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Focus on: Polymers for detection

28 Jul 2016

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 webwriter

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

29 Jun 2016

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 webwriter

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

02 Jun 2016

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 webwriter

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

27 Apr 2016

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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Focus on: Redox-Responsive Polymers

07 Mar 2016

Stimuli-responsive polymers exhibit interesting changes in chemical and/or physical properties with exposure to external stimuli which has lead to considerable research into this area of polymer chemistry. Various types of stimuli reported include: light, temperature, pH, mechanical and redox environment. In some cases polymeric materials can be responsive to more than one of these stimuli and as such are dual or multi-responsive. Various redox-responsive polymers have been reported in Polymer Chemistry this month, highlighted below, with applications ranging from sensing, nanolithography and magnetic devices to drug delivery applications.

Table of contents figure: Redox-controlled upper critical solution temperature behaviour of a nitroxide containing polymer in alcohol–water mixtures

1. Redox-controlled upper critical solution temperature behaviour of a nitroxide containing polymer in alcohol–water mixtures, Olivier Bertrand, Alexandru Vlad, Richard Hoogenboom, Jean-François Gohy, Polym. Chem., 2016, 7, 1088-1095.

The authors present the synthesis of poly(TEMPO methacrylate) which exhibited UCST behaviour in water/alcohol mixtures. The UCST could be tuned through the water/alcohol ratio as well as which alcohol was used. Oxidation of the nitroxide radical to the oxoammonium cation could be achieved chemically or electrochemically and with increasing oxidation the UCST was decreased. The polymer shows promise for sensing applications.

2. One for all: cobalt-containing polymethacrylates for magnetic ceramics, block copolymerization, unexpected electrochemistry, and stimuli-responsiveness, C. Rüttiger, V. Pfeifer, V. Rittscher, D. Stock, D. Scheid, S. Vowinkel, F. Roth, H. Didzoleit, B. Stühn, J. Elbert, E. Ionescu, M. Gallei, Polym. Chem., 2016, 7, 1129-1137.

A cobalt containing methacrylate was prepared and polymerized by different techniques to form homopolymer and block copolymers. The homopolymers were heated under nitrogen to give magnetic cobalt oxide. The block copolymers were investigated for their reversible reduction and oxidation which lead to the formation of micelles with varying the oxidation state of the cobalt. The polymers have potential in nanolithography and magnetic devices based on soft polymer templates.

3. Oxidation and temperature dual responsive polymers based on phenylboronic acid and N-isopropylacrylamide motifs, Mei Zhang, Cheng-Cheng Song, Ran Ji, Zeng-Ying Qiao, Chao Yang, Fang-Yi Qiu, De-Hai Liang, Fu-Sheng Du, Zi-Chen Li, Polym. Chem., 2016, 7, 1494-1504.

NIPAM and a phenylboronic pinacol ester containing monomer were polymerised to give diblock copolymers, with tunable LCSTs. Triblock copolymers were also prepared with PEG which self-assembled into micelles at 37 °C. The micelles were loaded with doxorubicin and triggered release was achieved through oxidation and elimination of the phenylboronic acid unit. These dual-responsive micelles may have applications in the treatment of inflammation-related diseases or cancers.

Dr. Fiona Hatton is a Web Writer for Polymer Chemistry. She is currently a postdoctoral researcher at KTH Royal Institute of Technology, Sweden, having completed her PhD in the Rannard group at the University of Liverpool, UK. Visit her webpage for more information.

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Focus on: Polymeric Composite Materials

28 Jan 2016

A composite material contains two or more constituents which when combined afford significantly different material properties than the individual components. Well-known composites include concrete, plywood and fibre-reinforced plastics. With regard to polymeric composite materials, they usually consist of fillers dispersed in a polymer matrix to improve desired mechanical properties of the polymer material. Recently, research efforts have also focused on nanocomposites, where the filler has at least one dimension in the nano-scale, for example, nanoparticles, carbon nanotubes, 2D-sheets, such as graphene oxide, and nanofibres. These nano-fillers have shown huge improvements to material properties at low mass fractions, primarily due to the high surface area to volume ratio that nanomaterials possess. The increased interfacial area between the nanomaterial and continuous polymer matrix results in increased polymer-filler strength. Various applications have been proposed for nanocomposites: biomedical applications, waste water treatment, structural materials to name but a few.

Each of the highlighted articles this month report polymeric nanocomposites with improved properties such as increased strength, thermal stability, and desired adsorption behaviour when compared to the non-composite materials.

ToC image for article 1

1. Enhancement of the crosslink density, glass transition temperature, and strength of epoxy resin by using functionalized graphene oxide co-curing agents, Jin Won Yu, Jin Jung, Yong-Mun Choi, Jae Hun Choi, Jaesang Yu, Jae Kwan Lee, Nam-Ho You, Munju Goh, Polym. Chem., 2016, 7, 36-43.

Graphene oxide (GO) was incorporated into epoxy resins through functionalisation of the edge of the GO with amino groups, subsequently utilised for reaction with epoxy groups present in the polymer matrix. The incorporation of the modified GO into the resin improved the tensile strength and thermal properties of the materials. Higher crosslinking densities were also observed due to the covalent linking of the GO thanks to the amino groups introduced.

2. Tailored high performance shape memory epoxy–silica nanocomposites. Structure design, S. Ponyrko, R. K. Donato, L. Matějka, Polym. Chem., 2016, 7, 560-572.

The authors describe the preparation of epoxy resins containing silica nanoparticles and shape memory behavior of the materials was investigated. The materials were prepared through in situ generation of nanosilica within the epoxy resin. The stimuli utilized for the shape memory behavior was temperature, exploiting the visco-elastic behavior of the epoxy resin. The results contribute to improved understanding of this type of shape memory materials.

3. A core–shell structure of polyaniline coated protonic titanate nanobelt composites for both Cr(VI) and humic acid removal, Tao Wen, Qiaohui Fan, Xiaoli Tan, Yuantao Chen, Changlun Chen, Anwu Xu, Xiangke Wang, Polym. Chem., 2016, 7, 785-794.

Core-shell polyaniline/hydrogen titanate nanobelt composites were prepared through in situ oxidative polymerisation which showed excellent absorption of Cr(VI) and humic acid for waste water treatment applications. The mechanisms of the Cr(VI) and humic acid removal were investigated as well as regeneration performance and reusability. The industrial implications on the composites appear promising; showing efficient and cost effective waste water treatment.

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Focus on: Polymers in Catalysis

05 Jan 2016

This month, focussing on polymers in catalysis, we look at three articles where catalytic activity has been inferred to a polymer chain through functionalisation of the polymer, or through using the polymer as a support for another catalyst.

In the body, reactions are usually catalysed by enzymes. Mimicking enzyme activity with synthetic polymers has been investigated for several types of enzymes, here, in the first article a polymer was prepared mimicking the activity of S-adenosyl methionine synthetase.

Transition metal catalysis is widely used in the preparation of polymers as well as organic molecules, one major disadvantage is the removal of the catalyst after completion of the reaction. The second article describes a proposed solution to this problem through a thermoresponsive catalytic polymer. In the third article a porous polymer support containing in situ generated gold nanoparticles highlights another route to circumvent the issues with removal of catalytic residues, by utilising solid supported catalysts.

ToC image for article

1. Synthetic polymeric variant of S-adenosyl methionine synthetase, Lakshmi Priya Datta, Binoy Maiti, Priyadarsi De, Polym. Chem., 2015, 6, 7796-7800.

The authors describe the synthesis of a polymer via RAFT and subsequent functionalisation with methionine moeities which mimicked the activity of the enzyme S-adenosyl methionine synthetase. Methionine plays major roles in the biosynthesis of proteins and DNA methylation. The resulting polymer was shown to methylate cytosine in the absence of a methyltransferase enzyme, highlighting the enzyme-like activity of the polymer.

2. A thermoresponsive polymer supporter for concerted catalysis of ferrocene with a ruthenium catalyst in living radical polymerization: high activity and efficient removal of metal residues, Kojiro Fujimura, Makoto Ouchi, Mitsuo Sawamoto, Polym. Chem., 2015, 6, 7821-7826.

With the aim to achieve the efficient removal of metal residues from ruthenium-ferrocene concerted catalysed living radical polymerisation, a thermoresponsive polymer support was prepared containing ruthenium as a catalyst and ferrocene as a cocatalyst. This was used to catalyse the polymerisation of MMA in toluene, and subsequent aqueous washing resulted in the almost quantitative removal of Ru (99.8% removal) and Fe (98.5% removal), showing promise for practical applications.

3. “Clickable” thiol-functionalized nanoporous polymers: from their synthesis to further adsorption of gold nanoparticles and subsequent use as efficient catalytic supports, Benjamin Le Droumaguet, Romain Poupart, Daniel Grande, Polym. Chem., 2015, 6, 8105-8111.

A porous polymeric material was prepared through a channel die processing technique, consisting of PS-b-PLA, where the two blocks were connected through a disulphide linkage. After removal of the PLA block, the remaining thiol groups were utilised in both post-modification “click” reaction and in situ gold nanoparticle (GNP) generation. The porous polymer GNP hybrid catalysed the reduction of 4-nitrophenol to 4-aminophenol with a yield of 68%, and retained this efficiency over 5 runs.

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Focus on: Supramolecular Polymer Networks

02 Dec 2015

Supramolecular interactions are defined as noncovalent bonds, including: hydrogen bonding, hydrophobic association, π-π stacking, transition metal complexation and ionic interactions. Supramolecular polymer networks consist of macromolecules which are interconnected through these transient noncovalent bonds. These materials are particularly interesting as they allow the capability of adaptive, self-healing materials which have mechanical properties that are dependent on the crosslinking interactions and the polymer topology. This month three articles are highlighted which demonstrate supramolecular interactions in polymer networks to give materials with interesting properties, such as self-healing, ductility and stimuli responsive changes in mechanical properties.

Graphical abstract from article (http://xlink.rsc.org/?doi=10.1039/C5PY01214G)

1. Self-healing, malleable and creep limiting materials using both supramolecular and reversible covalent linkages, Borui Zhang, Zachary A. Digby, Jacob A. Flum, Elizabeth M. Foster, Jessica L. Sparks, Dominik Konkolewicz, Polym. Chem., 2015, 6, 7368-7372.

The combination of supramolecular and reversible crosslinks was utilized to prepare materials with self-healing properties on different time scales. Supramolecular crosslinks between 2-ureido-4[1H]-pyrimidinone moieties gave dynamic crosslinks, whilst Diels-Alder coupling between a furan and a maleimide gave a considerably less dynamic linkage. The materials showed partial healing properties at room temperature and full healing at elevated temperatures.

2. Ultraductile, notch and stab resistant supramolecular hydrogels via host–guest interactions, Mei Tan, Yulin Cui, Aidi Zhu, Han Han, Mingyu Guo, Ming Jiang, Polym. Chem., 2015, 6, 7543-7549.

The authors describe the preparation of supramolecular hydrogels which were self-healing as well as extremely ductile and notch and stab resistant. The hydrogels were based on host-guest interactions between adamantane monomers and a low molecular weight polyfunctional cyclodextrin, prepared via free radical polymerisation. Native and healed gels gave similar tensile strain–stress trends, stretching to around 50 times their original lengths with almost complete recoverability.

3. Supramolecular polymer networks based on cucurbit[8]uril host–guest interactions as aqueous photo-rheological fluids, Cindy S. Y. Tan, Jesús del Barrio, Ji Liua, Oren A. Scherman, Polym. Chem., 2015, 6, 7652-7657.

Supramolecular polymer networks are reported based upon the host-guest interactions mediated by cucurbit[8]uril with naphthyl-functionalised hydroxyethyl cellulose, methyl viologen functional styrene copolymer and a photoisomerisable azobenzene imidazolium derivative. The resulting networks exhibited light-tunable rheological properties at low mass fractions (<0.75 wt%) showing a decrease in the zero-shear viscosity and viscoelastic moduli by UV irradiation.

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Focus on: Polymers from Renewable Resources

29 Oct 2015

With increasing demands upon our planet’s resources, more and more research efforts are focussing on preparing new materials from renewable resources. Especially considering the global plastic production (299 million tonnes in 2013), new routes towards renewable polymers are ever more desirable. Renewable polymers can generally be classified into the following three groups: naturally occurring polymers such as polysaccharides and proteins, polymers prepared by microbial fermentation and polymers synthesised from bioderived monomers. This month, focussing on polymers from renewable resources, we take look at three articles which utilize renewable plant-derived monomers to synthesise various polyesters. The plant-derived monomers described are based on the following compounds: erucic acid, commonly found in rapeseed oil, eugenol which is present in clove oil and δ-decalactone which can be extracted from Cryptocarya massoia.

1. Thermoplastic polyester elastomers based on long-chain crystallizable aliphatic hard segments, Florian Stempfle, Brigitta Schemmer, Anna-Lena Oechsle, Stefan Mecking, Polym. Chem., 2015, 6, 7133-7137.

Thermoplastic polyesters were prepared via polycondensation with a plant-oil based long chain (C23) α,ω-dicarboxylic acid and the corresponding diol comprising the hard segments, and poly(tetramethylene glycol) (PTMG) or carbohydrate-based poly(trimethylene glycol) (PPDO) soft segments. Physical crosslinking was achieved through crystallization of the long aliphatic segments, resulting in enhanced thermal properties when compared to the C12 analogues.

2. Synthesis and properties of polyesters derived from renewable eugenol and α,ω-diols via a continuous overheating method, Keling Hu, Dongping Zhao, Guolin Wu, Jianbiao Ma, Polym. Chem., 2015, 6, 7138-7148.

Aromatic monomers derived from eugenol were synthesised utilizing “click” chemistry and a subsequent Williamson ether synthesis. They were subsequently polymerised with various α,ω-diols via a continuous overheating method across the transesterification stage to form polyester thermoplastics. The Young’s modulus and ultimate strength of the resulting materials was not particularly high although they exhibited excellent ductility.

3. New biomaterials from renewable resources – amphiphilic block copolymers from δ-decalactone, Kuldeep K. Bansal, Deepak Kakde, Laura Purdie, Derek J. Irvine, Steven M. Howdle, Giuseppe Mantovani, Cameron Alexander, Polym. Chem., 2015, 6, 7196-7210.

Various polymers and copolymers were synthesized from the low-cost and easily-accessible renewable monomer δ-decalactone, which is an FDA approved flavouring agent. Amphiphilic copolymers were shown to self-assemble into micelles which were biodegradable and showed low toxicity in vitro. The micelles enabled sustained release of a model drug compound over 8 days, highlighting the possible biomedical application of these degradable δ-decalactone copolymers.

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Focus on: Polymeric Nanomaterials for Drug Delivery

24 Sep 2015

This month the “focus” is on polymeric nanomaterials which have been investigated for their applicability as drug delivery devices. The use of polymers in biomedical applications, specifically drug delivery, has markedly increased over the past decades with the advancement in polymerisation techniques. More precise synthetic methodologies have allowed for a higher degree of control over polymer compositions and architectures, therefore, expanding the polymer chemist’s toolbox. Drug delivery vehicles based on polymers aim to overcome problems with hydrophobic drug administration such as low bioavailability and/or rapid clearance, poor solubility and high off target toxicity. They usually should be biocompatible, achieve high drug loading efficiencies, show biodegradability and in some cases include site specific targeted drug delivery and/or sustained release of the bioactive compound(s). Perhaps unsurprisingly, PEG has been used in each report as it is well-known for giving stabilization and “stealth” properties to nanomaterials in the body. However, the variety of polymer architectures and core compositions employed in these reports alone highlights the diversity arising when investigated polymeric materials for drug delivery.

1. Biocompatible and bioreducible micelles fabricated from novel α-amino acid-based poly(disulfide urethane)s: design, synthesis and triggered doxorubicin release, Wentao Lu, Xiuxiu Wang, Ru Cheng, Chao Deng, Fenghua Meng and Zhiyuan Zhong, Polym. Chem., 2015, 6, 6001-6010.

Through the design of reductively biodegradable amino acid based poly(disulfide urethane)s (AAPU(SS)s), ABA triblock copolymers consisting of PEG-AAPU(SS)-PEG were prepared which formed micelles. Doxorubicin was encapsulated in the core of the micelles and an increase in drug release was observed in a reductive environment. Cell viability studies showed that the drug loaded micelles reduced cell viability and cell internalisation was investigated.

2. Amphiphilic core cross-linked star polymers as water-soluble, biocompatible and biodegradable unimolecular carriers for hydrophobic drugs, D. Gu, K. Ladewig, M. Klimak, D. Haylock, K. M. McLean, A. J. O’Connor and G. G. Qiao, Polym. Chem., 2015, 6, 6475-6487.

Unimolecular core cross-linked stars (CCS) were prepared by the ring opening polymerisation of caprolactone and a crosslinker utilizing a PEG macroinitiator. The formation of CCS with varying contents was investigated and a hydrophobic drug, pirarubicin, was encapsulated and release of the drug was studied at different pH. Cytotoxicity and cellular uptake tests showed that the materials exhibited low toxicities, while drug loaded CCS polymers were similar to the free drug.

3. A biodegradable and fluorescent nanovehicle with enhanced selective uptake by tumor cells, Jinxia An, Xiaomei Dai, Yu Zhao, Qianqian Guo, Zhongming Wu, Xinge Zhang and Chaoxing Li, Polym. Chem., 2015, 6, 6529-6542.

A PEGylated core cross-linked polymeric nanovehicle was prepared via RAFT, which contained reduction- and pH-dependent degradable moieties and fluorescence imaging functionalities in the core. Due to the fluorescence imaging functionality the cell internalization pathway into HEPG2 cells was investigated by cellular uptake and competition inhibition assays. Drug loaded nanovehicles were shown to inhibit cancer cell proliferation.

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Focus on: Polymers for detection

Focus on: Aggregation Induced Emission in Polymers

Focus on: Dendrimers and Dendritic Polymers

Focus on: Photopolymerisation

Focus on: Redox-Responsive Polymers

Focus on: Polymeric Composite Materials

Focus on: Polymers in Catalysis

Focus on: Supramolecular Polymer Networks

Focus on: Polymers from Renewable Resources

Focus on: Polymeric Nanomaterials for Drug Delivery

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