Journal of Materials Chemistry Blog

US researchers have made a transparent membrane that is highly electron and proton conductive.

Transparent materials with both ionic and electrical conductivity and mixed conducting properties are used in devices which require a membrane with both electrical and protonic conductivity but minimal light absorption– such as some water splitting solar cells. Blending conjugated polymers is one approach to achieve electrical and ionic conductivity; however, polymer membranes formed from blending two polymers often suffer from poor mechanical properties and polymer phase separation.

In this hot paper Paula T. Hammond and co-workers at Massachusetts Institute of Technology, USA, demonstrate that they can tune the ionic conductivity, the electrical, optical, and mechanical properties of PEDOT:sPPO by changing the composition ratio and by DMSO treatment. The polymer thin films become more transparent, smoother, softer, and exhibit higher proton conductivity as the sPPO ratio in PEDOT:sPPO is increased. After DMSO treatment, the polymer electrical conductivity dramatically increased without jeopardizing the protonic conductivity.

Highly transparent mixed electron and proton conducting polymer membranes: Junying Liu, Nicole R. Davis, David S. Liu and Paula T. Hammond, J. Mater. Chem., 2012, DOI: 10.1039/C2JM32296J (Advance Article)

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Electrothermally driven structural colour based on liquid crystal elastomers
Photonic crystal structures offer tremendous potential for use in a range of applications such as optical transistors and waveguides, data storage media, and chemical sensors. Liquid crystals are good candidates to form tunable photonic crystals because they can show optical anisotropy and their refractive index can be changed by an external electric field or temperature change; however, in most cases, liquid crystals are not used as inverse opaline materials directly, but instead, infiltrated into the voids of the inverse opaline films– which limits their suitability for some applications. In this hot paper a new type of electrothermally driven photonic crystal based on liquid crystal elastomers is reported, and its optical properties driven by voltage are described. The authors say this is the first example where a pure liquid crystal elastomer is introduced into photonic crystals as an inverse opaline structure material. (J. Mater. Chem., 2012, 22, 11943-11949)

Origin of long-range orientational pore ordering in anodic films on aluminium
Porous anodic aluminium oxide has long been used for colouring and to prevent corrosion. It’s now also finding uses in hi-tech nanostructured devices such as gas sensors, nanocapacitors and microcantilevers. In this hot paper Kirill S. Napolskii and co-workers at Lomonosov Moscow State University show that the long range in-plane orientational pore ordering originates from the anisotropy of oxidation rates of the substrate during the anodization process. This finding offers a new approach for tailoring and controlling the in-plane orientational pore ordering by crystallographic manipulation with the Al substrate. (J. Mater. Chem., 2012, 22, 11922-11926)

A chiral co-crystalline form of poly(2,6-dimethyl-1,4-phenylene)oxide (PPO)
The crystalline structure of an industrially relevant specialty polymer, poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) is resolved for the first time in this hot paper. The structure is a co-crystalline structure of the polymer with a chiral guest molecule (α-pinene), exhibiting a 2/1 monomer-unit–guest molar ratio. The authors say the most striking feature of this co-crystalline structure is its chirality. (J. Mater. Chem., 2012, 22, 11672-11680)

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Highlight
Recent advances in high mobility donor–acceptor semiconducting polymers
Laure Biniek, Bob C. Schroeder, Christian B. Nielsen and Iain McCulloch, J. Mater. Chem., 2012, DOI: 10.1039/C2JM31943H (Advance Article)

Click here to see all three reviews

Electrochemical sensing by surface-immobilized poly(ferrocenylsilane) grafts
Xiaofeng Sui ,  Xueling Feng ,  Jing Song ,  Mark A. Hempenius and G. Julius Vancso
J. Mater. Chem., 2012,22, 11261-11267

Poly(ferrocenylsilane) based materials have useful redox characteristics that make them suitable for the electrochemical detection of biological analytes; however, only a few accounts of covalently surface-tethered poly(ferrocenylsilane) films have been reported in the literature. In this hot paper chemically modified electrodes, decorated with covalently tethered poly(ferrocenylsilane) chains are fabricated. Led by G. Julius Vancso the team employed a “grafting to” approach for the covalent attachment of PFS chains to an electrode surface using amine alkylation reactions. Using this technique the team fabricated an ascorbic acid electrochemical sensor which showed high sensitivity and a stable response.

Incorporation of fused tetrathiafulvalene units in a DPP–terthiophene copolymer for air stable solution processable organic field effect transistors
Diego Cortizo-Lacalle ,  Sasikumar Arumugam ,  Saadeldin E. T. Elmasly ,  Alexander L. Kanibolotsky ,  Neil J. Findlay ,  Anto Regis Inigo and Peter J. Skabara
J. Mater. Chem., 2012, 22, 11310-11315

In this hot paper a team led by Anto Regis Inigo & Peter J. Skabara report the synthesis and properties of a new polymer p(DPP-TTF) featuring a fused thieno-TTF unit that has been copolymerised with a dithieno-DPP derivative. Bottom gate/bottom contact field effect transistors were fabricated from films of p(DPP-TTF). The transistors showed excellent air-stability which the team attribute to the incorporation of the TTF unit into the polymer.

Frozen polymerization for aligned porous structures with enhanced mechanical stability, conductivity, and as stationary phase for HPLC
Michael Barrow ,  Ali Eltmimi ,  Adham Ahmed ,  Peter Myers and Haifei Zhang
J. Mater. Chem., 2012,22, 11615-11620

Ice templating is a simple and versatile route to prepare a wide range of porous materials. In general, a solution or colloidal suspension is frozen prior to the removal of ice crystals by freeze drying– which leaves a porous structures; however, the structures produced are often fragile and mechanically weak. In this hot paper a directional freezing and frozen polymerization method is developed to prepare crosslinked aligned porous polymers with improved mechanical stability. In the process monomer solutions are directionally frozen in liquid nitrogen to orientate the growth of solvent crystals after which the frozen samples are polymerized by UV irradiation. Removal of the solvent under vacuum produces the aligned porous structure. The team behind the research say the mechanical stability is improved by two orders of magnitude compared to similar materials produced using a freeze-dried process. The team also showed the resulting materials can be modified with graphene and a conducting polymer.

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Scientists in Saudi Arabia have used a kitchen sponge as an electrode platform for supercapacitor devices. The MnO₂–carbon nanotube–sponge supercapacitor electrode demonstrates reasonably good electrochemical performance in both aqueous and organic electrolytes, they say.

Compared to aqueous electrolytes, the energy density of supercapacitors in 1M Et₄NBF₄ tripled and the value was improved six-fold when using 1M LiClO₄ as the electrolyte. The team behind the research also said that the cycling performance in organic electrolytes was inferior to aqueous electrolytes, but the devices in organic electrolytes retained a significant energy density advantage even after 10,000 cycles. (Read the article for free until the 5^th July)

High energy density supercapacitors using macroporous kitchen sponges: Wei Chen, Rakhi Raghavanbaby and Husam N Alshareef, J. Mater. Chem., 2012, DOI: 10.1039/C2JM32030D

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Synthesis and self-assembly of tetraphenylethene and biphenyl based AIE-active triazoles:
Wang Zhang Yuan,  Faisal Mahtab,  Yongyang Gong,  Zhen-Qiang Yu,  Ping Lu,  Youhong Tang,  Jacky W. Y. Lam,  Caizhen Zhu and Ben Zhong Tang, J. Mater. Chem., 2012, 22, 10472-10479.

Aggregation-caused quenching effects are often encountered when luminophores are condensed and aggregated. This hot paper reports a new family of luminophors which can be easily fabricated into high efficiency fluorescent helical nanofibers that show aggregation-induced emission. The biphenyl and TPE-containing luminogens are practically nonluminescent in solution, but become highly fluorescent when aggregated as nanosuspensions, solid powders, or thin films.

Photonic anti-counterfeiting using structural colors derived from magnetic-responsive photonic crystals with double photonic bandgap heterostructures:
Haibo Hu ,  Qian-Wang Chen ,  Jian Tang ,  Xian-Yi Hu and Xu-Hui Zhou, J. Mater. Chem., 2012, 22, 11048-11053.

A simple and low-cost method to fabricate photonic crystals with double photonic band-gap hetero-structures is reported by Chinese scientists. These photonic crystals could be suitable for use in anti-counterfeiting measures as they are more difficult to imitate than chemical dyes and pigments. Using a magnetic-induced self-assembly technique the team were able to create a range of structural colours.

Preparation of Pickering emulsions and colloidosomes using either a glycerol-functionalised silica sol or core–shell polymer/silica nanocomposite particles:
Lee A. Fielding and Steven P. Armes, J. Mater. Chem., 2012, 22, 11235-11244.

Microcapsules with shells constructed from colloidal particles have been widely reported; however, there are few reports on the formation of stable colloidosomes using solely nano-sized silica or polymer/silica nanocomposite particles using cross-linking chemistry. In this hot paper a glycerol-functionalised colloidal silica sol and core–shell polymer/silica nanocomposite particles are used to prepare oil-in-water Pickering emulsions.

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Sequestration of edible oil from emulsions using new single and double layered microcapsules from plant spores

Microcapsules developed from modified plant spores can sequester efficiently edible oils from oil-in-water emulsions. The microcapsules contain either a single layered shell or double layered shell and are modified by converting their surface hydroxyl groups (alcohols, phenols carboxylic acids) into salts (Na+ and K+), acetates and methyl ethers. (J. Mater. Chem., 2012, 22, 9767-9773)

Chemical reduction of an aqueous suspension of graphene oxide by nascent hydrogen

South Korean scientists have shown that nascent hydrogen can effectively reduce graphene oxide. Using a combination of X-ray photoelectron spectroscopy and thermogravimetric analysis they demonstrate that most of the labile oxygen functional groups were removed during nascent hydrogen reduction. Compared to other reducing agents the use of low cost, non-toxic metals for nascent hydrogen reduction is a promising method for bulk preparation of high quality reduced graphene oxide. (J. Mater. Chem., 2012, 22, 10530-10536)

Structural requirements for fast lithium ion migration in Li₁₀GeP₂S₁₂

Developing high performance electrolytes that combine fast lithium ion conductivity with electrochemical stability and safety is one of the challenges facing scientists creating the next generation of batteries. In this hot article atomistic molecular dynamics simulations shed new light on the dynamic lithium distribution, structural stability and ion transport mechanism in the ultrafast ion conductor Li₁₀GeP₂S₁₂. (J. Mater. Chem., 2012, 22, 7687-7691)

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