Individually Addressable Thermo‐ and Redox‐Responsive Block Copolymers by Combining Anionic Polymerization and RAFT Protocols

A novel diblock copolymer consisting of poly(vinylferrocene) (PVFc) and poly(N,N‐diethylacrylamide) (PDEA) is synthesized via a combination of anionic and RAFT polymerization. The use of a novel route to hydroxyl‐end‐functionalized metallopolymers in anionic polymerization and subsequent esterification with a RAFT agent leads to a PVFc macro‐CTA ( = 3800 g mol⁻¹; Đ = 1.17). RAFT polymerization with DEA affords block copolymers as evidenced by ¹H NMR spectroscopy as well as size exclusion chromatography (6400 ≤ ≤ 33700 g mol⁻¹; 1.31 ≤ Đ 1.28). Self‐assembly of the amphiphilic block copolymers in aqueous solution leads to micelles as shown via TEM. Importantly, the distinct thermo‐responsive and redox‐responsive character of the blocks is probed via dynamic light scattering and found to be individually and repeatedly addressable.

     

Redox‐Switchable Supramolecular Graft Polymer Formation via Ferrocene–Cyclodextrin Assembly

The redox switchable formation of very well‐defined supramolecular graft polymers in aqueous solution driven by host–guest interactions between ferrocene (Fc) and cyclodextrin (CD) is presented. The Fc‐containing acrylic backbone copolymer (PDMA‐stat‐Fc) is prepared via reversible addition–fragmentation chain transfer (RAFT) copolymerization of N,N‐dimethyl­acrylamide (DMA) and the novel monomer N‐(ferrocenoylmethyl)acrylamide (NFMA). Via the RAFT process, copolymers containing variable Fc ratios (5‐10 mol%) are prepared, affording polymers of molecular masses of close to 11 000 g mol⁻¹ and molar mass dispersities (Đ) of 1.2. The β‐cyclodextrin (β‐CD) containing building block is synthesized via RAFT‐polymerization, too, in order to afford a polymer with well‐defined molecular mass and low dispersity ( = 10 300 g mol⁻¹, Đ = 1.1), employing a propargyl‐functionalized chain transfer agent for the polymerization of N,N‐diethylacrylamide (DEA). The polymerization product is subsequently terminated with β‐CD via the regiospecific copper (I)‐catalyzed 1,3‐cycloaddition (PDEA‐βCD). Host–guest interactions between Fc and CD lead to the formation of supramolecular graft‐polymers, verified via nuclear Overhauser enhancement spectroscopy (NOESY). Importantly, their redox‐responsive character is clearly confirmed via cyclic voltammetry (CV). The self‐assembly of the statistical Fc‐containing lateral polymer chain in aqueous solution leads to mono‐ and multi‐core micelle‐aggregates evidenced via TEM. Only diffused cloud‐like, non‐spherical nanostructures are observed after addition of PDEA‐βCD (TEM).

     

An Efficient N‐Heterocyclic Carbene‐Ruthenium Complex: Application Towards the Synthesis of Polyesters and Polyamides

The ruthenium benzimidazolylidene‐based N‐heterocyclic carbene (NHC) complex 4 catalyzes the direct dehydrogenative condensation of primary alcohols into esters and primary alcohols in the presence of amines to the corresponding amides in high yields. This efficient new catalytic system shows a high selectivity towards the conversion of diols to polyesters and of a mixture of diols and diamines to polyamides. The only side product formed in this reaction is molecular hydrogen. Remarkable is the conversion of hydroxytelechelic polytetrahydrofuran ( = 1000 g mol⁻¹)—a polydispers starting material—into a hydrolytically degradable polyether with ester linkages ( = 32 600 g mol⁻¹) and, in the presence of aliphatic diamines, into a polyether with amide linkages in the back bone ( = 16 000 g mol⁻¹).

     

Tailored Thiol‐Functional Polyamides: Synthesis and Functionalization

In this article, a synthetic concept for the preparation of polyamides with functional side groups is described. First, the synthesis of a bis(thiolactone) monomer is shown in a concise three‐step route from itaconic acid and DL‐homocysteine thiolactone. The reactivity of the resulting bis(thiolactone) toward hexyl amine is examined. Next, the bis(thiolactone) is reacted as A,A‐type monomer with different B,B‐type comonomers (1,12‐diaminododecane and 1,3‐bis(aminopropyl)tetramethyldisiloxane). Ring opening of the thiolactones by the diamines leads to polyamides with pendant thiol groups. Using two diamines in different ratios, the properties of the resulting polyamides are tuned (thermal properties are determined) and different molecular weights are acquired. Subsequently, the thiol groups are reacted with methyl acrylate via Michael addition to functionalize the polyamides. Functionalization of thiol‐functional polyamides using poly(ethylene glycol) monomethyl ether (mPEG) acrylates ( = 480 and 1700 g mol⁻¹) results in water‐soluble amphiphilic poly­amides with molecular weights higher than 10 000 g mol⁻¹.

     

RAFT‐Polymerization‐Induced Self‐Assembly and Reorganizations: Ultrahigh‐Molecular‐Weight Polymer and Morphology‐Tunable Micro‐/Nanoparticles in One Pot

A one‐pot method is introduced for the successful synthesis of narrow‐distributed (Đ = 1.22) vinyl polymer with both ultrahigh molecular weight (UHMW) (M _w = 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.

     

UV‐Induced [2+2] Grafting‐To Reactions for Polymer Modification of Cellulose

Benzaldehyde‐functional cellulose paper sheets have been synthesized via tosylation of cellulose (Whatman No 5) followed by addition of p‐hydroxy benzaldehyde. Via UV‐induced Paterno–Büchi [2+2] cycloaddition reactions, these aldehyde functional surfaces are grafted with triallylcyanurate, trimethylolpropane allyl ether, and vinyl chloroacetate. In the following, allyl‐functional polymers (poly(butyl acrylate), pBA, M_n = 6990 g mol⁻¹, Đ = 1.12 and poly(N‐isopropyl acrylamide), pNIPAAm, M_n = 9500 g mol⁻¹, Đ = 1.16) synthesized via reversible addition fragmentation chain transfer polymerization are conjugated to the celloluse surface in a UV‐induced grafting‐to approach. With pBA, hydrophobic cellulose sheets are obtained (water contact angle 116°), while grafting of pNIPAAm allows for generation of “smart” surfaces, which are hydrophilic at room temperature, but that become hydrophobic when heated above the characteristic lower critical solution temperature (93° contact angle). The Paterno–Büchi reaction has been shown to be a versatile synthetic tool that also performs well in grafting‐to approaches whereby its overall performance seems to be close to that of radical thiol‐ene reactions.

     

Low‐Temperature Synthesis of Thermoresponsive Diblock Copolymer Nano‐Objects via Aqueous Photoinitiated Polymerization‐Induced Self‐Assembly (Photo‐PISA) using Thermoresponsive Macro‐RAFT Agents

Photoinitiated reversible addition‐fragmentation chain transfer (RAFT) dispersion polymerization of 2‐hydroxypropyl methacrylate is conducted in water at low temperature using thermoresponsive copolymers of 2‐(2‐methoxyethoxy) ethyl methacrylate and oligo(ethylene glycol) methacrylate (M_n = 475 g mol⁻¹) as the macro‐RAFT agent. Kinetic studies confirm that quantitative monomer conversion is achieved within 15 min of visible‐light irradiation (405 nm, 0.5 mW cm⁻²), and good control is maintained during the polymerization. The polymerization can be temporally controlled by a simple “ON/OFF” switch of the light source. Finally, thermoresponsive diblock copolymer nano‐objects with a diverse set of complex morphologies (spheres, worms, and vesicles) are prepared using this particular formulation.

     

Glucose Oxidase and Glucose for Redox‐Initiating the Free Radical Copolymerization of N‐(ferrocenoylmethyl)acrylamide in Aqueous Cyclodextrin Solution

The glucose oxidase and glucose mediated formation of amphipilic copolymers of N‐(ferrocenoylmethyl)acrylamide (NFMA) and N,N‐diethylacrylamide (DEA) in aqueous cyclodextrin solution is presented. Thereby, NFMA is not only a comonomer but also part of the redox initiation system. The obtained copolymers contain NFMA units between 1 and 10 mol%. The molecular masses of the copolymers are dependent on the ferrocene content, whereupon molecular weights between 38 000 and 71 000 g mol⁻¹ are achieved.

     

Ugi Reactions with CO2: Access to Functionalized Polyurethanes,Polycarbonates, Polyamides,and Polyhydantoins

A novel strategy for the incorporation of carbon dioxide into polymers is introduced. For this purpose, the Ugi five‐component condensation (Ugi‐5CC) of an alcohol, CO₂, an amine, an aldehyde, and an isocyanide is used to obtain step‐growth monomers. Polymerization via thiol‐ene reaction or polycondensation with diphenyl carbonate gives diversely substituted polyurethanes or alternating polyurethane‐polycarbonates, respectively. Furthermore, the application of 1,12‐diaminododecane and 1,6‐diisocyanohexane as bifunctional components in the Ugi‐5CC directly results in the corresponding polyamide bearing methyl carbamate side chains ( = 19 850 g mol⁻¹). The latter polymer is further converted into the corresponding polyhydantoin in a highly straightforward fashion.

     

High‐Efficiency Large‐Bandgap Material for Polymer Solar Cells

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 V_oc of 0.93 V, a J_sc of 14.11 mA cm⁻², and an FF of 0.56.

     

Improved Thin‐Film Transistor Performance Through a Melt of Poly(para‐phenyleneethynylene)

The performance of polymer field‐effect transistors (PFETs) based on short rigid rod semiconducting poly(2,5‐didodecyloxy‐p‐phenyleneethynylene) (D‐OPPE) is highlighted. The controlled heating and cooling of thin films of D‐OPPE allows for a recrystallization from the melt, boosting the performance of D‐OPPE‐based transistors. The improved film properties induced by controlled annealing lead to a hole field‐effect mobility around 0.014 cm² V⁻¹ s⁻¹, an on/off ratio of 10⁶, a sub‐threshold swing of 3 V dec⁻¹ and a threshold voltage of −35 V, employing a poly(methyl methacrylate) (PMMA) gate dielectric. Thus, PFETs out of D‐OPPE compete now with spin‐coated, polycrystalline poly(3‐hexylthiophene)‐based PFETs.

     

Controlled Polymerization of Protic Ionic Liquid Monomer by ARGET‐ATRP and TERP

The direct synthesis of structurally well‐defined protic polymeric ionic liquid (PIL) with controlled molecular weight and molecular weight distribution is examined using N,N‐diethyl‐N‐(2‐methacryloylethyl) ammonium bis(tri‐fluoromethylsulfonyl)imide (DEMH‐TFSI) as a monomer. Three polymerization methods, namely, atom transfer radical polymerization (ATRP), activators regenerated by electron transfer (ARGET)‐ATRP, and organotellurium‐mediated living radical polymerization (TERP) are employed in this study. While the polymerization by ATRP is slow and does not reach high monomer conversion that under ARGET‐ATRP and TERP proceeds smoothly and affords structurally well‐defined poly(DEMH‐TFSI)s. TERP is especially efficient for the control and poly(DEMH‐TFSI)s with low to high molecular weights ( = 49 100–392 500) and narrow molecular weight distributions (/ = 1.17–1.46) are obtained. These results represent the first example of synthesis of a structurally well‐defined protic, ammonium PIL by direct polymerization of the protic ionic liquid monomer. The polymerization of N,N‐diethyl‐N‐(2‐methacryloylethyl)‐N‐methylammonium bis(trifluoromethylsulfonyl)imide (DEMM‐TFSI), which possesses a quaternary ammonium salt, also proceeds in a highly controlled manner under TERP conditions. A diblock copolymer, polystyrene‐block‐poly(DEMH‐TFSI), is also successfully synthesized by TERP.

     

Synthesis of Ultrahigh‐Molecular‐Weight Ethylene‐1‐Hexene Copolymers with High Hexene Content via Living Polymerization with Fluorinated Bis(phenoxy–imine) Titanium(IV)

The fluorinated FI–Ti catalyst bis[N‐(3‐propylsalicylidene)‐pentafluoroanilinato] titanium(IV) dichloride (PFI) combined with dried methylaluminoxane (dMAO) is investigated for ethylene/1‐hexene copolymerization at 50 °C under atmospheric pressure. The reaction shows good livingness and has a high activity at high [H]/[E] molar ratios up to 14. Ultrahigh molecular weight (>1.4 × 10⁶ g mol⁻¹) copolymers with high 1‐hexene content (>25 mol%) are prepared. Kinetic parameters of the copolymerization with PFI are determined. The first‐order Markov statistics applies and the product of the reactivity ratios r₁r₂ is close to 1, giving random unit distributions.

     

Highly Ordered Structure Formation in RAFT‐Synthesized PtBOS‐b‐P4VP Diblock Copolymers

Linear poly(4‐tert‐butoxystyrene)‐b‐poly(4‐vinylpyridine) (PtBOS‐b‐P4VP) diblock copolymers are synthesized using reversible addition–fragmentation chain transfer polymerization. The self‐assembly of four different PtBOS‐b‐P4VP diblock copolymers is studied using small‐angle X‐ray scattering and transmission electron microscopy and a number of interesting observations are made. A tBOS₆₂‐b‐4VP₂₈ diblock copolymer with a weight fraction P4VP of 0.21 shows a disordered morphology of P4VP spheres with liquid‐like short‐range order despite an estimated value of of the order of 50. Increasing the length of the 4VP block to tBOS₆₂‐b‐4VP₁₉₉ results in a diblock copolymer with a weight fraction P4VP of 0.66. It forms a remarkably well‐ordered lamellar structure. Likewise, a tBOS₁₄₆‐b‐4VP₁₂₀ diblock copolymer with a weight fraction P4VP of 0.33 forms an extremely well‐ordered hexagonal structure of P4VP cylinders. Increasing the P4VP block of this block copolymer to tBOS₁₄₆‐b‐4VP₁₉₀ with a weight fraction P4VP of 0.44 results in a bicontinuous gyroid morphology despite the estimated strong segregation of . These results are discussed in terms of the architectural dissimilarity of the two monomers, characterized by the presence of the large side group of PtBOS, and the previously reported value of the interaction parameter, , for this polymer pair.

     

Methacrylic Zwitterionic,Thermoresponsive, and Hydrophilic (Co)Polymers via Cu(0)‐Polymerization: The Importance of Halide Salt Additives

The synthesis of hydrophilic, thermoresponsive, and zwitterionic polymethacrylates is reported by Cu(0)‐mediated reversible deactivation radical polymerization in water and/or water/alcohol mixtures. The predisproportionation of [Cu^I(PMDETA)Cl] in water prior to initiator and monomer addition is exploited to yield well‐defined polymethacrylates with full monomer conversions in 30 min. The addition of supplementary halide salts (NaCl) enables the synthesis of various molecular weight poly[poly(ethylene glycol) methyl ether methacrylate] (PEGMA₄₇₅) (DP_n = 10–80, M_n ≈ 10 000–40 000 g mol⁻¹) with full monomer conversion and narrow molecular weight distributions attained in all cases (Đ ≈ 1.20–1.30). A bifunctional PEG initiator (average M_n ≈ 1000 g mol⁻¹) is utilized for the polymerization of a wide range of methacrylates including 2‐dimethylaminoethyl methacrylate, 2‐morpholinoethyl methacrylate, [2‐(methacryloyloxy)ethyl]dimethyl‐(3‐sulfopropyl)ammonium hydroxide, and 2‐methacryloyloxyethyl phosphorylcholine. Despite the high water content, high end group fidelity is demonstrated by in situ chain extensions and block copolymerizations with PEGMA₄₇₅ yielding well‐defined functional telechelic pentablock copolymers within 2.5 h.

     

Boron‐Ketoiminate‐Based Polymers: Fine‐Tuning of the Emission Color and Expression of Strong Emission Both in the Solution and Film States

In this research, the synthesis of boron‐ketoiminate‐containing polymers is reported with large molecular weights ( = 20 000) and their optical properties are examined by UV–vis absorption and photoluminescence spectrometries. It is shown that the polymers exhibit strong emission both in the solution and solid states (Φ _PL,THF = 0.46–0.80, Φ _PL,film = 0.13–0.38). These optical properties can be explained by a donor–acceptor interaction between the boron ketoiminate and the electron‐donating comonomer such as fluorene or bithiophene. Furthermore, in the solid states, their emission colors can be successfully tuned from blue to orange by the substituents on the nitrogen atom with the difference of the steric hindrance (λ _PL,THF = 464–546 nm, λ _PL,film = 486–604 nm).

     

Well‐Defined High Molecular Weight Polystyrene with High Rates and High Livingness Synthesized via Two‐Stage RAFT Emulsion Polymerization

A highly living polymer with over 100 kg mol⁻¹ molecular weight is very difficult to achieve by controlled radical polymerization since the unavoidable side reactions of irreversible radical termination and radical chain transfer to monomer reaction become significant. It is reported that over 500 kg mol⁻¹ polystyrene with high livingness and low dispersity could be synthesized by a facile two‐stage reversible addition–fragmentation transfer emulsion polymerization. The monomer conversion reaches 90% within 10 h. High livingness of the product is ascribed to the extremely low initiator concentration and the chain transfer constant for monomer unexpectedly much lower than the well‐accepted values in the conventional radical polymerization. The two‐stage monomer feeding policy much decreases the dispersity of the product.

     

Two Enzyme Cooperatively Catalyzed Tandem Polymerization for the Synthesis of Polyester Containing Chiral (R)‐ or (S)‐Ibuprofen Pendants

An interesting cooperation between Candida antarctica Lipase B (CAL‐B) and alkaline protease from Bacillus subtilis (BSP) in the copolymerization of bulky ibuprofen‐containing hydroxyacid methyl ester (HAEP) and ε‐caprolactone (ε‐CL) is observed. This cooperation improved the of the polymers from 3130 (CAL‐B) to 9200 g mol^–1 (CAL‐B/BSP). Experimental results clearly indicate that CAL‐B mainly catalyzes the ring‐opening polymerization (ROP) of ε‐CL under the initiation of HAEP to form the homopolymer of ε‐CL, while BSP catalyzes the subsequent polycondensation of the ROP product to yield the copolymer with increased molecular weight. Furthermore, using suitable chemo‐enzymatic methods, valuable polyesters with chiral (R)‐ or (S)‐ibuprofen pendants can be tailor‐made.

     

Balanced Ambipolar Poly(diketopyrrolopyrrole‐alt‐tetrafluorobenzene) Semiconducting Polymers Synthesized via Direct Arylation Polymerization

The synthesis of an ambipolar π‐conjugated copolymer consisting of alternating diketopyrrolopyrrole and tetrafluorobenzene via direct arylation polymerization (DAP) is reported. Two different combinations of monomers are investigated under various catalytic conditions for DAP. The target polymer obtained under an optimized catalytic condition shows minimal structural defects, a number‐average molecular weight of 33.2 kDa, and balanced electron and hole mobility of 1 × 10⁻² cm² V⁻¹ S⁻¹ in the organic field‐effect transistors fabricated and tested under ambient conditions.

     

Thieno[3,4‐c]Pyrrole‐4,6‐Dione and Dithiophene‐Based Conjugated Polymer for Organic Field Effect Transistors: High Mobility Induced by Synergic Effect of H‐Bond and Vinyl Linkage

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 μ_h = 0.4 cm² V⁻¹ s⁻¹, I_on/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.