A new broad bandgap and 2D‐conjugated D‐A copolymer, PBDTBTz‐T , based on bithienyl‐benzodithiophene donor unit and bithiazole (BTz) acceptor unit, is designed and synthesized for the application as donor material in polymer solar cells (PSCs). The polymer possesses highly coplanar and crystalline structure with a higher hole mobility and lower HOMO energy level which is beneficial to achieve higher open circuit voltage (Voc) of the PSCs with the polymer as donor. The PSCs based on PBDTBTz‐T :PC71BM blend film with a lower PC71BM content of 40% demonstrate a power conversion efficiency (PCE) of 6.09% with a relatively higher Voc of 0.92 V. These results indicate that the lower HOMO energy level of the BTz‐based D–A copolymer is beneficial to a high Voc of the PSCs. The polymer, with highly coplanar and crystalline structure, can effectively reduce the content of fullerene acceptor in the active layer and can enhance the absorption and PCE of the PSCs.
Here, a conjugated polymer VTTPD based on thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) and dithiophene with vinyl as linker is synthesized and characterized. Electrochemical and optical studies indicate the LUMO and HOMO energies of the polymer are −3.70 and −5.39 eV. Theoretical calculation with density functional theory suggests that H‐bonds are formed between the TPD carbonyl (O) and its neighboring vinyl (H) which benefit the planarity and π‐conjugation of the polymer backbone. Bottom contact bottom gate organic field effect transistor devices based on VTTPD are fabricated and examined in air. After annealing at 160 °C, the devices exhibit excellent performance of μh = 0.4 cm2 V−1 s−1, Ion/off = 106, Vth within −10 V to −5 V. Thin film morphologies before and after the annealing process are also investigated with XRD and AFM.
Organic electrochromic materials change color rapidly under applied potential. A butterfly‐shaped compound, 5,5′,‐5″,‐5′″‐(thieno[3,2‐b]thiophene‐2,3,5,6‐tetrayl) tetrakis‐(2,3‐dihydrothieno[3,4‐b][1,4]dioxine) (t‐EDOT‐TT) is synthesized for the first time and polymerized at different potentials via electropolymerization technique. By applying different polymerization potentials, the optical and electrochromic properties of this newly synthesized polymer can be tuned. Owing to the dependence of functional group position in the polymer structure on the redox potential, this polymer can be utilized in very interesting organic optoelectronic applications.
Pentacyclic lactam acceptor unit TPTI invented by our group is proved to be a good building block for efficient D‐A copolymers used in organic solar cells. Here, two D‐A copolymers PBTTPTI and PTTTPTI are developed by copolymerizing TPTI with 2,2′‐bithiophene (BT) or thieno[3,2‐b]thiophene (TT). PBTTPTI and PTTTPTI exhibit good solubility and strong interchain π–π interaction even in dilute solution. They possess deep HOMO levels (ca. ‐5.3 eV), partial crystallinity, and good hole mobilities. Blending with PC71BM, PBTTPTI and PTTTPTI give decent power conversion efficiencies (PCE) up to 6.83% and 5.86%, with outstanding fill factors (FF) of 74.3% and 71.3%, respectively.
The synthesis of novel luminescent polymer containing p‐phenylene‐ethynylene and 9,12‐linked o‐carborane units alternately in the main chain is reported. The obtained polymer exhibits intense blue photoluminescence, providing the first insights into the optical properties of a 9,12‐disubstituted o‐carborane dye. π‐Conjugated substituent at 9 and/or 12‐positions in o‐carborane is electrically independent, and both the HOMO and the LUMO levels slightly increase, whereas LUMO of the π‐conjugated substituent at 1 and/or 2‐positions in o‐carborane decrease. Thus, it is deduced that polymers consisting of the 9,12‐linked o‐carborane unit are able to be applied as light‐emitting materials.
Two donor–acceptor copolymers based on isomeric acceptor units, [7,7′‐bithieno[2′,3′:4,5]thieno[2,3‐d ]thieno[3,2‐b ]pyridine]‐5,5′(4H ,4′H )‐dione (BTTP) and [2,2′‐bithieno[2′,3′:4,5]thieno[2,3‐d ]thieno[3,2‐b ]pyridine]‐5,5′(4H ,4′H )‐dione (iBTTP), are developed to study the effect of isomeric structures on photovoltaic performance. Compared with PBDTBTTP, PBDTiBTTP possesses a smaller bandgap for good light harvesting and a better π–π stacking for higher hole mobility. PBDTiBTTP solar cells present balanced mobilities and good nanoscale phase separation, giving a power conversion efficiency (PCE) of 6.51%, with higher short‐circuit current (J sc) and fill factor (FF).
The coordination polymerization of silyl‐protected ω‐alkenols such as ω‐alken‐α‐oxytriisopropylsilanes 1 provides poly(ω‐alkenyl‐α‐oxytriisopropylsilalne)s with a highly isospecific microstructure ([mmmm] > 95%) when a combination of [OSSO]‐type bis(phenolato) dichloro zirconium(IV) complex 2 and dried methylaluminoxane is used as the precatalyst and activator, respectively. The resulting siloxy‐substituted polymers could be efficiently transformed into the corresponding functionalized polyolefins, which contained up to 90% acetyl groups and ≈7% hydroxy groups in the terminal side chains.
The synthesis of symmetric cyclo poly(ε‐caprolactone)–block–poly(l (d )‐lactide) (c(PCL–b–PL(D)LA)) by combining ring‐opening polymerization of ε‐caprolactone and lactides and subsequent click chemistry reaction of the linear precursors containing antagonist functionalities is presented. The two blocks can sequentially crystallize and self‐assemble into double crystalline spherulitic superstructures. The cyclic chain topology significantly affects both the nucleation and the crystallization of each constituent, as gathered from a comparison of the behavior of linear precursors and cyclic block copolymers. The stereochemistry of the PLA block does not have a significant effect on the nonisothermal crystallization of both linear and cyclo PCL‐b‐PDLA and PCL‐b‐PLLA copolymers.
In order to improve the solution processability of 4,7‐bis(thiophen‐2‐yl)benzo[c][1,2,5]thiadiazole (DTBT)‐based polymers, novel donor–acceptor polymer PTOBDTDTBT containing DTBT and benzo[1,2‐b:4,5‐b′]dithiophene (BDT) with conjugated side chain is designed and synthesized with narrow band gap 1.67 eV and low lying HOMO energy level −5.4 eV. The blend film of PTOBDTDTBT and PC71BM exhibits uniform and smooth film with root‐mean‐square (RMS) surface roughness 1.15 nm because of the excellent solubility of PTOBDTDTBT when six octyloxy side chains are introduced. The hole mobility of the blend film is measured to be 4.4 × 10−5 cm2 V−1s−1 by the space‐charge‐limited current (SCLC) model. The optimized polymer solar cells (PSCs) based on PTOBDTDTBT /PC71BM exhibits an improved PCE of 6.21% with Voc = 0.80 V, Jsc = 11.94 mA cm−2 and FF = 65.10%, one of the highest PCE in DTBT containing polymers.
Since the development of supramolecular chemical biology, self‐organised nano‐architectures have been widely explored in a variety of biomedical applications. Functionalized synthetic molecules with the ability of non‐covalent assembly in an aqueous environment are typically able to interact with biological systems and are therefore especially interesting for their use in theranostics. Nanostructures based on π‐conjugated oligomers are particularly promising as theranostic platforms as they bear outstanding photophysical properties as well as drug loading capabilities. This Feature Article provides an overview on the recent advances in the self‐assembly of intrinsically fluorescent nanoparticles from π‐conjugated small molecules such as fluorene or perylene based chromophores for biomedical applications.
The present review focuses on the recent progress made in thin film orientation of semi‐conducting polymers with particular emphasis on methods using epitaxy and shear forces. The main results reported in this review deal with regioregular poly(3‐alkylthiophene)s and poly(dialkylfluorenes). Correlations existing between processing conditions, macromolecular parameters and the resulting structures formed in thin films are underlined. It is shown that epitaxial orientation of semi‐conducting polymers can generate a large palette of semi‐crystalline and nanostructured morphologies by a subtle choice of the orienting substrates and growth conditions.
Systematic optimization of the chemical structure of wide‐bandgap (≈2.0 eV) “donor–acceptor” copolymers consisting of indacenodithiophene or indacenodithieno[3,2‐b ]thiophene as the electron‐rich unit and thieno[3,4‐c ]pyrrole‐4,6‐dione as the electron‐deficient moiety in terms of alkyl side chain engineering and distance of the electron‐rich and electron‐deficient monomers within the repeat unit of the polymer chain results in high‐performance electron donor materials for organic photovoltaics. Specifically, preliminary results demonstrate extremely high open circuit voltages (V ocs) of ≈1.0 V, reasonable short circuit current density (J sc) of around 11 mA cm−2, and moderate fill factors resulting in efficiencies close to 6%. All the devices are fabricated in an inverted architecture with the photoactive layer processed by doctor blade equipment, showing the compatibility with roll‐to‐roll large‐scale manufacturing processes. From the correlation of the chemical structure—optoelectronic properties—photovoltaic performance, a rational guide toward further optimization of the chemical structure in this family of copolymers, has been achieved.
To enhance the limited degradability of poly(ethylene glycol) (PEG), a straightforward method of synthesizing poly[(ethylene glycol)‐co‐(glycolic acid)] (P(EG‐co‐GA)) via a ruthenium‐catalyzed, post‐polymerization oxyfunctionalization of various PEGs is developed. Using this method, a set of copolymers with GA compositions of up to 8 mol% are prepared with minimal reduction in molecular weight (<10%) when compared to their commercially available starting materials. The P(EG‐co‐GA) copolymers are shown to undergo hydrolysis under mild conditions.
High‐molecular‐weight conjugated polymer HD‐PDFC‐DTBT with N‐(2‐hexyldecyl)‐3,6‐difluorocarbazole as the donor unit, 5,6‐bis(octyloxy)benzothiadiazole as the acceptor unit, and thiophene as the spacer is synthesized by Suzuki polycondensation. HD‐PDFC‐DTBT shows a large bandgap of 1.96 eV and a high hole mobility of 0.16 cm2 V−1 s−1. HD‐PDFC‐DTBT:PC71BM‐based inverted polymer solar cells (PSCs) give a power conversion efficiency (PCE) of 7.39% with a Voc of 0.93 V, a Jsc of 14.11 mA cm−2, and an FF of 0.56.
A one‐pot method is introduced for the successful synthesis of narrow‐distributed (Đ = 1.22) vinyl polymer with both ultrahigh molecular weight (UHMW) (Mw = 1.31 × 106 g mol−1) and micro‐/nanomorphology under mild conditions. The method involves the following four stages: homogeneous polymerization, polymerization‐induced self‐assembly (PISA), PISA and reorganization, and PISA and multiple reorganizations. The key points to the production of UHMW polystyrene are to minimize radical termination by segregating radicals in different nanoreactors and to ensure sufficient chain propagation by promoting further reorganizations of these reactors in situ. This method therefore endows polymeric materials with the outstanding properties of both UHMW and tunable micro‐/nanoparticles under mild conditions in one pot.
A rapid access to 2,2′‐bithiazole‐based copolymers has been developed on the basis of the sequential palladium‐catalyzed C H/C X and C H/C H coupling reactions. To assemble a “copolymer” through homopolymerization, a type of symmetric A‐B‐A‐type building block is designed as the monomer and prepared via the regioselective C5 H arylation of thiazole. A PdCl2/CuCl‐cocatalyzed oxidative C H/C H homopolymerization has been established to afford the 2,2′‐bithiazole‐based copolymers with high Mn (up to 69400). The current protocol features atom‐ and step‐economy and exhibits a potential in the highly efficient construction of conjugated copolymers.
A convenient synthesis of sustainable polyamides, which contain side groups and stereocenters, starting from the biobased small terpene β‐pinene is reported. The polyamides, which are obtained via the pinene‐based lactam via ring‐opening polymerization, show excellent thermal properties, rendering this approach very interesting for the utilization of novel biobased and structurally significant high‐performance polymers and materials. Polymer masses and yields are shown to be dependent on different parameters, and the stereoinformation of the lactam monomer can thus be transferred into the polymer chain. In addition, another lactam side product can also be transformed to polyamides.
The controlled synthesis of poly(oligo(2‐ethyl‐2‐oxazoline)methacrylate) (P(OEtOxMA)) polymers by Cu(0)‐mediated polymerization in water/methanol mixtures is reported. Utilizing an acetal protected aldehyde initiator for the polymerization, well‐defined polymers are synthesized (>99% conversion, Ð < 1.25) with subsequent postpolymerization deprotection resulting in α‐aldehyde end group containing comb polymers. These P(OEtOxMA) are subsequently site‐specifically conjugated, via reductive amination, to a dipeptide (NH2‐Gly‐Tyr‐COOH) as a model peptide, prior to conjugation to the functional peptide oxytocin. The resulting oxytocin conjugates are evaluated in comparison to poly(oligo(ethylene glycol) methyl ether methacrylate) combs synthesized in the same manner for potential effects on thermal stability in comparison to the native peptide.
Two thermally cross‐linkable hole transport polymers that contain phenoxazine and triphenylamine moieties, X‐P1 and X‐P2, are developed for use in solution‐processed multi‐stack organic light‐emitting diodes (OLEDs). Both X‐P1 and X‐P2 exhibit satisfactory cross‐linking and optoelectronic properties. The highest occupied molecular orbital (HOMO) levels of X‐P1 and X‐P2 are −5.24 and −5.16 eV, respectively. Solution‐processed super yellow polymer devices (ITO/X‐P1 or X‐P2/PDY‐132/LiF/Al) with X‐P1 or X‐P2 hole transport layers of various thicknesses are fabricated with the aim of optimizing the device characteristics. The fabricated multi‐stack yellow devices containing the newly synthesized hole transport polymers exhibit satisfactory currents and power efficiencies. The optimized X‐P2 device exhibits a device efficiency that is dramatically improved by more than 66% over that of a reference device without an HTL.
The phase behavior of block copolymer based supramolecular complexes polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) and amphiphilic pentadecylphenol (PDP) molecules resembles the phase behavior of conventional block copolymers. Several PS‐b‐P4VP(PDP) complexes are found to self‐assemble into gyroid nanostructures. Typically, the grains are randomly oriented with a maximal size of several micrometers. Here, the orientation of a gyroid PS‐b‐P4VP(PDP) complex upon shearing is reported. It is found that the (111) gyroid lattice direction orients parallel to the shear direction after only several seconds of large amplitude oscillatory shearing. Oriented gyroid complexes can be used as templates for the preparation of metal nanofoams with improved ordering with potentially superior properties.
