Rachel C. Evans

Targeted β-Phase Formation in Poly(fluorene)–Ureasil Grafted Organic–Inorganic Hybrids

Co-reporter:Ilaria Meazzini, Jonathan M. Behrendt, Michael L. Turner, and Rachel C. Evans

Macromolecules June 13, 2017 Volume 50(Issue 11) pp:4235-4235

Publication Date(Web):May 16, 2017

DOI:10.1021/acs.macromol.7b00519

The development of synthetic strategies to control the molecular organization (and inherently linked optoelectronic properties) of conjugated polymers is critical for the development of efficient light-emitting devices. Here, we report a facile route using sol–gel chemistry to promote the formation of the β-phase through the covalent-grafting of poly[(9,9-dioctylfluorene)-co-(9,9-bis(8-hydroxyoctyl)fluorene)] (PFO-OH) to poly(oxyalkylene)/siloxane hybrids known as ureasils, due to the urea linkages binding the organic and inorganic components. Although grafting occurs within the siliceous domains, the degree of branching of the organic backbone determines the packing of the PFO-OH chains within the ureasil framework. Moreover, photoluminescence studies indicate that physical confinement also plays a key role in promoting the evolution of the β-phase of PFO-OH as the sol–gel transition proceeds. Spectroscopic and structural analyses reveal that dibranched ureasils promote linear packing of the PFO-OH chains, while tribranched ureasils exhibit a more open, distorted structure that restricts the packing efficacy and reduces the number of covalent anchorages. These results indicate that the organic–inorganic hybrid structure induces distinct levels of β-phase formation and that covalent grafting is a versatile approach to design novel poly(fluorene) hybrid materials with tailored optical properties.

Tunable White-Light Emission from Conjugated Polymer-Di-Ureasil Materials

Co-reporter:Niamh Willis-Fox;Mario Kraft;Jochen Arlt;Ullrich Scherf

Advanced Functional Materials 2016 Volume 26( Issue 4) pp:532-542

Publication Date(Web):

DOI:10.1002/adfm.201504017

Conjugated polymer (CP)-di-ureasil composite materials displaying a tunable emission color from blue to yellow through white have been prepared using a simple sol–gel processing method. The tunability of the emission color arises from a combination of energy transfer between the di-ureasil and the CP dopant and the excitation wavelength dependence of the di-ureasil emission. Incorporation of the CP does not adversely affect the bulk or local structure of the di-ureasil, enabling retention of the structural and mechanical properties of the host. Furthermore, CP-di-ureasils display superior thermal and photostability compared to the parent CPs. Thermogravimetric analysis shows that the onset of thermal decomposition can be increased by up to 130 °C for CP-di-ureasils, while photostability studies reveal a significant decrease in the extent of photodegradation. Steady-state photoluminescence spectroscopy and picosecond time-resolved emission studies indicate that the observed tunable emission arises as a consequence of incomplete energy transfer between the di-ureasil and the CP dopant, resulting in emission from both species on direct excitation of the di-ureasil matrix. The facile synthetic approach and tunable emission demonstrate that CP-di-ureasils are a highly promising route to white-light-emitters that simultaneously improve the stability and reduce the complexity of CP-based multilayer device architectures.

Threading the Needle: Fluorescent Poly-pseudo-rotaxanes for Size-Exclusion Sensing

Co-reporter:Niamh Willis-Fox, Christian Belger, John F. Fennell Jr., Rachel C. Evans, and Timothy M. Swager

Chemistry of Materials 2016 Volume 28(Issue 8) pp:2685

Publication Date(Web):April 11, 2016

DOI:10.1021/acs.chemmater.6b00186

Poly-pseudo-rotaxanes have been formed through the threading of cucurbit[n]urils (CB[n]) onto the cationic electron-poor poly(pyridyl vinylene), PPyV. The threading of CB[n] onto the PPyV backbone is confirmed by a broadening and upfield shift in the PPyV 1H NMR signals. Encapsulation of PPyV within the CB[n] macrocycles produces dramatic fluorescence enhancements with improved solubility. The threading ability of the CB[n] on the PPyV backbone is governed by the dimensions of the particular CB[n] portal, which grows with increasing number of methylene-bridged glycoluril repeat units. CB[5] is too small to thread onto the PPyV backbone. The portal of CB[6] requires extra time, suggesting high preorganization and/or macrocycle deformation are required to thread onto PPyV. Alternatively, the portal of CB[8] appears to be large enough such that it does not have sufficiently large dipole–dipole interactions with the PPyV chain to promote a strong threading equilibrium. However, we find that the portal of CB[7] is optimal for the threading of PPyV. The PPyV-CB[n] system was further exploited to demonstrate a dual-action sensor platform, combining the PL-responsive behavior demonstrated by PPyV toward electron-rich analytes with the size-exclusion properties imparted by volume of the respective CB[n] cavities. Thin films of PPyV-CB[7] were found to display reversible photoluminescence quenching when exposed to vapors of the biologically relevant molecule indole, which is recovered under ambient conditions, suggesting prospects for new size-exclusion based selective sensory schemes for volatile electron-rich analytes.

Targeted design leads to tunable photoluminescence from perylene dicarboxdiimide–poly(oxyalkylene)/siloxane hybrids for luminescent solar concentrators

Co-reporter:Ilaria Meazzini, Niamh Willis-Fox, Camille Blayo, Jochen Arlt, Sébastien Clément and Rachel C. Evans

Journal of Materials Chemistry A 2016 vol. 4(Issue 18) pp:4049-4059

Publication Date(Web):31 Mar 2016

DOI:10.1039/C5TC03952E

A series of organic–inorganic hybrid materials in which a perylene carboxdiimide-bridged triethoxysilane (PDI-Sil) is covalently grafted to the siliceous domains of poly(oxyalkylene)/siloxane hybrids from the ureasil family has been synthesised (PDI-Sil-ureasils), with the aim of tailoring the optical properties towards their future application in luminescent solar concentrators (LSCs). Steady-state and time-resolved photoluminescence studies revealed that the ureasil host is able to isolate PDI-Sil, which inhibits the formation of aggregates. The ureasil also functions as an active host, with its intrinsic photoluminescence contributing to the optical properties of the hybrid material. Through strategic variation of the branching and molecular weight of the poly(oxyalkylene) backbone, it was shown that the efficiency of energy transfer from the ureasil host to the PDI-Sil can be modulated, which tunes the emission colour from pink to orange. The chain length, rather than the number of branches, on the poly(oxyalkylene) backbone was shown to influence the photoluminescence most significantly. Since ureasils demonstrate waveguiding properties, the results indicate that covalent grafting of a fluorophore directly to a waveguide host may provide an attractive route to more efficient LSCs.

Design and Response of High-Efficiency, Planar, Doped Luminescent Solar Concentrators Using OrganicInorganic Di-Ureasil Waveguides

Co-reporter:Adarsh Kaniyoor;Barry McKenna;Steve Comby

Advanced Optical Materials 2016 Volume 4( Issue 3) pp:444-456

Publication Date(Web):

DOI:10.1002/adom.201500412

Luminescent solar concentrators (LSCs) offer significant potential for solar energy capture in the urban environment. Here, the first example of a planar, doped LSC using Lumogen Red (LR305) as the luminophore and a di-ureasil organic–inorganic hybrid as the waveguide is reported. The di-ureasil waveguide offers several advantages over organic polymer waveguides including facile solution-processing from benign solvents and extension of the absorption window through energy transfer. Spectral evaluation using absorption and photoluminescence spectroscopies is used to optimize the LSC composition, yielding optical efficiencies as high as 14.5% (300–800 nm). A power conversion efficiency (PCE) of 0.54% is obtained for the champion LSC coupled to a c-Si PV cell using the di-ureasil precursor as an optical glue to minimize interfacial losses. Finally, a simple figure of merit to evaluate the performance of LSC-solar cell composite systems is proposed that enables comparison of the actual improvement in the efficiency of solar cells due to the attachment of the LSC, irrespective of the LSC design, architecture or materials. A PCE of 17.4% for the solar cell in the emission region of the LSC is obtained, which is a remarkable improvement of ≈40% over its AM 1.5G value.

Sequential detection of multiple phase transitions in model biological membranes using a red-emitting conjugated polyelectrolyte

Co-reporter:Judith E. Houston, Mario Kraft, Ullrich Scherf and Rachel C. Evans

Physical Chemistry Chemical Physics 2016 vol. 18(Issue 18) pp:12423-12427

Publication Date(Web):21 Apr 2016

DOI:10.1039/C6CP01553K

The anionic conjugated polyelectrolyte, poly[3-(6-sulfothioatehexyl)thiophene] (P3Anionic), functions as a highly sensitive probe of membrane order, uniquely capable of sequentially detecting the three key phase transitions occurring within model phospholipid bilayers. The observed sensitivity is the result of charge-mediated, selective localisation of P3Anionic within the head-groups of the phospholipid bilayer.

Charge-Mediated Localization of Conjugated Polythiophenes in Zwitterionic Model Cell Membranes

Co-reporter:Judith E. Houston, Mario Kraft, Ian Mooney, Ann E. Terry, Ullrich Scherf, and Rachel C. Evans

Langmuir 2016 Volume 32(Issue 32) pp:8141-8153

Publication Date(Web):July 19, 2016

DOI:10.1021/acs.langmuir.6b01828

The selective engineering of conjugated polyelectrolyte (CPE)-phospholipid interfaces is poised to play a key role in the design of advanced biomedical and biotechnological devices. Herein, we report a strategic study to investigate the relationship between the charge of the CPE side group and their association with zwitterionic phospholipid bilayers. The interaction of dipalmitoylphosphatidylcholine (DPPC) phospholipid vesicles with a series of poly(thiophene)s bearing zwitterionic, cationic, or anionic terminal groups (P3Zwit, P3TMAHT and P3Anionic, respectively) has been probed. Although all CPEs showed an affinity for the zwitterionic vesicles, the calculated partition coefficients determined using photoluminescence spectroscopy suggested preferential incorporation within the lipid bilayer in the order P3Zwit > P3Anionic ≫ P3TMAHT. The polarity probe Prodan was used to further qualify the position of the CPE inside the vesicle bilayers via Förster resonance energy transfer (FRET) studies. The varying proximity of the CPEs to Prodan was reflected in the Stern–Volmer quenching constants and decreased in the order P3Anionic > P3TMAHT ≫ P3Zwit. Dynamic light scattering measurements showed an increase in the hydrodynamic diameter of the DPPC vesicles upon addition of each poly(thiophene), but to the greatest extent for P3Anionic. Small-angle neutron scattering studies also revealed that P3Anionic specifically increased the thickness of the headgroup region of the phospholipid bilayer. Epifluorescence and atomic force microscopy imaging showed that P3TMAHT formed amorphous agglomerates on the vesicle surface, P3Zwit was buried throughout the bilayer, and P3Anionic formed a shell of protruding chains around the surface, which promoted vesicle fusion. The global data indicate three distinctive modes of interaction for the poly(thiophene)s within DPPC vesicles, whereby the nature of the association is ultimately controlled by the pendant charge group on each CPE chain. Our results suggest that charge-mediated self-assembly may provide a simple and effective route to design luminescent CPE probes capable of specific localization within phospholipid membranes.

Synergistic photoluminescence enhancement in conjugated polymer-di-ureasil organic–inorganic composites

Co-reporter:Niamh Willis-Fox, Ana-Teresa Marques, Jochen Arlt, Ullrich Scherf, Luís D. Carlos, Hugh D. Burrows and Rachel C. Evans

Chemical Science 2015 vol. 6(Issue 12) pp:7227-7237

Publication Date(Web):17 Sep 2015

DOI:10.1039/C5SC02409A

Poly(fluorene) conjugated polyelectrolyte (CPE)-di-ureasil organic–inorganic composites have been prepared using a versatile sol–gel processing method, which enables selective localisation of the CPE within the di-ureasil matrix. Introduction of the CPE during the sol–gel reaction leads to a homogeneous distribution of the CPE throughout the di-ureasil, whereas a post-synthesis solvent permeation route leads to the formation of a confined layer of the CPE at the di-ureasil surface. The CPE and the di-ureasil both function as photoactive components, contributing directly to, and enhancing the optical properties of their composite material. The bright blue photoluminescence exhibited by CPE-di-ureasils is reminiscent of the parent CPE; however the distinct contribution of the di-ureasil to the steady-state emission profile is also apparent. This is accompanied by a dramatic increase in the photoluminescence quantum yield to >50%, which is a direct consequence of the synergy between the two components. Picosecond time-correlated single photon counting measurements reveal that the di-ureasil effectively isolates the CPE chains, leading to emissive trap sites which have a high radiative probability. Moreover, intimate mixing of the CPE and the di-ureasil, coupled with their strong spectral overlap, results in efficient excitation energy transfer from the di-ureasil to these emissive traps. Given the simple, solution-based fabrication method and the structural tunability of the two components, this approach presents an efficient route to highly desirable CPE-hybrid materials whose optoelectronic properties may be enhanced and tailored for a targeted application.

Self-assembled conjugated polyelectrolyte–surfactant complexes as efficient cathode interlayer materials for bulk heterojunction organic solar cells

Co-reporter:Michèle Chevrier, Judith E. Houston, Jurgen Kesters, Niko Van den Brande, Ann E. Terry, Sébastien Richeter, Ahmad Mehdi, Olivier Coulembier, Philippe Dubois, Roberto Lazzaroni, Bruno Van Mele, Wouter Maes, Rachel C. Evans and Sébastien Clément

Journal of Materials Chemistry A 2015 vol. 3(Issue 47) pp:23905-23916

Publication Date(Web):05 Nov 2015

DOI:10.1039/C5TA06966A

Interfacial engineering is poised to play a key role in delivering solution-processable organic solar cells that simultaneously feature low cost and high efficiency. Here, we report the strategic design, synthesis and characterisation of phosphonium-functionalised polythiophene homo- (P3HTPMe3) and diblock (P3HT-b-P3HTPMe3) conjugated polyelectrolytes (CPEs) coupled with either bromide (Br−) or dodecylsulfate (DS−) surfactant counterions, for application as cathodic interlayers in polymer solar cells. The counterion is shown to have a pronounced effect on the properties of the CPEs in solution. Optical studies revealed that the bulkier DS− counterion hinders interchain interactions more effectively, leading to a moderate blue-shift in the absorption and emission maxima. Similarly, small-angle neutron scattering (SANS) studies also indicated that the solution structures, solvent content, and therefore hydrophobicity, were extremely dependent on both the CPE structure and counterion. The effect of the CPE structure on the thermal properties of the CPE–surfactant complexes was also investigated by Rapid Heat–Cool calorimetry (RHC) measurements. CPE–DS complexes were subsequently employed as cathodic interfacial layers and shown to boost the efficiency of PBDTTPD:PC71BM solar cells, leading to enhanced power conversion efficiencies of 8.65% and 8.78% (on average) for P3HTPMe3,DS and P3HT-b-P3HTPMe3,DS, respectively. These values are significantly higher (∼20%) than those for the corresponding device incorporating a Ca interfacial layer (7.18%), which is attributed to an increase in short-circuit current density. Atomic force microscopy studies revealed distinctions in the adhesion efficiencies of the CPE–DS complexes to the photoactive layer, which is attributed to differences in the relative hydrophobicity of the CPEs in the deposition solution.

Charge-modulated self-assembly and growth of conjugated polyelectrolyte–polyoxometalate hybrid networks

Co-reporter:Judith E. Houston, Adam R. Patterson, Anil C. Jayasundera, Wolfgang Schmitt and Rachel C. Evans

Chemical Communications 2014 vol. 50(Issue 40) pp:5233-5235

Publication Date(Web):2013/12/12

DOI:10.1039/C3CC47552B

Self-assembly of an anionic polyoxometalate with cationic conjugated polyelectrolytes leads to hybrid supramolecular networks whose dimensionality is controlled by the chain length and steric charge distribution.

Lighting Up Two-Dimensional Lanthanide Phosphonates: Tunable Structure–Property Relationships toward Visible and Near-Infrared Emitters

Co-reporter:Adam R. Patterson ; Wolfgang Schmitt

The Journal of Physical Chemistry C 2014 Volume 118(Issue 19) pp:10291-10301

Publication Date(Web):May 1, 2014

DOI:10.1021/jp501359m

We report the solvothermal synthesis and characterization of the structure, morphology, and photoluminescence properties of a series of unprecedented layered, organic–inorganic lanthanide (LnIII) phosphonates based on tert-butyl- (But), 1-naphthalene (Naph)- and 4-biphenyl (Biphen)-phosphonic acid. Through systematic variation of the ligand and the LnIII, we discuss the key structure–property relationships that must be managed for the design of Ln-phosphonates with tailored functionality. Single crystal and X-ray powder diffraction studies revealed that the size and shape of the employed ligand affects the type of layered material that forms. In agreement with their molecular structures, two distinct crystal morphologies are observed, 1D nanorods and 2D platelets, demonstrating that the anisotropy in the crystal structure and the variable coordination behavior of the ligands is directly translated to the crystal growth. Judicious selection of the ligand enables us to switch-on Ln-centered photoluminescence in both the visible (EuIII, TbIII) and near-infrared (NdIII and YbIII) spectral regions. Notably, the presented Yb-phosphonates are rare examples of phosphonate-based near-infrared emitters. Furthermore, the EuIII spectral fingerprint provided unique insight into the coordination environment of the metal center, facilitating structural characterization where X-ray diffraction analysis was limited.

Harnessing self-assembly strategies for the rational design of conjugated polymer based materials

Co-reporter:Rachel C. Evans

Journal of Materials Chemistry A 2013 vol. 1(Issue 27) pp:4190-4200

Publication Date(Web):30 Apr 2013

DOI:10.1039/C3TC30543K

Targeted control of the aggregation, morphology and optoelectronic properties of conjugated polymers is critical for the development of high performance optoelectronic devices. In this Highlight, recent advances in the use of self-assembly approaches to strategically manipulate the order, conformation and spatial distribution of conjugated polymers in various states (e.g. solution, gels, films, solids) are discussed. Emphasis is placed on the complex relationship that exists between molecular composition, self-assembly and supramolecular organisation and their consequential influence on the optoelectronic properties and device performance.

Sugar-derived organogels as templates for structured, photoluminescent conjugated polymer–inorganic hybrid materials

Co-reporter:Patricia C. Marr, Katherine McBride and Rachel C. Evans

Chemical Communications 2013 vol. 49(Issue 55) pp:6155-6157

Publication Date(Web):28 May 2013

DOI:10.1039/C3CC43320J

Co-assembly of an inorganic–organic hybrid material through the combination of supramolecular organogel self-assembly, phase partitioning of a conjugated polymer (CP) and transcription of an inorganic oxide leads to a hybrid material with structured domains of organogel, CP and silica within tube and rod microstructures.

Chain confinement promotes β-phase formation in polyfluorene-based photoluminescent ionogels

Co-reporter:Rachel C. Evans and Patricia C. Marr

Chemical Communications 2012 vol. 48(Issue 31) pp:3742-3744

Publication Date(Web):20 Feb 2012

DOI:10.1039/C2CC18022G

The synthesis of photoluminescent conjugated polymer silica ionogels using sol–gel chemistry is described. Cooperative self-assembly of an ionic liquid, the silica precursor and poly(9,9-dioctylfluorene) (PFO) via hydrogen bonding and π-stacking interactions drives formation of the PFO β-phase.

Cationic Polythiophene–Surfactant Self-Assembly Complexes: Phase Transitions, Optical Response, and Sensing

Co-reporter:Rachel C. Evans, Matti Knaapila, Niamh Willis-Fox, Mario Kraft, Ann Terry, Hugh D. Burrows, and Ullrich Scherf

Langmuir 2012 Volume 28(Issue 33) pp:12348-12356

Publication Date(Web):July 27, 2012

DOI:10.1021/la302166a

The absorption and photoluminescence spectra of the cationic conjugated polyelectrolyte poly[3-(6-trimethylammoniumhexyl)thiophene] (P3TMAHT) were observed to be dramatically altered in the presence of anionic surfactants due to self-assembly through ionic complex formation. Small-angle neutron scattering (SANS), UV/vis, and photoluminescence spectroscopy were used to probe the relationship between the supramolecular complex organization and the photophysical response of P3TMAHT in the presence of industrially important anionic surfactants. Subtle differences in the surfactant mole fraction and chemical structure (e.g., chain length, headgroup charge density, perfluorination) result in marked variations in the range and type of complexes formed, which can be directly correlated to a unique colorimetric and fluorimetric fingerprint. Our results show that P3TMAHT has potential as an optical sensor for anionic surfactants capable of selectively identifying distinct structural subgroups through dual mode detection.

Fluorene Based Conjugated Polyelectrolyte/Silica Nanocomposites: Charge-Mediated Phase Aggregation at the OrganicInorganic Interface

Co-reporter:Rachel C. Evans;Andreia G. Macedo;Swapna Pradhan;Ullrich Scherf;Luís D. Carlos;Hugh D. Burrows

Advanced Materials 2010 Volume 22( Issue 28) pp:3032-3037

Publication Date(Web):

DOI:10.1002/adma.200904377

Synergistic photoluminescence enhancement in conjugated polymer-di-ureasil organic–inorganic composites

Co-reporter:Niamh Willis-Fox, Ana-Teresa Marques, Jochen Arlt, Ullrich Scherf, Luís D. Carlos, Hugh D. Burrows and Rachel C. Evans

Chemical Science (2010-Present) 2015 - vol. 6(Issue 12) pp:NaN7237-7237

Publication Date(Web):2015/09/17

DOI:10.1039/C5SC02409A

Poly(fluorene) conjugated polyelectrolyte (CPE)-di-ureasil organic–inorganic composites have been prepared using a versatile sol–gel processing method, which enables selective localisation of the CPE within the di-ureasil matrix. Introduction of the CPE during the sol–gel reaction leads to a homogeneous distribution of the CPE throughout the di-ureasil, whereas a post-synthesis solvent permeation route leads to the formation of a confined layer of the CPE at the di-ureasil surface. The CPE and the di-ureasil both function as photoactive components, contributing directly to, and enhancing the optical properties of their composite material. The bright blue photoluminescence exhibited by CPE-di-ureasils is reminiscent of the parent CPE; however the distinct contribution of the di-ureasil to the steady-state emission profile is also apparent. This is accompanied by a dramatic increase in the photoluminescence quantum yield to >50%, which is a direct consequence of the synergy between the two components. Picosecond time-correlated single photon counting measurements reveal that the di-ureasil effectively isolates the CPE chains, leading to emissive trap sites which have a high radiative probability. Moreover, intimate mixing of the CPE and the di-ureasil, coupled with their strong spectral overlap, results in efficient excitation energy transfer from the di-ureasil to these emissive traps. Given the simple, solution-based fabrication method and the structural tunability of the two components, this approach presents an efficient route to highly desirable CPE-hybrid materials whose optoelectronic properties may be enhanced and tailored for a targeted application.

Targeted design leads to tunable photoluminescence from perylene dicarboxdiimide–poly(oxyalkylene)/siloxane hybrids for luminescent solar concentrators

Co-reporter:Ilaria Meazzini, Niamh Willis-Fox, Camille Blayo, Jochen Arlt, Sébastien Clément and Rachel C. Evans

Journal of Materials Chemistry A 2016 - vol. 4(Issue 18) pp:NaN4059-4059

Publication Date(Web):2016/03/31

DOI:10.1039/C5TC03952E

A series of organic–inorganic hybrid materials in which a perylene carboxdiimide-bridged triethoxysilane (PDI-Sil) is covalently grafted to the siliceous domains of poly(oxyalkylene)/siloxane hybrids from the ureasil family has been synthesised (PDI-Sil-ureasils), with the aim of tailoring the optical properties towards their future application in luminescent solar concentrators (LSCs). Steady-state and time-resolved photoluminescence studies revealed that the ureasil host is able to isolate PDI-Sil, which inhibits the formation of aggregates. The ureasil also functions as an active host, with its intrinsic photoluminescence contributing to the optical properties of the hybrid material. Through strategic variation of the branching and molecular weight of the poly(oxyalkylene) backbone, it was shown that the efficiency of energy transfer from the ureasil host to the PDI-Sil can be modulated, which tunes the emission colour from pink to orange. The chain length, rather than the number of branches, on the poly(oxyalkylene) backbone was shown to influence the photoluminescence most significantly. Since ureasils demonstrate waveguiding properties, the results indicate that covalent grafting of a fluorophore directly to a waveguide host may provide an attractive route to more efficient LSCs.

Sequential detection of multiple phase transitions in model biological membranes using a red-emitting conjugated polyelectrolyte

Co-reporter:Judith E. Houston, Mario Kraft, Ullrich Scherf and Rachel C. Evans

Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 18) pp:NaN12427-12427

Publication Date(Web):2016/04/21

DOI:10.1039/C6CP01553K

The anionic conjugated polyelectrolyte, poly[3-(6-sulfothioatehexyl)thiophene] (P3Anionic), functions as a highly sensitive probe of membrane order, uniquely capable of sequentially detecting the three key phase transitions occurring within model phospholipid bilayers. The observed sensitivity is the result of charge-mediated, selective localisation of P3Anionic within the head-groups of the phospholipid bilayer.

Self-assembled conjugated polyelectrolyte–surfactant complexes as efficient cathode interlayer materials for bulk heterojunction organic solar cells

Co-reporter:Michèle Chevrier, Judith E. Houston, Jurgen Kesters, Niko Van den Brande, Ann E. Terry, Sébastien Richeter, Ahmad Mehdi, Olivier Coulembier, Philippe Dubois, Roberto Lazzaroni, Bruno Van Mele, Wouter Maes, Rachel C. Evans and Sébastien Clément

Journal of Materials Chemistry A 2015 - vol. 3(Issue 47) pp:NaN23916-23916

Publication Date(Web):2015/11/05

DOI:10.1039/C5TA06966A

Interfacial engineering is poised to play a key role in delivering solution-processable organic solar cells that simultaneously feature low cost and high efficiency. Here, we report the strategic design, synthesis and characterisation of phosphonium-functionalised polythiophene homo- (P3HTPMe3) and diblock (P3HT-b-P3HTPMe3) conjugated polyelectrolytes (CPEs) coupled with either bromide (Br−) or dodecylsulfate (DS−) surfactant counterions, for application as cathodic interlayers in polymer solar cells. The counterion is shown to have a pronounced effect on the properties of the CPEs in solution. Optical studies revealed that the bulkier DS− counterion hinders interchain interactions more effectively, leading to a moderate blue-shift in the absorption and emission maxima. Similarly, small-angle neutron scattering (SANS) studies also indicated that the solution structures, solvent content, and therefore hydrophobicity, were extremely dependent on both the CPE structure and counterion. The effect of the CPE structure on the thermal properties of the CPE–surfactant complexes was also investigated by Rapid Heat–Cool calorimetry (RHC) measurements. CPE–DS complexes were subsequently employed as cathodic interfacial layers and shown to boost the efficiency of PBDTTPD:PC71BM solar cells, leading to enhanced power conversion efficiencies of 8.65% and 8.78% (on average) for P3HTPMe3,DS and P3HT-b-P3HTPMe3,DS, respectively. These values are significantly higher (∼20%) than those for the corresponding device incorporating a Ca interfacial layer (7.18%), which is attributed to an increase in short-circuit current density. Atomic force microscopy studies revealed distinctions in the adhesion efficiencies of the CPE–DS complexes to the photoactive layer, which is attributed to differences in the relative hydrophobicity of the CPEs in the deposition solution.

Chain confinement promotes β-phase formation in polyfluorene-based photoluminescent ionogels

Co-reporter:Rachel C. Evans and Patricia C. Marr

Chemical Communications 2012 - vol. 48(Issue 31) pp:NaN3744-3744

Publication Date(Web):2012/02/20

DOI:10.1039/C2CC18022G

The synthesis of photoluminescent conjugated polymer silica ionogels using sol–gel chemistry is described. Cooperative self-assembly of an ionic liquid, the silica precursor and poly(9,9-dioctylfluorene) (PFO) via hydrogen bonding and π-stacking interactions drives formation of the PFO β-phase.

Harnessing self-assembly strategies for the rational design of conjugated polymer based materials

Co-reporter:Rachel C. Evans

Journal of Materials Chemistry A 2013 - vol. 1(Issue 27) pp:NaN4200-4200

Publication Date(Web):2013/04/30

DOI:10.1039/C3TC30543K

Targeted control of the aggregation, morphology and optoelectronic properties of conjugated polymers is critical for the development of high performance optoelectronic devices. In this Highlight, recent advances in the use of self-assembly approaches to strategically manipulate the order, conformation and spatial distribution of conjugated polymers in various states (e.g. solution, gels, films, solids) are discussed. Emphasis is placed on the complex relationship that exists between molecular composition, self-assembly and supramolecular organisation and their consequential influence on the optoelectronic properties and device performance.

Sugar-derived organogels as templates for structured, photoluminescent conjugated polymer–inorganic hybrid materials

Co-reporter:Patricia C. Marr, Katherine McBride and Rachel C. Evans

Chemical Communications 2013 - vol. 49(Issue 55) pp:NaN6157-6157

Publication Date(Web):2013/05/28

DOI:10.1039/C3CC43320J

Co-assembly of an inorganic–organic hybrid material through the combination of supramolecular organogel self-assembly, phase partitioning of a conjugated polymer (CP) and transcription of an inorganic oxide leads to a hybrid material with structured domains of organogel, CP and silica within tube and rod microstructures.

Charge-modulated self-assembly and growth of conjugated polyelectrolyte–polyoxometalate hybrid networks

Co-reporter:Judith E. Houston, Adam R. Patterson, Anil C. Jayasundera, Wolfgang Schmitt and Rachel C. Evans

Chemical Communications 2014 - vol. 50(Issue 40) pp:NaN5235-5235

Publication Date(Web):2013/12/12

DOI:10.1039/C3CC47552B

Self-assembly of an anionic polyoxometalate with cationic conjugated polyelectrolytes leads to hybrid supramolecular networks whose dimensionality is controlled by the chain length and steric charge distribution.

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