash University (with Professor Tom Davis) and the University of Warwick (with Professor Haddleton). In 2016, she was awarded an Elings fellowship and a Global Marie Curie Fellowship to conduct research at the University of California in Santa Barbara working alongside Professor Craig Hawker. She is now an Assistant Professor at the Materials Department of ETH Zurich and has published 100 peer-reviewed articles and she recently received the 2020 Hanwha-Total IUPAC Young Scientist Award and an ERC Starting Grant. Her research focuses on controlled radical polymerization, self-assembly of polymeric materials, polymerization mechanisms and complex materials of different dispersities and architectures. You can follow her on Twitter @AthinaAnastasa1.

 

Quote from Athina about the future of Polymer Chemistry: Polymers will continue playing an important role in our everyday life and I hope that we manage to become as good at unmaking them as we are at making them. Sustainability will play a key role for future polymer development and Polymer Chemistry will be the best forum for such articles

Check out our themed collections on ‘Sustainable polymers’ and ‘Plastics in a circular economy’ to read some of the exciting work we have published in this area.

 

Athina’s favourite Polymer Chemistry articles

Here are four publications that Athina has chosen as her favourite recent articles in Polymer Chemistry.

 

Sustainable thermoplastic elastomers produced via cationic RAFT polymerization
Scott Spring, Red Smith-Sweetser, Stephanie Rosenbloom, Renee Sifri and Brett Fors

Polymer Chemistry, 2021, 12, 1097-1104

 

 

 

 

Thermoresponsive dynamic BAB block copolymer networks synthesized by aqueous PISA in one-pot
Pauline Biais, Marie Engel, Olivier Colombani, Taco Nicolai, François Stoffelbach and Jutta Rieger

Polymer Chemistry, 2021, 12, 1040-1049

 

 

 

Diselenide–yne polymerization for multifunctional selenium-containing hyperbranched polymers
Xiaofang Lin, Sisi Chen, Weihong Lu, Ming Liu, Zhengbiao Zhang, Jian Zhu and Xiangqiang Pan

Polymer Chemistry, 2021, 12, 3383-3390

 

 

 

 

The block copolymer shuffle in size exclusion chromatography: the intrinsic problem with using elugrams to determine chain extension success
Kai Philipps, Tanja Junkers and Jasper Michels

Polymer Chemistry, 2021, 12, 2522-2531

 

 

 

 

All these articles are currently FREE to read until 15 November 2021!

 

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

2022 Polymer Chemistry Lectureship – Open for nominations

Do you know an early-career researcher who deserves recognition for their contribution to the polymer chemistry field?

 

Polymer Chemistry is pleased to announce that nominations are now being accepted for its 2022 Lectureship award and will close on 31 December 2021. This annual award was established in 2015 to honour an early-stage career scientist who has made a significant contribution to the polymer field.

 

Polymer Chemistry lectureship open for nominations

 

Eligibility

To be eligible for the lectureship, candidates should meet the following criteria:

  • Be an independent researcher, PhD students postdoctoral research associates are not eligible
  • Be actively pursuing research within the polymer chemistry field, and have made a significant contribution to the field
  • Be at an early stage of their independent career (this should typically be within 12 years of attaining their doctorate or equivalent degree, but appropriate consideration will be given to those who have taken a career break, work in systems where their time period to independence may vary or who followed an alternative study path)

 

How to nominate

Nominations must be made via email to polymers-rsc@rsc.org, and include the following:

  • The name, affiliation and contact details of the nominee, nominator and referee
  • An up-to-date CV of the nominee (1 – 3 A4 page maximum length)
  • A letter of recommendation from the nominator (500 words maximum length)
  • A supporting letter of recommendation from a referee (500 words maximum length). This could be from the nominee’s postdoc, PhD supervisor or academic mentor for instance
  • The nominator must confirm that to the best of their knowledge, their nominee’s professional standing is as such that there is no confirmed or potential impediment to them receiving the Lectureship

Please note:

  • Self-nomination is not permitted
  • The nominee must be aware that he/she has been nominated for this lectureship
  • Previous winners and current Polymer Chemistry Editorial Board members are not eligible
  • As part of the Royal Society of Chemistry, we have a responsibility to promote inclusivity and accessibility in order to improve diversity. Where possible, we encourage each nominator to consider nominating candidates of all genders, races, and backgrounds. Please see the RSC’s approach to Inclusion and Diversity.

 

Selection

  • All eligible nominated candidates will be assessed by a judging panel made up of the Polymer Chemistry Editorial Board, any Editorial Board members with a conflict of interest will be ineligible for the judging panel.
  • The judging panel will consider the following core criteria:
    • Excellence in research, as evidenced in reference to originality and impact
    • Quality of publications, patents or software
    • Innovation
    • Professional standing
    • Independence
    • Collaborations and teamwork
    • Evidence of promising potential
    • Other indicators of esteem indicated by the nominator
  • In any instance where multiple nominees are judged to be equally meritorious in relation to these core criteria, the judging panel will use information provided on the nominee’s broader contribution to the chemistry community as an additional criterion. Examples of this could include: involvement with RSC community activities, teaching or demonstrating, effective mentorship, service on boards, committees or panels, leadership in the scientific community, peer reviewing, promotion of diversity and inclusion, advocacy for chemistry, public engagement and outreach.

 

Previous winners

2021 – Brett Fors, Cornell University, USA

2020 – Rachel O’Reilly, University of Birmingham, UK

2019 – Frederik Wurm, University of Twente, The Netherlands

2018 – Cyrille Boyer, University of New South Wales, Australia

2017 – Julien Nicolas, Université Paris Sud, France

2016 – Feihe HuangZhejiang University, China

2015 – Richard HoogenboomGhent University, Belgium

 

Nominations deadline: 31 December 2021

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Paper of the month: Sequence-defined oligoampholytes using hydrolytically stable vinyl sulfonamides: design and UCST behaviour

Mertens et al. synthesized a series of sequence-defined oligoampholytes and evaluated their properties.

 

 

Polyampholytes are polymers compromising of positively and negatively charged groups and present a number of distinct properties which allows them to be employed in many applications including antifouling coatings and drug delivery systems. Polyampholytes are usually produced by conventional polymerizations strategies yielding materials with varied chain lengths and monomer composition, thus compromising the purity and the properties of these molecules. Du Prez’s group has contributed to this field by developing a chemical platform based on thiolactone chemistry which allowed the introduction of a variety of side-chain functionalities employing acrylic, amine or halide building blocks. In their current contribution, novel sequence-defined oligoampholytes with carboxylic acid and tertiary amine side-chains were elegantly synthesized through a thiolactone-based solid-phase synthesis protocol, in which the side-chain functionalities were incorporated through a thiol-Michael reaction. Although initially acrylate-based building blocks were employed to introduce the tertiary amine, severe side reactions were observed including hydrolysis or methanolysis. Instead, a tertiary amine bearing vinyl sulfonamide proved to be an efficient and stable alternative for the used acrylates and thus could be directly integrated into the synthetic protocol. A wide range of oligomers (up to a hexamer) were synthesized with an alternating or block-like arrangement of the tertiary amine and acid side-chains. These perfectly uniform oligomers were shown to be soluble in water and exhibited UCST-type thermoresponsive behaviour in alcoholic/aqueous mixtures. Such properties were influenced by both the length and the sequence of the oligoampholytes. As the authors elude in their conclusion, the ability to fully control the arrangement of the amphiphilic groups is a powerful tool to design the properties and functions of these uniform macromolecules.

 

Tips/comments directly from the authors:

  • The tertiary amine side-chains are attached to the backbone through a β-thioester bond resulting from the thiol-Michael addition, which was found to be susceptible towards hydrolysis and methanolysis. Prolonging the carbon spacer between the ester and the tertiary amine reduced the rate of this undesired degradation, yet it could not be completely inhibited.
  • Compared to acrylates, vinyl sulfonamides are a class of Michael acceptors that received considerably less attention within the area of polymer chemistry, although they can provide favourable properties. The thiol-vinyl sulfonamide adduct is stable towards hydrolysis, unlike an acrylate, while the reaction kinetics are comparable. These aspects are highlighted within the present work, as well as in the work of others.
  • While we demonstrate the synthesis of these oligomers together with the fundamental characterisation of their properties, further research is required to establish in-depth structure-property relationships.

 

Citation to the paper: Sequence-defined oligoampholytes using hydrolytically stable vinyl sulfonamides: design and UCST behaviour, Polym. Chem., 2021,12, 4193-4204, DOI: 10.1039/D1PY00662B

Link to the paper:

https://pubs.rsc.org/en/content/articlelanding/2021/py/d1py00662b 

 

Professor Athina AnastasakiDr. Athina Anastasaki is an Editorial Board Member and a Web Writer for Polymer Chemistry. Since January 2019, she joined the Materials Department of ETH Zurich as an Assistant Professor to establish her independent research group.

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Paper of the month: Novel imino- and aryl-sulfonate based photoacid generators for the cationic ring-opening polymerization of ε-caprolactone

Sardon’s group investigate the ring opening polymerization of cyclic esters using novel photo acid generators.

 

 

Light has emerged as a powerful stimulus allowing for spatial and temporal control over polymerization kinetics, macromolecular sequence, and composition and has enabled a number of high-end applications including coatings, microelectronics, additive manufacturing and 3D printing. However, the potential of light in polymer chemistry is far from being fully exploited. Photopolymerization is currently dominated by (controlled) radical polymerizations of vinyl monomers. Little attention has been paid to photo-induced cationic ring-opening polymerization (CROP) of cyclic esters. In a recent contribution to Polymer Chemistry, Sardon and co-workers developed six new photocatalysts for light-mediated CROP. Upon exposure to light, the new photocatalysts release strong sulfonic acids that can trigger the CROP of ε-caprolactone. The authors particularly focused on imino-sulfonates and aryl-sulfonates based photocatalysts, and this strategy was hugely successful. Complete monomer conversion was obtained after only 5 minutes of irradiation. This is an impressively high polymerization rate despite the catalyst efficiency being typically strongly related to the chromophore and the sulfonate substituent. In addition, several of these photocatalysts are stable even at 100 °C and were successfully used to produce not only linear biodegradable polymer polymers but also crosslinking poly(ε-caprolactone) exhibiting excellent mechanical properties. Furthermore, the authors employed density functional theory calculation to propose a photodissociation mechanism. The studied photopolymerization has also been successfully applied to surface coating. The potential applications of these new photocatalysts are certainly not limited to photocoating, and therefore, we look forward to seeing further exciting applications of these photocatalysts.

Tips/comments directly from the authors:

  • The efficiency of the PAGs was observed to be highly dependent on the chromophore and the photolabile bond; imino-sulfonates were more capable of producing sulfonic acids than aryl-sulfonates. However, their preparation is tedious and requires a multistep synthesis process. Aryl-sulfonates are not as efficient but their synthesis is performed in a single step in excellent yields up to 90%.

 

  • Imino-sulfonate based photocatalyst were able to promote the ring opening polymerization of ε-caprolactone at room temperature but 3 h were required for getting full conversion. Nevertheless, as several of these catalyst were stable up to 100 °C we were able to get full conversion in just 5 minutes at 100 °C

 

  • To further expand the applications of the studied PAGs, we demonstrated the ability of the photoacid to promote the crosslinking at room temperature in the presence of a dilactone. While the crosslinking reaction was successful, long reaction times were required for reaction completion, making impractical the use of these photocatalyst in 3 D printing applications.

 

Citation to the paper: Novel imino- and aryl-sulfonate based photoacid generators for the cationic ring-opening polymerization of ε-caprolactone, Polym. Chem., 2021,12, 4035-4042, DOI: 10.1039/D1PY00734C

Link to the paper:

https://pubs.rsc.org/en/content/articlelanding/2021/py/d1py00734c#!divAbstract

 

 

Professor Athina AnastasakiDr. Athina Anastasaki is an Editorial Board Member and a Web Writer for Polymer Chemistry. Since January 2019, she joined the Materials Department of ETH Zurich as an Assistant Professor to establish her independent research group.

 

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)