Archive for December, 2016

Stimulus-responsive polymers themed issue now online

Issue 1 of volume 8 of Polymer Chemistry is a themed issue on stimulus-responsive polymers, guest edited by Peter J. Roth (University of Surrey, UK) and Andrew B. Lowe (Curtin University, Australia). 

Stimulus-responsive, or “smart”, (co)polymers are fundamental to broad, and ever-growing, fields of research that encompass phase behaviour of unimer solutions, smart nanoparticles, and intelligent bulk materials with shape memory or self-healing abilities. In recent years, (co)polymers have been developed that respond to a fascinating range of chemical, physical, and mechanical stimulation and have been crafted into materials serving a multitude of applications. This special issue of Polymer Chemistry dedicated to stimulus-responsive polymers features articles on the cutting-edge development of novel “smart” materials, as well as up-to-date and in-depth reviews covering a range of specialist areas.

Check out the Editorial by the Guest Editors here.

 

A few articles from the themed issue are highlighted below

Is biopolymer hair a multi-responsive smart material?
Xueliang Xiao, Jinlian Hu, Xiaoting Gui, Jing Lu and Hongsheng Luo 

Field responsive materials: photo-, electro-, magnetic- and ultrasound-sensitive polymers
Theodore Manouras and Maria Vamvakaki

Self-healing of glucose-modified polyurethane networks facilitated by damage-induced primary amines
Ying Yang and Marek W. Urban

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Advisory Board Top Picks: Ben Zhong Tang

Ben Zhong Tang is a member of Advisory Board for Polymer Chemistry and K. C. Cheong Professor of Science and Chair Professor of Chemistry and Biomedical Engineering at The Hong Kong University of Science and Technology (HKUST). His research interests include macromolecular chemistry, materials science, and biomedical theranostics.

Tang’s research group has been working on the development of new polymerization routes from alkyne reactions, and has succeeded in the syntheses of a number of new functional conjugated polymers from acetylenic monomers.
Professor Tang has published over 900 papers which have been cited more than 40,000 times, leading to an h-index of 101. He has been listed by Thomson Reuters as a Highly Cited Researcher in both areas of Chemistry and Materials Science. He received a Natural Science Award from the Chinese Government and a Senior Research Fellowship from the Croucher Foundation in 2007.

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




Focus on Luminogenic Polymers

All articles are free to read until Sunday 22nd January.

 

CO2/pH-responsive particles with built-in fluorescence read-out

Anne B. Mabire, Quentin Brouard, Anaïs Pitto-Barry, Rebecca J. Williams, Helen Willcock, Nigel Kirby, Emma Chapman and Rachel K. O’Reilly
Polym. Chem., 2016, 7, 5943–5948.

K. O’Reilly and collaborators at the University of Warwick (UK), Australian Synchrotron (Australia) and BP Exploration Operating Company, Ltd. (UK) synthesized fluorescent CO2-responsive cross-linked polymeric particles via emulsion polymerization. In this system, a fluorescent monomer (aminobromomaleimide with high quantum yield was used as a probe for the core hydrophobicity; Poly(N,N-diethylaminoethylmethacrylate) and oligo(ethyleneglycol methacrylate) were utilized as the CO2-responsive core-forming segment and the hydrophilic shell-forming block, respectively. The polymer particles became swollen and the corresponding fluorescence intensity drastically decreased through simple CO2 bubbling. This contributed to the increased hydrophilicity of the particles. In addition, the swelling and emission processes were reversible by purging the mixture with nitrogen. The researchers also found that the ON/OFF cycles of fluorescence could be reproducible with CO2/N2 purges, indicating that the polymer can be used as a fluorescent sensor for CO2 detection.

 


Conventional fluorophore-free dual pH- and thermo-responsive luminescent alternating copolymer

Biswajit Saha, Kamal Bauri, Arijit Bag, Pradip K. Ghorai and Priyadarsi De
Polym. Chem., 2016, 7, 6895–6900.

In this work, P. De and coworkers at Indian Institute of Science Education and Research Kolkata synthesized a group of dual pH- and thermo-responsive fluorescent copolymers with a poly(maleimide-alt-styrene) skeleton that is free of traditional fluorophores. The emission intensity of the copolymers increases with increasing pH and decreases with increasing temperature from 20 to 70 °C at pH 4.5. Density functional theory calculations show that the π molecular orbital is located over the benzene ring as the HOMO and the π* on the maleimide unit as the LUMO, suggesting that the through-space π–π interaction between the benzene ring and the neighboring carbonyl group of the maleimide unit is the origin of the unexpected fluorescence in the copolymers.

 


Unanticipated bright blue fluorescence produced from novel hyperbranched polysiloxanes carrying unconjugated carbon–carbon double bonds and hydroxyl groups
Song Niu, Hongxia Yan, Zhengyan Chen, Song Li, Peilun Xu and Xiaoli Zhi
Polym. Chem. 2016, 7, 3747–3755.

Fluorescent polymers containing no aromatic rings have attracted much interest due to their environmental benignancy, cytocompatibility and biodegradability. S. Niu, H. Yan and coworkers at Northwestern Polytechnical University (China) designed and prepared new hyperbranched polysiloxanes by a one-pot transesterification reaction of excessive neopentyl glycol with triethoxyvinylsilane. The resultant non-conjugated polysiloxanes show bright blue photoluminescence. Their emission intensities are increased when the polymers are more aggregated by increasing their molecular weights and concentrations, showing the photophysical effect similar to aggregation-induced emission. The interaction between the unconjugated C=C and –OH units in the tight aggregate was proposed to be critical for such strong unconventional luminescence.

 


Pillar[5]arene-based amphiphilic supramolecular brush copolymers: fabrication, controllable self-assembly and application in self-imaging targeted drug delivery

Guocan Yu, Run Zhao, Dan Wu, Fuwu Zhang, Li Shao, Jiong Zhou, Jie Yang, Guping Tang, Xiaoyuan Chen and Feihe Huang
Polym. Chem., 2016, 7, 6178-6188.

Supramolecular brush copolymers (SBPs) fabricated from simple building blocks via non-covalent interaction have tremendous advantages, such as stimuli-responsiveness. X. Chen, F. Huang and coworkers at Zhejiang University (China) and National Institutes of Health (USA) constructed SBP-based supramolecular nanoparticles (SNPs), which were utilized as a self-imaging drug delivery vehicle by taking advantage of the photophysical effect of aggregation-induced emission. The fluorescence arising from tetraphenylethene and doxorubicin (DOX) was quenched due to the involved energy transfer relay effect. The silenced fluorescence was recovered at low pH and by reductase through the release of the loaded DOX, achieving in situ visualization of the drug release process. In vitro and in vivo experiments confirmed that the DOX-loaded SNPs showed excellent antitumor efficacy with negligible systemic toxicity. The present study provides a novel supramolecular method for the construction of self-imaging drug delivery systems, with promising applications in the field of cancer treatment.

 


Room temperature phosphorescence of 4-bromo-1,8-naphthalic anhydride derivative-based polyacrylamide copolymer with photo-stimulated responsiveness

Hui Chen, Lei Xu, Xiang Ma and He Tian
Polym. Chem., 2016, 7, 3989–3992

In this work, X. Ma, H. Tian and coworkers at the East China University of Science and Technology developed a new system of room temperature phosphorescence (RTP). The system was constructed from γ-cyclodextrin (γ-CD) and a polymer containing 4-bromo-1,8-naphthalic anhydride moiety (poly-BrNpA). While the aqueous solution of poly-BrNpA alone does not give any RTP signal, the poly-BrNpA/γ-CD binary system shows RTP emission centered at 580 nm with a lifetime of 0.32 ms. NMR spectroscopy was used to study the complexation behavior and to prove that the RTP of poly-BrNpA/γ-CD is from the host-guest interaction between poly-BrNpA and γ-CD. From poly-BrNpA/γ-CD, a pure organic RTP hydrogel was successfully prepared. Through incorporating azobenzene (Azo) unit, the RTP of the ternary mixture of poly-BrNpA/γ-CD/poly-Azo becomes reversibly tunable by the photo-isomerization of the Azo unit. This photo-regulation is achieved by the inclusion competition between the cis/trans isomers of the Azo unit and poly-BrNpA.

 


Synthesis and chiroptical properties of a π-conjugated polymer containing glucose-linked biphenyl units in the main chain capable of folding into a helical conformation

Tomoyuki Ikai, Syo Shimizu, Seiya Awata, Tomoya Kudo, Takayuki Yamada, Katsuhiro Maeda and Shigeyoshi Kanoh
Polym. Chem., 2016, DOI: 10.1039/c6py01759b

An optically active π-conjugated polymer containing chiral glucose-linked biphenyl units can interconvert between random-coil and helical-chain conformations in response to external environment, as demonstrated by T. Ikai et al. at Kanazawa University (Japan). The optically active polymer likely folds into a helical structure with a preferred handedness in the suspension containing high amounts of a poor solvent (acetonitrile), whereas the polymer conformation becomes a random coil in pure good solvent (chloroform). In addition, the chiral helical polymer shows efficient left-handed circularly polarized luminescence (CPL) with a green color. The solvent-dependent CPL signal change was also observed. The dissymmetry factor of the chiral helical polymer can reach 1.9×10-2 in the film state. The researchers thus offer a new approach to functional materials through utilization of the chirality of abundant biomass resources.

 

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Paper of the month: SET-LRP of acrylates catalyzed by a 1 penny copper coin

Aksakal et al. report the Cu(0)-mediated living radical polymerization of acrylates using a British penny coin.

Cu(0)-mediated living radical polymerization, typically referred to as single electron transfer living radical polymerization (SET-LRP), is a versatile tool for the synthesis of advanced materials. The groups of Becer and Resmini have further highlighted this versatility by reporting the SET-LRP of acrylates catalyzed by a penny copper coin. Impressively, a wide range of hydrophobic and hydrophilic monomers were successfully polymerized yielding well-defined polymers with low dispersities, near-quantitative conversions and high end group functionality. The scope of the system was subsequently expanded to include the synthesis of star polymers through the core first approach. Interestingly, the authors used two type of coins, the first one (issued in 1971-1992) consisting of 97% of copper and the second one (issued after 1992) consisting of 6% of copper. Both coins exhibited near identical polymerization results. A series of polymerizations targeting different degrees of polymerization were also conducted, all proceeding with very good control over the molecular weight distributions. In comparison to traditional Cu(0)-wire systems, British penny coins have the additional advantage of prohibiting the induction period, which is typically observed for many SET-LRP reactions. Finally, the scalability of these polymerizations up to 50 gram scale was also successful and thus demonstrating an economic, efficient and easily accessible catalyst for SET-LRP of various acrylic monomers.


Tips/comments directly from the authors:

Comments:

In this study, we provide direct evidence that the traditionally used Cu(0)-wire can be replaced with a copper coin, regardless to its year of issue. To avoid any induction period, this method can be employed for the synthesis of well-defined polymers of acrylates with both linear and star shaped initiators.


Tips:

  1. Since the coins are usually contaminated due to prior circulation, we suggest for reproducibility purposes a quick rinse with a freshly prepared HCl before the polymerization.
  2. As mentioned in the manuscript, both penny coins issued before and after 1992 exhibit near identical polymerization results. However, the coins issued after 1992 consist of 94% steel and are magnetic. Due to this, it should be taken into account that the magnetic stirrer can occasionally spin out of its axis. Therefore, we suggest the use of narrow and long Schlenk tube to avoid any splashing of the polymerization mixture.
  3. Due to the reactivity of the polymerization mixture, samples for both NMR and GPC should be diluted immediately in order to avoid errors during kinetic sampling.
  4. The inhibitor of monomers can be easily removed by passing over a plug of basic aluminium oxide. Due to the high viscosity of the OEGA480 monomer, larger volumes can be diluted in a volatile solvent to decrease viscosity. Evaporation of the solvent will provide the inhibitor-free monomer.

Read this exciting research for free until 25/11/2016 through a registered RSC account:

SET-LRP of acrylates catalyzed by a 1 penny copper coin
R. Aksakal, M. Resmini and C.R. Becer
Polym. Chem.
, 2016, 7, 6564-6569
DOI: 10.1039/C6PY01295G

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About the webwriterAthina Anastasaki

Dr. Athina Anastasaki is a web writer for Polymer Chemistry. She is currently an Elings 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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Focus on: Boron Functional Polymers

This month we take a look at three articles published in Polymer Chemistry reporting the use of boron, either as boron-functional polymers or polymerisation catalyst. Boron is an interesting element, essential to life, and has mainly been investigated in the field of polymer chemistry through boronic acid, organoborate and carborane functional polymers. The incorporation of boronic acid into various polymers is of interest due to its responsiveness to pH, and ability to bind 1,2- and 1,3-diols resulting in anionic boronate ester complexes. This has been probably most widely investigated as materials for the detection of glucose which has broad biomedical implications.

The first two articles here focus on the incorporation of boronic acid into polymeric materials, whilst the final article presents the use of a boronate-urea as a co-catalyst for ring opening polymerisation.

ToC figure

1. Bioinspired synthesis of poly(phenylboronic acid) microgels with high glucose selectivity at physiological pH
Qingshi Wu, Xue Du, Aiping Chang, Xiaomei Jiang, Xiaoyun Yan, Xiaoyu Cao, Zahoor H. Farooqi, Weitai Wu
Polym. Chem., 2016, 7, 6500-6512; DOI: 10.1039/C6PY01521B

Here, poly(phenyl boronic acid) microgels were prepared through the free radical polymerisation of 4-vinylphenylboronic acid and a cross-linker in the presence of a surfactant. The microgels swelled in the presence of glucose (0-30 mM) at physiological pH (7.4), with an enhanced swelling ratio when compared to other monosaccharides, and a highly selective glucose-dependant fluorescence emission. These materials showed potential for use as sensors for glucose detecting.

2. Synthesis of novel boronic acid-decorated poly(2-oxazoline)s showing triple-stimuli responsive behavior
Gertjan Vancoillie, William L. A. Brooks, Maarten A. Mees, Brent S. Sumerlin, Richard Hoogenboom
Polym. Chem., 2016, 7, 6725-6734; DOI: 10.1039/C6PY01437B

The authors describe boronic acid functional poly(2-alkyl-2-oxazoline)s through the cationic ring opening copolymerisation of 2-n-propyl-2-oxazoline and a methyl ester oxazoline, followed by subsequent post-polymerisation modification to functionalise the polymer with boronic acid moeities. The subsequent polymers exhibited LCST behaviour, with pH and glucose concentration dependancy for the thermal transitions, highlighting possible applications in drug delivery, for example.

3. Internal Lewis pair enhanced H-bond donor: boronate-urea and tertiary amine co-catalysis in ring-opening polymerization
Songquan Xu, Herui Sun, Jingjing Liu, Jiaxi Xu, Xianfu Pan, He Dong, Yaya Liu, Zhenjiang Li, Kai Guo
Polym. Chem., 2016, 7, 6843-6853; DOI: 10.1039/C6PY01436D

In this article, the use of a boronate-urea (BU)  has been presented as a Lewis pair enhanced H-bond donor for the co-catalysis of the ring opening polymerisation of ʟ-lactide. The polymerisations reached high conversions and the resultant polymers exhibited controlled molecular weights and low dispersites. The BU was shown to be mild, tunable and compatible with several tertiary amines, and more efficient than a common urea.

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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 Global Conference on Polymer and Composite Materials (PCM 2017)

The 2017 Global Conference on Polymer and Composite Materials (PCM 2017) will be held in the beautiful city of Guangzhou, China.

This well-established conference series is 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 PCM2016 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, oral and poster presentations.

Keynote speakers

Abstract submission: Click here

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