Archive for June, 2016

Polymer Chemistry’s Impact Factor increases to 5.687

Polymer Chemistry is pleased to announce that its latest Impact Factor is 5.687.

Polymer Chemistry is the home for the most innovative and exciting polymer research, with an emphasis on the synthesis of polymers and their applications. Led by Editor-in-Chief David Haddleton, and our expert team of international Associate Editors and Editorial Board members, Polymer Chemistry has the highest immediacy index (1.408) of any primary research journal in the Polymer Science category.

Immediate impact: Our Immediacy Index has been consistently higher than those of our competitors since our launch.

High citation rate: We have a higher fraction of articles cited than our competitors, with 98% of papers receiving at least 1 citation.*

Rapid publication: We have an average time from receipt to publication of just 50 days, and less than 19 days from receipt to first decision.

Continued growth: For the 6th year in a row both our number of publications and our impact factor have increased.

We are extremely grateful to all our readers, authors and referees for their contribution to Polymer Chemistry’s continued success, and to our Editorial and Advisory Board members for their hard work and dedication.

Join the many leading scientists who have already chosen to publish in Polymer Chemistry and submit today!

Find out how other Royal Society of Chemistry journals were ranked in the latest Impact Factor release.

*As of 29 June 2016, based on citations to articles published in 2013 and 2014.

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Focus on: Aggregation Induced Emission in Polymers

Aggregation induced emission (AIE) is the phenomenon through which luminophores exhibit an enhanced luminescence in the aggregated state. To date, various types of luminogens have demonstrated AIE, including: hydrocarbon, heteroatom, cyano-substituted, hydrogen bonded, polymeric and organometallic based luminogens.

Here we take a look at three articles which focus on AIE in polymers that were published in Polymer Chemistry this month.

ToC

1. Aggregation-induced emission: the origin of lignin fluorescence
Yuyuan Xue, Xueqing Qiu, Ying Wu, Yong Qian, Mingsong Zhou, Yonghong Deng, Yuan Li
Polym. Chem., 2016, 7, 3502-3508; DOI: 10.1039/C6PY00244G

Lignin is commonly defined as a complex and irregular phenylpropanoid heteropolymer, with wide variability in structure, and its fluorescence has been well studied. The authors demonstrate that AIE is the cause of the blue lignin fluorescence commonly observed, due to clustering of carbonyl groups and restriction of intrmolecular rotation. This system aids the development of non-conventional chromophores originating from biomass.


2. Fabrication of a cross-linked supramolecular polymer on the basis of cucurbit[8]uril-based host–guest recognition with tunable AIE behaviors
Lili Wang, Zhe Sun, Miaomiao Ye, Yu Shao, Lei Fang, Xiaowei Liu
Polym. Chem., 2016, 7, 3669-3673; DOI: 10.1039/C6PY00500D

A supramolecular cross-linked polymer based on the ternary host-guest interaction between cucurbit[8]uril, 1,1-dimethyl-4,4-bipyridinium dication and an azobenzene derivative was prepared. The resulting material was photoresponsive due to the azobenzene derivative and the introduction of tetraphenylethylene gave the network AIE properties. This novel photoresponsive cucurbit[8]uril-based supramolecular polymer with AIE, enables further development of fluorescent cucurbituril-based materials.


3. Acid–base-controlled and dibenzylammonium-assisted aggregation induced emission enhancement of poly(tetraphenylethene) with an impressive blue shift
Lipeng He, Lijie Li, Xiaoning Liu, Jun Wang, Huanting Huang, Weifeng Bu
Polym. Chem., 2016, 7, 3722-3730; DOI: 10.1039/C6PY00275G

Suzuki cross-coupling polymerisation was used to prepare several poly(tetraphenylethylene) based polymers, grafted with dibenzo-24-crown-8 groups (DB24C8), connected at different positions (ortho, meta or para). The polymers exhibited AIE, which was highly dependant upon the substitution and could also be caused by complexation of the DB24C8 groups with dibenzyl ammonium chloride. These polymers show promising properties required for optoelectronic, chemical and biomedical sensors.

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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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Paper of the month: Bespoke cationic nano-objects via RAFT aqueous dispersion polymerisation

Williams et al. utilise addition-fragmentation chain transfer aqueous dispersion polymerisation for the synthesis of bespoke cationic nano-objects directly in water.

Polymerisation-induced self-assembly (PISA) via reversible addition-fragmentation chain transfer (RAFT) polymerisation enables the direct and efficient formation of various diblock copolymer morphologies (e.g. spherical micelles, work-like micelles, vesicles etc.) in aqueous solution. Here the first block is selected to be water-soluble, while the growing second block is water-insoluble and hence drives in situ self-assembly. This versatile approach can be conducted at much higher copolymer concentrations than traditional block copolymer self-assembly based on post-polymerisation processing.

Now Williams and co-workers report the synthesis of a range of cationic diblock copolymer nano-objects utilising a judicious binary mixture of chain transfer agents, namely non-ionic poly(glycerol monomethacrylate) (PGMA) and cationic poly[2-(methacryloyloxy)ethyl trimethylammonium chloride] (PQDMA) and using poly(2-hydroxypropyl methacrylate) (PHPMA) as the hydrophobic core-forming block. Systematic variation of the PQDMA mol fraction and the mean degree of polymerisation of the core-forming PHPMA block enabled the formation of well-defined spheres, worms or vesicles that remain cationic over a wide pH range.

Interestingly, higher cationic character led to the formation of kinetically-trapped spheres; this is because more effective electrosteric stabilisation prevents sphere-sphere fusion. In addition, using 5 mol% PQDMA stabiliser enabled preparation of a 12.5% w/w cationic worm gel that exhibited a zeta potential of +20 mV and a storage modulus of 137 Pa, as demonstrated by variable temperature rheology studies. This worm gel proved to be thermoresponsive: it underwent reversible degelation on cooling from 25 °C to 5 °C. Finally, such cationic gels exhibited weak antimicrobial activity towards the pathogen Staphylococcus aureus.

Tips/comments directly from the authors:

  1. It is really important to map out a detailed phase diagram for the reliable and reproducible identification of pure copolymer phases. This is particularly true for the elusive worm phase, since this occupies relatively narrow phase space.
  2. Using pairs of stabiliser blocks is a powerful and versatile means of tuning the copolymer morphology. If a wholly cationic stabiliser is used, only spheres can be obtained. However, using a binary mixture of a non-ionic and a cationic stabiliser allows access to cationic spheres, worms or vesicles. This is because the non-ionic stabiliser dilutes the charge density within the coronal layer. If maximum cationic character is desired, then the ionic block should have a higher degree of polymerisation than the non-ionic block. This will enable it to protrude from the layer of non-ionic stabiliser chains and influence the electrophoretic footprint of the diblock copolymer nano-objects.
  3. When diluting thermoresponsive worm dispersions to the relatively low concentrations typically used for TEM or DLS analysis, it is important for dispersions to be stored at ambient temperature. This is because the thermoresponsive degelation behaviour becomes irreversible below a certain critical copolymer concentration. Thus storing highly dilute (< 1 %) dispersions in a refrigerator at 4-5 °C simply leads to kinetically-trapped spheres – worms are no longer reformed on returning to ambient temperature under these conditions.



Read this exciting research for free until 31/07/2016 through a registered RSC account:

Bespoke cationic nano-objects via RAFT aqueous dispersion polymerisation
M. Williams, N. J. W. Penfold, J. R. Lovett, N. J. Warren, C. W. I. Douglas, N. Doroshenko, P. Verstraete, J. Smets and S. P. Armes
Polym. Chem., 2016, 7, 3864-3873
DOI: 10.1039/C6PY00696E

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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).

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Warwick Polymer Conference 2016

Warwick Polymer Conference 2016 is the premier conference on polymer chemistry, which focus on the chemical synthesis and chemical properties of polymers.

Held 11–14 July 2016 in Warwick, UK, this year’s conference is the fourth in their series of international polymer chemistry meetings and the largest so far with almost 600 delegates. The program is designed for all to spend social time as well as scientific time.

Polymer Chemistry proudly sponsors this conference, which will feature a number of lectures by both established researchers from across the globe and early-career scientists who are making recent, novel contributions. Contributed oral and poster presentations will also add to the mix.

Mark your calendar today and register now!


Executive Editor, Polymer ChemistryMeet the team:

Dr Neil Hammond (Executive Editor of Polymer Chemistry) will be attending the event. He would love to hear about your research and meet with our readers, authors and referees. Please do get in touch with Neil if you would like to arrange a meeting in advance.

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Paper of the month: Thermoresponsive hydrogels from triblock copolymers

Despax et al. report the synthesis of triblock copolymers and their application as thermoresponsive hydrogels.

c6py00499g

Temperature responsive gelators can benefit a wide range of biomedical applications and typically comprised of triblock copolymers with a central hydrophilic block and terminal blocks that undergo a hydrophilic to hydrophobic transition at a specific temperature. However, typical ABA triblock copolymers obtained from commercially available monomers require concentrations of at least 50-100 g L-1.

Harrisson, Destarac and co-workers have managed to circumvent this by synthesizing high molecular weight triblock copolymers via low temperature reversible addition-fragmentation chain-transfer (RAFT) gel polymerization. The targeted triblock copolymers were based on polydimethylacrylamide (PDMA) as the long central hydrophilic block and poly(N-isopropylacrylamide) (PNIPAM) as the shorter terminal blocks and the gel formation was initially demonstrated via vial-inversion tests.

Two different molecular weight triblock copolymers were tested with the PDMA block varying from 58 kg mol-1 to 421 kg mol-1 showing self-supporting gels at 30 g L-1 and 6 g L-1 concentration respectively, which is already a significant improvement over previously reported materials. As the vial-inversion test is subject to experimental variations, a more objective measure of the effect of the temperature was obtained from the evolution of the storage and loss moduli of aqueous polymer solutions.

For the lower molecular weight polymer, a two-step transition consisting of an initial thickening of the solution at the lower critical solution temperature (LCST) of PNIPAM occurred followed by gel formation at 38–39 °C requiring a minimum concentration of 20 g L-1. For the longer polymer, only the second transition was observed; gel formation occurred at 40-45 °C with a minimum concentration of 4 g L-1. With a storage modulus of only 0.1 Pa however, this gel is likely too soft for practical use.

In an attempt to improve the mechanical properties of the gels, 2-acrylamido-2-methylpropanesulfonic acid was also incorporated (20 mol% of DMA) resulting on the formation of self-supporting gels at 2 g L-1, an order of magnitude improvement over previously-reported ABA copolymers. These results approach the performance obtained from exotic polymers such as polyisocyanopeptides.

Tips/comments directly from the authors:

  1. High monomer concentrations are helpful to obtain high molecular weights. However, the polymerization of acrylamides is very exothermic so it is important not to exceed 30 wt%.
  2. As very low initiator concentrations are used, it is important to thoroughly degas all solutions prior to polymerization.
  3. Take care to exclude any air bubbles from the solution when carrying out rheology measurements.



Read this exciting research for free until 03/07/2016 through a registered RSC account:

Low concentration thermoresponsive hydrogels from readily accessible triblock copolymers
L. Despax, J. Fitremann, M. Destarac and S. Harrisson
Polym. Chem., 2016, 7, 3375-3377
DOI: 10.1039/C6PY00499G
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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).

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Focus on: Dendrimers and Dendritic Polymers

Dendrimers are perfectly symmetrical macromolecules, which exhibit interesting properties relative to their linear analogues, such as low intrinsic viscosities and high surface functionalities. Research into the applications of dendrimers has perhaps mainly focussed on biomedical applications, such as drug delivery and diagnostics, but also includes solar cells, catalysis and electrochemical sensors.

Dendrimers have proven to be extremely interesting macromolecules, which has sparked research into structurally similar dendritic polymers. Whilst dendritic polymers do not possess the perfect dendrimer branched structure, they can be easier to prepare and still maintain most of the positive dendrimer attributes, such as high surface functionality.

This month we take a look at 3 articles which focus on dendrimers and dendritic polymers published in Polymer Chemistry, where structure-property relationships were investigated and functional materials were prepared, including photoactive fluorescent dendrimers and cross-linkable dendrimers for electronic applications.

ToC figure for article 3



1. Hydrodynamic behaviors of amphiphilic dendritic polymers with different degrees of amidation
Cuiyun Zhang, Cong Yu, Yuyuan Lu, Hongfei Li, Yu Chen, Hong Huo, Ian William Hamley, Shichun Jiang
Polym. Chem., 2016, 7, 3126-3133; DOI: 10.1039/C6PY00394J

The authors have investigated and determined the hydrodynamic radii and intrinsic viscosities of a range of amphiphilic dendritic polymers consisting of a hydrophilic polyethyleneimine dendritic core and hydrophobic palmitite tails at the surface. It was found that the degree of amidation affected these properties significantly, and that the dendritic polymers were more compact than their linear analogues.


2. Aggregation enhanced excimer emission (AEEE) with efficient blue emission based on pyrene dendrimers
Alaa S. Abd-El-Aziz, Amani A. Abdelghani, Brian D. Wagner, Elsayed M. Abdelrehim
Polym. Chem., 2016, 7, 3277-3299; DOI: 10.1039/C6PY00443A

Three generations of novel fluorescent organoiron dendrimers were prepared and the dendrimer surfaces were functionalised with pyrene moeities bearing different lengths of alkyl chains. The resultant iron-containing dendrimers were investigated for their electrochemical properties. The demetalated analogues exhibited aggregation enhanced excimer emission, when using solvent mixtures of water and THF, highlighting potential in photoactive dendrimer applications.


3. Dendrimeric organosiloxane with thermopolymerizable –OCF=CF2 groups as the arms: synthesis and transformation to the polymer with both ultra-low k and low water uptake
Jiajia Wang, Kaikai Jin, Jing Sun, Qiang Fang
Polym. Chem., 2016, 7, 3378-3382; DOI: 10.1039/C6PY00576D

A novel dendrimeric macromolecule was synthesised, comprising a cyclic siloxane at the core and aryl-trifluorovinyl-ether units as the arms. The resulting dendrimeric macromolecule was easily cross-linked through thermal induced reaction. The transparent cross-linked network showed good thermal stability, ultra-low dielectric constant and low water uptake. This material utilises an industrially applicable cross-linking reaction, with several potential applications in the electronics industry.

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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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