We describe here the synthesis of multidentate comb-shaped polypeptides bearing trithiocarbonate functionality and their application in the preparation of water-soluble quantum dots (QDs). A new l-lysine-based N-carboxyanhydride monomer containing trithiocarbonate functionality was designed and synthesized. Ring-opening polymerization of the resulting monomer initiated by hexamethyldisilazane affords polypeptides bearing pendent trithiocarbonate groups (P(TTCLys)) with controllable molecular weights. P(TTCLys) was then applied to mediate the reversible addition-fragmentation chain-transfer polymerization of oligo(ethylene glycol)acrylate for the metal-free preparation of hydrophilic comb-shaped polypeptides. Simple reduction of trithiocarbonate functionality enabled the introduction of multiple thiol anchoring groups to the above-mentioned comb-shaped polypeptides. Finally, the obtained multidentate polypeptide-based ligands were successfully applied in the ligand exchange procedures to generate water-soluble QDs. The fluorescent microscopic images suggested that the resultant water-soluble QDs could be effectively internalized into HeLa cells to realize bright cellular imaging. Therefore, our work can result in a new kind of valuable polypeptide-based QDs with hydrophilic character and biocompatibility for cellular imaging.

An elevated-temperature dispersing (ETD) strategy was developed to disperse prepolymers at 80 °C for producing waterborne CO2-based polyurethane (CO2-WPU) in a whole-procedure organic solvent-free route. The obstacle of high viscosity challenging the traditional prepolymer-dispersing process was overcome, and the concern of significant NCO loss at high temperature was eliminated because prepolymer dispersion ensured >90% NCO retention. The particle size of the typical CO2-WPU emulsion lay between 45 nm and 70 nm, and it showed excellent stability even after centrifugation for 30 min at 3000 rpm. The dried CO2-WPU film showed not only good mechanical performance with a tensile strength of 54.3 MPa and elongation at break of 641%, but also excellent hydrolysis resistance owing to the unique structure of the CO2-polyol. This ETD strategy showed clear feasibility for commercial polyether or polyester oligomerols. It avoids the cooling step and solvent-removal procedure required in a traditional prepolymer-dispersing process, thereby greatly shortening the preparation period and reducing energy consumption.

Carbon dioxide based oligo(carbonate–ether) diols (CO2-polyols) with both carbonate units and ether units in one polymer chain were prepared by copolymerization of CO2 and propylene oxide (PO) using a zinc–cobalt double metal complex as the catalyst, and used to prepare CO2 based waterborne polyurethanes (CO2-WPUs). The carbonate units in CO2-polyols improved the mechanical and oxidation resistance properties of CO2-WPUs, while the ether units in CO2-polyols enhanced the hydrolysis resistance of CO2-WPUs. The tensile strength of CO2-WPUs didn't show any obvious drop during immersion in a 0.25% sodium hydroxide solution, whereas that of oligoesterol based WPUs dropped over 50% after 300 min, and lost their mechanical properties after 520 min of immersion. Meanwhile, the retention of the tensile strength of the CO2-WPUs was ca. 72% even after 46 h of immersion in a 6 wt% H2O2 solution, while it was only ca. 32% for the oligoetherol based WPUs. Moreover, the thermal–mechanical performance of CO2-WPU films can be conveniently improved by adjusting the carbonate unit content (CU%) in CO2-polyols, i.e. when CU% in CO2-polyol increased from 30% to 66%, the glass transition temperature (Tg) increased from −7.8 °C to 18.8 °C, accompanied by an increase of tensile strength from 35.6 MPa to 52.2 MPa, and a decrease of elongation at break from 630% to 410%. This work suggests that the CO2-WPU may be a promising alternative to conventional WPU whose oligoetherol and oligoesterol were from fossil resources, and its comprehensive hydrolysis/oxidation resistance may be a bonus unavailable from common oligomerol based WPUs.

Oxalic acid, the cheapest dicarboxylic acid, was used as an effective initiator to synthesize polyols by copolymerization of CO2 and propylene oxide over a zinc–cobalt double metal cyanide catalyst. Generally, reaction times as long as 255 min were observed for complete PO conversion, due to the existence of the free carboxylic acid group of oxalic acid. To overcome this disadvantage, we proposed a novel preactivation approach by formation of oxalic acid based oligo-ether-diol in advance. About 4.75 PO monomers were initiated at 80 °C, which was independent of time and oxalic acid amount; the diol then acted as a chain transfer agent for the following copolymerization. Under the optimal conditions the reaction could proceed to completion in 150 min, which was a remarkable reduction in reaction time compared to the previous reaction time of 255 min. Notably, the resulting CO2-based diol was stable up to 190 °C, indicating that oxalic acid may be applied as an effective initiator for this copolymerization.

Polypeptoids represent a significant class of synthetic analogues of natural polypeptides with potential biomimetic applications in materials, catalysis, and pharmaceuticals, but their simple and general synthesis still remains a key challenge. Herein, we demonstrate that Ugi reaction of natural amino acids leads to structurally diverse polypeptoids, including γ- and δ-, as well as poly(ε-peptoid)s, under mild conditions (open to air, room temperature, and catalyst free). Moreover, this strategy also offers manifold opportunities to introduce functional groups such as fluorescent and clickable alkenes groups into polypeptoids. Such poly(ε-peptoid)s not only exhibit good biocompatibility and antibacterial activity, but perform very effectively as a drug-delivery system. The bacterial inhibition rate of poly(ε-peptoid) was up to 88.8% at concentration of 20 μg mL–1 in comparison to 61.8% of the poly(ε-lysine) control. Overall, this study offers us a general methodology toward facile preparation of polypeptoids for bioapplications.

Synthesis of polyols from carbon dioxide (CO2) is attractive from the viewpoint of sustainable development of polyurethane industry; it is also interesting to adjust the structure of the CO2-polyols for versatile requirement of polyurethane. However, when renewable malonic acid was used as a starter, the copolymerization reaction of CO2 and propylene oxide (PO) was uncontrollable, since it proceeded slowly (13 h) and produced 40.4 wt% of byproduct propylene carbonate (PC) with a low productivity of 0.34 kg/g. A careful analysis disclosed that the acid value of the copolymerization medium was the key factor for controlling the copolymerization reaction. Therefore, a preactivation approach was developed to dramatically reduce the acid value to ~0.6 mg(KOH)/g by homopolymerization of PO into oligo-ether-diol under the initiation of malonic acid, which ensured the controllable copolymerization, where the copolymerization time could be shortened by 77% from 13 to 3 h, the PC content was reduced by 76% from 40.4 wt% to 9.4 wt%, and the productivity increased by 61% from 0.34 to 0.55 kg/g. Moreover, by means of preactivation approach, the molecular weight as well as the carbonate unit content in the CO2-diol was also controllable.

ε-Poly-lysine (ε-PL) is an uncommon cationic, naturally-occurring homopolymer produced by the fermentation process. Due to its significant antimicrobial activity and nontoxicity to humans, ε-PL is now industrially produced as an additive, e.g. for food and cosmetics. However, the biosynthetic route can only make polymers with a molecular weight of about 3 kDa. Here, we report a new chemical strategy based on ring-opening polymerization (ROP) to obtain ε-PL from lysine. The 2,5-dimethylpyrrole protected α-amino-ε-caprolactam monomer was prepared through cyclization of lysine followed by protection. ROP of this monomer, followed by the removal of the protecting group, 2,5-dimethylpyrrole, ultimately yielded ε-PL with varying molecular weights. The structure of this chemosynthetic ε-PL has been fully characterized by 1H NMR, 13C NMR, and MALDI-TOF MS analyses. This chemosynthetic ε-PL exhibited a similar pKa value and low cytotoxicity as the biosynthetic analogue. Using this new chemical strategy involving ROP without the need for phosgene may enable a more cost effective production of ε-PL on a larger-scale, facilitating the design of more advanced biomaterials.

An aluminum porphyrin complex with a quaternary ammonium salt cocatalyst exhibits high activity (i.e., a turnover frequency as high as 1.85 × 105 h−1) and selectivity (>99%) for cyclic carbonates synthesis from CO2 and epoxides; the catalyst can be reused at least 4 times with only a slight loss in activity.

A trivalent titanium complex combining salen ligand (salen-H2═N,N-bis(3,5-di-tert-butylsalicylidene)-1,2-benzenediamine) was synthesized as catalyst for copolymerization of CO2 and cyclohexene (CHO). In combination with onium salt [PPN]Cl, (Salen)Ti(III)Cl showed impressive activity and selectivity, yielding completely alternating copolymer without the formation of cyclohexene carbonate (CHC), with turnover frequency (TOF) of 557 h–1 at 120 °C, which was more than 10 times higher than that of our previously reported (Salalen)Ti(IV)Cl, and close to the Cr counterparts. In addition to the biocompatibility of Ti, thermally robust character resulting from the reducibility of trivalent Ti was industrially desirable.Keywords: carbon dioxide; copolymerization; cyclohexene oxide; homogeneous catalysis; salen; titanium

A CO2-based oligo(carbonate-ether) tetraol was synthesized in a controlled manner by immortal copolymerization of carbon dioxide (CO2) and propylene oxide (PO) in the presence of 1,2,4,5-benzenetetracarboxylic acid (btcH4) catalyzed by using a zinc–cobalt double metal cyanide (Zn–Co–DMC) catalyst. The number average molecular weight (Mn) of the tetraol was in a good linear relationship with the molar ratio of PO and btcH4 (PO/btcH4), and hence can be precisely controlled. Besides, the rapid chain transfer in immortal copolymerization afforded the tetraol with a narrow polydispersity index (PDI) of 1.08 at a Mn of 1400 g mol−1. Notably, the weight fraction of the byproduct propylene carbonate (WPC) was reduced to as low as 4.0 wt%, which is the lowest Wpc ever reported for the synthesis of branched polyols. The structure of the oligo(carbonate-ether) tetraol was confirmed, providing new evidence for the effect of the acidity (pKa1 value) of the chain transfer agent (CTA) on the initial catalytic mechanism. The acid only acts as the CTA directly participating in the copolymerization via the chain transfer reaction when its pKa1 value is higher than that of adipic acid (pKa1 = 4.43). However, when its pKa1 value is lower than that of succinic acid (pKa1 = 4.2), it acts as the initiate-transfer agent, which first initiates PO homopolymerization to an oligo-ether polyol, and then the in situ formed polyol acts as a new CTA for the copolymerization.

A novel conjugated microporous polymer was solvothermally synthesized using an aluminum porphyrin as a main building block, which had a high Brunauer–Emmett–Teller specific surface area up to 839 m2 g−1 and a pore volume of 2.14 cm3 g−1. The polymer displayed excellent capacity to capture carbon dioxide (4.3 wt%) at 273 K and 1 bar, and good catalytic activity for cyclic carbonate synthesis with TOF up to 364 h−1.

Amorphous poly(propylene carbonate) (PPC) is brittle at room temperature, but the studies related to the toughening of PPC is rare. Herein, two types of polyurethane (PCO2PU) synthesized from a CO2-based diol and toluene diisocyanate were used as rubbery particles to toughen PPC. The notched impact strength of PPC increased from 20.8 J m−1 to 54.2 J m−1 at a PCO2PU loading of 20 wt%, comparable with that of neat nylon 6, and reached 228.3 J m−1 at a PCO2PU loading of 30 wt%, 10.9 fold that of neat PPC and even higher than bisphenol A polycarbonate. Matrix yielding as well as cavitation was observed during the impact process, which was responsible for the increase of impact strength. Moreover, the toughening efficiency was related with the carbonate content of PCO2PU, and the transition of fracture behavior from brittle to ductile occurred when the PCO2PU with a weight average diameter of 0.20 μm was uniformly dispersed in PPC substrate.

Polyglutamate bottlebrushes with poly(oligo(ethylene glycol)acrylate) as side chains were successfully prepared for the first time by combination of N-carboxyanhydride polymerization and reversible addition–fragmentation chain transfer (RAFT) polymerization. This work has provided a metal-free polymerization strategy and can be applicable to synthesize well-defined polypeptide bottlebrushes for bio-application purposes.

Lysine, a renewable resource from biomass fermentation, was simply converted to its corresponding α-hydroxyl acids and then cyclized to give the pure O-carboxyanhydride (OCA) monomer. Ring-opening polymerization of the resulting monomer was carried out using dimethylaminopyridine (DMAP) as a catalyst in CH2Cl2 at room temperature, and gave well-defined lysine-derived polyesters bearing pendant carbobenzyloxy (Cbz)-protected amino groups with number average molecular weight of up to 45 kg mol−1 in narrow polydispersity. 1H NMR, GPC, and MALDI-TOF MS measurements of the products clearly indicated the controlled/living character of the polymerization. Moreover, amino-functionalized polyesters were readily prepared by the removal of the Cbz protecting group, and the integrity of the polyester backbone was confirmed by 1H NMR. These amino-functionalized polyesters showed a tunable glass transition temperature and exhibited excellent cell compatibility, suggesting their potential to be used as novel materials in biomedical applications.

•Non-isocyanate polyurethane (NIPU) was synthesized and used to toughen PPC.•The transition of PPC from brittle to marginally tough occurred.•Equilibrium between two kinds of hydrogen bonding affected the miscibility.To overcome the brittleness of poly(propylene carbonate) (PPC), rubbery non-isocyanate polyurethane (NIPU) with rich hydrogen bonding moiety was synthesized for toughening PPC. Debonding phenomenon of NIPU was observed during the impact process of PPC/NIPU blends, which was beneficial for toughening PPC. When the NIPU loading increased to 10 wt%, the unnotched impact strength increased 3 times compared with neat PPC. The NIPU dispersed uniformly and a transition from brittle to marginally tough occurred when L/d reached a critical value, 1.74, where L and d were center-to-center distance and the diameter of the particle, respectively. The debonding of NIPU accounted for the increase of toughness, and shear yielding of the matrix was limited around the microvoids. When the NIPU loading reached 13 wt%, NIPU flocculated in the matrix leading to decline in toughness. The equilibrium between self-associating hydrogen bonding and intermolecular one formed between PPC and NIPU affected their miscibility and thereby the morphology of the blends.

Carbon dioxide is becoming increasingly important synthetic feedstock for chemicals and materials, since it is abundant, low-cost, non-toxic. One growing area in CO2 chemistry utilization is the development of catalysts for the polymerization of CO2 and epoxides to prepare CO2 based copolymers, including high molecular weight aliphatic polycarbonates and low molecular weight poly(carbonate-ether) polyols. Among all the aliphatic polycarbonates, poly(propylene carbonate) (PPC) has the best opportunity for scale-up commercialization. PPC is not only cheap since it contains over 40 wt% CO2, but it also exhibits good biodegradability, which has wide application in throw-away packaging materials, or even gas barrier films. Poly(carbonate-ether) polyols are low-molecular weight polyether carbonates with terminating hydroxyl groups, which are potential large scale raw materials in polyurethane industry. Herein, the recent progress of the CO2 based polymers will be highlighted, and the future in this area will be discussed.

The world polymer industry claims over 2 million tons per year, though most synthetic polymers use petroleum feedstocks, there is a growing effort to prepare polymers from renewable raw materials concerning the depleting fossil fuel resources. In this short review, we would like to emphasize the potential that CO2 based polymers, polycarbonates and polyurethanes from copolymerization of CO2 and epoxides, have to mitigate the above concerns, where the newly developed metal catalyst systems allow not only their high efficient synthesis, significant advances have been achieved in stereo-controlled copolymerization. It is also noteworthy that the physical and chemical properties of CO2 based polymers may be tailored, which help to pave the way from their lab curiosities to practical application, as new applications have been realized such as biodegradable disposal bags, and hydrolysis and oxidation resistant water borne adhesives.

Binder is critical component to maintain the cathode integrity in lithium-sulfur battery, but it is generally non-conductive. Here sulfuric acid doped polyaniline was successfully developed as conductive binder, which showed multifunctionality when used in Li-S battery cathode, i.e., in addition to necessary adhesion function, it could trap polysulfide species to abate shuttling affect while provide good electrical conductivity. The unique adhesive behavior of conductive polyaniline was attributed to the sufficiently long polar chains consisting of amine salt, iminium and aromatic ring. Based on theoretical analysis, all the electrode components could be bound together by Van der Waals and electrostatic interactions even under very low polyaniline loading. Such low loading could form conductive polyaniline cobweb which helped the polyaniline binder to resist sulfur swelling while provide adequate channels for ion transportation. In an optimal condition, the polyaniline binder loading in cathode could be reduced to Ca. 2.0 wt%, and the sulfur loading in cathode increased by 11.0 wt% compared with that using common non-conductive binder. Compared with cathode employing common PVDF binder, the specific capacity using polyaniline binder increased by Ca. 104% and 74% at current density of 122 mA g−1-sulfur and 610 mA g−1-sulfur, respectively, which was mainly attributed to the stable conducting feature of polyaniline binder during the charging-discharging process, as reflected from low charge transfer resistance of 37 ohm for the cathode.

Polyglutamate bottlebrushes with poly(oligo(ethylene glycol)acrylate) as side chains were successfully prepared for the first time by combination of N-carboxyanhydride polymerization and reversible addition–fragmentation chain transfer (RAFT) polymerization. This work has provided a metal-free polymerization strategy and can be applicable to synthesize well-defined polypeptide bottlebrushes for bio-application purposes.

ε-Poly-lysine (ε-PL) is an uncommon cationic, naturally-occurring homopolymer produced by the fermentation process. Due to its significant antimicrobial activity and nontoxicity to humans, ε-PL is now industrially produced as an additive, e.g. for food and cosmetics. However, the biosynthetic route can only make polymers with a molecular weight of about 3 kDa. Here, we report a new chemical strategy based on ring-opening polymerization (ROP) to obtain ε-PL from lysine. The 2,5-dimethylpyrrole protected α-amino-ε-caprolactam monomer was prepared through cyclization of lysine followed by protection. ROP of this monomer, followed by the removal of the protecting group, 2,5-dimethylpyrrole, ultimately yielded ε-PL with varying molecular weights. The structure of this chemosynthetic ε-PL has been fully characterized by 1H NMR, 13C NMR, and MALDI-TOF MS analyses. This chemosynthetic ε-PL exhibited a similar pKa value and low cytotoxicity as the biosynthetic analogue. Using this new chemical strategy involving ROP without the need for phosgene may enable a more cost effective production of ε-PL on a larger-scale, facilitating the design of more advanced biomaterials.