Incorporation of fluorene‐based emitting polymers into silica

Novel polyfluorene copolymers with pendant hydroxyl groups, poly[2,7‐(9,9‐dihexylfluorene)‐2,7‐(9,9‐bis(6‐hydroxyhexyl)fluorene)‐co‐2,7‐(9,9‐dihexylfluorene)‐1,4‐phenylene] (PFP‐OH) and poly[2,7‐(9,9‐dihexylfluorene)‐2,7‐(9,9‐bis(6‐hydroxyhexyl)fluorene)‐co‐2,7‐(9,9‐dihexylfluorene)‐4,7‐(2,1,3‐benzothiadiazole)] (PFBT‐OH) were prepared. Acid‐catalyzed polycondensations of tetraethoxysilane were carried out in the presence of these polymers to obtain homogeneous hybrids. Photoluminescence spectra of these hybrids suggested the polymers were immobilized in silica matrix retaining their π‐conjugated structures. Further, hybrids of coat film were prepared utilizing perhydropolysilazane as a silica precursor. Their optical properties were examined. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Selective dispersion of single-walled carbon nanotubes with specific chiral indices by poly(N-decyl-2,7-carbazole)

Physico-chemical methods to sort single-walled carbon nanotubes (SWNTs) by chiral index are presently lacking but are required for in-depth experimental analysis and also for potential future applications of specific species. Here we report the unexpected selectivity of poly(N-decyl-2,7-carbazole) to almost exclusively disperse semiconducting SWNTs with differences of their chiral indices (n - m) ≥ 2 in toluene. The observed selectivity complements perfectly the dispersing features of the fluorene analogue poly(9,9-dialkyl-2,7-fluorene), which disperses semiconducting SWNTs with (n - m) ≤ 2 in toluene. The dispersed samples are further purified by density gradient centrifugation and analyzed by photoluminescence excitation spectroscopy. All-atom molecular modeling with decamer model compounds of the polymers and (10,2) and (7,6) SWNTs suggests differences in the π-π stacking interaction as origin of the selectivity. We observe energetically favored complexes between the (10,2) SWNT and the carbazole decamer and between the (7,6) SWNT and the fluorene decamer, respectively. These findings demonstrate that subtle structural changes of polymers lead to selective solvation of different families of carbon nanotubes. Furthermore, chemical screening of closely related polymers may pave the way toward simple, low-cost, and index-specific isolation of SWNTs.     

Influence of Polymer Electronics on Selective Dispersion of Single‐Walled Carbon Nanotubes

The separation and isolation of semiconducting and metallic single‐walled carbon nanotubes (SWNTs) on a large scale remains a barrier to many commercial applications. Selective extraction of semiconducting SWNTs by wrapping and dispersion with conjugated polymers has been demonstrated to be effective, but the structural parameters of conjugated polymers that dictate selectivity are poorly understood. Here, we report nanotube dispersions with a poly(fluorene‐co‐pyridine) copolymer and its cationic methylated derivative, and show that electron‐deficient conjugated π‐systems bias the dispersion selectivity toward metallic SWNTs. Differentiation of semiconducting and metallic SWNT populations was carried out by a combination of UV/Vis‐NIR absorption spectroscopy, Raman spectroscopy, fluorescence spectroscopy, and electrical conductivity measurements. These results provide new insight into the rational design of conjugated polymers for the selective dispersion of metallic SWNTs.     

“Click” generation of a conjugated polymer library for SWNT dispersion

Noncovalent functionalization of single‐walled carbon nanotubes (SWNTs) with conjugated polymers enhances SWNT processability and allows for selective dispersion of various SWNT species. Selective dispersions can be obtained by tuning the nature of the polymer, which can involve using various polymer backbones or side‐chains. However, a clear understanding of selectivity determinants is elusive, as the degree of polymerization (DP) has a large effect on SWNT selectivity. Additionally, preparing libraries of conjugated polymers with varying functionality while keeping DP consistent is difficult. Here, we report the utilization of a strained cyclooctyne‐containing conjugated polymer that serves as a versatile scaffold, enabling systematic preparation of a small library of conjugated polymers with different side‐chain functionality, while maintaining a consistent DP. The resulting polymers were used as dispersants for SWNTs, forming supramolecular polymer‐SWNT complexes that were characterized by UV‐Vis‐NIR absorption and Raman spectroscopy. In the series of polymers, we were able to probe the effect of small changes within the side chains, such as the incorporation of a carbonyl group or an aromatic unit, on the quality of the polymer‐SWNT dispersion. The results of these studies provide new insight into the factors that dictate the ability of a polymer to form strong interactions with SWNTs. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2053–2058     

Effect of Backbone Chemical Structure of Polymers on Selective (n,m)Single‐Walled Carbon Nanotube Recognition/Extraction Behavior

The development of a simple and facile method to extract single‐walled carbon nanotubes (SWNTs) with a specific chirality index is one of the most‐crucial issues in the fundamental study and applications of the SWNTs. We have compared the selective recognition/extraction of the SWNT chirality of poly(9,10‐dioctyl‐9,10‐dihydrophenanthrene‐2,7‐diyl) (2C8‐PPhO) to that of poly(9,9‐dioctyfluoreny1‐2,7‐diyl) (2C8‐PFO) that are able to extract specific semiconducting SWNTs free of any metallic SWNTs. Vis/NIR absorption, 2D photoluminescence, and Raman spectroscopy as well as molecular mechanical simulations were used to analyze and understand the obtained chiral selective solubilization behavior. We found that 2C8‐PPhO selectively extracts and enriches the (8,6), (8,7), and (9,7)SWNTs, whose behaviors are different from that of 2C8‐PFO, which preferentially extracts the (7,5), (7,6), (8,6), and (8,7)SWNTs. Our results indicate that 2C8‐PPhO preferably recognizes larger‐diameter SWNTs with higher chiral angles compared to those recognized by 2C8‐PFO. These findings demonstrate that the difference in the non‐aromatic ring numbers on the polymers results in different SWNT chirality recognition/extraction behaviors.     

Conjugated block copolymers via functionalized initiators and click chemistry

Conjugated block copolymers are potentially useful for organic electronic applications and the study of interfacial charge and energy transfer processes; yet few synthetic methods are available to prepare polymers with well‐defined conjugated blocks. Here, we report the synthesis and thin film morphology of a series of conjugated poly(3‐hexylthiophene)‐block‐poly(9,9‐dioctylfluorene) (P3HT‐b‐PF) and poly(3‐dodecylthiophene)‐block‐poly(9,9‐dioctylfluorene) (P3DDT‐b‐PF) block copolymers prepared by functional external initiators and click chemistry. Functional group control is quantified by proton nuclear magnetic resonance spectroscopy, size‐exclusion chromatography, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. The thin film morphology of the resulting all‐conjugated block copolymers is analyzed by a combination of grazing‐incidence X‐ray scattering, atomic force microscopy, and transmission electron microscopy. Crystallization of the P3HT or P3DDT blocks is present in thin films for all materials studied, and P3DDT‐b‐PF films exhibit significant PF/P3DDT co‐crystallization. Processing conditions are found to impact thin film crystallinity and orientation of the π–π stacking direction of polymer crystallites. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 154–163     

Syntheses of Conjugated Polymers for Photonics

Summary: By the Suzuki coupling reaction of 9,9-dioctyl-2,7-bis(1,3,2-dioxaborinan-2-yl)fluorene ( I ) and 3,5-di-tert-butylphenyl 2,5-dibromobenzenesulfonate ( II ) the alternating poly{[9,9-dioctylfluoren-2,7-diyl]-alt-[2-(3,5-di-tert-butyl-phenoxysulfonyl)-1,4-phenylene]} ( III ) was synthesized. Alkaline hydrolysis of III gave a conjugated polyelectrolyte carrying sulfonic acid groups ( IV ). Monomers 2,5-dibromo-3-[2-(pyren-1-yl)vinyl]thiophene and 2,5-dibromo-3-[2-(quinolin-4-yl)vinyl)thiophene were prepared and copolymerized with I to afford poly{[9,9-dioctylfluoren-2,7-diyl]-alt-[3-(2-(pyren-1-yl)vinyl)thiophen-2,5-diyl]} ( V ) and poly{[9,9-dioctylfluoren-2,7-diyl]-alt-[3-(2-(quinolin-4-yl)-vinyl)thiophen-2,5-diyl] ( VI ), respectively. Conjugated backbone of V contains the conjugated pyrene unit in the side chain. Similarly the side chain of VI contains the conjugated quinoline structure unit which can be for instance protonated. By the Suzuki polycondensation reaction of I and of the prepared methyl 3-(2,7-dibromocarbazole-9-yl)propionate ( VII ) the new poly{[9,9-dioctylfluorene-2,7-diyl]-alt-[9-(2-methoxycarbonylethyl)carbazole-2,7-diyl]} ( VIII ) was synthesized and characterized.     

Electronic Properties of Two Series of Blue-Emitting Conjugated Oligomers and Polymers Based on Cyanostilbene： A Quantum Chemistry Study

One of the drawbacks of the electroluminescence （EL） polymers is that they are usually much better at accepting and transporting holes than electrons due to their inherent richness of π-electrons. One approach improving electron injection and transport in conjugated polymers is to incorporate moieties with high electron affinities. In this theoretical work, to gain an insight into the chemical structure-property relationships was aimed by controllable modification of the main chain structures. Two cyanovinylene derivatives with 2,7-fluorenylene and p-phenylene moieties in the main chains, namely, poly { （2,5-dimethoxy-p-phenylene- 1,4-ylene）-alt-[ 1,2-bis（p-phenylene）- 1- cyanovinylene]} （PPhCN） and poly{[9,9-dimethyl-2,7-fluorenylene]-alt-[1,2-bis（p-phenylene）-1-cyanovinylene]} （PFCN）, were studied employing density functional theory （DFT） and time dependent density functional theory （TD-DFT） with B3LYP functional. The electronic properties of the neutral molecules, extrapolated ionization potentials （IP） and electron affinities （EA）, and energy gaps were investigated in comparison with pristine poly（2,7- fluorenylene）. From comparison with poly（2,7-fluorenylene） （PF）, the 1,2-bis（p-phenylene）-1-cyanovi-nylene unit was found to be a good electron-withdrawing moiety for electronic materials and the incorporation of 1,2-bis（p- phenylene）-1-cyanovinylene resulted in a narrow band gap and a red shift of both the absorption and photoluminescence emission peaks. Most importantly, the LUMO energies of PFCN are around 1 eV lower than those of PF, which results in the decrement of EA about 0.9 eV, indicating that the 1,2-bis（p-phenylene）-1-cyanovinylene unit has significantly improved the electron-accepting properties of the copolymer PFCN. Substitution of 2,5-dimethoxy-p-phenylene for 9,9-dimethyl-2,7-fluorenylene induced larger band gaps and thus a blue-shift in absorption and emission peaks, which can be attributed to the better conjugated backbone in PFCN.     

Bulk dispersion of single-walled carbon nanotubes in silicones using diblock copolymers

The interactions of a series of poly(3-decylthiophene)-block-polydimethylsiloxanes (P3DT-b-PDMS) with single-walled carbon nanotubes (SWNTs) are investigated. The formation of supramolecular complexes of P3DT-b-PDMS with SWNTs is studied in THF, toluene, xylenes, and CHCl₃, and the resulting complexes are characterized by UV-Vis-NIR absorption and fluorescence spectroscopy. The P3DT-b-PDMS-SWNT and P3DT-SWNT complexes are further incorporated into a commercially available silicone rubber formulation. Percolation thresholds of <0.02% (P3DT-b-PDMS-SWNT) and <0.05% (P3DT-SWNT) are measured. A decrease in the percolation threshold when using the block copolymer for nanotube dispersion is observed, suggesting that the presence of a covalently-linked PDMS block improves SWNT distribution in the silicone elastomer and allows a percolation network to form at low SWNT loadings. In addition, it is found that entanglement of the silicone block of P3DT-PDMS with bulk silicones results in anchoring of the nanotubes within the composite, and leads to reversible conductivity changes upon repeated stretching and relaxation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 265–273     

Rational concept to recognize/extract single-walled carbon nanotubes with a specific chirality

Single-walled carbon nanotubes (SWNTs) have remarkable and unique electronic, mechanical, and thermal properties, which are closely related to their chiralities; thus, the chirality-selective recognition/extraction of the SWNTs is one of the central issues in nanotube science. However, any rational materials design enabling one to efficiently extract/solubilize pure SWNT with a desired chirality has yet not been demonstrated. Herein we report that certain chiral polyfluorene copolymers can well-recognize SWNTs with a certain chirality preferentially, leading to solubilization of specific chiral SWNTs. The chiral copolymers were prepared by the Ni(0)-catalyzed Yamamoto coupling reaction of 2,7-dibromo-9,9-di-n-decylfluorene and 2,7-dibromo-9,9-bis[(S)-(+)-2-methylbutyl]fluorene comonomers. The selectivity of the SWNT chirality was mainly determined by the relative fraction of the achiral and chiral side groups. By a molecular mechanics simulation, the cooperative interaction between the fluorene moiety, alkyl side chain, and graphene wall were responsible for the recognition/dissolution ability of SWNT chirality. This is a first example describing the rational design and synthesis of novel fluorene-based copolymers toward the recognition/extraction of targeted (n,?m) chirality of the SWNTs.     

Light-controlled single-walled carbon nanotube dispersions in aqueous solution

We have succeeded in dispersing single-walled carbon nanotubes (SWNTs) into an aqueous solution of poly(ethylene glycol)-terminated malachite green derivative (PEG-MG) through simple sonication. It was found that UV exposure caused reaggregation of these predispersed SWNTs in the same aqueous medium, as adsorbed PEG-MG photochromic chains could be effectively photocleavaged from the nanotube surface. The observed light-controlled dispersion and reaggragation of SWNTs in the aqueous solution should facilitate the development of SWNT dispersions with a controllable dispersity for potential applications.     

Block copolymers of poly(ethylene oxide) and poly(vinyl alcohol) synthesized by the RAFT methodology

A methodology for the synthesis of well‐defined poly(ethylene oxide)‐block‐poly(vinyl alcohol) (PEO‐b‐PVA) and PVA‐b‐PEO‐b‐PVA polymers was reported. Novel xanthate end‐functionalized PEOs were synthesized by a series of end‐group transformations. They were then used to mediate the reversible addition–fragmentation chain transfer polymerization of vinyl acetate to obtain well‐defined poly(ethylene oxide)‐b‐poly(vinyl acetate) (PEO‐b‐PVAc) and PVAc‐b‐PEO‐b‐PVAc. When these block copolymers were directly hydrolyzed in methanol solution of sodium hydroxide, polymers with brown color were obtained, which was due to the formation of conjugated unsaturated aldehyde structures. To circumvent these side reactions, the xanthate groups were removed by adding a primary amine before hydrolysis and the products thus obtained were white powders. The polymers were characterized by gel permeation chromatography, ¹H NMR spectroscopy and FT‐IR. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1901–1910, 2009     

Single-walled carbon nanotube-based coaxial nanowires: synthesis, characterization, and electrical properties

We report herein the template-directed synthesis, characterization, and electric properties of single-walled carbon nanotube- (SWNT-) based coaxial nanowires, that is, core (SWNT)-shell (conducting polypyrrole and polyaniline) nanowires. The SWNTs were first dispersed in aqueous solutions containing cationic surfactant cetyltrimethylammonium bromide (CTAB) or nonionic surfactant poly(ethylene glycol) mono-p-nonyl phenyl ether (O pi-10). Each individual nanotube (or small bundle) was then encased in its own micellelike envelope with hydrophobic surfactant groups orientated toward the nanotube and hydrophilic groups orientated toward the solution. And thus a hydrophobic region within the micelle/SWNT (called a micelle/SWNT hybrid template) was formed. Insertion and growth of pyrrole or aniline monomers in this hybrid template, upon removal of the surfactant, produce coaxial structures with a SWNT center and conducting polypyrrole or polyaniline coating. Raman and Fourier transform infrared (FTIR) spectroscopy and scanning (SEM) and transmission (TEM) electron microscopy were used to characterize the composition and the structures of these coaxial nanowires. The results revealed that the micellar molecules used could affect the surface morphologies of the resulting coaxial nanowires but not the molecular structures of the corresponding conducting polymers. Electric properties testing indicated that the SWNTs played the key roles in the conducting polymer/SWNT composites during electron transfer in the temperature range 77 K to room temperature. Compared with the SWNT network embedded in the conducting polymers, the composites within which SWNTs were coated perfectly by the identical conducting polymers exhibited higher barrier heights during electron transfer.     

Synthesis and properties of σ-π conjugated porous polymers obtained with Mizoroki–Heck reaction of tetra vinyl cyclic siloxane with dibromo fluorene

σ-π Conjugated porous polymers were synthesized by the Mizoroki–Heck reaction of cyclic siloxane with vinyl groups, 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (TVMCTS), and 2,7-dibromo-9,9-dialkylfluorene (RFl) compounds, using a Pd catalyst in N,N-dimethylformamide (DMF) at 100°C. The reactions of TVMCTS in combination with 2,7-dibromo-9,9-dihexylfluorene (HFl), 2,7-dibromo-9,9-dioctylfluorene (OFl), and 2,7-dibromo-9,9-ethylhexylfluorene (EHFl) yielded porous polymers whose morphologies were induced by phase separation during the network formation. The reactions in combination with binary RFl systems, TVMCTS-HFl/OFl, and HFl/EHFl systems, also yielded porous polymers. Scanning electron microscope images showed porous structures, which were composed by connected globules and/or isolated-deformed holes. The long and branching structure of the alkyl side chains in RFl decreased Young's modulus of porous polymers in compression test. The porous polymers showed emission derived from σ-π conjugated fluorene units on photo excitation. An increase in monomer concentration in the reaction induced red shifts of the emission bands of the porous polymer due to π-stacking of the fluorene units. The porous polymers showed relatively high fluorescence quantum yields of about 0.2–0.3. Quantum yield of the porous polymers with HFl decreased with increasing monomer concentration in the reaction systems.     

Enhanced photovoltaic performance of quasi-solid-state dye-sensitized solar cells via incorporating quaternized ammonium iodide-containing conjugated polymer into PEO gel electrolytes

In this study, a series of gel electrolytes prepared from blends of alternating conjugated polymer electrolytes (CPEs)/poly(ethylene oxide) (PEO) were developed for use in quasi-solid-state dye-sensitized solar cells (DSSCs). The alternating CPEs poly[(N-(3′-((N,N-dimethyl)-N-ethylammonium)propyl)-3,6-carbazole)-alt-(9,9-dioctyl-2,7-fluorene)]diiodide, poly[(N-(3′-((N,N-dimethyl)-N-ethylammonium)propyl)-3,6-carbazole)-alt-(9,9-bis(2-(2-methoxyethoxy)ethyl)-2,7-fluorene)]diiodide (MPCFO-E), and poly[(N-(3′-((N,N-dimethyl)-N-ethylammonium)propyl)-3,6-carbazole)-alt-(siloxane substituted-2,7-fluorene)]diiodide (MPCFS-E) were synthesized through copolymerization of carbazole units (featuring quaternized ammonium iodide groups) and fluorene units featuring flexible side chains (9,9-dioctylfluorene, ethylene oxide-substituted fluorene, and siloxane-substituted fluorene, respectively). The MPCFO-E/PEO-based and MPCFS-E/PEO-based DSSCs exhibited lower electrochemical resistances, superior photovoltaic (PV) properties, and improved PV stabilities relative to those of the corresponding PEO-based DSSC. Among the studied systems, the DSSC based on the MPCFO-E (0.5 wt.%)/PEO blend electrolyte exhibited the best PV performance, with a short current density of 4.97 mA cm⁻² and a photoenergy conversion efficiency of 1.17%.     

Synthesis and electroluminescent properties of fluorene‐based copolymers containing electron‐withdrawing thiazole derivatives

We synthesized two fluorene‐based copolymers poly[(2,5‐bis(4‐hexylthiophen‐2‐yl)thiazolo[5,4‐day]thiazole‐5,5′‐diyl)‐alt‐(9,9′‐dioctylfluorene‐2,7‐diyl)] ( PF‐TTZT), and poly[(5,5′‐bis(4‐hexylthiophen‐2‐yl)‐2,2′‐bithiazole‐5,5′‐diyl)‐alt‐(9,9′‐dioctylfluorene‐2,7‐diyl)] (PF‐TBTT), which contain the electron‐withdrawing moieties, thiazolothiazole, and bithiazole, respectively. Through electrochemical studies, we found that these two polymers exhibit stable reversible oxidation and reduction behaviors. Moreover, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of PF‐TBTT are lower than those of PF‐TTZT, and the bandgap of PF‐TBTT is smaller than that of PF‐TTZT. Thus the bithiazole moiety in PF‐TBTT is more electron‐withdrawing than the thiazolothiazole moiety in PF‐TTZT. Light‐emitting devices with indium tin oxide (ITO)/poly(3,4‐ethylene dioxythiophene):poly(styrenesulfonate)(PEDOT)/polymer/bis(2‐methyl‐8‐quinolinato)‐4‐phenylphenolate aluminum (BAlq)/LiF/Al configurations were fabricated. The performance of the PF‐TBTT device was found to be almost three times better than that of the PF‐TTZT device, which is because electron injection from the cathode to PF‐TBTT is much easier than for PF‐TTZT. We also investigated the planarity and frontier orbitals of the electron donor‐acceptor (D‐A) moieties with computational calculations using ab initio Hartree–Fock with the split‐valence 6‐31G* basis set. These calculations show that TBTT has a more nonplanar structure than TTZT and that the bithiazole moiety is more electron‐withdrawing than thiazolothiazole. These calculations are in good agreement with the experimental results. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7148–7161, 2008     

Enhanced efficiency of polyfluorene derivatives: Organic–inorganic hybrid polymer light‐emitting diodes

Two novel organic–inorganic hybrid polyfluorene derivatives, poly{(9,9′‐dioctyl‐2,7‐fluorene)‐co‐(9,9′‐di‐POSS‐2,7‐fluorene)‐co‐[2,5‐bis(octyloxy)‐1,4‐phenylene]} (PFDOPPOSS) and poly{(9,9′‐dioctyl‐2,7‐fluorene)‐co‐(9,9′‐di‐POSS‐2,7‐fluorene)‐co‐bithiophene} (PFT2POSS), were synthesized by the Pd‐catalyzed Suzuki reaction of polyhedral oligomeric silsesquioxane (POSS) appended fluorene, dioctyl phenylene, and bithiophene moieties. The synthesized polymers were characterized with ¹H NMR spectroscopy and elemental analysis. Photoluminescence (PL) studies showed that the incorporation of the POSS pendant into the polyfluorene derivatives significantly enhanced the fluorescence quantum yields of the polymer films, likely via a reduction in the degree of interchain interaction as well as keto formation. Additionally, the blue‐light‐emitting polyfluorene derivative PFDOPPOSS showed high thermal color stability in PL. Moreover, single‐layer light‐emitting diode devices of an indium tin oxide/poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration fabricated with PFDOPPOSS and PFT2POSS showed much improved brightness, maximum luminescence intensity, and quantum efficiency in comparison with devices fabricated with the corresponding pristine polymers PFDOP and PFT2. In particular, the maximum external quantum efficiency of PFT2POSS was 0.13%, which was twice that of PFT2 (0.06%), and the maximum current efficiency of PFT2POSS was 0.38 cd/A, which again was twice that of PFT2 (0.19 cd/A). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2943–2954, 2006     

Synthesis and characterization of aba-type block copolymer of poly(ϵ-caproplactone) with poly(ethylene glycol), by mean of activation end groups

Poly(?-caprolactone)-b-poly(ethylene glycol)-b-poly(?-caprolactone) (PCL-b-PEG-b-PCL) triblock copolymer were synthesized by mean anionic activation of the hydroxyl end groups of poly(ethylene glycol) in presence of diphenylmethylsodium. Copolymers were characterized by SEC, FT-IR and ¹H-NMR spectroscopy, TGA and DSC. Size exclusion chromatographic analysis of obtained copolymers indicated incorporation of CL monomer into PEG without formation of PCL homopolymer. Characterization by FT-IR and ¹H NMR spectroscopy of the resulting polymeric products, with respect to their structure, end-groups and composition, showed that they are best described as ester-ether-ester triblock copolymers, whose compositions can be adjusted changing the feeding molar ratio of PEG to CL. The thermal stability of triblock copolymers was less that PEG precursor, but higher that PCL homopolymer. Analysis by mean DSC showed that all copolymers were semi-crystalline and their thermal behavior depending on their composition.     

Functionalized PEG‐b‐PAGE‐b‐PLGA triblock terpolymers as materials for nanoparticle preparation

A series of poly(ethylene glycol)‐block‐poly(allyl glycidyl ether) (PEG‐b‐PAGE) macroinitiators are prepared using the living anionic ring‐opening polymerization (AROP) technique, and applied for further copolymerization studies. To overcome the low reactivity of the secondary hydroxyl end‐group of the PAGE block, a primary hydroxyl group is introduced into the macroinitiators via trityl and tert‐butyl‐dimethylsilane protective groups. The modified macroinitiators are used for copolymerization by applying different amounts of PEG‐b‐PAGE (5, 10, and 15%) and different PLGA lengths. To study their properties, nanoparticles from selected polymers are prepared and characterized by dynamic light scattering and scanning electron microscopy showing spherical particles with diameters around 200 nm and low PDI_particle values of 0.03–0.1. An advantage of the obtained polymers is the presence of double bonds in the side chain, which enables the modification via, for example, thiol‐ene reactions. For this purpose tertiary 2‐(dimethylamino)ethanethiol), acetylated thiogalactose and thiomannose are attached onto the double bonds of the PAGE‐blocks. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2163–2174     

Control of all‐conjugated block copolymer crystallization via thermal and solvent annealing

Control of the crystallization of conjugated polymers is of critical importance to the performance of organic electronics, such as organic photovoltaic devices, due to the effect on charge separation and transport, particularly for all‐polymer devices. The block copolymer poly(3‐dodecylthiophene)‐block‐poly(9,9‐dioctylfluorene) (P3DDT‐b‐PF), which has matched crystallization temperatures for each block, is used to study the effects of processing history on resulting crystallization. For longer annealing times and rapid quenching to room temperature, P3DDT crystals are preferred whereas for shorter annealing times and slower quenching, PF crystals are preferred. Both crystal forms are evidenced for long annealing time and slow quenching. Additionally, for room temperature annealing in the presence of a chloroform vapor, PF crystals are found in the PF β phase with the predominant crystal peak oriented perpendicular to the thermally annealed case. These results will provide guidance for optimizing annealing strategies for future donor/acceptor block copolymer photovoltaic devices. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 900–906