Random Terpolymer Research Articles

Nonhalogenated Solvent-Processed High-Performance Indoor Photovoltaics Made of New Conjugated Terpolymers with Optimized Monomer Compositions

Conjugated random terpolymers, PJ-25, PJ-50, and PJ-75 were successfully synthesized from three different monomers. Fluorine-substituted benzotriazole (2F-BTA) was incorporated into 4,8-bis(4-chlorothiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene (BDT-T-Cl) and a 1,3-bis(4-(2-ethylhexyl)thiophen-2-yl)-5,7-bis(2-alkyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione (BDD)-based alternating copolymer PM7 as a third monomeric unit. The solubility of the random terpolymers in nonhalogenated solvents increased with the number of 2F-BTA units in PM7. The random terpolymers were mixed with 3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6,7-difluoro)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (IT-4F) to fabricate organic photovoltaic (OPV) cells. Among the three terpolymers and two related binary copolymers (e.g., PM7 and J52-Cl), outdoor photovoltaic (PV) cells (AM 1.5G) based on the PJ-50:IT-4F blend showed a high power conversion efficiency (PCE) of 11.34%. In addition, PJ-50 was employed as a donor in indoor PV (IPV) cells and was blended with nonfullerene acceptors, which have different absorption ranges. Among them, the PJ-50:IT-4F-based IPV device had the highest PCE of 17.41% with a Jsc of 54.75 μA cm-2 and an FF of 0.77 under 160 μW cm-2 light-emitting diode (LED) light. The terpolymer introduced in this study can be regarded as a promising material for the fabrication of outdoor PV and IPV cells with excellent performance involving the use of an eco-friendly solvent.

Boron‐Catalyzed Polymerization of Dienyltriphenylarsonium Ylides: On the Way to Pure C5 Polymerization

AbstractThe first C5 polymerization is reported, where the main‐chain is growing by five carbon atoms of the monomer at a time. Three dienyltriphenylarsonium ylide monomers were synthesized and polymerized with triethylborane as an initiator, leading to random terpolymers (C1, C3, C5) with mainly C5 repeating units (up to 84.1 %). It has been found that the methyl group (electron‐donating substituent) on the conjugated double bond of the ylides facilitates the formation of C5 segments. A mechanism was proposed based on NMR characterization and DFT calculations. The high C5 content ensures that things are on the right track for pure C5 homopolymerization.

Boron-Catalyzed Polymerization of Dienyltriphenylarsonium Ylides: On the Way to Pure C5 Polymerization.

The first C5 polymerization is reported, where the main‐chain is growing by five carbon atoms of the monomer at a time. Three dienyltriphenylarsonium ylide monomers were synthesized and polymerized with triethylborane as an initiator, leading to random terpolymers (C1, C3, C5) with mainly C5 repeating units (up to 84.1 %). It has been found that the methyl group (electron‐donating substituent) on the conjugated double bond of the ylides facilitates the formation of C5 segments. A mechanism was proposed based on NMR characterization and DFT calculations. The high C5 content ensures that things are on the right track for pure C5 homopolymerization.

In-vitro Degradation Behaviors of Poly(L-lactide-co-glycolide-co-ε-caprolactone) Microspheres

Among drug delivery systems, polymer microspheres have been proved to be the most promising carriers during the past several years. In this paper we describe the preparation of poly(L-lactide-co-glycolide-co-ε-caprolactone) (PLLGC) random terpolymer microspheres; their in-vitro degradation behaviors, including the changes of pH value, mass loss, molecular mass and surface morphology, were investigated during various degradation periods and compared with poly(lactic-co-glycolic acid) (PLGA) microspheres. The results showed that the introduction of the ε-caprolactone (ε-CL) unit reduced the degradation rate of the PLGA polymers. Therefore, we suggest the PLLGC microspheres with controllable degradation rate could supply a wider application future in drug delivery field than pure PLGA microspheres.

Cholesteric mesophase based 1D photonic materials from self-assembly of liquid crystalline block and random terpolymers containing chromonic molecules.

We describe the influence of competing self-organizing phenomena on the formation of cholesteric mesophase in liquid crystalline brush block terpolymers (LCBBTs) and liquid crystalline random brush terpolymers (LCRBTs) containing chromonic molecules. A library of LCBBTs and LCRBTs are synthesized using ring-opening metathesis polymerization (ROMP) of norbornene side-chain functionalized monomers comprising cholesteryl mesogen (NBCh9), chromonic xanthenone (NBXan), and poly(ethylene glycol) (NBMPEG). Compression molded films of LCRBTs containing chromonic molecules display multilevel hierarchical structure in which cholesteric mesophase co-exists with π–π stacking of the chromonic mesophase along with PEG microphase segregated domains. This is unexpected as conventional LCBCPs and LCBBCs that lack chromonic molecules do not form cholesteric mesophases. The presence of π–π interactions modifies the interface at the IMDS so that both chromonic and cholesteric mesophases coexist leading to the manifestation of cholesteric phase for the first time within block architecture and is very reminiscent of previously published LCRBCs without chromonic molecules. The key to the observed hierarchical assembly in these LCBBTs containing chromonic molecules lies in the interplay of LC order, chromonic π–π stacking, PEG side chain microphase segregation, and their supramolecular cooperative motion. This unique “single component” polymer scaffold transforms our capacity to attain nanoscale hierarchies and optical properties from block architecture similar to nanoscale mesophases resulting in random architecture.

New Random Terpolymers Based on Bis(4,5-didodecylthiophen-2-yl)-[1,2,5]thiadiazolo[3,4-i]dithieno[3,2-a:2',3'-c]phenazine with Variable Absorption Spectrum as Promising Materials for Organic Solar Cells

A series of new random terpolymers was synthesized by copolymerization of one electron-donor alkyl-substituted benzodithiophene unit and two electron-acceptor units, diketopyrrolopyrrole (DPP) and bis(4,5-dodecylthiophen-2-yl)-[1,2,5]thiadiazol[3,4-i]dithieno[3,2-a:2',3'-c]phenazine (DF). The influence of the DPP/DF ratio on the thermal, optoelectronic, and electrochemical properties of the terpolymers was investigated using thermogravimetric analysis, UV-Vis spectroscopy, and cyclic voltammetry. The optical properties of the synthesized terpolymers were controlled by varying the DPP/DF ratio. An increase in the DF mole fraction in the polymer chain caused an increase in absorption intensity in the 300‒600 and 600‒1100 nm ranges, while increasing mole fraction of DPP resulted in stronger absorption in the 600‒900 nm range and lower absorption intensity in the 350‒600 nm range. The terpolymers exhibited broad and intense absorption over the spectral range from 300 to 1100 nm. The results demonstrate that random terpolymers with complementary absorption spectra have a great potential for increasing the photocurrent and efficiency of polymer solar cells.

Amphiphilic random and random block terpolymers with PEG, octadecyl, and oleyl pendants for controlled crystallization and microphase separation

Amphiphilic random and random block terpolymers bearing PEG chains, crystalline octadecyl groups, and amorphous oleyl groups were designed to control crystallization and microphase separation in the solid state.

Rheological behavior, crystallization properties, and foaming performance of chain-extended poly (lactic acid) by functionalized epoxy.

The inherently linear poly (lactic acid) suffers unsatisfying foaming behavior due to its low melt strength and poor crystallization properties. To overcome this drawback, a random terpolymer of ethylene, acrylic ester and glycidyl methacrylate (EGMA) was employed to improve the rheological behavior, crystallization properties, and foaming performance of poly (lactic acid) (PLA) through a chain extension reaction. The branched/micro-crosslinked structure formed by the chain extension reaction between EGMA and PLA effectively improved the dynamic rheological properties of PLA. As the content of EGMA increased from 0 wt% to 20 wt%, the crystal nucleation and crystal growth rate of various PLA samples have been significantly accelerated, resulting in a larger number and smaller size of spherulites, and the crystallinity of various PLA samples increased from 7.9% to 38.54%. The cell size of various PLA foams decreased from 53.5 to 22.0 μm and the cell density increased from 3.5 × 106 cells per cm3 to 2.5 × 107 cells per cm3, meanwhile, the cellular morphology of PLA foam was obviously improved. Moreover, the actual weight loss of PLA foams reached 26.1%, which is higher than the theoretical weight loss.

Stimuli-responsive smart nanoparticles with well-defined random and triblock terpolymers for controlled release of an anticancer drug

Stimuli-responsive nanoplatforms have shown great potential especially in efficient drug release systems. The rate of the anticancer drug release, adverse side effects, and toxicity can be controlled by designing nanoplatforms. Herein, mesoporous hydroxyapatite (HAp) nanoparticles were prepared. Fluorescent and pH-responsive biocompatible well-defined polymer chains were covalently attached by one step and sequential surface-initiated ATRP. The diameter of HAp increased from 120 to 147 and 158 nm with copolymerization. Polyethyleneglycol, poly(dimethylamino)propyl methacrylamide), and poly(fluorescent methacrylate) chains enhanced stimuli responsiveness of drug delivery. The drug release of the DOX@HAp/terpolymer nanoparticles was low under physiological conditions (pH 7.4). However, the release rate of DOX increased when pH was decreased to 5.5. The results of cytotoxicity indicated that the DOX-loaded HAp/terpolymer nanoparticles exhibited high biocompatibility and also caused apoptosis of cancer cells.

Synthesis of novel low bandgap random and block terpolymers with improved performance in organic solar cells

Novel conjugated random and block terpolymers composed of two electron-donating blocks - fluorene (Flo) and carbazole (Cz) - as well as one electron-accepting unit of thiophene-benzothiadiazole-thiophene (TBT) with the same (Flo:TBT:Cz) molar ratio of 0.5:1:0.5 were synthesized. The effects of their microstructure on physico-chemical properties and the performance of photovoltaic conversion were characterized. These conjugated terpolymers displayed two absorption peaks in UV–Vis analysis around 400 and 600 nm with a similar and narrow bandgap (1.9 eV, UV–Vis film), which is suitable to be applied as p-type semiconductors in an organic solar cell (OSC). Both synthesized terpolymers presented a high average molecular weight and degradation temperature above 400 °C. OSCs were assembled for determining the power conversion efficiency (PCE). Block terpolymer with a PCE of 1.3%, higher than that of 0.9% for the random terpolymer, was used as the electron donor in a conventional cell configuration. The device's optimization improved the photovoltaic parameters, mainly the short circuit current density, which allowed a PCE of 3.2% to be achieved. These results demonstrate that the synthesis of block terpolymers is a simple and practical approach for optimizing a conjugated polymer for an efficient OSC.

Terpolymer acceptors based on bithiophene imide for all-polymer solar cells

In order to improve light absorption and promote n-type performance, random copolymerization strategy was employed to afford a series of random terpolymer acceptors with acceptor1-acceptor2-acceptor3 (A1-A2-A3) type backbone. The polymers were synthesized from distannylated electron-deficient bithiophene imide monomer with various electron-deficient dibrominated co-monomers using the typical palladium-catalyzed Stille coupling condensation polymerization. Compared with their parent polymers, these A1-A2-A3 type terpolymer acceptors, particularly the dihexylthieno[3,4-b]pyrazine based terpolymer PBTP, can exhibit good miscibility, appropriate polymer crystallinity, and improved absorption in the long-wavelength region due to the incorporation of a third strong electron-withdrawing acceptor moiety thieno[3,4-b]pyrazine. Benefitting from the noncovalent S⋯N interactions, PBTP possessed a planar skeleton and achieved the highest power conversion efficiency (PCE) of 7.35% in the polymer series when serving as the acceptor material in all-polymer solar cells. These results indicate that the A1-A2-A3 type terpolymer acceptors should be promising candidates for developing high-performance all-polymer solar cells.

New Donor–Acceptor Random Terpolymers with Wide Absorption Spectra of 300–1000 nm for Photovoltaic Applications

The development of conjugated polymers with wide absorption spectra is imperative to achieve high efficiency in polymer solar cells (PSCs), since most of these polymers usually absorb only a limited range of the solar spectrum. Random terpolymers consisting of three blocks (one electron-donor and two electron-acceptor blocks) are promising p-type polymers for PSCs, because the inclusion of a third block in the polymer macromolecules provides a synergistic effect of physical properties, such as absorption capacity, charge transfer, HOMO/LUMO energy levels, and photovoltaic characteristics. In this regard, we have developed and synthesized random terpolymers consisting of two different chromophores (DPP and BFCTP) with complementary absorption spectra as co-acceptor blocks in conjugated donor–acceptor (D–A) copolymers. Random copolymers exhibit both broad absorption and low HOMO levels favoring short-circuit current and idle voltage in PSCs. It is expected that new terpolymers consisting of one electron-donor unit and two electron-acceptor moieties will make a significant contribution to the development of highly efficient PSCs. It is expected that new ternary copolymers consisting of one electron-donor unit and two electron-acceptor fragments will make a significant contribution to the development of high-performance PSСs.

Optimizing polymer aggregation and blend morphology for boosting the photovoltaic performance of polymer solar cells via a random terpolymerization strategy

Two random terpolymers were designed and synthesized to systematically study their photovoltaic performances. The PBNB80 -based device shows an outstanding PCE of 16.0%, which is much higher than those of their binary parent polymers. Compared to regular conjugated polymers, the random conjugated terpolymers are usually not beneficial to achieve highly efficient non-fullerene (NF)-based polymer solar cells (PSCs) due to their disordered chemical structures. In this work, we report two random terpolymer donors ( PBNB80 and PBNB50 ) by tuning the molar ratio of electron-accepting units of 1,3-di(thiophen-2-yl)naphtho[2,3-c]thiophene-4,9-dione (NTD) and 1,3-bis(4-chlorothiophen-2-yl)-4H,8H-benzo[1,2-c:4,5-c']dithiophene-4,8-dione (Cl-BDD), at the same time, the parent polymers ( PBNB100 and PBNB00 ) are also compared to study. These four polymer donors exhibit similar optical bandgaps and gradually deepen highest occupied molecular orbital levels. Importantly, aggregation and self-organization properties of the random terpolymer donors are optimized, which result in the better morphology and crystal coherence length after blending with NF acceptor of BO-4Cl. Particularly, a PBNB80 :BO-4Cl blend forms an optimal nanoscale phase-separation morphology, thereby producing an outstanding power conversion efficiency of 16.0%, which is much higher than those (12.8% and 10.7%) of their parent binary polymer donor-based devices. This work demonstrates that rational using terpolymerization strategy to prepare random terpolymer is a very important method to achieve highly efficient NF-PSCs.

Backbone Engineering of Diketopyrrolopyrrole-Based Conjugated Polymers through Random Terpolymerization for Improved Mobility-Stretchability Property.

Conjugated polymers synthesized through random terpolymerization have recently attracted great research interest due to the synergetic effect on the polymer's crystallinity and semiconducting properties. Several studies have demonstrated the efficacy of random terpolymerization in fine-tuning the aggregation behavior and optoelectronic property of conjugated polymers to yield enhanced device performance. However, as an influential approach of backbone engineering, its efficacy in modulating the mobility-stretchability property of high-performance conjugated polymers has not been fuller explored to date. Herein, a series of random terpolymers based on the diketopyrrolopyrrole-bithiophene (DPP-2T) backbone incorporating different amounts of isoindigo (IID) unit are synthesized, and their structure-mobility-stretchability correlation is thoroughly investigated. Our results reveal that random terpolymers containing a low IID content (DPP95 and DPP90) show enhanced interchain packing and solid-state aggregation to result in improved charge-transporting performance (can reach 4 order higher) compared to the parent polymer DPP100. In addition, owing to the enriched amorphous feature, DPP95 and DPP90 deliver an improved orthogonal mobility (μh) of >0.01 cm2 V-1 s-1 under a 100% strain, higher than the value (∼0.002 cm2 V-1 s-1) of DPP100. Moreover, DPP95 even yields 20% enhanced orthogonal μh retention after 800 stretching-releasing cycles with 60% strain. As concluded from a series of analyses, the improved mobility-stretchability property exerted by random terpolymerization arises from the enriched amorphous feature and enhanced aggregation behavior imposed by the geometry mismatch between different acceptors (DPP and IID). This study demonstrates that backbone engineering through rational random terpolymerization not only enhances the mobility-stretchability of a conjugated polymer but also realizes a better mechanical endurance, providing a new perspective for the design of high-performance stretchable conjugated polymers.

Precisely Controlling the Position of Bromine on the End Group Enables Well-Regular Polymer Acceptors for All-Polymer Solar Cells with Efficiencies over 15.

Recent advances in the development of polymerized A-D-A-type small-molecule acceptors (SMAs) have promoted the power conversion efficiency (PCE) of all-polymer solar cells (all-PSCs) over 13%. However, the monomer of an SMA typically consists of a mixture of three isomers due to the regio-isomeric brominated end groups (IC-Br(in) and IC-Br(out)). In this work, the two isomeric end groups are successfully separated, the regioisomeric issue is solved, and three polymer acceptors, named PY-IT, PY-OT, and PY-IOT, are developed, where PY-IOT is a random terpolymer with the same ratio of the two acceptors. Interestingly, from PY-OT, PY-IOT to PY-IT, the absorption edge gradually redshifts and electron mobility progressively increases. Theory calculation indicates that the LUMOs are distributed on the entire molecular backbone of PY-IT, contributing to the enhanced electron transport. Consequently, the PM6:PY-IT system achieves an excellent PCE of 15.05%, significantly higher than those for PY-OT (10.04%) and PY-IOT (12.12%). Morphological and device characterization reveals that the highest PCE for the PY-IT-based device is the fruit of enhanced absorption, more balanced charge transport, and favorable morphology. This work demonstrates that the site of polymerization on SMAs strongly affects device performance, offering insights into the development of efficient polymer acceptors for all-PSCs.

Fluorinated benzotriazole-modified random terpolymer acceptors towards less thickness-sensitive all-polymer solar cells

Naphthalene diimide (NDI)-based n-type polymers have been reported as the most widely employed polymer acceptors so far. However, all-polymer solar cells (all-PSCs) based on NDI-typed acceptors commonly suffer from low short-circuit current density (Jsc) due to the deficient absorption coefficients of polymer acceptors and unsatisfactory morphologies. In this work, based on the most widely used copolymer acceptor N2200, we designed terpolymer acceptors named PNDI-BTzx (x = 5 and 10) by randomly embedding a certain amount of fluorinated benzotriazole (2f-BTz) into N2200 backbone. The enhanced absorption coefficients, relatively weakened polymer crystallinities and improved polymer miscibility were obtained from terpolymer acceptors compared to N2200. Synchronously benefited from improved absorption and optimized morphology, all-PSCs based on PNDI-BTz5 demonstrated enhanced photovoltaic performance with power conversion efficiency (PCE) and Jsc of 6.72% and 12.54 mA cm−2 than 5.67% and 10.80 mA cm−2 from N2200-control. In addition, satisfactory reproducibility was obtained with comparable performance among different batches of PNDI-BTzx (x = 5 and 10). And more interestingly, all-PSCs based on PNDI-BTz5 possessed better thickness tolerance than N2200. These results offered useful guidelines to realize reproducible-performance and thick-film practical all-polymer photovoltaic applications through designing random terpolymer acceptors.

Amphiphilic QP(DMAEMA-co-LMA)-b-POEGMA Random-Block Terpolymers as Nanocarriers for Insulin.

We report on the utilization of the amphiphilic poly[quaternized (2-(N,N-dimethylamino) ethyl methacrylate)]-co-(lauryl methacrylate))-b-poly[(oligo ethylene glycol) methyl ether methacrylate] QP(DMAEMA-co-LMA)-b-POEGMA cationic diblock terpolymer aggregates as nanocarriers for insulin delivery applications. QP(DMAEMA-co-LMA)-b-POEGMA random diblock terpolymer is derived from the chemical modification of the precursor amino diblock copolymer via quaternization, producing permanent positive charges on the macromolecular chain. The QP(DMAEMA-co-LMA)-b-POEGMA diblock terpolymer as well as its amino precursor investigated self-assemble in aqueous media, forming aggregates. In vitro cytotoxicity and in vivo biocompatibility studies on QP(DMAEMA-co-LMA)-b-POEGMA and its amino precursor aggregates, showed good cytocompatibility and biocompatibility. QP(DMAEMA-co-LMA)-b-POEGMA aggregates were chosen to be complexed with insulin due to their self-assembly features and the permanent positive charge in each amino group. QP(DMAEMA-co-LMA)-b-POEGMA aggregates were complexed with insulin through electrostatic interactions. Light scattering techniques were used in order to study the ability of the polymer aggregates to complex with insulin, to determine critical physicochemical parameters such as size, mass, and surface charge of the stable complexes and study the effect of salt addition on their properties. The results showed that in both cases, the complexation process was successful and as the insulin concentration increases, nanosized complexes of different physicochemical characteristics (mass, size, surface charge) and spherical morphology are formed. UV-Vis and fluorescence spectroscopy studies showed that no conformational changes of insulin occurred after the complexation.

Alternating terpolymerization of carbon dioxide, propylene oxide, and various epoxides with bulky side groups for the tuning of thermal properties

Terpolymerization of carbon dioxide (CO2), propylene oxide (PO), and epoxide with bulky side groups (styrene oxide (SO), cyclohexylethylene oxide (CyEO), tert-butylethylene oxide (tBuEO), or 1-adamantylethylene oxide (AdEO)) was conducted by using a tetraphenylporphyrinatocobalt(III) chloride ((TPP)CoCl)/4-dimethylamino pyridine (DMAP) catalyst system. Compared with the copolymerizations of CO2 and epoxides with bulky side groups, it took less than half (AdEO) or even one-third (CyEO and tBuEO) of the polymerization time to synthesize polycarbonates with degrees of polymerization of 100 or above. In this (TPP)CoCl/DMAP system, a highly random terpolymer of CO2, PO, and SO was realized for the first time, which has not been observed in other catalyst systems, such as cobalt salen complex systems. In contrast, gradient terpolymers were formed in the cases of CyEO, tBuEO, and AdEO. The glass transition temperatures (Tgs) of these terpolymers are tunable between that of the copolymer of CO2 with PO (34 °C) and that of the copolymer of CO2 with the corresponding epoxide with bulky side groups by changing the initial ratio of PO to epoxide with bulky side groups. A highly random terpolymer of CO2, styrene oxide (SO), and propylene oxide (PO) was realized by using a tetraphenylporphyrinatocobalt(III) chloride ((TPP)CoCl)/4-dimethylamino pyridine (DMAP) catalyst system. In contrast, gradient terpolymers were formed in the cases of CO2, cyclohexylethylene oxide (CyEO), tert-butylethylene oxide (tBuEO) or 1-adamantylethylene oxide (AdEO), and PO. The glass transition temperatures (Tgs) of these terpolymers are tunable between that of the copolymer of CO2 with PO (34 °C) and that of the copolymers of CO2 with the corresponding epoxide with bulky side groups.

Random terpolymer based on thiophene-thiazolothiazole unit enabling efficient non-fullerene organic solar cells

Developing a high-performance donor polymer is critical for achieving efficient non-fullerene organic solar cells (OSCs). Currently, most high-efficiency OSCs are based on a donor polymer named PM6, unfortunately, whose performance is highly sensitive to its molecular weight and thus has significant batch-to-batch variations. Here we report a donor polymer (named PM1) based on a random ternary polymerization strategy that enables highly efficient non-fullerene OSCs with efficiencies reaching 17.6%. Importantly, the PM1 polymer exhibits excellent batch-to-batch reproducibility. By including 20% of a weak electron-withdrawing thiophene-thiazolothiazole (TTz) into the PM6 polymer backbone, the resulting polymer (PM1) can maintain the positive effects (such as downshifted energy level and reduced miscibility) while minimize the negative ones (including reduced temperature-dependent aggregation property). With higher performance and greater synthesis reproducibility, the PM1 polymer has the promise to become the work-horse material for the non-fullerene OSC community.

Chlorinated Random Terpolymers with Efficient Solar Conversion and Low Batch-to-Batch Variation

The strategy of random terpolymerization has been shown to be a flexible and effective method with which to construct state-of-the-art polymer donors, and chlorination has frequently been utilized ...