Paper of the month: Mild and efficient synthesis of ω,ω-heterodifunctionalized polymers and polymer bioconjugates

Figg et al. report the efficient synthesis of ω,ω-heterodifunctionalized polymers and polymer bioconjugates under mild reaction conditions.

 

The versatile and high yielding modification of polymer end groups is a critical tool for controlling materials properties. However, when multiple different functionalities are needed, pre-installation of two different functional groups at the polymer end groups is typically a tedious requirement. Sumerlin, Castellano and co-workers managed to circumvent this by developing a mild approach that enables the efficient synthesis of ω-ω-heterodifunctionalized polymers and polymer bioconjugates. Key to this strategy is the use of the recently introduced reagent benzotrifuranone (BTF) which allows the introduction of differentially “clickable” functional groups to monomethyl ether poly(ethylene glycol) amine (mPEG amine). In contrast to conventional polymer heterofunctionalization approaches that require high temperatures, significant excess of reagents and numerous synthetic steps, BTF serves as an ideal functionalization handle that operates at ambient temperature using near-stoichiometric amounts of reagents. Importantly, following functionalization of BTF with alkyne and alkene functional groups a fluorescent (coumarin) dye and biotin could be successfully conjugated to the end of mPEG-amine. These polymer bioconjugates were then able to bind avidin while showing an unexpected disruption of avidin tetramer formation. Overall, the compatibility of BTF with a broad scope of amine nucleophiles and thermally sensitive moieties (e.g. proteins) in combination with the highly efficient and mild nature of this reagent holds great promise for more elaborate heterofunctionalization strategies.

 

 

Tips/comments directly from the authors:

 

  1. The reaction time of the first and second addition to BTF should be monitored (typically by thin layer chromatography) to ensure minimal over/under functionalization occurs.
  2. The trisubstitution products are tolerant to many reaction conditions; however, when performing reactions that include radical intermediates, higher than usual reagent equivalents may be needed due to the radical scavenging nature of the phloroglucinol
  3. When one-pot homodifunctionalizations are performed, be sure to add enough nucleophile to consume both electrophilic sites on the polymer end group and the three electrophilic sites on any unreacted BTF.
  4. Regarding BTF synthesis: 1) Using fresh polyphosphoric acid and monitoring the reaction temperature is very important for the ring-closing in the last step of the synthesis, and 2) BTF and the mono- and difuranone derivatives are sensitive to silica gel, so avoid letting the compounds reside in a column too long during purification.

 

Read this exciting research for free until 21/06/2017 through a registered RSC account.

 

Mild and efficient synthesis of ω,ω-heterodifunctionalized polymers and polymer bioconjugates
Polym. Chem., 2017,8, 2457-2461, DOI: 10.1039/C7PY00225D

 

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About the webwriterAthina Anastasaki

Dr. 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 website for more

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Focus on: Polymer Self-Assembly

Self-assembly of block copolymers is well-known to form polymeric particles with various morphologies, for example, spherical, cylindrical and vesicular morphologies. This month we focus on three research articles published in Polymer Chemistry involving polymer self-assembly.

Polymer self-assembly is driven by the respective solubilities of the blocks of the copolymer in the solvent media present. For example, when water is the desired media the polymer is designed so that one block is water soluble and one block is water insoluble. Either post-polymerisation self-assembly, or in situ polymerisation-induced self-assembly can be employed to form a range of particle morphologies. Post-polymerisation self-assembly typically relies on a solvent switch technique whereby the block copolymer is dissolved in a good solvent for the whole polymer, and is subsequently added to another miscible solvent which is a good solvent for one block and a non-solvent for another. On the other hand, polymerisation-induced self-assembly involves the chain extension of a soluble stabiliser block with a monomer, which when polymerised is insoluble, therefore the polymerisation of the monomer drives the self-assembly process.

The first two articles here utilise polymerisation-induced self-assembly, whilst the third employs post-polymerisation self-assembly. Interestingly, all of the articles highlighted here have employed reversible addition-fragmentation chain-transfer (RAFT) polymerisation as the polymerisation technique of choice to prepared the polymers studied.

 

 

1. In situ synthesis of a self-assembled AB/B blend of poly(ethylene glycol)-b-polystyrene/polystyrene by dispersion RAFT polymerization
Bing Yuan, Xin He, Yaqing Qu, Chengqiang Gao, Erika Eiser, Wangqing Zhang
Polym. Chem., 2017,8, 2173-2181; DOI: 10.1039/C7PY00339K

In this article, the authors present the self-assembly of diblock copolymers and homopolymers through a dispersion RAFT polymerisation. The use of a poly(ethylene glycol) macromolecular chain-transfer agent (macro-CTA) and a small molecule CTA led to the formation of various self-assembled morphologies that were considerably different from the pre-synthesised equivalent blends. Morphologies obtained include: vesicles, compartmentalized vesicles and porous nanospheres.

2. RAFT/MADIX emulsion copolymerization of vinyl acetate and N-vinylcaprolactam: towards waterborne physically crosslinked thermoresponsive particles
Laura Etchenausia, Abdel Khoukh, Elise Deniau Lejeune, Maud Save
Polym. Chem., 2017, 8, 2244-2256; DOI: 10.1039/C7PY00221A

Here, the RAFT/MADIX batch emulsion copolymerisation of vinyl acetate (VAc) and N-vinyl caprolactam (VCL) was performed using a poly(ethylene glycol) macro-CTA. The resulting particles were physically crosslinked and thermoresponsive, and particles with a core composition of VAc and VCL of 47:53 exhibited a reversible swelling-to-collapse transition with heating. The hydrolysis of VAc units to vinyl alcohol gave thermoresponsive biocompatible statistical copolymers.

3. CO2-Triggered UCST transition of amphiphilic triblock copolymers and their self-assemblies
Shaojian Lin, Jiaojiao Shang, Patrick Theato
Polym. Chem., 2017, 8, 2619-2629; DOI: 10.1039/C7PY00186J

RAFT polymerisation was used to prepare triblock copolymers consisting of poly[(ethylene glycol)methyl ether]-b-poly(acrylamide-co-acrylonitrile)-b-poly(diethylamino ethyl methacrylate), which self-assembled in water to form vesicles. As this triblock copolymer contains a temperature responsive segment and a COresponsive block, a morphological transition from vesicles to micelles could be achieved with a COpurge, and then to unimers with an increase in temperature.

Read these articles for free until June 21th


About the webwriterFiona Hatton

Dr. Fiona Hatton is a web writer for Polymer Chemistry. She is currently a postdoctoral researcher in the Armes group at the University of Sheffield, UK. Find her on Twitter: @fi_hat

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2017 Polymer Chemistry Lectureship awarded to Julien Nicolas

It is with great pleasure that we announce Dr Julien Nicolas (Université Paris Sud, France) as the recipient of the 2017 Polymer Chemistry Lectureship.

This award, now in its third year, honours an early-career researcher who has made significant contribution to the polymer chemistry field. The recipient is selected by the Polymer Chemistry Editorial Board from a list of candidates nominated by the community.

Read on to find out more about Julien…

Dr Julien Nicolas

Julien Nicolas obtained his Doctor of Philosophy in Chemistry and Physical Chemistry of Polymers in 2005 from the Laboratory of Polymer Chemistry, at the Université Pierre and Marie Curie, in Paris, France, under the supervision of Prof. Bernadette Charleux. He then joined Prof. David Haddleton’s group at the University of Warwick as a postdoctoral fellow in 2006. In 2007, he became a CNRS researcher at Institut Galien, Paris Sud, and became a Director of Research in the same institute in 2016. He has published more than 80 refereed scientific articles (h-index 36), filled 5 patents and is currently Associate Editor for Chemistry of Materials (ACS).

Julien’s current research interests are multidisciplinary and span from organic chemistry and polymer synthesis to nanoparticulate systems and biomedical applications. The current interests of his group are focused on multifunctional biodegradable nanoparticles, well-defined molecular/polymer prodrug nanoparticles and controlled polymerization techniques from both fundamental and applied standpoints, with an emphasis on their application for the synthesis of biodegradable vinyl polymers and innovative biomaterials. Awards and honours he has received to date include the French Polymer Society (GFP) / French Chemical Society (SCF) award in 2016, and the 2017 Polymer Chemistry Lectureship award.

 

 

To learn more about Julien’s research, have a look at some of his publications in Polymer Chemistry:

Structure–cytotoxicity relationship of drug-initiated polymer prodrug nanoparticles
Yinyin Bao and Julien Nicolas
Polym. Chem., 2017, DOI: 10.1039/C7PY00536A

Efficient synthesis of 2-methylene-4-phenyl-1,3-dioxolane, a cyclic ketene acetal for controlling the NMP of methyl methacrylate and conferring tunable degradability
Johanna Tran,Elise Guégain, Nada Ibrahim, Simon Harrisson and Julien Nicolas
Polym. Chem., 2016, 7, 4427-4435

On the structure–control relationship of amide-functionalized SG1-based alkoxyamines for nitroxide-mediated polymerization and conjugation
Elise Guégain, Vianney Delplace, Thomas Trimaille, Didier Gigmes, Didier Siri, Sylvain R. A. Marque, Yohann Guillaneuf and Julien Nicolas
Polym. Chem., 2015,6, 5693-5704

Recent trends in the design of anticancer polymer prodrug nanocarriers
Vianney Delplace, Patrick Couvreur and Julien Nicolas
Polym. Chem., 2014, 5, 1529-1544

We would like to thank everybody who nominated a candidate for the Lectureship; we received many excellent nominations, and the Editorial Board had a difficult task in choosing between some outstanding candidates.

Please join us in congratulating Julien on his award!

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3rd Functional Polymeric Materials Conference

The third FPM series will bring together leaders in polymers and polymeric materials from around the world to describe their most recent and cutting edge discoveries.

The aim of the conference, which takes place in Rome, Italy from 7-10 July, is to capture the multidisciplinary nature of polymer chemistry with topics spanning “basic synthesis and methodology” to “nanoscale and bioinspired materials”.

This conference will appeal to academics, students, postdoctoral research associates, industrial scientists and leaders, governmental researchers and those currently involved in the development of polymeric material applications to address the most critical needs in areas such as medicine, energy and sustainability.

Talk submission ends 1 Mayregsiter here

Poster submission ends 10 Maysubmit here

For more information and to see the full list of invited speakers, visit the conference website.

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Focus on: Polymers and Rotaxanes

This month the focus is on Polymers and Rotaxanes, inspired by a recent lecture I attended, given by Sir J. Fraser Stoddart. He received the Nobel Prize in Chemistry in 2016, which was awarded jointly between himself, Jean-Pierre Sauvage and Bernard L. Feringa. His talk, which was part of the Krebs series of lectures at the University of Sheffield, featured his research in the field of mechanically interlocked molecules: rotaxanes and catenanes, which led to his pioneering work on “Molecular Machines”, for which the Nobel Prize was awarded.

Rotaxanes and catenanes are mechanically interlocked molecules; rotaxanes consist of a dumbbell shaped unit, with an encircled ring trapped by the dumbbell ends, whilst catenanes contain a number of interlocked macrocycles. The pioneering work of the Nobel laureates mentioned above has seen these systems developed, whereby through controlling the complexity and chemical functionality of the interlocked structures, work is possible, therefore leading to the term “Molecular Machines”.

Whilst rotaxane and catenane chemistry is well established, the same concept applied in polymer chemistry is currently a smaller area of research interest. However, this area of polymer chemistry research is emerging, with one article featured in Polymer Chemistry this month on the use of a non-polymeric rotaxane crosslinker to form toughened polymer networks. Looking back at previous Polymer Chemistry issues, two further articles utilising rotaxanes have been highlighted below.

1. A vinylic rotaxane cross-linker for toughened network polymers from the radical polymerization of vinyl monomers
J. Sawada, D. Aoki, M. Kuzume, K. Nakazono, H. Otsuka, T. Takata
Polym. Chem., 2017, 8, 1878-1881; DOI: 10.1039/c7py00193b

The authors describe the use a non-polymeric rotaxane crosslinker (RC), with two polymerisable vinyl groups, one on each constituent of the rotaxane unit, for the preparation of rotaxane crosslinked polymers (RCP). The RCPS were prepared via the free radical polymerisation of either butyl acrylate or ethylhexyl acrylate with the RC. The RCPs showed a higher toughness and fracture energy when compared with an equivalent polymer crosslinked with a standard divinyl monomer.

2. Mechanically linked poly[2]rotaxanes constructed from the benzo-21-crown-7/secondary ammonium salt recognition motif
Peng Wang, Zhao Gao, Ming Yuan, Junlong Zhua, Feng Wang
Polym. Chem., 2016, 7, 3664-3668; DOI: 10.1039/c6py00494f

Here, poly[2]rotaxanes were prepared through Cu(I) catalysed click polymerisation of the individual rotaxane units to give a linear polymer. The rotaxane monomer was prepared via a so-called “threading-followed-by-stoppering” strategy. The rheological properties of the poly[2]rotaxanes were investigated and exhibited shear-thinning behaviour not observed for the poly(caprolactone) precursors.

3. Phototriggered supramolecular polymerization of a [c2]daisy chain rotaxane
Xin Fu, Rui-Rui Gu, Qi Zhang, Si-Jia Rao, Xiu-Li Zheng, Da-Hui Qu, He Tian
Polym. Chem., 2016, 7, 2166-2170; DOI: 10.1039/c6py00309e

The formation of a polyrotaxane was achieved through the initial protection of two 2-ureido-4-pyrimidinone (Upy) end groups with photolabile coumarin groups. Exposure to UV light removed the coumarin protecting groups, which led to the self-assembly of the Upy groups and supramolecular polymerisation of the [c2] daisy chain rotaxane monomer. This work represents an interesting stimuli-responsive supramolecular polymers utilising rotaxanes.

Read these articles for free until May 21th


About the webwriterFiona Hatton

Dr. Fiona Hatton is a web writer for Polymer Chemistry. She is currently a postdoctoral researcher in the Armes group at the University of Sheffield, UK. Find her on Twitter: @fi_hat

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Paper of the month: Novel alkoxyamines for the successful controlled polymerization of styrene and methacrylates

Simula et al. report the synthesis of poly(styrene) and poly(methacrylates) using novel alkoxyamines.

Reversible addition-fragmentation chain transfer polymerization (RAFT) and transition metal-mediated radical polymerization (TMM-RDRP) are two widely used techniques employed for the preparation of controlled polymeric architectures. However, both of them exhibit significant colouring and complete purification of the final materials is challenging. On the other hand, nitroxide mediated polymerization (NMP) requires no or minimal purification although designing alkoxyamines that can facilitate the controlled polymerization of both styrene and methacrylates is a challenge. In this contribution, Asua and co-workers employed three different alkoxyamines to study the homopolymerization of styrene and its chain extension with methacrylates. Upon careful evaluation of the reaction kinetics as well as variation of the polymerization temperature, high monomer conversions with uncompromised end group fidelity could be achieved. A wide range of molecular weights were targeted in order to identify the limitations of the system. It was found that for targeted degrees of polymerization beyond 333, there was an increased difference between theoretical and experimental molecular weights, due to the thermal initiation of styrene. In addition, the nature of the substituents in the nitroxide adduct was also found to be crucial for the controlled polymerization of styrene with bulkier adducts providing more extensive control. The retention of the reactive alkoxyamine chain end was further confirmed via nuclear magnetic resonance (NMR) and matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-ToF-MS). Well-defined PS-b-PBMA and PMMA-b-PS block copolymers were also successfully prepared highlighting these classes of alkoxyamines as a versatile mediator for the controlled polymerization of both methacrylates and styrene.

 

 

Tips/comments directly from the authors:

  1. It is important to monitor the temperature throughout the polymerisation in order to ensure optimum kinetics.

 

  1. The appropriate temperature should be employed for methacylates (< 100 °C) and styrene (> 110 °C). For instance, this can influence the final molar mass distributions of a block copolymer. The preparation of a poly(methyl methacrylate) macro-alkoxyamine first, followed by the chain extension with styrene provides a PMMA-b-PS block copolymer with moderate MMD. However, the preparation of the PS block first would yield a block copolymer with high dispersity value due, in part, to the high temperatures employed.

 

  1. Several matrix/salt combinations should be tested when conducting MALDI-ToF MS analysis. The reactive chain ends might not be observed with some matrixes, such as trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB).

 

 

Read this exciting research for free until 16/05/2017 through a registered RSC account:

 

Novel alkoxyamines for the successful controlled polymerization of styrene and methacrylates
Polym. Chem., 2017,8, 1728-1736, DOI: 10.1039/c6py02190e

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About the webwriterAthina Anastasaki

Dr. 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 website for more information.

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Chemical weapons trapped the swell way

Hypercrosslinked polymers absorb deadly agents

UK researchers have shown that polymers can absorb chemical warfare agents. When dried, the densely crosslinked polystyrene networks can swell to accommodate organic molecules. They can therefore act not just as universal sorbents for soaking up a wide range of chemicals, but also as a new way to decontaminate stockpiles of chemical weapons.

 

Source: © Royal Society of Chemistry
Reaction used to prepare the hypercrosslinked polymer networks



Read the full story by Hugh Cowley in Chemistry World.


This article is free to access until 26 April 2017.

C Wilson et al, Polym. Chem., 2017, DOI: 10.1039/c7py00040e

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Global Conference on Polymer and Composite Materials 2017

23-25 May 2017, Guangzhou, China

 

Polymer and Composite Materials 2017, which takes place at the South China University of Technologyis dedicated to cover all theoretical and experimental aspects of polymers and composite materials. Building on the hugely successful preceding conferences (PCM 2014 in Ningbo, PCM 2015 in Beijing, and PCM 2016 in Hangzhou), PCM 2017 will provide an ideal academic platform for researchers to present their latest findings, and to facilitate networking and in-depth discussion with peers from Asia, Europe and USA.

The scientific program will focus not only on current advances in the research, but also in the production and use of polymers and composite materials in different fields. The conference setting has a highly focused technical program through plenary, invited, contributed, and poster presentations, supported by Polymer Chemistry and Molecular Systems Design & Engineering.

In addition, the conference will also offer the possibility to publish your research either in the conference proceedings (Indexed by Ei, Scopus, Inspec, CPCI, etc) or in well-known journals with ISI impact factors. You can find out more about how to submit your paper via the publication guide.

Keynote speakers:

Register for the event here.

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Focus on: Carbon Dioxide and Polymers

Carbon dioxide constitutes a small amount of our atmosphere (currently around 0.04%) however it is vital for the survival of life on our planet. CO2 has been found to be a useful trigger for stimuli-responsive materials as it is benign, abundant, “green” and inexpensive. The reversible self-assembly of polymers and their response to the presence of CO2 has been of particular interest, for example in biomedical applications.

There is also a growing interest in carbon capture as environmental concerns increase, due to the rise in CO2 levels since the industrial age. Carbon capture has been proposed as a method to reduce the amount of CO2 in the atmosphere. Therefore several researchers have been interested in preparing materials which could be used absorb and store CO2 to remove it from the atmosphere.

This month we look at three articles published in Polymer Chemistry; two articles which describe CO2 responsive polymers, and one which investigates materials for CO2 absorption.

1. Oxygen and carbon dioxide dual gas-responsive homopolymers and diblock copolymers synthesized via RAFT polymerization
Xue Jiang, Feng Chun, Guolin Lu, Huang Xiaoyu
Polym. Chem., 2017, 8, 1163-1176; DOI: 10.1039/C6PY02004F

Firstly a monomer containing both O2 and CO2 responsive groups was prepared (containing a CF3 and tertiary amine group), and polymerised by reversible addition-fragmentation chain-transfer (RAFT) polymerisation. This polymer and a diblock copolymer containing PEG, showed responsivity when O2 and CO2 were bubbled through the solution compared with N2. The results suggest potential biomedical applications for the PEG containing polymer which formed micelles in solution.

2. CO2-Responsive graft copolymers: synthesis and characterization
Shaojian Lin, Anindita Das, Patrick Theato
Polym. Chem., 2017, 8, 1206-1216; DOI: 10.1039/C6PY01996J

Through a combination of controlled radical polymerisation and a grafting-to post-polymerisation modification, the authors describe the synthesis of CO2 responsive graft-copolymers, where the incorporation of a tertiary amine monomer imparts the CO2 responsive behaviour. The graft copolymers could be self-assembled to form vesicles in aqueous media, which swelled upon purging with CO2, for applications such as responsive drug delivery vehicles.

3. Microporous polyimide networks constructed through a two-step polymerization approach, and their carbon dioxide adsorption performance
Hongyan Yao, Na Zhang, Ningning Song, Kunzhi Shen, Pengfei Huo, Shiyang Zhu, Yunhe Zhang, Shaowei Guan
Polym. Chem., 2017, 8, 1298-1305; DOI: 10.1039/C6PY01814A

In contrast to the two previous articles, this paper reports the preparation of microporous polyimide networks, through polycondensation reaction and subsequent crosslinking. The formation of micropores was promoted due to the crosslinked structure, which restricted macromolecular conformational changes. The materials exhibited BET surface areas up to 497 m2g-1, with comparable CO2 uptake values to other microporous polyimides prepared from rigid tri-dimensional monomers.

Read these articles for free until April 16th


About the webwriterFiona Hatton

Dr. Fiona Hatton is a web writer for Polymer Chemistry. She is currently a postdoctoral researcher in the Armes group at the University of Sheffield, UK. Find her on Twitter: @fi_hat

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Paper of the month: Vesicles of double hydrophilic pullulan and poly(acrylamide) block copolymers: a combination of synthetic- and bio-derived blocks

Willersinn et al. report the synthesis of double hydrophilic pullulan and poly(acrylamide) block copolymers.

Double hydrophilic block copolymers (DHBC) self-assemble to various structures in aqueous solutions due to a strong difference in hydrophilicity. This is in contrast to amphiphilic block copolymers that self-assemble due to the insolubility of the hydrophobic block in water. In their recent contribution, Schmidt and co-workers were able to extend the principle of double hydrophilic self-assembly to novel polysaccharide-polyacrylamide block copolymers namely pullulan-b-poly(N,N-dimethylacrylamide) (Pull-b-PDMA) and pullulan-b-poly(N-ethylacrylamide) (Pull-b-PEA). The bio-derived pullulan block was obtained via acid catalyzed depolymerisation, while the polyacrylamide homopolymer blocks were synthesized via reversible addition-fragmentation chain-transfer (RAFT) polymerization. Subsequently the blocks were conjugated via copper catalyzed azide alkyne cycloaddition (CuAAC). The presence of formed vesicular structures was investigated via cryogenic electron microscopy (cryo SEM), static light scattering (SLS) and dynamic light scattering (DLS) measurements showing diameters in the range of 200 to 500 nm. Finally, laser confocal scanning microscopy (LSCM) was employed using Rhodamine B staining or Rhodamine B labelled block copolymers to image the formed particle structures. These novel vesicular structures may find use in a wide range of applications including drug delivery.


Tips/comments directly from the authors:

1. The synthesis of block copolymers via CuAAc can be significantly simplified via the utilization of azide functionalized resins. As described in the paper the alkyne functionalized building block is utilized in excess. The resin is added after sufficient reaction time directly to the reaction mixture to react with residual alkyne end functionalized polymer and finally the resin is easily removed via filtration after the reaction. Therefore, no optimization of equivalents or absolute molecular weight data is needed to obtain a pure product without homopolymer contamination.
2. The choice of blocks is crucial for DHBC self-assembly in water. The blocks have to feature a significant difference in hydrophilicity. Moreover, high polymer concentrations are needed to obtain self-assembled structures.
3. For a pure DHBC self-assembly the utilized blocks should not feature LCST or other stimulus responsive behaviour that alters the solubility of the individual blocks. Otherwise the self-assembly might be driven via hydrophobic interactions as with an amphiphilic block copolymer.

Read this exciting research for free until 16/04/2017 through a registered RSC account:

Vesicles of double hydrophilic pullulan and poly(acrylamide) block copolymers: a combination of synthetic- and bio-derived blocks
Polym. Chem., 2017,8, 1244-1254, DOI: 10.1039/c6py02212j

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About the webwriterAthina Anastasaki

Dr. 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 website for more information.

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