Recently, we reported a series of reversibly interlocked polymer networks (RILNs), whose mechanical robustness and functionalities improvement was believed to be derived from topological interlocking of two sub-networks, although the direct evidence for the deduction is still lacking. Herein, a specially-designed RILNs system, in which the inter-component hydrogen bonds can be shielded as needed, was prepared and used to study the micro-structures of RILNs, aiming to verify the existence of mechanical interlocking in RILNs. By changing the pH of the swelling solvent, the effect exerted by the inter-component non-covalent bonds was eliminated, so detailed information of the networks structure was exposed. The small angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) results indicated that swelling-induced structural evolution of the two sub-networks mutually affected each other, even when the inter-component hydrogen bonds were absent, proving the presence of topological interlocking. The findings may help to draw a more accurate physical image and reveal the detailed structure-property relationship of RILNs.

Membrane technology has become one of the most promising separation technologies for its energy saving, high separation efficiency, environmental friendliness, and economic feasibility. Covalent organic frameworks (COFs) with intrinsically high porosity, controllable pore size, uniform pore size distribution and long-range ordered channel structure, have emerged as next-generation materials to fabricate advanced separation membranes. This feature article summarizes some latest studies in the development of pure COF membranes in our lab, including their fabrication and applications in chemical separations. Finally, current challenges facing high-performance COF separation membranes are discussed.

Chemoselective, living/controlled polymerizations of allyl methacrylate (AMA) and vinyl methacrylate (VMA) with/without methyl methacrylate (MMA) by using the phosphonium ylide/organoaluminum based Lewis pairs (LPs) have been realized. The P-ylide-2/AlMe(BHT)₂ (P-ylide-2 = Ph₃P=CHMe and BHT = 2,6-iBu₂-4-MeC₆H₂O) was demonstrated to be superior by which homopolymers PAMAs (M_n=27.6−111.5 kg/mol and Ð=1.14−1.25) and PVMAs (M_n=28.4−78.4 kg/mol and Ð=1.12−1.18) and block copolymers PMMA-b-PAMA, PAMA-b-PVMA, PAMA-b-PMMA, PMMA-b-PAMA-b-PMMA, PAMA-b-PMMA-b-PAMA, and PAMA-b-PVMA-b-PAMA were synthesized. In the polymerizations, all of the monomers were reacted by the conjugated ester vinyl groups leaving intactly the nonconjugated acryloxy groups. The pendant acryloxy groups attached to the main chain enable further to post-functionalization by the AIBN-induced radical “thiol-ene” reaction using PhCH₂SH. The thiolether side group-containing polymers PAMA-SCH₂Ph and PAMA-SCH₂Ph-b-PMMA-b-PAMA-SCH₂Ph were thus prepared.

Polyester and polyether are two key oxygenated polymers, and completely alternative sequence of poly(ester-alt-ether) could efficiently combine the advantages (including flexibility, degradability, etc.) of both segments. Currently, despite their copolymers could be synthesized from one-pot mixture of cyclic esters and epoxides, perfectly alternative microstructure is very challenging to realize and typically restricted to certain monomer pairs. Moving forward, synthesizing poly(ester-alt-ether) from commercially available and largescale monomers would be a significant advance. For example, successfully commercialized poly(glycolic acid) (PGA), which is not easily soluble in polymers due to its high crystallinity and is brittle and difficult to control the degradation cycle, would encounter a new paradigm if engineered into poly(ester-alt-ether). In this work, starting from the design of monomer with hybrid structures, we successfully synthesized a series of 1,4-dioxan-2-one containing different substituents based on glycolide (GA) and epoxides using commercially available Salen-Cr(III) and PPNCl catalytic systems. The new monomers underwent ring-opening polymerization (ROP) to form a series of poly(ester-alt-ether) with perfectly alternating glycolic acid and propylene glycol repeat units under catalytic system of thiourea/base. The poly(ester-alt-ether) have significantly lower glass-transition temperature than PGA. Additionally, the poly(ester-alt-ether) can be chemically recovered to monomer using Sn(Oct)₂ or 1,8-diazabicyclo[5.4.0]undecane-7-ene (DBU) as a catalyst in solution, thus establishing a closed-loop life cycle. From monomers derived from GA and epoxides, this work furnishes a novel strategy for the synthesis of poly(ester-alt-ether) with chemical recyclability.

Temperature-responsive polymers have garnered significant attention due to their ability to respond to external stimuli. In this work, dual temperature-responsive block copolymers are synthesized via reversible addition-fragmentation chain transfer polymerization (RAFT) polymerization utilizing zwitterionic monomer methacryloyl ethyl sulfobetaine (SBMA) and N-isopropyl acrylamide (NIPAAm) as monomers. The thermal responsive behaviors can be easily modulated by incorporating additional hydrophobic monomer benzyl acrylate (BN) or hydrophilic monomer acrylic acid (AA), adjusting concentration or pH, or varying the degree of polymerization of the block chain segments. The cloud points of the copolymers are determined by UV-Vis spectrophotometry, and these copolymers exhibit both controlled upper and lower critical solubility temperatures (LCST and UCST) in aqueous solution. This study analyzes and summarizes the influencing factors of dual temperature responsive block copolymers by exploring the effects of various conditions on the phase transition temperature of temperature-sensitive polymers to explore the relationship between their properties and environment and structure to make them more selective in terms of temperature application range and regulation laws. It is very interesting that the introduction of poly-acrylic acid (PAA) segments in the middle of di-block copolymer PSBMA₅₅-b-PNIPAAm₈₀ to form PSBMA₅₅-b-PAA_x-b-PNIPAAm₈₀ results in a reversal of temperature-responsive behaviors from ‘U’ (LCST < UCST) to ‘n’ (LCST > UCST) type, while the copolymer PSBMA₅₅-b-P(NIPAAm₈₀-co-AA_x) not. This work provides a clue for tuning the phase transition behavior of polymers for manufacture of extreme smart materials.

The N,N,N'-ferrous chloride complexes, [2-{CMeN(2,4-(CHPh)₂-6-FC₆H₂)}-6-(CMeNAr)C₅H₃N]FeCl₂ (Ar = 2,6-Me₂C₆H₃ Fe1, 2,6-Et₂C₆H₃ Fe2, 2,6-ⁱPr₂C₆H₃ Fe3, 2,4,6-Me₃C₆H₂ Fe4 and 2,6-Et₂-4-MeC₆H₂ Fe5), each possessing one N-2,4-dibenzhydryl-6-fluorophenyl group, were readily synthesized from their respective unsymmetrical bis(imino)pyridines, L1–L5. Structural identification of Fe2 highlighted the variation in the steric properties provided by the dissimilar N-aryl groups. Following pre-treatment with either MAO or MMAO, complexes Fe1–Fe5 all displayed, at an operating temperature of 80 °C, high activities for ethylene polymerization with levels falling in the order: Fe4 > Fe1 > Fe5 > Fe2 > Fe3. Notably, Fe4/MAO displayed the highest activity of 1.94×10⁷ g_PE·mol_Fe⁻¹·h⁻¹ of the study with only a modest loss in performance at 90 °C. Generally, the resulting polyethylenes were highly linear (T_m range: 122–132 °C), narrowly disperse and of low molecular weight (M_w range: 6.73−46.04 kg·mol⁻¹), with the most sterically hindered Fe3 forming the highest molecular weight polymer of the series. End-group analysis by ¹H- and ¹³C-NMR spectroscopy revealed saturated alkyl (n-propyl and i-propyl) and unsaturated vinyl chain ends indicative of the role of both β-H elimination and chain transfer to aluminum as termination pathways. By comparison with previously reported iron precatalysts with similar tridentate ligand skeletons, it is evident that the introduction of a large benzhydryl group in combination with a fluorine as the ortho-substituents of one N-aryl group has the effect of enhancing thermal stability of the iron polymerization catalyst whilst maintaining appreciable polymer molecular weight.

The efficient copolymerization of olefin with polar monomers using nickel-based catalysts presents a longstanding challenge. In this contribution, three phosphine-benzocyclone ligands and corresponding neutral nickel catalysts (Ni1: Ar = Ph; Ni2: Ar = 2-(C₆H₅)C₆H₄; Ni3: Ar = 2-[2',6'-(MeO)₂-C₆H₃]C₆H₄) were prepared and applied for the ethylene polymerization and copolymerization with polar monomers without any cocatalyst. The bulky substituent groups in complexes Ni2 and Ni3 contributed to high catalytic activities (up to 7.24×10⁶ and 9.04×10⁶ g·mol_Ni^‒1·h^‒1, respectively), and produced high-molecular-weight polyethylene (M_w up to 545.7 kDa). Complex Ni3 exhibited high activities for ethylene polymerization at the level of 10⁶ g·mol_Ni^‒1·h^‒1 across a wide range from 30 °C to 120 °C, exhibiting excellent high temperature tolerance. These nickel complexes were also effectively employed in the copolymerization of ethylene with methyl acrylate, ethyl acrylate, butyl acrylate and lauryl acrylate, producing copolymers with high molecular weights (M_w up to 80.5 kDa) and high polar monomer incorporation (up to 8.2 mol%). Microstructure analyses revealed that the introduction of large sterically hindered substituents facilitated the incorporation of polar functional units into the polymer backbone. This study demonstrates the potential of these nickel-based catalysts for efficient copolymerization of olefin with polar monomers.

The melt memory effect is a widely observed phenomenon in semi-crystalline polymers. In practical applications, various additives are usually introduced into polymers, which may affect their melt memory behavior. In this work, the effect of talc on the melt memory effect of metallocene-made isotactic polypropylene (M-PP) was investigated in detail by using the differential scanning calorimetry. The results indicated that the introduction of talc significantly strengthened the melt memory effect of M-PP. Specifically, the upper limit temperature of Domain II increased from 161 °C to 174 °C, resulting in a substantial widening of the temperature range of Domain IIa from 1 °C to 14 °C. Analysis of the crystal orientation of the M-PP containing talc cooled from various T_s suggested that the remarkably enhanced melt memory effect could be ascribed to the stabilization of oriented nuclei facilitated by talc. This stabilizing effect was likely attributable to the prefreezing effect or the sorption interaction between talc and the M-PP chains.

Coordination polymerization of renewable β-ocimene has been investigated using asymmetric diiminophosphinate lutetium complex 1, β-diketiminate yttrium complex 2, bis(phosphino)carbazolide yttrium complex 3, half-sandwich benzyl fluorenyl scandium complex 4 and pyridyl-methylene-fluorenyl rare-metal complexes 5a–5c. Complexes 1, 4 and 5a–5c show trans-1,2-regioselectivities and high activities, of which 5c exhibits excellent isoselectivity (mmmm>99%). Conversely, complexes 2 and 3 promote β-ocimene polymerization to produce isotactic cis-1,4-polyocimenes (cis-1,4>99%, mm>95%). Diblock copolymers cis-1,4-PIP-block-cis-1,4-POc and cis-1,4-PBD-block-cis-1,4-POc are obtained in one-pot reactions of β-ocimene with isoprene and butadiene using complex 3. Epoxidation and hydroxylation of polyocimene afford functionalized polyolefins with enhanced T_g (from −20 °C to 79 °C and 74 °C) and hydrophilicity.

Poly(lactic acid) (PLA) as a bio-based polymer with biodegradability and biocompatibility has attracted much attention. To manipulate its properties for different applications, regulation of crystal structure and crystalline morphology becomes an attractive research topic. In this work, the structure evolution of layered samples containing an amorphous poly(D-lactide) (PDLA) layer and a crystalline poly(L-lactide) (PLLA) layer with highly oriented edge-on α lamellar crystals after annealing at 150 °C or/and after melt-recrystallization has been studied by AFM, FTIR, and TEM combined with electron diffraction. The results demonstrate that melt recrystallization of the as-prepared sample leads to the formation of abundant randomly oriented PLA stereo-complex (PLA SC) crystals. Annealing at 150 °C results in the formation of a small amount of oriented PLA SC crystals at the interface. These PLA SC crystals show great impact on the recrystallization behavior of sample after melting at 190 °C and then crystallizing at 90 °C. First, they impede the mutual diffusion of the overlying PDLA and underlying PLLA, and thus reduce their stereo-complexation ability as manifested by the decreased amount of PLA SC crystals. Second, they act as substrate to initiate the epitaxial crystallization of the overlying PDLA and underlying PLLA, which ensures the production of a highly oriented structure of PDLA and PLLA after melt recrystallization again.

Poly(aryl ether ketone) (PAEK) films with different crystallinities were obtained by controlling the cooling rate, which were subjected to the absorption and desorption of methylene chloride (CH₂Cl₂). We employed attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy analyses to investigate the diffusion behavior of CH₂Cl₂ in PAEK films with different crystallinities. According to the Fickian diffusion model, the calculated diffusion coefficients of CH₂Cl₂ in PAEK films were observed to decrease with increasing crystallinity. The effect of CH₂Cl₂ absorption and desorption on the mechanical properties of PAEK films with different crystallinity was further analyzed using tensile tests. The tensile tests exhibited that CH₂Cl₂ has two concurrent effects: plasticization and solvent-induced crystallization. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WXRD) techniques further confirmed solvent-induced crystallization behavior. The results would be beneficial to understand the solvent resistance of PAEK materials and consequently provide the practical application conditions of PAEK with a theoretical basis.

Easy hydrolysis in alkaline environments limits the use of polyimide fibers in environmental protection. The hydrolysis resistance levels of polyimide fibers can be improved by crosslinking of the macromolecular chains. In this work, crosslinked polyimide fibers (CPI fibers) were produced by intrinsic carboxyl decarboxylation for the first time. The thermal stability of the polyimide fibers containing the intrinsic carboxyl groups (PIC fibers) was studied, and the temperature of the decarboxylation-crosslinking reaction was determined to be 450 °C. The PIC fibers were hot-drawn to initiate thermal crosslinking of the carboxyl groups and molecular chain orientation at high temperature. The CPI fibers had high tensile strengths (0.72−1.46 GPa) and compressive strengths (401−604 MPa). The oriented macromolecules and chemically crosslinked structure improved the tightness of the molecular chains and endowed the CPI fibers with excellent hydrolytic resistance. The CPI-50 fiber did not dissolve in a 0.5 wt% NaOH solution during heating at 90 °C for 10 h, and the tensile strength retention reached 87% when treated in 0.5 wt% NaOH solutions at 90 °C for 1 h, providing a guarantee for its application in alkaline corrosive environments.

Polypropylene (PP) exhibits suboptimal creep resistance due to the presence of methyl groups on its main chain, leading to irregular chain segment distribution, diminished inter-chain interaction, and crystallinity. This structural feature causes chain slippage in PP under stress, significantly constraining its service lifetime. In this study, thermally reduced graphene oxide (TrGO) nanosheets were incorporated into the PP matrix, yielding a nanocomposite with exceptional creep resistance performance. Results demonstrated that at a stress of 25 MPa, a 2.0 wt% TrGO content could enhance the creep failure lifetime of PP by 21.5 times compared to neat PP. Rheology, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) characterization techniques were employed to analyze the mechanism of TrGO's influence on PP's creep behavior. It was observed that when TrGO content exceeded 1.0 wt%, an effective particle network structure formed within the PP matrix. This homogeneously dispersed TrGO-formed particle network structure restricted the migration and rearrangement of PP molecular chains, enabling prolonged stress resistance without structural failure. By combining the time-strain superposition method with the critical failure strain as a criterion, generalized creep compliance curves for PP and its composites were established, facilitating the prediction of material creep failure lifetimes, with a strong agreement between experimental and predicted lifetime values. This research proposes a novel strategy aimed at developing polypropylene materials and products with enhanced long-term stability and durability, thus extending service life, reducing failure risk, and broadening their potential across various application domains.

Aiming at the difficult problem of solving the conformation statistics of complex polymers, this study presents a novel and concise conformation statistics theoretical approach based on Monte Carlo and Neural Network method. This method offers a new research idea for investigating the conformation statistics of complex polymers, characterized by its simplicity and practicality. It can be applied to more complex topological structure, more higher degree of freedom polymer systems with higher dimensions, theory research on dynamic self-consistent field theory and polymer field theory, as well as the analysis of scattering experimental data. The conformation statistics of complex polymers determine the structure and response properties of the system. Using the new method proposed in this study, taking the semiflexible ring diblock copolymer as an example, Monte Carlo simulation is used to sample this ring conformation to construct the dataset of polymer. The structure factor describing conformation statistics are expressed as continuous functions of structure parameters by neural network supervised learning. This is the innovation of this work. As an application, the structure factors represented by neural networks were introduced into the random phase approximation theory to study the microphase separation of semiflexible ring diblock copolymers. The influence of the ring’s topological properties on the phase transition behavior was pointed out.