Facile Synthesis of Polycarbonate Diol via Copolymerization of CO_(2) and Cyclohexene Oxide Catalysed by a Combination of One-Component Phosphonium Borane Lewis Pair and Water

Well-defined polycarbonate diol was successfully synthesized through a strategy using a combination of organocatalyst and water.Such strategy was less developed in organocatalyzed polymerization and frequently regarded as side reactions.Herein,one-component phosphonium borane Lewis pairs PB1-PB8 were successfully applied in the copolymerization of CO_(2) and cyclohexene oxide(CHO)to generate poly(CHO-alt-CO_(2))carbonate(PCHC).Parameters of linker length and counter anion effects on the catalyst activity were investigated.It was found that Lewis pair PB3 served as a dual initiator and catalyst in the copolymerization of CHO and CO_(2) with or without the presence of water.In contrast,Lewis pair PB8 can serve as a true catalyst for the preparation of well-definedα,ω-hydroxyl PCHC diols.This was achieved by introducing a labile CF3COO group as counter anion through anion exchange reaction while water molecules acted as chain transfer agents.The function of trifluoroacetate group in the polymerization process was investigated in detail and possible mechanism was proposed.Upon changing the amount of water and catalyst loading,PCHC diols with varied molecular weight(1.5 kg/mol to 7.5 kg/mol),low dispersities(D<1.2)and carbonate content(>99%)could be easily obtained.The low molecular weight PCHC diol was used as a bifunctional macroinitiator for the ring-opening polymerization of L-lactide(LLA)to afford ABA triblock copolymer in one-pot synthesis.

Stereoselective Ring-Opening Polymerization of rac-Lactide Catalyzed by Squaramide Derived Organocatalysts at Room Temperature

Substa ntial progresses have bee n made toward the developme nt of meta I-free catalysts for stereoselective rin g-ope ning polymeriza-tion(ROP)of rac-lactide.Yet the discovery of organic catalysts effective at ambient temperature remains a major challenge.Here,the bifunctional H-bonding catalyst SQ-1 containing a basic tertiary amine and squaramide motif proved to be good candidate for the stereoselective ROP of rac-lactide at room temperature,yielding stereoregular polylactide with controlled molecular weights(up to 21.1 kg/mol)and high tacticity(PjESC up to 0.88).Furthermore,binary H-b on ding catalytic system con sisti ng of squaramides(SQ-2 to SQ-6)and 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU)could efficiently promote the ROP of rac-lactide at room temperature within short reaction time.Among them,the most bulky squaramide SQ-2 exhibited the best steroselectivity towards the ROP of rac-lactide without transesterification side reactions during the polymerization process.The resulting polylactides were proved to have controlled molecular weights as high as 22.2 kg/mol and narrow distributions(1.10-1.24).

Bimetallic Aluminum Complexes Supported by Bis(salicylaldimine) Ligand: Synthesis, Characterization and Ring-opening Polymerization of Lactide

Two types of bifunctional bis（salicylaldimine） ligands（syn-L and anti-L） were designed and synthesized to support bimetallic aluminum complexes. Owing to the rigid anthracene skeleton, syn-L and anti-L successfully locked two Al centers in close proximity（syn-Al2） and far apart（anti-Al2）, respectively. The distance between two Al centers in syn-Al2 was defined by X-ray diffraction as 6.665 ？, which is far shorter than that in anti-Al2. In the presence of stoichiometrical Bn OH, syn-Al2 and anti-Al2 were both efficient for ring-opening polymerization（ROP） of rac-LA with the former being more active. In the presence of excess Bn OH, syn-Al2 showed an efficient and immortal feature, consistent with high conversions, matched Mns, narrow molecular weight distributions and end group fidelity, while anti-Al2 had a much lower activity or even became entirely inactive due to rapid decomposition, indicated by in situ ～1H-NMR experiments of Al complexes with Bn OH.

Chemoselective Polymerization of Fully Biorenewableα-Methylene-γ-Butyrolactone Using Organophosphazene/Urea Binary Catalysts Toward Sustainable Polyesters

Despite the great potential of biorenewableα-methylene-γ-butyrolactone(MBL)to produce functional,recyclable polyester,the ring-opening polymerization(ROP)of MBL remains a challenge due to the competing polymerization of the highly reactive exocyclic double bond and low-strained five-membered ring.In this contribution,we present the first organocatalytic chemoselective ROP of MBL to exclusively produce functional unsaturated polyester by utilizing a phosphazene base/urea binary catalyst.We show that delicate chemoselectivity can be realized by controlling the temperature and using selected urea catalysts.The obtained polyester can be completely recycled back to its monomer by chemolysis under mild conditions.Experimental and theoretical calculations provide mechanistic insights and indicate that the ROP pathway is kinetically favored by using urea with stronger acidity at low temperatures.

Self-assembly Promoted Crystallization of Diblock Copolypeptoids in Solution

Comprehensive Summary,Great efforts have been lately devoted to fabricating well-defined nanostructures using crystallization-driven self-assembly(CDSA)strategy.The influence of self-assembly on crystallization is also of great interest.Here,a series of amphiphilic diblock copolypeptoids poly(N-allylglycine)-b-poly(N-octylglycine)modified with cysteamine hydrochloride((PNAG-g-NH_(2))-b-PNOG)were synthesized by ring-opening polymerization(ROP)and post-polymerization functionalization.The diblock copolypeptoid is comprised of one hydrophobic crystalline PNOG block and one hydrophilic amorphous block,which can aggregate into nanostructured assemblies with soluble PNAG-g-NH_(2) as the corona layer and PNOG as the inner core in aqueous solution.With a systematic study by differential scanning calorimetry(DSC)and wide-angle X-ray scattering(WAXS),we demonstrated that the self-assembly of the block copolymers strengthens the crystallization of the PNOG block.

Titanium Complexes Bearing NNO-Tridentate Ligands: Highly Active Olefin Polymerization Catalysts with Great Control on Molecular Weight and Distribution

A series of titanium amido complexes (1-Ti(NMe_(2))_(2) to 4-Ti(NMe_(2))_(2)) bearing NNO-tridentate ligands was synthesized from the reactions of phenoxy-imine-amine ligands with one equivalent of Ti(NMe_(2))_(4). Subsequently, titanium dichloride complexes (1-TiCl_(2) to 4-TiCl_(2)) were prepared by treatment of titanium amido complexes with excess Me3SiCl in toluene. All metal complexes were characterized by 1H and 13C NMR spectroscopy, and the molecular structures of complexes of 2-Ti(NMe_(2))_(2), 2-TiCl_(2), and 4-TiCl_(2) in the solid state were determined by single-crystal X-ray diffraction. Upon activation with MAO, titanium dichloride complexes as single-site catalysts were extremely active toward ethylene homopolymerization with great control on molecular weight and distribution. In particular, 3-TiCl_(2)/MAO exhibited an activity as high as 1.35 × 108 g(PE)·mol−1(Ti)·h−1 at 70°C and produced polyethylene with high molecular weight (41.7 × 10^(4) g∙mol^(−1)) and very narrow distribution (Đ = 1.23). In the presence of 1-octene as comonomer, linear low-density polyethylenes (LLDPEs) with ultrahigh molecular weights (Mw = 136—326 × 10^(4) g∙mol^(−1)) and narrow distributions (Đ = 1.20—1.50) were successfully synthesized.

Biocompatible hierarchical zwitterionic polymer brushes with bacterial phosphatase activated antibacterial activity

Hierarchical polymer brushes have been considered as an effective and promising method for preventing implant-associated infections via multiple antibacterial mechanisms.Herein,a bacterial phosphatase re-sponsive surface with hierarchical zwitterionic structures was developed for timely dealing with the poly-meric implant-associated bacterial infection.The hierarchical polymeric architecture was subtly realized on model polypropylene(PP)substrate by sequential photo living grafting of poly(2-(dimethylamino)ethyl methacrylate(PDMAEMA)bottom layer and zwitterionic poly(sulfobetaine methacrylate)(PSBMA)upper layer,followed by the conversion of the PDMAEMA into the zwitterionic structure via succes-sive quaternization and phosphorylation reactions.Owing to shielding the bottom polycations,the hi-erarchical zwitterionic polymer brushes guaranteed the surface with the optimal biocompatibility under the normal physiological environment.Once bacteria are invaded,the surface bactericidal activity of the bottom layer can be rapidly and automatically activated owing to the transition triggered by bacterial phosphatase from zwitterion to polycation.Additionally,ameliorated by the upper layer,the hierarchical surface showed obvious adhesion resistance to dead bacterial cells and notably migrated the cytotoxic-ity of exposed polycation after completion of the bactericidal task.As a proof-of-principle demonstration,this self-adaptive hierarchical surface with sensitive bacterial responsiveness and biocompatibility showed great potential in combating hernia mesh-related infection.This work provides a promising and universal strategy for the on-demand prevention of medical device-associated infections.

Erratum to“Single-crystal structure of two-dimensional organic framework based on donor-acceptor interactions with chargetransfer effect”[Sci.China Chem.,2021,64:1510–1514]

Erratum to:Sci China Chem,2021,64:1510-1514,doi:10.1007/s11426-021-1030-7 Due to the error during the production process,the Figure 3 was missing in the above referenced publication[1].The corrected Figure 3 is as follows.The online version of the original article can be found at doi:10.1007/s11426-021-1030-7.

Single-crystal structure of two-dimensional organic framework based on donor-acceptor interactions with charge-transfer effect

Two charge-transfer single crystals induced by donor-acceptor interactions were obtained.The presence of different solvent molecules led to 1D(linear)or 2D self-assembly modes.More interestingly,the 2 D organic framework,a layer-by-layer 2D organic framework single crystal,showed a stronger charge-transfer effect than the 1D cocrystal.

Stimuli-Responsive Polypeptide-Based Supramolecular Hydrogels Mediated by Ca^2+ Ion Cross-Linking

Background and Originality Content Hydrogels,which retain a large amount of water,possess tunable porous three-dimensional nanostructure.They are known to resemble human tissue that can offer many advantages in biomedical applications such as tissue engineering,drug delivery and surgical dressings.1141 Stimuli-responsive hydrogels,referred as smart hydrogels can rapidly respond in a controlled manner to external stimuli,such as temperature,pH,light,etc.[s]In particular,the thermal-responsive hydrogels exhibit sol-to-gel phase transi­tion upon heating up to lower critical gelation temperatures(CGTs).

Enzyme responsive supramolecular hydrogels assembled from nonionic peptide amphiphiles

Smart peptide hydrogels are of great interest for their great potential applications. Here, we report a facile approach to prepare a class of enzyme-responsive hydrogels in a scalable manner. These hydrogels self-assemble from a family of nonionic peptide amphiphiles(PAs) synthesized by sequential ring-opening polymerization(ROP) of γ-benzyl-L-glutamate N-carboxyanhydride(BLG-NCA) and L-tyrosine N-carboxyanhydride(Tyr-NCA), followed by subsequent aminolysis. These PA samples can readily form a clear hydrogel with a critical gelation concentration as low as 0.5 wt%. The incorporation of tyrosine residues offers hydrophobicity, hydrogen-bonding interaction and enzyme-responsive properties. The hydrogel-to-nanogel transition is observed under physiological conditions in the presence of horseradish peroxidase(HRP) and hydrogen peroxide(H2 O2). The obtained PA hydrogels are ideal candidates for the new generation of smart scaffolds.

Anion-π interactions:From concept to application

Anion-π interactions as a new member of supramolecular weak interactions are still in the young stage,but they already attract considerable attentions. Now the concerns are shifting from recognition to construction of functional systems. In this review, the anion-π functional systems especially anion-πcatalysis and self-assembly were highlighted and summarized together with several solid and recent examples of host-guest recognition. These applications suggest that the great potential of these new interactions.