Author Archive

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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Focus on: Polymers in Emulsions

This month we look at three articles that feature in Polymer Chemistry that report the use of polymers in emulsions.  Both in emulsion polymerisation and high internal phase emulsions.

Emulsion polymerisation can be utilised to prepare polymers as polymeric particles with high solids content, and is commonly used in industry and academia alike. Seeded emulsion polymerisation is a technique where a seed particle is utilised in an emulsion polymerisation, to overcome any variability in the nucleation step.

High internal phase emulsions (HIPE) are those that have a droplet (internal) phase that constitutes 74.05% or more of the total emulsion volume. PolyHIPEs have gained a great deal of interest, where the polymerisation occurs in the continuous phase forming voids around the dispersed droplets, leading to highly porous materials.

1. Impressed pressure-facilitated seeded emulsion polymerization: design of fast swelling strategies for massive fabrication of patchy microparticles
Lei Tian, Xue Li, Panpan Zhao, Zafar Ali, Qiuyu Zhang
Polym. Chem., 2016, 7, 7078-7085; DOI: 10.1039/C6PY01778A

The authors present a pressure-facilitated seeded emulsion polymerisation of poly(glycidyl methacrylate)/poly(styrene), whereby the utilisation of high pressure and temperature allowed for an accelerated seed swelling process, overcoming typical disadvantages of seeded emulsion polymerisation.  The resulting particles could be designed to be patchy and anisotropic in shape, through tuning the polymerisation time and dibutyl phthalate/styrene ratios.

2. Rational design of functionalized polyacrylate-based high internal phase emulsion materials for analytical and biomedical uses
Gloria Brusotti, Enrica Calleri, Chiara Milanese, Laura Catenacci, Giorgio Marrubini, Milena Sorrenti, Alessandro Girella, Gabriella Massolini, Giuseppe Tripodo
Polym. Chem., 2016, 7, 7436-7445; DOI: 10.1039/C6PY01992G

PolyHIPEs (with water contents of 80-90%) were designed through the polymerisation of (meth)acrylate monomers: butyl acrylate, glycidyl methacrylate and trimethylolpropane triacrylate as the oil phase. Various parameters were optimised, such as the monomer, cross-linker and surfactant concentrations, to give structural porous polyHIPEs with interesting morphology, thermal stability and porosity. The materials have potential for the immoblization of biomolecules for various applications.

3. Closed-cell and open-cell porous polymers from ionomer-stabilized high internal phase emulsions
Tao Zhang, Zhiguang Xu, Qipeng Guo
Polym. Chem., 2016, 7, 7469-7476; DOI: 10.1039/C6PY01725H

PolyHIPEs were prepared, utilising an ionomer as a stabiliser and either styrene (Sty) or butyl acrylate (BA) as the continuous phase. Sty based polyHIPEs resulted in closed-cell pores, whereas BA gave open-cell structures. When increasing the internal phase, the average pore diameters in the Sty polyHIPES decreased, whilst the average pore diameters for the BA polyHIPEs increased. Also, the amphiphilicity of the polyHIPEs could be tuned by simply exposing them to different water of different pH values.

Read these articles for free until March 17th


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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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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Focus on: Supramolecular Polymerisation

This month we focus on three articles appearing in Polymer Chemistry which report various types of Supramolecular Polymerisation. Supramolecular polymers are polymers formed through reversible non-covalent bonds, such as hydrogen bonding, π-π interactions, coordination and host-guest interactions. Advantages of supramolecular polymers include self-healing properties, improved processability, degradability and recyclability; these materials have found applications in fields including optoelectronics, tissue engineering, drug delivery, gene transfection, self healing films and networks to name a few. The articles highlighted this month demonstrate supramolecular polymerisation directed by coordination and host-guest interactions.

Graphical abstract

1. Ligand effects on cooperative supramolecular polymerization of platinum(II) acetylide complexes
Zhao Gao, Junlong Zhu, Yifei Han, Xiaoqin Lv, Xiaolong Zhang, Feng Wang
Polym. Chem., 2016, 7, 5763-5767; DOI: 10.1039/C6PY01440B

The authors present the formation of helical nano-fibers and organogels by supramolecular polymerisation of a rod-like platinum(II) acetylide monomer with less bulky ligand substituents. The self-assembly mechanism was found to be through a cooperative nucleation–elongation mechanism, and the more-bulky monomers showed no aggregation. These results highlight the importance of minor monomer variations on the supramolecular polymerisation mechanism.

2. Supramolecular main-chain polycatenanes formed by orthogonal metal ion coordination and pillar[5]arene-based host–guest interaction
Hao Xing and Bingbing Shi
Polym. Chem., 2016, 7, 6159-6163; DOI: 10.1039/C6PY01617K

The combination of catenanes and supramolecular polymers has been reported here, where the authors show the orthogonal use of coordination between zinc ions and terpyridyl groups and pillar[5]arene host-guest interactions. The materials exhibited glue-sol transitions with a change of temperature or hydroxide ion concentration. The mechanical properties were assessed by rheology, which showed improvement compared with a supramolecular polymer without catenane functionality.

3. 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 Feihe Huang
Polym. Chem., 2016, 7, 6178-6188; DOI: 10.1039/C6PY01402J

Supramolecular brush copolymers were prepared utilising host-guest interactions between pillar[5]arene and a viologen salt. The supramolecular brush copolymers self-assembled into single chain nanoparticles which were fluorescent due to the aggregation-induced emission effect. Doxorubicin loading was achieved and biotin labelling resulted in targeted drug delivery and imaging capabilities. The single-chain nanoparticles showed excellent anti-tumour efficacy with limited systemic toxicity in vivo.

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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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Focus on: Polymer-Grafted Surfaces

The ability to modify surfaces with polymers has been readily exploited to alter various surface properties, such as wettability, biocompatibility and chemical functionality. Covalently-bound polymer-grafted surfaces can be prepared either through a “grafting-from” or “grafting-to” approach.

“Grafting-from” entails the modification of the surface, followed by polymerisation of monomer units from the modified surface. “Grafting-to” is achieved when a pre-formed polymer chain is coupled to a functional surface. Various surfaces have been investigated for polymer grafting, both planar surfaces and 3D morphologies such as nanoparticles.

This month we take a look at three articles, published in Polymer Chemistry, which report polymer-grafted surfaces, via surface-initiated “grafting-from”  polymerisations in all cases, and in one article the authors have compared the “grafting-from” approach to “grafting-to”. In each report the properties of the respective substrates have been dramatically altered by the polymer grafting.

ToC figure

Yang Zheng, Yucheng Huang, Zaid M. Abbas, Brian C. Benicewicz
Polym. Chem., 2016, 7, 5347-5350; DOI: 10.1039/C6PY01319H

SiO2 nanoparticles were utilized for the grafting of PHEMA and PBzMA by RAFT polymerisation. The PHEMA/PBzMA grafted SiO2 nanoparticles were prepared through first, growing PHEMA chains from the surface, subsequent immobilisation of more RAFT agent onto the SiO2 surface, then polymerisation of BzMA. The grafted nanoparticles were observed to self-assemble, which was proposed to be due to phase separation of the two blocks and hydrophobic interactions between PBzMA domains.


Pei-Xi Wang, Yi-Shi Dong, Xiao-Wen Lu, Jun Du, Zhao-Qiang Wu
Polym. Chem., 2016, 7, 5563-5570; DOI: 10.1039/C6PY01223J

A dopa-functional photoiniferter was used to polymerise NiPAAm, DMAEMA and NVP by UV photopolymerisation. These pre-formed polymers were subsequently grafted-to a titanium surface through the dopa groups. Comparatively, a gold surface was functionalised with the dopa photoiniferter followed by polymerisation from the surface (grafting-from). In each case grafting was confirmed by XPS and contact angle measurements, showing efficient functionalisation of the substrates.



Michał Szuwarzyński, Karol Wolski, Szczepan Zapotoczny
Polym. Chem., 2016, 7, 5664-5670; DOI: 10.1039/C6PY00977H

Polyacetylene based ladder-like polymer brushes were grafted-from gold surfaces and investigated for their long-term stability and conductivity. The doped conjugated polyacetylene was less susceptible to degradation/oxidation when supported by another chain. The stability was improved when the surface grafting density was higher and the conductivity was only reduced by 1 order of magnitude after storage in air at room temperature for 6 months.


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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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Focus on: Cationic Polymerisation

Cationic polymerisation is a type of chain growth polymerisation which proceeds through the reaction of a cationic initiator with monomer, followed by further propagation. Cationic “living” polymerisation is well-known to produce precise polymers with narrow molecular weight distributions. Initial investigations in cationic polymerisation were reported as early as the beginning of the 20th century, whilst further developments in the 1970s and 80s have led to vast growth in this field of study. Now, many different monomer types can be successfully polymerised, including: styrenic, vinyl ethers, isobutene, and heterocyclic monomers, such as: lactones, lactams and cyclic amines.

Three articles appearing in Polymer Chemistry this month have described the use of cationic polymerisation to polymerise either oxazolidine based monomers or p-methylstyrene. In the case of the cyclic oxazolidine monomers the polymerisation is termed cationic ring-opening polymerisation, and in both cases the resulting polymers are interesting for biomedical applications. The polymerisation of p-methylstyrene was conducted in ionic liquids as a green substitute for organic solvents.

ToC image

1. Cationic ring-opening polymerization of protected oxazolidine imines resulting in gradient copolymers of poly(2-oxazoline) and poly(urea)
Meike N. Leiske, Matthias Hartlieb, Fabian H. Sobotta, Renzo M. Paulus, Helmar Görls, Peter Bellstedt, Ulrich S. Schubert
Polym. Chem., 2016, 7, 4924-4936; DOI: 10.1039/C6PY00785F

A Boc-protected oxazolidine monomer was synthesised and utilized to prepare poly(urea)s through  cationic ring opening polymerisation. The polymerisations were studied and resulting homopolymers and copolymers were characterised and subsequently deprotected. Through deprotection and solvent switch to water self-assmebled nanostructures were obtained, which will be further investigated for their biological application.

2. Cationic polymerization of p-methylstyrene in selected ionic liquids and polymerization mechanism
Xiaoqian Zhang, Wenli Guo, Yibo Wu, Liangfa Gong, Wei Li, Xiaoning Li, Shuxin Li, Yuwei Shang, Dan Yang, Hao Wang
Polym. Chem., 2016, 7, 5099-5112; DOI: 10.1039/C6PY00796A

The authors describe extensive experimental and computational investigations of the cationic polymerisation of p-methylstyrene in ionic liquids. Using quantum chemically based computations (the COSMO-RS method) following by solubility and viscosity measurements, a range of ionic lquids were screened. Subsequently, cationic polymerisation were investigated using various initiating systems.

3. Formation of polyoxazoline-silica nanoparticles via the surface-initiated cationic polymerization of 2-methyl-2-oxazoline
G. Bissadi, R. Weberskirch
Polym. Chem., 2016, 7, 5157-5168; DOI: 10.1039/C6PY01034B

Silica nanoparticles were modified to bear initiating sites to polymerise 2-methyl-2-oxazoline from the surface. This cationic surface-initiated grafting-from polymerisation resulted in higher grafting densities compared to previous grafting-to studies, and the molecular weight of the grafted polymer could be tuned by varying the monomer/initiator ratio. The resulting polymer-grafted nanoparticles were conjugated with biomolecules for fluorescence imaging and targeting for biomedical applications.


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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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Focus on: Polymers for detection

This month we focus on articles describing polymers designed for the detection of small organic molecules, published in Polymer Chemistry.

Here, polymers have been reported which, through incorporation of either functional groups or varying structural architecture, could be used to detect compounds including organic vapours, various anions and aromatic explosives. Detection of compounds is important in various applications, such as the detection of explosives in airports and border controls, doping in sports, contamination of water supplies and air pollution.


1. BODIPY based hyperbranched conjugated polymers for detecting organic vapors
Choong Ping Sen, Vanga Devendar Goud, Rekha Goswami Shrestha, Lok Kumar Shrestha, Katsuhiko Ariga Suresh Valiyaveettil
Polym. Chem., 2016, 7, 4213-4225; DOI: 10.1039/C6PY00847J

The authors describe the preparation of three soluble BODIPY containing hyperbranched polymers through Sonogashira coupling polymerisation. The sensing of organic solvents (toluene, benzene, acetone and methanol) was assessed using QCM, through preparing polymer films on the QCM crystal by solvent dropcasting. Varying masses adsorbed to the surface showed the different sensitivities of the hyperbranched polymers which showed a higher selectivity towards aromatic solvents.

2. Well-defined polymers containing a single mid-chain viologen group: synthesis, environment-sensitive fluorescence, and redox activity
Zhaoxu Wang, Nicolay V. Tsarevsky
Polym. Chem., 2016, 7, 4402-4410; DOI: 10.1039/C6PY00628K

Viologen containing polymers were prepared which exhibited strong fluorescence in solution. A di-functional ATRP initiator containing a viologen group was used to polymerise methyl methacrylate. The addition of salts with polarisable anions resulted in a reduction of the fluorescence, as did the presence of nitrobenzene, highlighting possible detection capabilities. In addition to this the polymers also showed  efficient catalysis of the oxidation of phenylhydrazine by air.

3. Fiber-optic detection of nitroaromatic explosives with solution-processable triazatruxene-based hyperbranched conjugated polymer nanoparticles
Yuxiang Xu, Xiaofu Wu, Yonghong Chen, Hao Hang, Hui Tong, Lixiang Wang
Polym. Chem., 2016, 7, 4542-4548; DOI: 10.1039/C6PY00930A

Two conjugated polymer nanoparticle systems, based on triazatruxene and fluorine units, were prepared by Pd-catalysed Suzuki coupling in mini-emulsion. Films were assessed for their vapour detection to TNT and DNT, and were also prepared on fibre optic tips and papers. Owing to the steric hindrance of spirobifluorene units in one of the systems, the sensitivity of detection of nitroaromatic vapours was increased in solid state and TNT was visually detectable using the coated paper.


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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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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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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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Focus on: Photopolymerisation

Photochemistry is an incredibly useful field of chemistry which allows for temporal control of reactions through the presence of light. Specifically when applied in polymer chemistry, light can be used to achieve conformational changes, modify polymer chains and to polymerise monomers. This month, focusing on photopolymerisation, we take a look at three papers and a communication, featured in Polymer Chemistry, which utilise light to polymerise various monomers via different techniques, including: reversible-deactivation radical polymerisations and curing of coatings and bulk materials. The vast scope of these articles highlights the applicability of photochemistry as a versatile approach to polymer synthesis.

ToC

1. Room temperature synthesis of poly(poly(ethylene glycol) methyl ether methacrylate)-based diblock copolymer nano-objects via Photoinitiated Polymerization-Induced Self-Assembly (Photo-PISA), Jianbo Tan, Yuhao Bai, Xuechao Zhang, Li Zhang, Polym. Chem., 2016, 7, 2372-2380.

The authors describe the chain extension of a hydrophilic macromolecular chain transfer agent (macroCTA) with hydroxypropyl methacrylate, through a light-mediated PISA approach. A visible light LED (405 nm) was used and the aqueous photo-PISA reactions achieved high conversion within 30 min irradiation time. Nano-objects with various morphologies were realised and investigated for their thermoresponsive properties.

2. Extremely deep photopolymerization using upconversion particles as internal lamps, Ren Liu, Hao Chen, Zhiquan Li, Feng Shi, Xiaoya Liu, Polym. Chem., 2016, 7, 2457-2463

Photopolymerisation was reported through thick samples by using upconversion nanoparticle (UCNP) assisted photochemistry. Through near-infrared laser excitation, the UCNPs produce visible light, which is adsorbed by a photo-initiator and causes curing of the material. Using this technique 60% conversion of double bonds has been achieved through a sample depth of 13.7 cm, and shows promise for ultra-high density data storage and preparation of functional composites.

3. Towards mussel-like on-demand coatings: light-triggered polymerization of dopamine through a photoinduced pH jump, David Perrot, Céline Croutxé-Barghorn, Xavier Allonas, Polym. Chem., 2016, 7, 2635-2638.

In this communication, the authors present a light triggered polymerisation of dopamine to give highly adhesive coatings. The irradiation of quaternary ammonium salts of phenylglyoxylic acid acted as photobase generators. This release of a strong base in water causes the polymerisation of dopamine through a self-oxidative polymerisation process. The presented methodology shows potential as a one-pot on-demand approach for the polymerisation of dopamine on various substrates.

4. Efficient multiblock star polymer synthesis from photo-induced copper-mediated polymerization with up to 21 arms, B. Wenn, A. C. Martens, Y.-M. Chuang, J. Gruber, T. Junkers, Polym. Chem., 2016, 7, 2720-2727

Here, utilising different multi-functional initiators, various star copolymers have been prepared via a photo-induced copper mediated polymerisation technique. Using a UV-microflow reactor, various multiarm-multiblock star-copolymers were prepared with varying acrylic block copolymer compositions, with low dispersities. Through post-polymerisation hydrolysis amphiphilic materials were prepared which showed pH-responsiveness and complex self-assembly in solution.


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.

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