Fascinating Morphological Behavior of A2-star-(B-alt-C) Molecules in the Melts and Solutions

We employ dissipative particle dynamics (DPD) to examine the self-assembling behavior of A₂-star-(B-alt-C) molecules in the melt and solution states. When these molecules are in the melts, we successfully observe various types of hierarchical structure-within-structures, such as A-formed spheres in the matrix formed by B and C alternating layers, hexagonally packed A-formed cylinders in the matrix with B and C segregated layers, B and C alternating layers-within-lamellae, coaxial B and C alternating domains within hexagonally packed BC-formed cylinders, and concentric BC-alternating domains within BC-formed spheres, by increasing the A composition. These hierarchical structures by varying the composition are reported theoretically for the first time in the copolymer systems consisting of the alternating blocks, and in good agreement with the most recent experimental work by Matsushita and co-workers (Macromolecules 2007 , 40, 4023). Generally speaking, the small-length-scale B and C segregated domains are in parallel to the large-length-scale structures for the melt case. While when a selective solvent is added, we find that varying the solvent selectivity and the amount of solvent can induce the molecules to form quite different morphological patterns, such as the so-called segmented worm like micelles.     

Hierarchical Structure‐within‐Structure Morphologies in A‐block‐(B‐graft‐C) Molecules

We have used dissipative particle dynamics (DPD) to simulate the self‐assembling behavior of A‐block‐(B‐graft‐C) coil‐comb molecules, in which each B segment is covalently bonded with one C segment. In addition to the composition, we found that by varying any of the interaction parameters between each pair of components I and J, where I, J = A, B, C, we can also induce a series of morphology transitions associated with two length scales. Moreover, we observed that if the length of the BC‐comb block is not long enough, the resulting morphology is mainly in the large‐length‐scale, ordering between the A‐rich and C‐rich domains with most of the B in the interfaces. By increasing the length of the BC‐comb block, one may expect that both B and C can pack orderly to form a lamellar structure. As a result, various experimentally observed structure‐within‐structures have been simulated via DPD.

     

Significantly improved photovoltaic performances of the dithiophene‐benzothiadiazole‐alt‐fluorene copolymers by incorporating carbazole units in fluorene moiety

To exploit an effective way to improve polymeric photovoltaic performance, a series of dithiophene‐benzothiadiazole‐alt‐fluorene copolymers containing carbazole groups at C‐9 positions of the alternating fluorene units (PFO‐FCz‐DBT) were synthesized and characterized. The effect of the carbazole groups on the optophysical, electrochemical, and photovoltaic properties of these copolymers was investigated. By comparison, this type of copolymers with carbazole units exhibited significantly improved photovoltaic properties than poly(2,7‐(9,9‐dioctyl‐fluorene)‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole) (PFO‐DBT) in the bulk heterojunction solar cells. A maximum power‐conversion efficiency (PCE) of 2.41% and a highest short‐circuit current density (J_sc) of 9.68 mA cm^?2 were obtained for the PFO‐FCz‐DBT30, which are about two times higher than the corresponding levels for the PFO‐DBT30. This work demonstrated that introducing a hole‐transporting carbazole unit into copolymer is a simple and effective method to improve the J_sc and PCE. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Amphiphilic liquid‐crystalline 4‐miktoarm star copolymers with a siloxane junction leading to cylindrically nanostructured templates for a siloxane‐based nanodot array

Well‐defined A₃B‐, A₂B₂‐, and AB₃‐type 4‐miktoarm star copolymers (M_n = 10,500–16,200, M_w/M_n = 1.16–1.18) consisting of poly(ethylene oxide) (PEO) and polymethacrylate bearing an azobenzene mesogen (PMA(Az)) as the arms and cyclotetrasiloxane as the core unit were synthesized using a combined route composed of a thiol‐ene click reaction and atom transfer radical polymerization. Microphase‐separated structures of the star copolymers in thin films with a thickness of approximately 100 nm were investigated by GISAXS and TEM. The A₃B‐type star‐(PEO)₃[PMA(Az)]₁ copolymer formed a more highly ordered PEO cylinder array with perpendicular alignment in the PMA(Az) matrix than that of the corresponding linear‐type block copolymer. The center‐to‐center distance of the PEO cylinders and the cylinder diameter were 13 and 4 nm, respectively. The highly ordered star‐(PEO)₃[PMA(Az)]₁ thin film was directly transferred to a siloxane‐based nanodot array by oxygen reactive ion etching. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1175–1188     

Alternating Ring‐Opening Metathesis Copolymerization by Grubbs‐Type Initiators with Unsymmetrical N‐Heterocyclic Carbenes

A series of Ru^IV–alkylidenes based on unsymmetrical imidazolin‐2‐ylidenes, that is, [RuCl₂{1‐(2,4,6‐trimethylphenyl)‐3‐R‐4,5‐dihydro‐(3H)‐imidazol‐1‐ylidene}(CHPh)(pyridin)] (R=CH₂Ph ( 5 ), Ph ( 6 ), ethyl ( 7 ), methyl ( 8 )), have been synthesized. These and the parent initiators [RuCl₂(PCy₃){1‐(2,4,6‐trimethylphenyl)‐3‐R‐4,5‐dihydro‐(3H)‐imidazol‐1‐ylidene}(CHC₆H₅)] (R=CH₂C₆H₅ ( 1 ), C₆H₅ ( 2 ), ethyl ( 3 )) were used for the alternating copolymerization of norborn‐2‐ene (NBE) with cis‐cyclooctene (COE) and cyclopentene (CPE), respectively. Alternating copolymers, that is, poly(NBE‐alt‐COE)_n and poly(NBE‐alt‐CPE)_n containing up to 97 and 91 % alternating diads, respectively, were obtained. The copolymerization parameters of the alternating copolymerization of NBE with CPE under the action of initiators 1 – 3 and 5 – 8 were determined by using both a zero‐ and first‐order Markov model. Finally, kinetic investigations using initiators 1 – 3 , 6 , and 7 were carried out. These revealed that in contrast to the 2nd‐generation Grubbs‐type initiators 1 – 3 the corresponding pyridine derivatives 6 and 7 represent fast and quantitative initiating systems. Hydrogenation of poly(NBE‐alt‐COE)_n yielded a fully saturated, hydrocarbon‐based polymer. Its backbone can formally be derived by 1‐olefin polymerization of CPE (1,3‐insertion) followed by five ethylene units and thus serves as an excellent model compound for 1‐olefin polymerization‐derived copolymers.     

Preparation,characterization, and thermal properties of alt‐copoly[1,9‐decaphenylpentasiloxanylene/1,3‐bis(ethylene)permethyloligosiloxanylene]s

alt‐Copoly[1,9‐decaphenylpentasiloxanylene/1,3‐bis(ethylene)tetramethyldisiloxanylene], alt‐copoly[1,9‐decaphenylpentasiloxanylene/1,5‐bis(ethylene)hexamethyltrisiloxanylene], alt‐copoly[1,9‐decaphenylpentasiloxanylene/1,7‐bis(ethylene)octamethyltetrasiloxanylene], and alt‐copoly[1,9‐decaphenylpentasiloxanylene/1,9‐bis(ethylene)decamethylpentasiloxanylene] were synthesized by Pt‐catalyzed hydrosilylation reactions of 1,9 divinyldecaphenylpentasiloxanes with a series of oligodimethylsiloxanes. The molecular weights of these copolymers were determined by gel permeation chromatography. Their glass‐transition temperatures (T_g's) were obtained by differential scanning calorimetry. The thermal stabilities of the copolymers were measured by thermogravimetric analysis. The structures of the copolymers were verified by ¹H, ¹³C, and ²⁹Si NMR as well as IR and UV spectroscopy. The copolymers displayed high thermal stabilities and a single T_g, indicating that phase separation between the two short blocks did not occur. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6146–6152, 2005     

Living polymerization of D,L‐3‐methylglycolide initiated with bimetallic (Al/Zn) μ‐oxo alkoxide and copolymers thereof

D,L ‐3‐Methylglycolide (MG) was successfully polymerized with bimetallic (Al/Zn) μ‐oxo alkoxide as an initiator in toluene at 90 °C. The effect of the initiator concentration and monomer conversion on the molecular weight was studied. It is shown that the polymerization of MG follows a living process. A kinetic study indicated that the polymerization approximates the first order in the monomer, and no induction period was observed. ¹H NMR spectroscopy showed that the ring‐opening polymerization proceeds through a coordination–insertion mechanism with selective cleavage of the acyl–oxygen bond of the monomer. On the basis of ¹H NMR and ¹³C NMR analyses, the selective cleavage of the acyl–oxygen bond of the monomer mainly occurs at the least hindered carbonyl groups (P₁ = 0.84, P₂ = 0.16). Therefore, the main chain of poly(D,L ‐lactic acid‐co‐glycolic acid) (50/50 molar ratio) obtained from the homopolymerization of MG was primarily composed of alternating lactyl and glycolyl units. The diblock copolymers poly(ϵ‐caprolactone)‐b‐poly(D,L ‐lactic acid‐alt‐glycolic acid) and poly(L ‐lactide)‐b‐poly(D,L ‐lactic acid‐alt‐glycolic acid) were successfully synthesized by the sequential living polymerization of related lactones (ϵ‐caprolactone or L ‐lactide). ¹³C NMR spectra of diblock copolymers clearly show their pure diblock structures. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 357–367, 2001     

Green‐emitting poly[(1,3‐phenylenevinylene)‐alt‐ (1,4‐phenylenevinylene)]s: Effect of the substitution patterns on the optical properties

Green‐emitting substituted poly[(2‐hexyloxy‐5‐methyl‐1,3‐phenylenevinylene)‐alt‐(2,5‐dihexyloxy‐1,4‐phenylenevinylene)]s ( 6 ) were synthesized via the Wittig–Horner reaction. The polymers were yellow resins with molecular weights of 10,600. The ultraviolet–visible (UV–vis) absorption of 6 (λ_max = 332 or 415 nm) was about 30 nm redshifted from that of poly[(2‐hexyloxy‐5‐methyl‐1,3‐phenylenevinylene)‐alt‐(1,4‐phenylenevinylene)] ( 2 ) but was only 5 nm redshifted with respect to that of poly[(1,3‐phenylenevinylene)‐alt‐(2,5‐dihexyloxy‐1,4‐phenylenevinylene)] ( 1 ). A comparison of the optical properties of 1 , 2 , and 6 showed that substitution on m‐ or p‐phenylene could slightly affect their energy gap and luminescence efficiency, thereby fine‐tuning the optical properties of the poly[(m‐phenylene vinylene)‐alt‐(p‐phenylene vinylene)] materials. The vibronic structures were assigned with the aid of low‐temperature UV–vis and fluorescence spectroscopy. Light‐emitting‐diode devices with 6 produced a green electroluminescence output (emission λ_max ～ 533 nm) with an external quantum efficiency of 0.32%. Substitution at m‐phenylene appeared to be effective in perturbing the charge‐injection process in LED devices. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1820–1829, 2004     

Novel blue‐greenish electroluminescent poly(fluorenevinylene‐alt‐dibenzothiophenevinylene)s and their model compounds

Poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐2,8‐vinylene) (PS) and poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐5,5‐dioxide‐2,8‐ vinylene) (PSO) as well as corresponding model compounds were synthesized by Heck coupling. Both the polymers and model compounds were readily soluble in common organic solvents such as tetrahydrofuran, dichloromethane, chloroform, and toluene. The polymers showed a decomposition temperature at ～430 °C and a char yield of about 65% at 800 °C in N₂. The glass‐transition temperatures of the polymers were almost identical (75–77 °C) and higher than those of the model compounds (26–45 °C). All samples absorbed around 390 nm, and their optical band gaps were 2.69–2.85 eV. They behaved as blue‐greenish light emitting materials in both solutions and thin films, with photoluminescence emission maxima at 450–483 nm and photoluminescence quantum yields of 0.52–0.72 in solution. Organic light‐emitting diodes with an indium tin oxide/poly(ethylene dioxythiophene):poly(styrene sulfonic acid)/polymer/Mg:Ag/Ag configuration with polymers PS and PSO as emitting layers showed green electroluminescence with maxima at 530 and 540 nm, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6790–6800, 2006     

Simple synthesis,photophysics, and electroluminescent properties of poly[2,7‐bis(4‐tert‐butylstyryl)fluorene‐9, 9‐diyl‐alt‐alkane‐α,ω‐diyl]

A simple synthetic route was used for the synthesis of a novel series of alternating copolymers based on substituted 2,7‐distyrylfluorene bridged through alkylene chains. First, 2,7‐dibromofluorene was reacted with 2 equiv of butyllithium, and this was followed by a treatment with 1 equiv of α,ω‐dibromoalkane to yield the intermediate, poly(2,7‐dibromofluorene‐9,9‐diyl‐alt‐alkane‐α,ω‐diyl). ( 1 ) Heck coupling of the latter with 1‐tert‐butyl‐4‐vinylbenzene afforded the target, poly[2,7‐bis(4‐tert‐butylstyryl)fluorene‐9,9‐diyl‐alt‐alkane‐α,ω‐diyl] ( 2 ). The two versions of 2 ( 2a and 2b which have hexane and decane, respectively, as alkane groups) were readily soluble in common organic solvents. Their glass‐transition temperature was relatively low (52 and 87 °C). An intense blue photoluminescence emission with maxima at about 408 and 409 nm was observed in tetrahydrofuran solutions, whereas thin films exhibited an orange emission with maxima at 569 and 588 nm. Very large redshifts of the photoluminescence maxima and Stokes shifts in thin films indicated strong aggregation in the solid state. Both polymers oxidized and reduced irreversibly. Single‐layer light‐emitting diodes with hole‐injecting indium tin oxide and electron‐injecting aluminum electrodes were fabricated. They emitted orange light with external electroluminescence efficiencies of 0.52 and 0.36% photon/electron, as determined in light‐emitting diodes made of 2a and 2b , with alkylenes of (CH₂)₆ and (CH₂)₁₀, respectively. An increase in the external electroluminescence efficiency up to 1.5% was reached in light‐emitting diodes made of polymer blends consisting of 2a and poly(9,9‐dihexadecylfluorene‐2,7‐diyl), which emitted blue‐white light. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 809–821, 2007.     

Synthesis of star‐shaped poly(D,L‐lactic acid‐alt‐glycolic acid)‐b‐poly(L‐lactic acid) with the poly(D,L‐lactic acid‐alt‐glycolic acid) macroinitiator and stannous octoate catalyst

Two types of three‐arm and four‐arm, star‐shaped poly(D,L ‐lactic acid‐alt‐glycolic acid)‐b‐poly(L ‐lactic acid) (D,L ‐PLGA50‐b‐PLLA) were successfully synthesized via the sequential ring‐opening polymerization of D,L ‐3‐methylglycolide (MG) and L ‐lactide (L ‐LA) with a multifunctional initiator, such as trimethylolpropane and pentaerythritol, and stannous octoate (SnOct₂) as a catalyst. Star‐shaped, hydroxy‐terminated poly(D,L ‐lactic acid‐alt‐glycolic acid) (D,L ‐PLGA50) obtained from the polymerization of MG was used as a macroinitiator to initiate the block polymerization of L ‐LA with the SnOct₂ catalyst in bulk at 130 °C. For the polymerization of L ‐LA with the three‐arm, star‐shaped D,L ‐PLGA50 macroinitiator (number‐average molecular weight = 6800) and the SnOct₂ catalyst, the molecular weight of the resulting D,L ‐PLGA50‐b‐PLLA polymer linearly increased from 12,600 to 27,400 with the increasing molar ratio (1:1 to 3:1) of L ‐LA to MG, and the molecular weight distribution was rather narrow (weight‐average molecular weight/number‐average molecular weight = 1.09–1.15). The ¹H NMR spectrum of the D,L ‐PLGA50‐b‐PLLA block copolymer showed that the molecular weight and unit composition of the block copolymer were controlled by the molar ratio of L ‐LA to the macroinitiator. The ¹³C NMR spectrum of the block copolymer clearly showed its diblock structures, that is, D,L ‐PLGA50 as the first block and poly(L ‐lactic acid) as the second block. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 409–415, 2002     

Morphological behavior of model poly(ethylene‐alt‐propylene)‐b‐polylactide diblock copolymers

A set of well‐defined poly(ethylene‐alt‐propylene)‐b‐polylactide (PEP‐PLA) diblock copolymers containing volume fractions of PLA (f_PLA) ranging between 0.08 and 0.91 were synthesized by a combination of living anionic polymerization, catalytic hydrogenation, and controlled coordination‐insertion ring‐opening polymerization. The morphological behavior of these relatively low‐molecular‐weight PEP‐PLA diblock copolymers was investigated with a combination of rheology, small‐angle X‐ray scattering, and differential scanning calorimetry. The ordered microstructures observed were lamellae (L), hexagonally packed cylinders (C), spheres (S), and gyroid (G), a bicontinous cubic morphology having Ia3 d space group symmetry. The G morphology existed in only a small region between the L‐C morphologies in close proximity to the order–disorder transition (ODT). Transformations from L to G were observed upon heating in several samples. The efficacy of the reverse G to L transition in one sample was cooling rate dependent. The PEP‐PLA Flory–Huggins interaction parameter as a function of temperature χ_PEP‐PLA(T) was estimated from T_ODT's by mean‐field theory and subsequently used in the construction of the experimental PEP‐PLA morphology diagram (χN versus f_PLA). The resultant morphology diagram was symmetric there were the well‐defined L‐C morphology boundaries. The low molecular weight of the materials imparted no significant deviation from previously documented diblock systems. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2364–2376, 2002     

Organometallic‐Mediated Alternating Radical Copolymerization of tert‐Butyl‐2‐Trifluoromethacrylate with Vinyl Acetate and Synthesis of Block Copolymers Thereof

Organometallic‐mediated radical polymerization (OMRP) has given access to well‐defined poly(vinyl acetate‐alt‐tert‐butyl‐2‐trifluoromethacrylate)‐b‐poly(vinyl acetate) and poly(VAc‐alt‐MAF‐TBE) copolymers composed of two electronically distinct monomers: vinyl acetate (VAc, donor, D) and tert‐butyl‐2‐trifluoromethacrylate (MAF‐TBE, acceptor, A), with low dispersity (≤1.24) and molar masses up to 57 000 g mol⁻¹. These copolymers have a precise 1:1 alternating structure over a wide range of comonomer feed compositions. The reactivity ratios are determined as r _VAc = 0.01 ± 0.01 and r _MAF‐TBE = 0 at 40 °C. Remarkably, from a feed containing >50% molar VAc content, poly(VAc‐alt‐MAF‐TBE)‐b‐PVAc block copolymers are produced via a one‐pot synthesis. Such diblock copolymers exhibit two glass transition temperatures attributed to the alternating and homopolymer sequences. The OMRP of this fluorine‐containing alternating monomer system may provide access to a wide range of new polymer materials.

     

Biomimetic Synthesis of Metal Ion‐Doped Hierarchical Crystals Using a Gel Matrix: Formation of Cobalt‐Doped LiMn2O4 with Improved Electrochemical Properties through a Cobalt‐Doped MnCO3 Precursor

We have synthesized spinel type cobalt‐doped LiMn₂O₄ (LiMn_2?yCo_yO₄, 0≤y≤0.367), a cathode material for a lithium‐ion battery, with hierarchical sponge structures via the cobalt‐doped MnCO₃ (Mn_1‐xCo_xCO₃, 0≤x≤0.204) formed in an agar gel matrix. Biomimetic crystal growth in the gel matrix facilitates the generation of both an homogeneous solid solution and the hierarchical structures under ambient condition. The controlled composition and the hierarchical structure of the cobalt‐doped MnCO₃ precursor played an important role in the formation of the cobalt‐doped LiMn₂O₄. The charge–discharge reversible stability of the resultant LiMn_1.947Co_0.053O₄ was improved to ca. 12 % loss of the discharge capacity after 100 cycles, while pure LiMn₂O₄ showed 24 % loss of the discharge capacity after 100 cycles. The parallel control of the hierarchical structure and the composition in the precursor material through a biomimetic approach, promises the development of functional materials under mild conditions.     

Photoluminescent,liquid‐crystalline,and electrochemical properties of para‐phenylene‐based alternating conjugated copolymers

Novel liquid‐crystalline alternating conjugated copolymers [ P(P(6)CN‐alt‐Cz) and P(P(6)CN‐alt‐MeP) ] with phenylene and carbazolylene or phenylene with methyl substitution onto the main chain have been synthesized through palladium‐catalyzed Suzuki coupling reactions. The influence of the incorporation of carbazolylene and the substituted phenylene into the main chain on the thermal, mesomorphic, and luminescent properties has been investigated by Fourier transform infrared spectroscopy, thermogravimetry, differential scanning calorimetry, polarized optical microscopy, ultraviolet–visible spectroscopy, photoluminescence (PL), and cyclic voltammetry. These polymers show highly thermal stability, losing little of their weights when heated to 360 °C. The conjugated copolymers exhibit liquid crystallinity at elevated temperature. The existence of the chromophoric terphenyl core endows the copolymers with high PL and the polymer P(P(6)CN‐alt‐Cz containing carbazolylene unit can emit more pure blue light. All the copolymer films with low band gaps about 2.3–2.4 eV undergo reversible oxidation and reduction processes, significantly lower than the band gap of poly(p‐phenylene). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 434–442, 2010     

Synthesis of bio‐based poly(N‐phenylitaconimide) by atom transfer radical polymerization

Poly(N‐phenylitaconimide) (polyPhII) was prepared using initiators for continuous activator regeneration atom transfer radical polymerization of PhII using FeBr₃ complexes as catalysts. Conversion reached 69% in 24 h, yielding polyPhII with a number average molecular weight M_n = 11,900 and a molecular weight distribution M_w/M_n = 1.52. Copolymerizations of PhII with styrene at various molar ratios were performed providing a range of polyPhII‐copolySt polymers. When the copolymerization was carried out with higher [St]₀ > [PhII]₀ ratio, a one‐pot synthesis of poly(St‐alt‐PhII)‐b‐polySt was achieved. The thermal properties of the obtained copolymers were studied by differential scanning calorimetry. PolyPhII prepared by ATRP showed high glass transition temperature (T_g) of 216 °C and the poly(St‐alt‐PhII)‐b‐polySt exhibited two T_gs, at 162 and 104 °C, corresponding to a poly(St‐alt‐PhII) and polySt segments, respectively. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 822–827     

Alternating and Diblock Donor–Acceptor Conjugated Polymers Based on Diindeno[1,2‐b:2′,1′‐d]thiophene Structure: Synthesis,Characterization, and Photovoltaic Applications

Pentacyclic diindeno[1,2‐b:2′,1′‐d]thiophene ( DIDT ) unit is a rigid and coplanar conjugated molecule. To the best of our knowledge, this attractive molecule has never been incorporated into a polymer and thus its application in polymer solar cells has never been explored. For the first time, we report the detailed synthesis of the tetra‐alkylated DIDT molecule leading to its dibromo‐ and diboronic ester derivatives, which are the key monomers for preparation of DIDT ‐based polymers. Two donor–acceptor alternating polymers, poly(diindenothiophene‐alt‐benzothiadiazole) PDIDTBT and poly(diindenothiophene‐alt‐dithienylbenzothiadiazole) PDIDTDTBT , were synthesized by using Suzuki polymerization. Copolymer PTDIDTTBT was also prepared by using Stille polymerization. Although PTDIDTTBT is prepared through a manner of random polymerization, we found that the different reactivities of the dibromo‐monomers lead to the resulting polymer having a block copolymer arrangement. With the higher structural regularity, PTDIDTTBT , symbolized as (thiophene‐alt‐ DIDT )_0.5‐block‐(thiophene‐alt‐BT)_0.5, shows the higher degree of crystallization, stronger π–π stacking, and broader absorption spectrum in the solid state, as compared to its alternating PDIDTDTBT analogue. Bulk heterojunction photovoltaic cells based on ITO/PEDOT:PSS/polymer:PC₇₁BM/Ca/Al configuration were fabricated and characterized. PDIDTDTBT /PC₇₁BM and PTDIDTTBT /PC₇₁BM systems exhibited promising power‐conversion efficiencies (PCEs) of 1.65 % and 2.00 %, respectively. Owing to the complementary absorption spectra, as well as the compatible structures of PDIDTDTBT and PTDIDTTBT , the PCE of the device based on the ternary blend PDIDTDTBT / PTDIDTTBT /PC₇₁BM was further improved to 2.40 %.     

Morphology control and inducing a curvature on the domain interface by increasing the steric bulk of polymethacrylate in POSS‐containing diblock copolymers

Herein, a novel rod‐coil type polyhedral oligomeric silsesquioxane (POSS)‐containing diblock copolymer was designed to enable the self‐assembly of hexagonally packed cylinders of the POSS‐containing domain in a poly(n‐butyl methacrylate) (PnBMA) matrix. When POSS‐containing diblock copolymers were synthesized with polyisoprene or poly(methyl methacrylate), cylindrical structures could not be obtained as POSS‐containing polymers form stretched rigid rods. This makes the formation of cylindrical structures with the POSS‐containing domain entropically unfavorable. Therefore, to obtain the cylindrical structures, we constructed a novel diblock copolymer using PnBMA to increase the steric bulk and segment volume of the flexible coil. Steric crowding of the butyl groups reduces the entropic free stretching energy of the PnBMA chains, which in turn encourages the formation of a POSS‐containing hexagonally packed cylindrical structure within the PnBMA matrix as the system minimizes the total free energy of the thermodynamically stable nanostructure. Small angle X‐ray scattering and transmission electron microscopy analyses indicated that cylinders of the POSS domain had formed. Oxygen plasma etching was then used on the thin film to selectively remove the PnBMA domain to yield line and space structures with a high degree of long‐range order and a 14 nm feature size. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2234–2242     

Photovoltaic devices using semiconducting polymers containing head‐to‐tail‐structured bithiophene,pyrene, and benzothiadiazole derivatives

An alternating copolymer composed of heal‐to‐tail‐structured 3,4′‐dihexyl‐2,2′‐bithiophene (DHBT) and pyrene units [poly(DHBT‐alt‐PYR)] was synthesized using a Stille coupling reaction for use in photovoltaic devices as a p‐type donor. For the reduction of the bandgap energy of poly(DHBT‐alt‐PYR), 4,7‐bis(3′‐hexyl‐2,2′‐bithiophen‐5‐yl)benzo[c][1,2,5]thiadiazole (BHBTBT) units were introduced into the polymer. Poly(DHBT‐co‐PYR‐co‐BHBTBT)s were synthesized using the same polymerization reaction. The synthesized polymers were soluble in common organic solvents and formed smooth thin films after spin casting. The optical bandgap energies of the polymers were obtained from the onset absorption wavelengths. The measured optical bandgap energy of poly(DHBT‐alt‐PYR) was 2.47 eV. As the BHBTBT content in the ter‐polymers increased, the optical bandgap energies of the resulting polymers decreased. The bandgap energies of poly(50DHBT‐co‐40PYR‐co‐10BHBTBT) and poly(50DHBT‐co‐20PYR‐co‐30BHBTBT) were 1.84 and 1.73 eV, respectively. Photovoltaic devices were fabricated with a typical sandwich structure of ITO/PEDOT:PSS/active layer/LiF/Al using the polymers as electron donors and [6,6]‐phenyl C₇₁‐butyric acid methyl ester as the electron acceptor. The device using poly(50DHBT‐co‐20PYR‐co‐30BHBTBT) showed the best performance among the fabricated devices, with an open‐circuit voltage, short‐circuit current, fill factor, and maximum power conversion efficiency of 0.68 V, 5.54 mA/cm², 0.35, and 1.31%, respectively. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Controlled random and alternating copolymerization of (meth)acrylates,acrylonitrile, and (meth)acrylamides with vinyl ethers by organotellurium‐, organostibine‐, and organobismuthine‐mediated living radical polymerization reactions

Random and alternating copolymerizations of acrylates, methacrylates, acrylonitorile, and acrylamides with vinyl ethers under organotellurium‐, organostibine‐, and organobismuthine‐mediated living radical polymerization (TERP, SBRP, and BIRP, respectively) have been studied. Structurally well‐controlled random and alternating copolymers with controlled molecular weights and polydispersities were synthesized. The highly alternating copolymerization occurred in a combination of acrylates and vinyl ethers and acrylonitorile and vinyl ethers by using excess amount of vinyl ethers over acrylates and acrylonitorile. On the contrary, alternating copolymerization did not occur in a combination of acrylamides and vinyl ethers even excess amount of vinyl ethers were used. The reactivity of polymer‐end radicals to a vinyl ether was estimated by the theoretical calculations, and it was suggested that the energy level of singly occupied molecular orbital (SOMO) of polymer‐end radical species determined the reactivity. By combining living random and alternating copolymerization with living radical or living cationic polymerization, new block copolymers, such as (PBA‐alt‐PIBVE)‐block‐(PtBA‐co‐PIBVE), PBA‐block‐(PBA‐alt‐PIBVE), and (PTFEA‐alt‐PIBVE)‐block‐PIBVE, with controlled macromolecular structures were successfully synthesized. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012