Polymer Chemistry Blog

Paper of the month: From drug to adhesive: a new application of poly(dihydropyrimidin-2(1H)-one)s via the Biginelli polycondensation

29 Jul 2015

Zhao et al. describe the potential of the Biginelli polycondensation to improve metal bonding strength.

Recently, the introduction of efficient reactions (e.g. click reactions, Diels-Alder reactions) to polymer chemistry aiming to synthesize new condensation polymers with improved properties and characteristics has attracted considerable interest. However, on many occasions, the requirement of extensive synthetic steps (e.g. for monomer synthesis) in combination with the usage of unsafe reagents (e.g. toxic, explosive etc.) necessitates the need for the development of alternative strategies that will provide access to large scale functional materials. Towards this goal Tao and co-workers employed the Biginelli polycondensation reaction to polymerize a novel difunctional monomer consisting of benzaldehyde and beta-keto ester groups, to yield poly(dihydropyrimidin-2(1H)-one)s (poly(DHMPs) (M_n ~ 22000 g mol^-1) within 1 h. Interestingly and in contrast with the small molecular DHMPs, the Biginelli polycondensates presented metal bonding capability and adhesive properties (up to ~ 2.8 Mpa). In addition, when monomers containing more functional groups were employed, stronger tensile shear strength was demonstrated indicating that the cross-linked polymer network has a positive effect on the bonding strength (3.9-5.9 Mpa). Finally, the efficiency of the reaction was further demonstrated by performing the reaction using an electric heat gun. The preparation of the monomers on a large scale, the facile nature of the polymerisation and the excellent metal bonding performance paves the way for the synthesis of new functional polymers.

Tips/comments directly from the authors:

1. When finishing the polycondensation of monomer AB, the final polymer should be precipitated into cold water immediately, because the viscosity of they system will increase after cooling down (solid can even be formed), which will make the purification challenging.

2. When precipitating the polymer, adding some base (e.g. NaOH) in water is helpful for the removal of the acetic acid. In addition, strong stirring during the precipitation is necessary to achieve satisfactory purification.

3. During the metal bonding test, evenly heating could improve the efficiency of bonding. An open system for the volatilization of water will also enhance the glue effect.

4. As the monomer A2B2 is viscous, gentle heating prior to use is helpful for measuring.

From drug to adhesive: a new application of poly(dihydropyrimidin-2(1H)-one)s via the Biginelli polycondensation, by Y. Zhao, Y. Yu, Y. Zhang, X. Wang, B. Yang, Y. Zhang, Q. Zhang, C. Fu, Y. Wei and L. Tao, Polym. Chem., 2015, 6, 4940-4945.

Dr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently a Warwick (UK)/ Monash (Australia) research fellow working under the Monash Alliance. Visit http://haddleton.org/group-members for more information.

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Editorial Board’s Top Picks: Wei You

21 Jul 2015

By Pete Livermore, Deputy Editor.

Wei You is an Associate Editor for Polymer Chemistry and an Associate Professor in the Department of Chemistry, University of North Carolina Chapel Hill, USA. His research focuses on the synthesis and characterization of novel multifunctional materials for a variety of applications, predominately in electronics and photonics. Wei’s group uses an interdisciplinary approach, interfacing chemistry, physics, materials science and engineering.

You can find all Editorial Board’s Top Picks papers in our web collection

Focus on Conjugated Polymers (Associate Editor: Prof. Wei You, UNC Chapel Hill, USA)

Conjugated polymers, due to their interesting optical and electrochemical properties, have found many applications, from solar cells, to light-emitting diodes, transistors, and sensors, to name a few. Design and synthesis of novel conjugated polymers have been a very research-active area, illustrated by the fact that Polymer Chemistry has published more than 450 contributions in the past five years (~10% of the total number of publications).

In my Editorial Board’s Top Picks, I highlight four papers, and two review articles:

1. Benzodifuran-alt-thienothiophene based low band gap copolymers: substituent effects on their molecular energy levels and photovoltaic propertiesLijun Huo, Zhaojun Li, Xia Guo, Yue Wu, Maojie Zhang, Long Ye, Shaoqing Zhang and Jianhui Hou
Polym. Chem., 2013,4, 3047-3056

Conjugated polymers for solar cells is one of hottest research areas in the past decade. Hou’s group took the conjugated backbone of benzodifuran-alt-thieno[3,4-b]thiophene (BDF-alt-TT) to carry out a comprehensive study on the impact of electron-withdrawing group on the optical and electrochemical properties of the parent polymer. It is an elegant study that covers design and synthesis, physical properties, computational modeling, and photovoltaic device characteristics. Such a comprehensive study of structure-property relationship is very impressive and useful to the field of conjugated polymer for solar cells.

2. Synthesis of donor–acceptor conjugated polymers based on benzo[1,2-b:4,5-b′]dithiophene and 2,1,3-benzothiadiazole via direct arylation polycondensation: towards efficient C–H activation in nonpolar solvents
Xiaochen Wang and Mingfeng Wang
Polym. Chem., 2014,5, 5784-5792

Though most conjugated polymers are made through Stille, Suzuki type polycondensations, recently, direct-arylation cross-coupling has emerged as an economically efficient and environment-friendly approach. Wang’s group focused on a particular polymer, PBDTBT, consists of alternating benzo[1,2-b:4,5-b0]dithiophene (BDT) as an electron donor (D) and 2,1,3-benzothiadiazole (BT) as the electron acceptor (A). What is really impressive is that they systematically investigated almost all reaction factors including catalysts, solvents, ligands, bases, additives, concentration of reactants and phase transfer agents. The great efforts had a good payoff: their optimized condition was able to achieve a weight averagemolecular weight (Mw) as high as 60 kg/mol in nearly quantitative yield and excellent C–H selectivity.

3. Optical and electrical properties of dithienothiophene based conjugated polymers: medium donor vs. weak, medium, and strong acceptors
Bijitha Balan, Chakkooth Vijayakumar, Akinori Saeki, Yoshiko Koizumi, Masashi Tsuji and Shu Seki
Polym. Chem., 2013,4, 2293-2303

Donor-acceptor to create conjugated polymers is the most popular approach to control the band gap and energy level of conjugated polymers. The Seki group conducted an interesting study to investigate the strength of acceptor (weak, medium and strong) with a fixed donor, dithienothiophene in deciding optical and electrochemical properties of the resulting polymers. Furthermore, they did the computational modeling and device mobilities with different methods. An elegant work with thorough synthetic details and comprehensive study.

4. Low band-gap benzothiadiazole conjugated microporous polymers
Shijie Ren, Robert Dawson, Dave J. Adams and Andrew I. Cooper
Polym. Chem., 2013,4, 5585-5590

Conjugated microporous polymers (CMPs), combining microporosity, high surface areas with extended conjugation, can find a range of potential applications, including light-harvesting and sensing. The Cooper group created a low band gap CMP by incorporating the popular benzothiadiazole unit, via transition metal catalyzed cross-coupling polycondensation. Most interestingly, the fluorescence of one of the polymers was quenched by the inclusion of C60 in the pores, demonstrating the potential applications of such materials in efficient light harvesting or energy conversion.

Review articles:

1. Controlled polymerizations for the synthesis of semiconducting conjugated polymers
Ken Okamoto and Christine K. Luscombe
Polym. Chem., 2011,2, 2424-2434

Conjugated polymers synthesize by chain-growth mechanism (directly or indirectly), though much less explored when compared with the more popular step-growth mechanism, offer a number of unique advantages, including controlled molecular weight, low dispersity, and ease of preparing block copolymers. This review by the Luscombe group provided a rather comprehensive review (up to 2011) on this topic, covering various controlled polymerization methods to synthesize conjugated polymers, including living anion polymerization, ring-opening metathesis polymerization and chain-growth condensation polymerization.

2. Well-defined two dimensional covalent organic polymers: rational design, controlled syntheses, and potential applications
Zhonghua Xiang, Dapeng Cao and Liming Dai
Polym. Chem., 2015,6, 1896-1911

Two-dimensional (2D) covalent organic polymers (COPs) and derivatives are an emerging category of conjugated polymers, which hold great potential for a large variety of applications, including gas storage, energy conversion and storage, and sensing. The Dai group reviewed the recent progress in this exciting field of research, covering the rational design, controlled syntheses and potential applications of 2D COPs with various well-defined structures and properties. An up-to-date review on this topic with many beautiful structures.

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Paper of the month: Preparation of complex multiblock copolymers via aqueous RAFT polymerization at room temperature

07 Jul 2015

By Athina Anastasaki, Web Writer.

Martin et al. describe the synthesis of multiblock copolymers via RAFT polymerization at room temperature.

The preparation of high-order multiblock copolymers in a one pot process using reversible addition-fragmentation chain transfer (RAFT) is highly attractive due to the rapid polymerization rates, the achievement of quantitative conversions for each block, the lack of purification steps between the intermediate monomer additions (time effective and resource effective) and the narrow molecular weight distributions that can be attained. The “secret” of this success is the choice of high k_p acrylamide monomers and water as the reaction solvent allowing for full monomer conversion to be obtained whilst employing very low amounts of free radical initiator. However, applying this polymerization methodology to lower k_p monomers, such as methacrylates and acrylates, can be problematic as a higher concentration of initiator will be required to “push” the reaction towards completion and side reactions are also likely to occur at elevated temperatures, typically employed for this polymerization protocol. High temperatures are also disadvantageous for the polymerization of monomers that possess an LSCT upon polymerization (e.g. N-isopropyl acrylamide (NIPAM)).

In this work, a new approach to prepare multiblock copolymers via room temperature aqueous RAFT is presented. The authors implement the suitable redox couple tert-butyl hydroperoxide/ascorbic acid (TBHP/AsAc) to polymerize both acrylate and acrylamide multiblock copolymers with low dispersity values and high end-group fidelity exemplified by several in situ chain extensions. The challenge of working with slightly lower k_p monomers is also highlighted as both low and high molecular weight tailing is evident for the acrylate multiblocks whilst only gradual broadening and no shoulders are observed for the acrylamide analogues. A multiblock that consists of both acrylamide and acrylate monomers has also been targeted, demonstrating the versatility of the approach to obtain more complex multiblock structures. The main advantage of this work is the possibility of incorporating thermoresponsive blocks (e.g. NIPAM and diethyl acrylamide (DEA)) in the multiblock composition and limiting side reactions, often occurring at higher temperatures. Another interesting feature of this paper is the ability to control the polymerization of more hydrophobic (and not water soluble) monomers (e.g. methyl acrylate and ethylene glycol methyl ether acrylate) which were also successfully included in the multiblock sequence with a high degree of control. In contrast with multiblock copolymers obtained via single electron transfer living radical polymerization (SET-LRP) or atom transfer living radical polymerization (ATRP) methods, RAFT offers the additional advantage of allowing the incorporation of acidic monomers in the multiblock composition. The next challenge to tackle is to polymerize even lower k_p monomers (such as methacrylates) with a similar level of control.

Tips/comments directly from the authors:

1) When working at room temperature the viscosity is high. To avoid a loss of MW control after few block extension, a strong stirring for a good homogenization of the polymerization mixture is necessary.

2) The mixing of acrylate and acrylamide blocks is rather difficult because of the difference in reactivity of each family of monomers. Normally poly(acrylates) are better reinitiating group than poly(acrylamides) and therefore should be polymerized first.

3) In the redox initiator couple tert-butyl hydroperoxide/ascorbic acid (TBHP/AsAc), we found that a lot less AsAc could be used than that reported, and yet still give efficient initiation. In fact we observed that AsAc could act as an inhibitor of the radical polymerization. We are currently investigating the optimal ratio of the reducing and oxidizing agents.

4) The water soluble hydroxyethylacrylate monomer needs to be carefully purified because of diacrylate contamination, which is responsible for the shoulder observed at high MW on SEC analyses.

Preparation of complex multiblock copolymers via aqueous RAFT polymerization at room temperature, by L. Martin, G. Gody and S. Perrier, Polym. Chem., 2015, 6, 4875-4886

Dr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently a Warwick (UK)/ Monash (Australia) research fellow working under the Monash Alliance. Visit http://haddleton.org/group-members for more information.

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The Editorial Board pick their favourite Polymer Chemistry articles

26 Jun 2015

By Katie Nicholson, Development Editor.

Polymer Chemistry is dedicated to publishing the most exciting research encompassing all aspects of synthetic and biological macromolecules, and related emerging areas. As well as a dedicated readership, our Editorial Board members are also passionate consumers of journal content. We felt, therefore, that it might be useful for our Editorial Board to direct readers towards the papers published in the journal they find most exciting, based on their personal interests.

In our new “Editorial Board’s Top Picks” section of the journal blog, Editorial Board members will, in turn, highlight their favourite papers.

Accompanying the blog posts, is a web collection of the selected Polymer Chemistry articles.

Each month a different member of the Editorial Board will be picking their top articles, so be sure to keep checking the website for the latest additions!

Let us know which Polymer Chemistry articles are your favourite by joining the conversation on Twitter @PolymChem.

The first installment of Editor’s pick comes from Editorial Board member Heather Maynard:

Heather Maynard is a member of the Polymer Chemistry Editorial Board and a Professor in the Department of Chemistry & Biochemistry, UCLA, USA. Heather’s research lies at the frontiers of chemistry, biomaterials, and nanotechnology and involves a combination of organic and polymer synthesis, materials characterization, and biomedical research.

Heather has selected these Polymer Chemistry articles from 2015:

Dual side chain control in the synthesis of novel sequence-defined oligomers through the Ugi four-component reaction
Susanne C. Solleder, Katharina S. Wetzel and Michael A. R. Meier
Polym. Chem., 2015,6, 3201-3204

Degradable cross-linked polymer vesicles for the efficient delivery of platinum drugs
Q. Fu, J. Xu, K. Ladewig, T. M. A. Henderson and G. G. Qiao
Polym. Chem., 2015,6, 35-43

The power of one-pot: a hexa-component system containing π–π stacking, Ugi reaction and RAFT polymerization for simple polymer conjugation on carbon nanotubes
Bin Yang, Yuan Zhao, Xu Ren, Xiaoyong Zhang, Changkui Fu, Yaling Zhang, Yen Wei and Lei Tao
Polym. Chem., 2015,6, 509-513
This article was also highlighted on the Polymer Chemistry blog as Remzi Becer’s Paper of the Week.

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Polymer Chemistry welcomes new Associate Editor Emily Pentzer

25 Jun 2015

By Katie Nicholson, Development Editor.

We are delighted to welcome our newest Polymer Chemistry Associate Editor: Emily Pentzer (Case Western Reserve University, USA).

Emily will start her role as Associate Editor on 1 July 2015.

Emily obtained a Bachelor of Science in Chemistry from Butler University, USA in 2005. She then moved to Northwestern University, USA where she completed her PhD in 2010 under the supervision of Professor SonBinh T. Nguyen working on the development of new monomers for ring-opening metathesis polymerisation. Between 2010 and 2013 she was a postdoctoral researcher at the University of Massachusetts Amherst, USA where she investigated the synthesis and assembly of n-type and p-type materials for organic photovoltaic applications, supervised by Professor Todd Emrick in the Department of Polymer Science and Engineering. Since July 2013, Emily has been at Case Western Reserve University, USA as an Assistant Professor of Chemistry. Her research addresses application-based materials problems in the areas of energy harvesting, management, and storage. She uses synthetic chemistry to tailor molecular design and control self-assembly for the preparation and study of novel conductive materials with controlled domain sizes and interfaces.

To find out more about Emily’s research take a look at her group’s website.

As a Polymer Chemistry Associate Editor, Emily will be handling submissions to the journal. Why not submit your next paper to her Editorial Office?

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Polymer Chemistry’s Impact Factor increases to 5.520

19 Jun 2015

By Katie Nicholson, Development Editor.

Polymer Chemistry is delighted to announce its Impact Factor has increased to 5.520.

Polymer Chemistry is dedicated to publishing research on all aspects of synthetic and biological macromolecules, and related emerging areas. The impressive Impact Factor of 5.520 and great Immediacy Index of 1.81 is a strong assurance that research published in Polymer Chemistry will have excellent visibility and relevance to the polymer chemistry community.

Publishing your research in Polymer Chemistry means that your article will be read and cited quickly by your colleagues. Did you know:

Polymer Chemistry‘s outstanding Immediacy Index has been consistently higher than its competitors since its launch. (Data based on Immediacy Indexes from 2011, 2012, 2013 and 2014)
Articles published in Polymer Chemistry receive on average 10 citations.
Since 2011 we have grown our content by over 290% AND our Impact Factor has continued to increase.
Articles published in Polymer Chemistry are less likely to receive zero citations compared to other journals in the field. In fact, 30% of articles published in Polymer Chemistry in 2014 received a minimum of 5 citations, which is higher than other journals in the field.

(Data downloaded from ISI Web of Science on 17 June 2015)

Our fast times to publication ensure that your research is reviewed and announced to the community rapidly.

From receipt, your research papers will be published in 56 days. Communications articles will be published in a rapid 40 days. (Data taken from 2015 average manuscript handling times)

Our unique combination of high quality articles, outstanding Editorial and Advisory Board, free colour and flexible manuscript format make it clear to see why Polymer Chemistry is one of the leading journals within the polymer science field. Why not take a look at our top 10 most downloaded articles from Q1 of 2015 and read the fantastic articles we publish.

So join the many leading scientists that have already chosen to publish in Polymer Chemistry and submit your research today to be seen with the best!

Submit your research

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Author of the Month: Dr. Andreas Walther

10 Jun 2015

By Cyrille Boyer.

Dr. Andreas Walther graduated from Bayreuth University in Germany in 2008 with a PhD focusing on the self-assembly behaviour and applications of Janus particles and other soft, complex colloids. After a postdoctoral stay with a focus on biomimetic hybrid materials at Aalto University (Helsinki, Finland), he returned to Germany and established his independent research group at the DWI – Leibniz Institute for Interactive Materials in Aachen. His research interests concentrate on developing and understanding hierarchical self-assembly concepts inside and outside equilibrium, and on utilising and connecting such processes to soft materials research – often following bioinspired design principles. Andreas has published more than 90 papers and has recently been awarded the Bayer Early Excellence in Science Award (for Materials) and the Reimund Stadler Young Investigator Award of the German Chemical Society.

What was your inspiration in becoming a chemist?

I believe one of the big chemical companies is responsible for attracting me to chemistry by sending a “polymer science kit”, containing foams, resins and a toolkit to prepare Nylon fibres, to my senior class when I was still back in secondary school. Even nowadays, I still think that the classical experiment of pulling a polyamide fibre from the interface of oil/water monomer mixtures is one of the most intriguing and instructive experiments in a polymer class.

What was the motivation to write your Polymer Chemistry article?

Our main interest lies in developing self-assembly concepts to create new soft materials, for which we heavily rely on very well defined building blocks with tailored functionalities and interactions. Modern polymer chemistry provides us with the tools to make desirable building blocks with relative ease of synthesis. In this case we were interested in a straightforward way to modify the surfaces of colloidal particles to provide us with very specific biorecognition units, while at the same time rejecting all non-specific protein adhesion. Interestingly enough, despite all the common knowledge about the protein-repellent properties of polyethylene glycol (PEG) coatings, we could only find a very small amount of systematic studies discussing how for instance the architecture and composition of adsorbed PEG-based block copolymers influence protein repellency. So we went through a systematic study and optimised the building blocks to provide us with the required features for our future work. The underlying structure/property relationships at this point will be interesting for other researchers working on surface modification, biorecognition and protein-fouling.

Why did you choose Polymer Chemistry to publish your work?

Polymer Chemistry strives for high-level and interdisciplinary scientific contributions covering all modern aspects of polymer chemistry. We felt it to be the right place to achieve highest reach and recognition in the field.

In which upcoming conferences may our readers meet you?

European Polymer Federation Meeting, 21-26 June 2015, at Dresden, Germany.

How do you spend your spare time?

Keeping the work/life balance is probably one of the hardest challenges when working in science. I very much enjoy cooking to take my mind off stressful events, and I enjoy travelling to see new places and meet interesting people.

Which profession would you choose if you were not a scientist?

Indeed a very good question, I would probably follow another creative passion. Best-case scenario would then be running a restaurant in a picturesque place.

Combining the incompatible: Block copolymers consecutively displaying activated esters and amines and their use as protein-repellent surface modifiers with multivalent biorecognition

Daniel Hoenders, Thomas Tigges and Andreas Walther

We present the facile synthesis and orthogonal functionalization of diblock copolymers containing two mutually incompatible segments, i.e. primary amines and activated esters, that are displayed chronologically and synthesized by consecutive radical addition fragmentation transfer polymerization (RAFT) of suitably modified monomers. Post-polymerization modification of the active ester moieties with functionalized triethylene glycol derivatives (TEG-NH₂/BiotinTEG-NH₂) furnishes a protein-repellent block with specific biorecognition, and the activation of the amine groups via deprotection results in newly reactive primary amines. We subsequently use these amines as an anchoring layer for the coating of aldehyde-functionalized polystyrene (PS) colloids and demonstrate tight adhesion and enhanced protein-repellent characteristics combined with specific and multivalent biorecognition of avidin as a function of block ratios. Our strategy demonstrates a viable approach for orthogonal combination of widely needed, but mutually incompatible, functional groups into complex polymer architectures.

Cyrille Boyer is a guest web-writer for Polymer Chemistry. He is currently an associate professor and an ARC-Future Fellow in the School of Chemical Engineering, University of New South Wales (Australia), deputy director of the Australian Centre for NanoMedicine and member of Centre for Advanced Macromolecular Design.

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Recent Appointees in Materials Science 2015 Conference (RAMS2015)

28 May 2015

By Katie Nicholson, Development Editor.

We are delighted to announce that the Recent Appointees in Materials Science 2015 Conference (RAMS2015) will be held at the University of Warwick on 16-17^th September 2015.

Deadlines and dates

Registration will open shortly so be sure to sign up to this essential meeting before 1^st September 2015! The cost of registration is £125 for accommodation and meals, including the conference banquet at Warwick Castle. A reduced rate of £70 is offered for those not requiring accommodation.

Abstract submissions are now being accepted for oral and poster presentation but make sure you submit your abstracts by the deadline on 30^th June 2015.

Bursaries

A small number of bursaries are available for those with limited travel budgets and will be assessed on an individual basis. Enquire about bursaries here.

Keynote speakers

Biomaterials Science Advisory Board member Andrew Dove (University of Warwick) will be speaking along with other keynote speakers Aron Walsh (University of Bath) and Mary Ryan (Imperial College London). View the full list of invited speakers here.

For full details visit the RAMS2015 website. We hope you can join the materials science community for this fantastic event.

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Paper of the Month: Rapid synthesis of ultrahigh molecular weight and low polydispersity polystyrene diblock copolymers by RAFT-mediated emulsion polymerization

26 May 2015

By Pete Livermore, Deputy Editor.

Truong et al. describe the synthesis of ultrahigh molecular weight and low polydispersity polystyrene diblock copolymers by RAFT-mediated emulsion polymerisation.

aper of the month: Rapid synthesis of ultrahigh molecular weight and low polydispersity polystyrene diblock copolymers by RAFT-mediated emulsion polymerization

Ultra high molecular weight (UHMW) polymers have always been an ambitious target for synthetic polymer chemists. However, synthesising these materials using controlled radical polymerisation is challenging due to high levels of bimolecular termination and chain transfer to monomer that impede the growth of polymer chains. Monomers with higher propagation rate coefficient (k_p) such as acrylamides and acrylates (and even methacrylates) have been successfully polymerised up to 10⁶ g mol^-1 but lower k_p monomers (e.g. styrene) typically present broad molecular weight distributions when high molecular weight (e.g. 10⁶ g mol^-1) is targeted.

Truong et al. envisaged that a high polymerisation rate for the polymer chains would be required in order to produce well-defined UHMW polystyrene, whilst at the same time termination and side reactions would need to be minimised. The authors addressed this by employing the use of novel macromolecular chain transfer agents (CTA) in reversible addition fragmentation chain transfer polymerisation (RAFT)-mediated emulsion polymerisation. N-hydroxyethyl acrylamide (HEAA) and poly(ethylene glycol) methyl ether acrylate (PEGA) were copolymerised under judiciously selected reaction conditions to identify the most effective macrostabiliser for the emulsion polymerisation. The choice of these monomers proved crucial for the polymerisation, with PEGA conferring excellent antifouling characteristics while HEAA improves the water solubility of the macromolecular CTA and reduces partitioning of the macro-stabilisers within the styrene droplets and/or at the water/droplet interfaces. Under carefully optimised conditions, UHMW polystyrene of 10⁶ g mol^-1 could be obtained with relatively low dispersity values (<1.4) and unimodal molecular weight distributions even at near-quantitative conversions (>90%). Moreover, UV-Vis analysis confirmed the presence of the CTA, further suggesting that the reversible-deactivation radical polymerisation mechanism remained operative even to this very high conversion and molecular weight. Another interesting feature of this work is the linear relationship between particle size and molecular weight in this system, which seems to depart from the packing parameter theory, typically used to explain morphology transformations during emulsion or aqueous dispersion polymerisations. TEM analysis in all samples revealed uniformly spherical nanoparticles, even when the chain length of the polystyrene core was well above the threshold for the worm and vesicle formation. These experiments suggest that the packing parameter theory cannot be applied for all polymerisation-induced self-assembly systems and that further theoretical models are potentially required to fully understand the equilibrium morphology of soft nanoparticles.

In short, this article has overcome a longstanding challenge in the synthesis of UHMW polymers and created a new nanomaterial which offers great potential in numerous applications.

Summary points from the authors:

4,4′-Azobis(4-cyanopentanoic acid (ACPA) (free radical initiator) completely dissolves in water only after stirring for about 30 min. The stock ACPA solution should be made up fresh and not be stored for later use.
To avoid the loss of styrene monomer (by evaporation) during polymerisation, there is no need to keep the emulsion polymerisation under the continuous flow of nitrogen.
Samples prepared for dynamic light scattering measurements were not filtered, and as such filtration might enable a further reduction in the particle size distribution.
The molar ratio of HEAA to PEGA in the macromolecular CTAs was optimised at 1 to 1. A higher molar ratio of HEAA to PEGA results in aggregation when targeting ultra-high molecular weight polystyrene. A lower molar ratio of HEAA to PEGA results in a higher portion of macromolecular CTAs partitioning within the styrene droplets.

Rapid synthesis of ultrahigh molecular weight and low polydispersity polystyrene diblock copolymers by RAFT-mediated emulsion polymerization by Nghia P. Truong, Marion V. Dussert, Michael R. Whittaker, John F. Quinn and Thomas P. Davis, Polym. Chem., 2015, 6, 3865-3874

Dr. Athina Anastasaki is a is a guest web-writer for Polymer Chemistry. She is currently a Warwick University (UK) and Monash University (Australia) research fellow working under the Monash Alliance. Visit the Haddleton group’s website for more information.

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Polymer Chemistry Blog

Paper of the month: From drug to adhesive: a new application of poly(dihydropyrimidin-2(1H)-one)s via the Biginelli polycondensation

Top 10 most-read Polymer Chemistry articles – Q2 2015

Editorial Board’s Top Picks: Wei You

Paper of the month: Preparation of complex multiblock copolymers via aqueous RAFT polymerization at room temperature

The Editorial Board pick their favourite Polymer Chemistry articles

Polymer Chemistry welcomes new Associate Editor Emily Pentzer

Polymer Chemistry’s Impact Factor increases to 5.520

Submit your research

Author of the Month: Dr. Andreas Walther

Combining the incompatible: Block copolymers consecutively displaying activated esters and amines and their use as protein-repellent surface modifiers with multivalent biorecognition

Recent Appointees in Materials Science 2015 Conference (RAMS2015)

Paper of the Month: Rapid synthesis of ultrahigh molecular weight and low polydispersity polystyrene diblock copolymers by RAFT-mediated emulsion polymerization

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