Helical polymers have attracted a great deal of attention and been extensively investigated due to their various applications. One of the most important applications of helical polymers is chiral recognition and resolution of enantiomers for the reason that a pair of enantiomers is commonly with different physiological and toxicological behaviors in biological systems. Helical polymers usually present unexpected high chiral recognition ability to a variety of racemic compounds. What’s more, the chiral recognition and resolution abilities of the system are dependent on the highly ordered helical structures of the helical polymers. This mini review mainly focuses on the recent progress in chiral recognition and resolution based on helical polymers. The synthetic methodology for helical polymers is firstly discussed briefly. Then recent advances of chiral recognition and resolution systems based on helical polymers, especially polyacetylenes and polyisocyanides, are described. We hope this mini review will inspire more interest in developing helical polymers and encourage further advances in chiral-related disciplines.

In this contribution, we utilized surface-initiated atom transfer radical polymerization (SI-ATRP) to prepare organic-inorganic hybrid core/shell silica nanoparticles (NPs), where silica particles acted as cores and polymeric shells (PAzoMA*) were attached to silica particles via covalent bond. Subsequently, chiroptical switch was successfully constructed on silica NPs surface taking advantage of supramolecular chiral self-assembly of the grafted side-chain Azo-containing polymer (PAzoMA*). We found that the supramolecular chirality was highly dependent on the molecular weight of grafted PAzoMA*. Meanwhile, the supramolecular chirality could be regulated using 365 nm UV light irradiation and heating-cooling treatment, and a reversible supramolecular chiroptical switch could be repeated for over five cycles on silica NPs surface. Moreover, when heated above the glass transition temperature (T_g) of PAzoMA*, the organic-inorganic hybrid nanoparticles (SiO₂@PAzoMA* NPs) still exhibited intense DRCD signals. Interestingly, the supramolecular chirality could be retained in solid film for more than 3 months. To conclude, we have prepared an organic-inorganic hybrid core/shell chiral silica nanomaterial with dynamic reversible chirality, thermal stability and chiral storage functions, providing potential applications in dynamic asymmetric catalysis, chiral separation and so on.

Dented nanospheres show promising potential in drug delivery, nanomotors, etc. However, it is still challenging to prepare them by homopolymer self-assembly because of the strict structural requirements of the homopolymer. Herein, we propose a strategy for preparing dented nanospheres from homopolymers by co-assembly with a short peptide. They were co-assembled from poly(2-hydroxy-3-((4-(ethoxycarbonyl)phenyl)amino)propyl methacrylate) (PHBzoMA₅₉) and (S)-2-((S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-3-phenylpropanamido)-3-phenylpropanoic acid (Fmoc-FF-OH). PHBzoMA homopolymers can only self-assemble into nanospheres without dent, and the addition of a short peptide introduced hydrogen bonding and complementary π-π stacking interactions led to the final dented nanosphere morphology. The weight fractions of the short peptide can be adjusted to regulate the final morphology. It was confirmed that the radius of curvature of the dent on the surface was related to the organic bubble inside the protospheres prepared at critical aggregation concentration (CAC). The organic bubble can be adjusted by altering the kind of organic solvent and solution pH, which allowed control over the dented nanosphere dimension. The use of different organic solvents with various polarities allows adjustment of the interfacial tension, and hence the denting degree. This degree can also be controlled by manipulating the solution pH to (de)protonate the short peptide and homopolymer. Furthermore, the versatility of this method was highlighted by using a different homopolymer and the applicability of the resulting dented nanospheres was demonstrated by decoration with gold nanoparticles. Overall, this study provided important insights and a new simple strategy to prepare dented nanospheres in a controlled fashion.

The novel amphiphilic acylated dextran-g-polyisobutylene (AcyDex-g-PIB) graft copolymers with different branch lengths (M_n,PIB, 2600–5800 g/mol) and grafting numbers (G_N, 5–28 per 1000 Dex monosaccharide) were successfully synthesized via the nucleophilic substitution of the hydroxyl (―OH) side groups along AcyDex backbone by the living PIB-THF₄⁺ chains prepared through cationic polymerization. The crystallization of AcyDex backbone in AcyDex-g-PIB graft copolymers was confined due to the presence of PIB branches and the morphology changed from short rod-like crystals to fragment-like crystals with increasing M_n,PIB and G_N. The obvious microphase separation occurred due to the incompatibility between hard AcyDex backbone and soft PIB branches. AcyDex-g-PIB graft copolymers exhibit excellent biocompatibility towards HeLa cells and good hemocompatibility with red blood cells (RBCs), both of which increase with increasing G_N. The increases of water contact angle and roughness on the surface of the graft copolymers with increasing M_n,PIB and G_N manifest the anti-protein adsorption performance. The amphiphilic AcyDex-g-PIB graft copolymers could self-assemble in aqueous solution into nanospheres, which can be used as pH-sensitive drug carriers and can release 100% of the loaded drug within 72 h at pH=7.4. AcyDex-g-PIB graft copolymers bearing silver nanoparticles (Ag-NPs, 0.8 wt%–3.9 wt%, 4.5–9.5 nm) show good antibacterial properties. This kind of amphiphilic graft copolymer would have a promising prospect in biological and medical fields.

The growing demands of supramolecular hyperbranched polymers integrating noncovalent interaction and unique topological structure merits had received considerable interest in the fabrication of novel materials for advanced applications. Herein, we prepared A₂B₆-type POSS-containing supramolecular hyperbranched polymers with multiple morphologies including lamellar-like, branched, hollow, core-shell and porous spherical structures through regulating self-assembling monomer concentrations and solvent polarities. The incorporation of appropriate emulative guest molecules would further trigger morphological transformations (such as vesicles and spherical micelles) by synergistic effects of unique POSS aggregation ability, supramolecular complexations and hydrophilic-hydrophobic interactions. Thus, this facile and universal strategy may enable a modular nanofabrication of supramolecular hyperbranched polymers with diversiform topological structure and sophisticated multifunctionality for their potential applications.

Biodegradable poly(propylene carbonate) (PPC)/epoxidized soybean oil (ESO) blends with different component ratios were prepared by melt blending to improve the performance of PPC. The phase morphology, thermal properties, rheological properties and mechanical properties of the blends were investigated in detail. SEM examination revealed good interfacial adhesion between PPC matrix and ESO. According to DSC and DMA, as the content of ESO increased, the glass transition temperature of the PPC component increased, indicating that there was a strong interfacial interaction between the PPC matrix and ESO. The interfacial interaction may be caused by ring-opening reaction between the hydroxyl end groups of PPC and the epoxy groups of ESO, which restricted the chain movement of PPC matrix. The disappearance of the epoxy groups in FTIR indicated that the interfacial interaction between the two phases was due to the ring-opening reaction between PPC and ESO. With the addition of ESO, the thermal stabilities were enhanced. With the increasing ESO content, the modulus gradually decreased. However, the strength at yield, the strength at break and the elongation at break were increased for the PPC/ESO blends, suggesting that the enhancement of the strength and toughness of PPC was achieved by the incorporation of ESO. The rheological measurement revealed that the complex viscosity, storage modulus and loss modulus of PPC were increased with the increasing ESO content at low frequency, which indicated that the addition of ESO enhanced the melt strength of PPC instead of plasticizing PPC.

In order to promote development of linear/branched block polyethylenes based on new catalytic systems, we synthesized a novel α-diimine nickel(II) complex with isopropyl substituents on ortho-N-aryl and hydroxymethyl phenyl substituents on para-N-aryl structures. The activity of α-diimine nickel(II) catalyst was 3.02×10⁶ g·mol_Ni⁻¹·h⁻¹ at 70 °C, and resultant polyethylene possessed 135/1000C branches. The linear/branched block polyethylenes were synthesized from ethylene polymerization catalyzed by the α-diimine nickel(II) complex/bis(phenoxy-imine) zirconium in the presence of diethyl zinc. With the addition of ZnEt₂ (from 0 to 400), the melting peak of resultant polyethylene changed from a single melting peak to bimodal melting peaks. The molecular weights of resultant polyethylene ranging from 26.8 kg/mol to 17.1 kg/mol and PDI values varying gradually from 24.4 to 15.2 were obtained via adjusting ZnEt₂ equiv. and molar ratio of two catalysts. In addition, the branching degree of the polyethylene increased from 13/1000C to 56/1000C with the increase of the proportion of α-diimine nickel(II) catalyst. Using this binary catalyst system, the reaction temperature of chain shuttling polymerization can be carried out at 70 °C, which is more conducive to industrial application.

Due to the poor solubility of aromatic polyesters in common organic solvents, trifluoroacetic acid is usually used as a co-solvent to increase their solubility for characterizations. However, only few studies have reported the side reactions induced by it. We present here the application of in situ ¹H-NMR techniques to explore its effect on the hydroxyl end-groups, which are usually used for the molecular weight determination of polyesters by end-group estimation method. Using bis(2-hydroxyethyl) terephthalate (BHET) as model compound, ¹H quantitative NMR results show the peak integration of hydroxyethyl end-groups decreased with time via a pseudo-first-order kinetics in d-trifluoroacetic acid/d-chloroform mixture solvent (1:10, V:V). This is due to the esterification of hydroxyethyl groups with trifluoroacetic acid, revealed by the ¹H-¹³C gradient-enhanced heteronuclear multiple bond correlation (gHMBC) spectrum. The mixtures of dimethyl terephthalate and BHET with different molar ratios were used to represent poly(ethylene terephthalate) (PET) with different degrees of polymerization, and the effect of trifluoroacetic acid on the estimation of hydroxyethyl groups and subsequent molecular weight determination of polyesters was studied. Our results show that if a relative error of 5% is allowed, the NMR measurements must be finished within 1.3 h of solution preparation at 25 °C in the mixture solvent. The results were confirmed in PET sample, while in poly(ethylene adipate), the obtained esterifaction constant is faster that those in aromatic system. The results can be applied to other polymer systems with alcohol functionalized groups, and used as a guideline for the characterization of polyesters and polyethers by end-group estimation method.

Nanocomposite hydrogels are one of the most important types of biomaterials which can be used in many different applications such as drug delivery and tissue engineering. Incorporation of nanoparticles within a hydrogel matrix can provide unique characteristics like remote stimulate and improved mechanical strength. In this study, the synthesis of graphene oxide and graphene oxide nanocomposite hydrogel has been studied. Nanocomposite hydrogel was synthesized using carboxymethyl cellulose as a natural base, acrylic acid as a comonomer, graphene oxide as a filler, ammonium persulfate as an initiator, and iron nanoparticles as a crosslinking agent. The effect of reaction variables such as the iron nanoparticles, graphene oxide, ammonium persulfate, and acrylic acid were examined to achieve a hydrogel with maximum absorbency. Doxorubicin, an anti-cancer chemotherapy drug, was loaded into this hydrogel and its release behaviors were examined in the phosphate buffer solutions with different pH values. The structure of the graphene oxide and the optimized hydrogel were confirmed by Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and atomic force microscopy.

Reversible switching from a highly rough surface to another entirely smooth surface under external stimuli is crucial for intelligent materials applied in the fields of anti-fogging, self-cleaning, oil-water separation and biotechnology. In this work, a thermal-responsive liquid crystal elastomer (LCE) surface covered with oriented micropillars is prepared via a facile two-step crosslinking method coupled with an extrusion molding program. The reversible change of topological structures of the LCE surface along with temperature is investigated by metallographic microscope, atomic force microscopy and optical contact angle measuring system. At room temperature, the LCE sample is filled with plenty of micropillars with an average length of 8.76 μm, resulting in a super-hydrophobic surface with a water contact angle (WCA) of 135°. When the temperature is increased to above the clearing point, all the micropillars disappear, the LCE surface becomes entirely flat and presents a hydrophilic state with a WCA of 64°. The roughness-related wetting property of this microstructured LCE surface possesses good recyclability in several heating/cooling cycles. This work realizes a truly reversible transformation from a highly rough surface to an entirely smooth surface, and might promote the potential applications of this dynamic-responsive LCE surface in smart sensors and biomimetic control devices.

Photo-responsive cholesteric liquid crystals (CLCs) have attracted much attention in recent years due to their wide applications in filters, tunable optical lasers, dynamic display devices, etc. However, UV light is usually used as the external stimulus source, which is not environment-friendly enough. On the other hand, the mechanical properties of CLCs are not strong enough for these practical applications. Therefore, it still remains a challenge to endow the CLCs with visible light response and high mechanical properties at the same time. Herein, an axially chiral tetra-fluorinated binaphthyl azobenzene gelator (S-4F-AG) is synthesized. Upon 550 and 450 nm light irradiations, S-4F-AG exhibits excellent photo-switchable behaviors. Notably, the maximum content of cis-isomer and its half-life are as high as 35% and 89 h in acetonitrile, respectively. A self-supporting CLC physical gel with a storage modulus around 10⁴ Pa can be obtained when 3wt% S-4F-AG and 12wt% binaphthyl azobenzene derivative (dopant 2) are co-doped into a nematic LC host P0616A. This CLC physical gel exhibits a temperature-driven blue, green, and red reflection colors reversibly. Importantly, such three primary RGB colors can also be realized by adjusting the exposure time of 550 nm green light. This work lays a solid foundation for the applications ranging from information storage to high-tech anticounterfeit.

Herein, we designed a core-shell structured bottlebrush copolymer (BBP), which is composed of rubbery poly(butyl acrylate) (PBA) core and an epoxy miscible/reactive poly(glycidyl methacrylate) (PGMA) shell, as an epoxy toughening agent. The PGMA shell allows BBP to be uniformly dispersed within the epoxy matrix and to react with the epoxy groups, while the rubbery PBA block simultaneously induced nanocavitation effect, leading to improvement of mechanical properties of the epoxy resin. The mechanical properties were measured by the adhesion performance test, and the tensile and fracture test using universal testing machine. When BBP additives were added to the epoxy resin, a significant improvement in the adhesion strength (2-fold increase) and fracture toughness (2-fold increase in K_Ic and 5-fold increase in G_Ic) compared to the neat epoxy was observed. In contrast, linear additives exhibited a decrease in adhesion strength and no improvement of fracture toughness over the neat epoxy. Such a difference in mechanical performance was investigated by comparing the morphologies and fracture surfaces of the epoxy resins containing linear and BBP additives, confirming that the nanocavitation effect and void formation play a key role in strengthening the BBP-modified epoxy resins.

Polynaphthalimide (PNI) with six-membered imide ring (₆-PI) has better chemical resistance than five-membered imide ring (₅-PI), but is difficult to be processed into nanofibers due to the poor processability. In this work, we proposed a template strategy to fabricate nanofiber ₆-PI membranes and their composite membranes. Neat ₆-PI and ₆-PI composite fibrous membranes were prepared using high-molecular-weight polymers ₅-PAA and PVP as templates by electrospinning. FTIR, DMA, TGA and tensile tests were used to characterize their chemical structures, thermal stability and mechanical properties. Further eye-observation, micro-morphology investigation and tensile tests were applied to evaluate the chemical resistance of nanofibrous membranes in strong acid, strong alkaline, and concentrated salt. The results demonstrated that ₆-PI nanofibrous membranes possessed the best thermal stability, best acid, alkaline, and salt resistance with the highest mechanical retention. This study will provide basic information for high-performance electrospun ₆-PI nanofiber membranes and provide opportunities for applications of PIs in different chemically harsh environments.

The fully biodegradable polymer blends remain challenges for the application due to their undesirable comprehensive performance. Herein, remarkable combination of superior mechanical performance, bacterial resistance, and controllable degradability is realized in the biodegradable poly(L-lactide)/poly(butylene succinate) (PLLA/PBSU) blends by stabilizing the epoxide group modified titanium dioxide nanoparticles (m-TiO₂) at the PLLA-PBSU interface through reactive blending. The m-TiO₂ can not only act as interfacial compatibilizer but also play the role of photodegradation catalyst: on the one hand, binary grafted nanoparticles were in situ formed and stabilized at the interface to enhance the compatibility between polymer phases. As a consequence, the mechanical properties of the blend, such as the elongation at break, notched impact strength and tensile yield strength, were simultaneously improved. On the other hand, antibacterial and photocatalytic degradation performance of the composite films was synergistically improved. It was found that the m-TiO₂ incorporated PLLA/PBSU films exhibit more effective antibacterial activity than the neat PLLA/PBSU films. Moreover, the analysis of photodegradable properties revealed that that m-TiO₂ nanoparticles could act as a photocatalyst to accelerate the photodegradation rate of polymers. This study paves a new strategy to fabricate advanced PLLA/PBSU blend materials with excellent mechanical performance, antibacterial and photocatalytic degradation performance, which enables the potential utilization of fully degradable polymers.

Study of stable liquid crystal (LC) microdroplets is of great significance for LC dynamics in confined space or at topological surface. However, the fabrication of LC microdroplets with diverse shape without ionic gelation agents still remains challenging due to the fluid instability. Here, we utilize the microfluidic technology to prepare graphene oxide (GO) LC microdroplets with various morphologies based on the anomalous rheological property of GO aqueous dispersion. Different from LC of one-dimensional polymer, LC containing two-dimensional GO sheets exhibits considerable viscoelasticity and weak extensibility, resulting from the planar molecular conformation and the absence of intermolecular entanglements. The low extensibility ensures that GO aqueous suspension is discretized into monodispersed microdroplets rather than thin thread in the microfluidic channels. The large viscoelasticity and ultra-long relaxation time of GO LC enable the diverse stable morphologies of microdroplets. The droplet morphology is well controlled from sphere to teardrop by modulating the competition between GO viscoelasticity and interfacial tension. The two-dimensional GO LC featuring unique rheological property provides a novel system for the microfluidic field, and corresponding topological stability enriches the LC dynamics and opens a new pathway for designing graphene-based materials.

Macroscopic and microscale creep deformations of UHMWPE were investigated by using in situ SAXS. A methodology for the measurement of the local creep deformation of inter-lamellar amorphous phase has been proposed. The local strain of inter-lamellar amorphous phase ($ {\varepsilon }_{\rm{a}} $) and macroscopic strain ($ {\varepsilon }_{\rm{macro}} $) were evaluated and they were compared to study the relationship between macroscopic and microscale creep deformation of UHMWPE. Both of them exhibit two deformation regions against creep time. The entanglements show a strong impact on both the macroscopic and local inter-lamellar amorphous phase creep behavior and they can be well correlated to the molecular weight between two entanglements estimated from strain-hardening modulus. Compared to the macroscopic creep deformation, local inter-lamellar amorphous layers have a smaller creep deformation. From the local creep measurement, the apparent modulus of inter-lamellar amorphous phase can also be estimated (200 < Ma < 500 MPa). These values are much higher than the Young’s modulus of bulk amorphous PE, which can be well explained by the confinement of the lamellar stacks and the enhancement of the amorphous phase with the relatively high concentration of entanglements. This study provides a useful means and quantitative data for achieving the scale transition between the micro and the macro structural levels for the study of viscos-elastic deformation.

In this work, we modify the traditional Brusselator model to incorporate the intermolecular interactions, based on which a systematic study is performed on the pattern formation mediated by chemical reaction and phase separation. It is found that if the chemical reaction dominates, the pattern formation will be inhibited by the phase separation while if the phase separation dominates, the chemical reaction will prevent, under certain conditions, the domain size from growing which results in dissipative patterns other than macroscopic phase separations.

Entanglement network is an important structural feature in concentrated polymer solutions and polymer melts, which has a great influence on the transient rheological behavior and molecular configuration evolution. However, the existing constitutive models have limitations in describing the influence of dynamic entanglement behavior on molecular chain motion, resulting in inaccurate descriptions of the transient rheological behavior. Thus, a molecular configuration evolution model for polymer solutions considering the dynamic entanglement effect is proposed by introducing an intermolecular force that changes with the orientation of the molecular chain in this work. The intermolecular force is introduced by considering the friction coefficient as anisotropic, and the orientation effect is considered by introducing an excluded volume dependent anisotropic diffusion. The proposed model can better describe the stress relaxation, stress growth, and dielectric anisotropy of polymer solutions compared with the anisotropy FENE model and FENE model. In addition, the influence of different model parameters on the transient and steady shear response of polymer solution is investigated, and the results show that the influence of volume loss on the friction anisotropy factor k_σ increases as the solution concentration increases.