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Asymmetric brush block copolymers (BBCPs) with polystyrene (PS) and polydimethylsiloxane (PDMS) side chains, gPS-b-gPDMS, were synthesized by ring-opening metathesis polymerization of corresponding norbornene macromonomers. The morphologies of the BBCP were systematically investigated with small-angle X-ray scattering and scanning electron microscopy. As the volume fraction of PS increases, the polymer self-assembles into spherical, cylindrical, and lamellar structures. Due to the shape asymmetry of the BBCP macromolecule, nanostructures with curved interfaces are easily formed. With a large d-spacing, most samples self-assemble into photonic crystals that selectively reflect ultraviolet light. Simulations have been conducted to calculate the photonic band structures of the two-dimensional photonic crystals. It is found that this system shows a wider partial band gap than other polymer systems with smaller refractive index contrast.

Many factors affect the formation of lyotropic liquid crystals (LLCs) in the poly(p-phenylene terephthamide) (PPTA)/H2SO4 system. In this systematic work, we prove that the hydrogen bonding between PPTA and H2SO4 plays a very important role for the LLC formation by using a combination of several characterization methods. Texture features and transition temperatures of different phases owing to hydrogen bonding in the PPTA/H2SO4 system were obtained by using polarized light microscopy and differential scanning calorimetry. 13C NMR and FTIR spectroscopy were applied to investigate the chemical structures in different phases, especially the hydrogen bonding between PPTA and H2SO4. The effect of molecular weight on phase transition was also examined. Moreover, guest compounds such as H2O, CH3SO3H, and carbon nanotube added will destroy the hydrogen-bonding network in the PPTA/H2SO4 system, resulting in different phase behaviors. All these results demonstrate that hydrogen bonding between PPTA and H2SO4 is the key factor for the highly ordered arrangement of polymer chains in the LLC state that is a nematic phase.

A series of aramids containing hydroxyl side group (NOM-OHc, where c is the molar fraction of hydroxyl substitution in the polymer, and c = 0, 10, 20, 40, 60, 80, 100) were synthesized by direct high-temperature polycondensation. The synthesis employed a facile process. The monomer, 4,4'-(terephthaloylbis(azanediyl))bis(2-hydroxybenzoic acid), was prepared simply via an esterification reaction. The chemical structures of the soluble aramids were confirmed by 1H NMR. And the molecular weight and mass dispersity of the aramids were obtained by size exclusion chromatography, instead of the traditional intrinsic viscosity method. The use of unsymmetrical monomers and the introduction of hydroxyl side group into the aramid structure decrease the conjugation of the polymer main chain, and thus the resulting aramid has excellent solubility in relatively polar solvents, such as N-methy-2-pyrrolidone, dimethylsulfoxide, N,N-dimethylacetamide, and N,N-dimethylformamide. As a result, the molding processability of the aramids and their composites is greatly improved. For example, films can be made by solution spinning and casting. The films have good mechanical strength, with tensile strength, tensile modulus, and elongation at break in the range of 68–95 MPa, 2.65–3.12 GPa, and 5–10%. The thermal resistance of the aramids is still quite good, with 5% weight loss temperatures in nitrogen and in air in the range of 360–430 oC.

A series of mesogen-jacketed liquid crystalline polymers (MJLCPs) with polynorbornene as the main chain and cholesteryl mesogenic units at the ends of the side chain, PNb n Chol ( n = 1, 3, 5, which is the number of benzene rings in the rigid side-chain core), were prepared by ring-opening metathesis polymerization. The phase behaviors of the polymers were investigated by differential scanning calorimetry, polarized light microscopy, and one-dimensional/two-dimensional X-ray scattering. The polymer with one benzene as the rigid core in the side chain shows only a smectic phase with interdigitated packing of cholesteryl units at low temperatures and is amorphous at high temperatures. While polymers containing three or five benzenes in the rigid side-chain core provide two different SmA phases at different temperatures, a smectic phase with double-layer-like packing of cholesteryl units at low temperatures and the smectic phase with interdigitated packing of cholesteryl units at high temperatures. The introduction of cholesteryl to MJLCPs can fabricate precisely controlled sub-10 nm scale ordered structures that can be maintained at high temperatures.

In order to obtain high-temperature resistant thermoplastic elastomers (TPEs), we designed and synthesized a new kind of ABA triblock copolymer containing a mesogen-jacketed liquid crystalline polymer, poly(4′-(methoxy)-2-vinylbiphenyl-4-methyl ether) (PMVBP), as the hard blocks and polybutadiene (PB) as the soft block. PB was synthesized by ring-opening metathesis polymerization in the presence of a chain transfer agent, and PMVBP was synthesized by nitroxide-mediated radical polymerization. The glass transition temperature of the PMVBP block is 186–211 °C, which is much higher than that of polystyrene. More importantly, PMVBP can maintain its liquid crystallinity even when the temperature is as high as 270 °C, which can enhance the mechanical properties of TPEs based on PMVBP, especially at high temperatures. All the resulting PMVBP-PB-PMVBP triblock copolymer samples form lamellar microphase-separated structures after combined treatment of solvent annealing and thermal annealing. They are good candidates for TPEs with a high operating temperature of more than 200 °C.

Two monomers o -( m -triphenyl)-terephthaloyl chloride (TPH1-COCl) and m -( m -triphenyl)- isophthaloyl chloride (TPH2-COCl) with bulky pendant groups were prepared, and they were polymerized with p -phenylenediamine (PPD) or copolymerized with PPD and terephthaloyl chloride (TPC) to prepare aromatic polyamides which were named TPH1 polymer and TPH2 polymer, respectively. The structures of the monomers with bulky pendant groups and the polymers were characterized by 1 H NMR and gel permeation chromatography. The resulting polymers are soluble in some organic solvents such as N -methyl-2-pyrrolidone. However, the solubility of the two series of polymers was different due to the different structures of the two monomers, and it is affected by the feeding ratio of the monomers. Both kinds of polymers have good thermal stabilities with 5% weight loss temperatures close to 500 °C. And glass transitions of some TPH2 polymers were observed. Most of these polyamides show lyotropic liquid crystalline (LLC) behaviors as evidenced by polarized light microscopy results. And the LLC properties are influenced by the structures, molecular weights, and concentrations of the polymers.

Main-chain/side-chain combined liquid crystalline polymers (MCSCLCPs) are usually difficult to synthesize and their degrees of polymerization are relatively low, which bring difficulties in studying their structure–property relationships. In order to solve this problem, we prepared a new series of MCSCLCPs containing mesogen-jacketed liquid crystalline polymer (MJLCP) main chains via hydrogen-bonding (H–B). A pyridine derivative with a triphenylene (Tp) unit is the H–B acceptor. In addition to the temperature dependence, the phase behavior of the resulting complex is strongly influenced by the content of the H–B acceptor and the rigidity of the side-chain core of the MJLCP. The resulting complexes exhibit different phase structures: (1) a columnar nematic phase or a smectic A (SmA) phase formed by the supramolecular MJLCP chain as a whole; (2) hierarchical nanostructures including a hexagonal columnar phase or a SmA phase of the whole polymer chain plus a discotic nematic phase associated with the Tp moieties.

Liquid crystalline polymers (LCPs) have drawn much interest because of their superior properties and widespread applications in high-performance polymer fibers, optics, energy storage, shape memory, surface modification, data storage, actuator, etc. LCPs can self-assemble into various liquid crystalline (LC) phases, such as nematic, smectic, columnar, and cholesteric phases. The self-assembling structures of LCPs can be influenced by architectures and chemical structures of the polymer backbone, mesogenic unit, flexible spacer, surrounding alkyl tail, etc. In the last decades, the structure-property relationships of LCPs have been researched extensively. In this perspective, the history, self-assembly, and applications of main-chain, side-chain, mesogen-jacketed, dendronized, main-chain/side-chain, and crosslinked LCPs are briefly reviewed. Finally, the future direction of research on LCPs is also discussed.

Polyhedral polymeric particles are desirable for various applications, but the fabrication is limited due to thermodynamic favorability of sphere formation. Herein, we employed a new strategy to prepare anisotropic nanopillars by thermally annealing bottlebrush block copolymers (BBCPs) with geometric asymmetry. Screw nut-like assembly and hexagonal nanopillars are formed after thermal annealing at 50 °C and 60 °C, respectively, which is rare in self-assembly of block copolymers. The shape transformation of the particles is thermodynamically driven, while the formation of hexagonal nanopillars is mainly attributed to entropic origin (the molecular geometry of the BBCP). This work provides a new strategy to prepare nanomaterials with noval structures.

With a pyridine derivative containing a calamitic mesogen 4-((6-((4'-((4-hexylphenyl)ethynyl)-[1,1′-biphenyl]-4-yl)oxy)hexyl)oxy)pyridine (HEBC6) used as the hydrogen-bonding acceptor and polydimethylsiloxane-b-poly(2,5-bis(4-carboxy phenyl)styrene) (PDMS-b-PM3H) as the hydrogen-bonding donor, a series of supramolecular liquid crystalline block copolymers (SLCBCPs) were prepared through hydrogen bonding. In the supramolecular block, the calamitic mesogen was decoupled from the motion of PM3H chains by using a flexible spacer. Different microphase-separated nanostructures and liquid crystalline (LC) structures were obtained by varying the degree of polymerization of the PM3H block and the molar ratio of HEBC6 to PDMS-b-PM3H. The SLCBCPs can self-assemble into hexagonally packed cylinders (HEX), lamellae (LAM), and inverted HEX. Smectic A phase and parallel packing of the calamitic mesogens were also observed on a smaller length scale, and these two ordered structures are synergistic and promotional. Therefore, hierarchically ordered structures can be obtained from these SLCBCPs.

Mesogen-jacketed liquid crystalline polymer (MJLCP) is a typical rod-shaped macromolecule. Its unique molecular architecture allows one to tune the geometric parameters of the macromolecular rod. Moreover, the rod surface chemistry can be controlled by designing the peripheral groups of the lateral mesogens. In previous work in this system, short alkyl chains have been used and the resultant macromolecular rods therefore have a hydrophobic surface. In this paper, we report using oligo(oxyethylene) groups as the peripheral groups of the lateral mesogens. Poly{{2,5-bis[4-methoxyoligo(oxyethylene)phenyl]oxycarbonyl}styene} (PnEOPCS) with different oligo(oxyethylene) chain length has been synthesized. These oligo(oxyethylene) groups led to macromolecular rods with hydrophilic surface. Differential scanning calorimetry, polarized light microscopy, and one-/two-dimensional wide-angle X-ray diffraction experiments were carried out to study the phase structures and phase behaviors of this series of polymer. The existence of flexible polar groups lowered the glass transition temperatures of PnEOPCS. All polymers studied showed supramolecular columnar nematic or hexatic columnar nematic phase, which arose from the parallel alignment of the polymer supramolecular rods. The diameter of the cylindrical building block increased with increasing the length of the oligo(oxyethylene) groups. The macromolecular rod surface can be further tuned by complexation the oligo(oxyethylene) with lithium salts. Detailed study showed that this complexation also tremendously affected the liquid crystalline phase of the polymer.

Three novel allyl–maleimide monomers (i.e., A 2 B, AB and AB 2 ) were designed, synthesized and thermally cured to yield a series of high-performance allyl–maleimide resins. All the monomers obtained are readily soluble in common organic solvents enabling an easy solution processing. The thermal properties of the three monomers were studied by the differential scanning calorimetry (DSC). A 2 B and AB showed fairly low melting temperature ( T m 2 B, PAB and PAB 2 ) was studied by the thermogravimetric analysis (TGA). Dynamic mechanical analysis (DMA) was used to investigate the dynamic mechanical properties of the composites based on the cured allyl–maleimide resins. PA 2 B and PAB 2 showed good glass transition temperatures ( T g > 270 °C) and their corresponding composites showed high bending modulus ( E ′ > 1900 MPa). Allyl-compound-modified BMI resins based on AB monomer were prepared. Rheometer revealed that the processability of the prepolymer (BR–AB-pre) was improved by the addition of AB monomer. The cured BMI resins (BR and BR–AB) showed good thermal stability ( T d > 400 °C, both in nitrogen and in the air), high glass transition temperature ( T g > 320 °C), and good mechanical properties and low water uptake (

A mesogen-jacketed polymer P-Ct {poly{2,5-bis[(5-tert-butylphenyl)-1,3,4-oxadiazole]styrene}} has been investigated as a host material for IrMDPP [Ir(III)bis(5-methyl-2,3-diphenylpyrazine) (acetyl acetonate)] doped polymer electrophosphorescent device. It was found that the device with P-Ct was more efficient than that with PVK. The maximum luminance and external luminous efficiency can reach 3702 cd/m2 and 0.83 cd/A, respectively, which were higher than those of device with PVK (1999 cd/m2 and 0.68 cd/A), which can be partly explained by the more balanced carrier injection and transportation and longer lifetime of excitons in P-Ct–TPD–IrMDPP. It was also found that as the IrMDPP content increased in P-Ct–TPD, the EL spectra color shifts from green-yellow to yellow-orange and were different from PL spectra, which was partly due to the dominating role of direct charge-trapping and recombination in the EL process over the energy-transfer routes.

A series of novel mesogen-jacketed polymers, poly{2,5-bis[(5-tert-butylphenyl)-1,3,4-oxadiazole]styrene} (P-Ct) and poly{2,5-bis[(5-alkoxyl-phenyl)-1,3,4-oxadiazole]styrene} (P-OCn, n is the number of carbons in the alkoxyl groups, n = 6, 8, 10, 12, 14), were incorporated into polymer light-emitting device as the light-emitting layers. All of the polymers had excellent solubility in common organic solvents. The UV and PL spectra for P-Ct were 312 and 400 nm while for P-OCn they were around 328 and 420 nm in the film. There was no red shift in the PL spectrum of P-Ct after heat treatment which maybe related to the jacketed structure. All of the polymers showed high PL quantum yields in THF solution. From the cyclic voltammetry measurement at room temperature, HOMO levels of the polymers were varied from −5.66 to −6.12 eV, LUMO levels were varied from −2.45 to −2.81 eV. Furthermore, the influence of the alkoxyl lengths in four different device configurations was compared. For the device configuration c: ITO/PVK/P-OC8/Ca/Ag, the maximum luminance and maximum external quantum efficiency were obtained for P-OC8 which maybe related to the easier electron injection and transport. Efficiency of P-OC8 was not improved with device d which proved the electron transporting characteristics of P-OC8.

Two novel bismaleimide (BMI) monomers containing 1,3,4-oxadiazole, i.e., 5- tert -butyl-1,3-di[5-(4-maleimidophenyl)-1,3,4-oxadiazole-2-yl]benzene (Buoxd) and 4,4′-[5-(4-maleimidophenyl)-1,3,4-oxadiazole-2-yl]diphenyldimethylsilane (Sioxd), were designed, synthesized and copolymerized with 4,4′-bismaleimidodiphenylmethane (BMDM) to yield a new series of high-performance bismaleimide resins. Both monomers obtained are readily soluble in common organic solvents, such as dichloromethane and chloroform, enabling an easy solution processing. The thermal properties of the two monomers were carefully studied by the differential scanning calorimetry (DSC), optical microscopy and thermogravimetric analysis (TGA, simultaneous DSC). The BMI resins based on a mixture of Buoxd (or Sioxd) and BMDM in a weight ratio of 10% were prepared. DSC investigations showed that the thermal curing of the BMI resins could be accomplished at a lower temperature than the thermal curing temperatures of Buoxd and Sioxd, and the thermal processing window, i.e., the temperature range between the melting transition and thermal curing process, was over 26 °C. The thermal properties and thermal mechanical properties of the resulting BMI resins were investigated by DSC, thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). No glass transition temperature was found in the range of 50–350 °C, and very good thermal stability ( T d > 490 °C in nitrogen) and high thermo-oxidative stability ( T d > 460 °C in air) were revealed. Composites composed of the above BMI resins and glass cloth were also prepared, which showed high bending modulus (>1.6 GPa) at a very high temperature (e.g., 400 °C).

Diblock copolymers comprising crystallizable poly(e-caprolactone) and poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PMPCS) were synthesized by ring-opening polymerization of e-caprolactone and subsequent atom transfer radical polymerization (ATRP) of MPCS. The molecular structure of the copolymers was confirmed by 1H NMR spectroscopy and GPC. Kinetic study of ATRP showed that the polymerization proceeded in a controlled way up to high conversions. Three series of diblock copolymers were obtained with relatively narrow polydispersity indices (PDI≤1.11) and PCL blocks of 8000, 12,900, and 22,800 molecular weights, respectively. The existence of microphase separation was identified by differential scanning calorimetry (DSC) and directly observed through transmission electron microscopy (TEM). The melting behavior of PCL block was significantly affected by the length of PCL block and composition of PMPCS. The thermotropic liquid crystalline behavior was examined by polarized optical microscopy (POM) and DSC. The result showed that the diblock copolymer exhibited liquid crystalline behavior when the degree of polymerization (DP) of PMPCS block was not less than 44.