Rich phase structures and evolutions of the blends of smectic–nematic (S–N) liquid crystalline (LC) diblock copolymers and a nematic solvent (5CB) are investigated in a concentrated regime. These types of fully LC systems are macroscopically homogeneous with ordered phase-separated structures on the nanometer scale. By varying the temperature as well as the content of 5CB, the phase diagram of the blends is constructed, where the order-to-order transition (OOT) between lamellar and cylindrical nanostructures can be induced either lyotropically or thermotropically. The temperature and concentration dual-responsive properties are found to be closely related to the selectivity and distribution of 5CB, in addition to its phase transformation at the nematic–isotropic transition. As inferred from the miscibility and phase behaviors of its blends with the respective smectic and nematic homopolymers, the partition of 5CB in the S–N diblock copolymers and its influence on the phase structures reveal the important role of the LC interactions on the self-assembly of the diblock copolymers.

A study of the reaction kinetics of the copolymerization of two major categories of epoxy monomers, glycidyl ether (GE) and alkylene oxide (AO) derivatives, via the in situ NMR technique has been performed in a combinatorial strategy. GEs or AOs show similar reactivities when copolymerizing within either category, leading to a special azeotropic copolymerization, while they exhibit distinct reactivities between them. The underlying kinetics along with the living anionic copolymerization mechanism allow the generation of gradient and azeotropic copolymers, azeotropic-gradient terpolymers and double azeotropic-gradient tetrapolymers. Through the quantitative determination of rate constants and reactivity ratios with the aid of a numerical calculation in a simulated annealing scenario, we provide a widely applicable design principle for the sophisticated construction of sequence distribution-regulated, functional polyethers via a simple and efficient one-pot approach.

Hierarchically assembled superstructures of block copolymers are discovered by introduction of the competition of anisotropy attributed from liquid crystalline ordering and nano-phase separation. When the two prototypical fields of liquid crystals (LCs), smectics (S) and nematics (N), are adjoined within the framework of diblock copolymers (S–N) in a variety of precisely tuned compositions, a novel class of superlattices with an interdigitated array of smectic layers between the nearest lamellae or cylinders are observed. This generates unconventional nano-phase separated orthorhombic (Lo) and pseudo-hexagonal (Ho) structures, where the stretched N tethers, projected regularly from the S layers, could transfer the local organization and guide the correlated assembly. This type of superstructure is highly frustrated in reversed cylindrical morphology and absent in S-coil diblock copolymers. The collective interplay of the S and N interactions with nano-phase separation induces the formation of the final complex yet equilibrium structures, providing unprecedented opportunities towards exquisite structural diversity.

A metallo-supramolecular triblock copolymer polystyrene-b-polyisoprene–[Ni2+]–polystyrene (SI–[Ni2+]–S′) has been efficiently prepared using a one-pot, two-step procedure, where the blocks are held by bis-terpyridine complexes at the junction of SI–S′. This specific metallo-supramolecular chemistry is demonstrated to be a robust approach to potentially broaden the diversity of block copolymers. The location of the metal–ligand complexes has a profound influence on the phase separation of the triblock copolymer in the bulk, which results in a distinctive phase segregation between the end blocks and leads to an unexpected asymmetry of the triblock copolymer. The metal–ligand complexes are found to be preferentially located on the adjacent spherical domain and form a core–shell structure. The resulting multiphase material exhibits distinct elastomeric properties with significant toughness and creep recovery behavior. This type of triblock copolymer is anticipated to be a novel class of hybrid thermo-plastic elastomeric material with wide tunability and functionality.

Reactivity ratio is a traditional parameter quantifying the reaction kinetics in copolymerization, which is important for potentially controlling microstructures of polymers and guiding the copolymerization process. Our recent experiments using tube-NMR technique enable us to in situ monitor the concentration profiles of the co-monomers during the anionic copolymerization process. This motivates us to revisit the Mayo-Lewis (ML) equation, which is the basis for derivation of reactivity ratio and has been extensively utilized in addition copolymerization. We found that although an explicit ML expression is desirable for ease of calculation and correlation with experimental data, it fails in our anionic copolymerization experiment as well as some data available in the literature. The origin is ascribed to the validity of the steady state assumption which is essential in the ML equation. This assumption can be released in anionic copolymerization and replaced by the fact that the overall concentration of the living chain ends keeps constant throughout the copolymerization. Alternative numerical method has been utilized to obtain the rate constants and consequently the reactivity ratios. Our work suggests that the ML equation should be applied with caution.

A set of gradient copolymers composed of liquid crystalline polyether and poly(butylene oxide) with narrow molecular weight distributions and well-defined, continuous growing composition profiles were synthesized via anionic ring-opening polymerization. For comparison, the corresponding diblock copolymers without a compositional gradient were also prepared. The thermal transitions, phase structures and the evolutions of these two sets of liquid crystalline copolymers with composition and temperature were systematically investigated. The compositional gradient copolymers were found to possess a remarkable sensitivity on the phase structures on multiple length scales. Compared with the corresponding liquid crystalline block copolymers, they exhibited a broad glass transition region and a large breadth of liquid crystalline phase transformation associated with disordered mesogenic packing and a thickness distribution of liquid crystalline layers. Ordered, nanophase separated structures were observed to gradually develop with an increase of gradient length. They exhibited distinct ordering and evolution processes with continuous liquid crystalline melting, which are different from the reference samples of diblock copolymers. Those behaviors are speculated to originate from the heterogeneity intrinsic to the liquid crystalline gradient copolymer.

Coexistence of smectic and nematic orders in 3D curvaceous bicontineous cubic or hexagonal hierarchical structures is observed in a novel class of nanophase separated, flexible double liquid crystalline (LC) diblock copolymers of different molecular weights (MWs) but similar compositions, obtained via sequential anionic polymerization. The diblock copolymer of higher MW exhibits an exceptional order–order transition (OOT) from lamellae (Lam) to hexagonal-packed cylinder (HPC) upon nematic ordering. In contrast, the polymer with lower MW forms a thermodynamically stable, ordered gyroid structure, interwining with LC defects on nanoscale. Delicate balance of collective LC interactions and geometric frustration dictates this unique behavior, which offers a genuine way to fine-tune 2D and 3D complex structures with sub-10 nm feature sizes.

•Terpyridine end-functionalized polystyrene-b-polyisoprene diblock polymer is synthesized via anionic polymerization.•Various metal-ligand complexes form nano-sized hybrid clusters.•The multiple phases in metallo-supramolecular diblock copolymer impart distinct, tunable mechanic properties.Orthogonal multi-phase strategy has been applied to generate a novel type of thermoplastic elastomeric block copolymer which was obtained via anionic polymerization. Functional terpyridine groups which can potentially form metallo-supramolecular complexes with a variety of metal ions has been introduced to the polystyrene-b-polyisoprene (PS-PI) living chain ends through the termination reaction in an optimized condition. Iron(II), cobalt(II) and zinc(II) metal ions have been used to form metal-ligand complexes with the terpyridine end groups, which can phase separate from the polymer matrix to form hybrid clusters. The formation of metallo-supramolecular hybrid clusters have dramatic effects on the micro-phase separated structures of the PS-PI diblock copolymer, which have been characterized by transmission electron microscopy, small-angle X-ray scattering and atomic force microscopy. This type of hybrid material containing hard PS nanophase and metal-ligand clusters exhibit distinct mechanic properties such as increased modulus, higher yield strength and improved toughness, which is further discussed in light of nature of the metal-ligand bonds and the liability of the clusters. The utilization of metallo-supramolecular complex and its high tunability is potential to fabricate new types of supramolecular nanocomposite materials.

Both chain dynamics and statistics of side-chain liquid crystalline polymer are experimentally explored. Dielectric measurements over a wide range of frequencies and temperature windows demonstrate that the chain dynamics in the liquid crystalline phase (SmA) is retarded and has higher apparent activation energy compared to that in isotropic melt. The molecular weight dependence of the normal mode relaxation time in the isotropic melt conforms to the Zimm model with excluded volume effect, while it shows Rouse behavior in the liquid crystalline phase. The mean squared end-to-end distance of polymer chain in the liquid crystalline phase decreases compared to that in the isotropic melt. The main chain takes a self-avoiding walk with ⟨Re2⟩ ∼ N2ν, ν = 0.54–0.6 in the isotropic melt, whereas a random walk between smectic layers with ν ≅ 0.5, consistent with the results from chain dynamics.

Side-chain liquid crystalline (SCLC) polyethers with different spacers are successfully synthesized via anionic polymerization for the first time. The molecular weights of the polymers can range up to ∼53 kg/mol with Mw/Mn <1.1. The precise chemical structures including end groups have been characterized by employing Matrix-Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) and the polymerization condition free of side reactions is further discussed. The phase behavior and structures of the polyethers have been investigated by combining various techniques including differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS) and polarized light microscopy (PLM). Two phase transformations are generally observed for each type of SCLC polyethers. Based on 2-dimensional (2D) X-ray patterns of oriented fiber and mechanically sheared samples, the low ordered liquid crystalline phase at high temperature is identified as a SmA phase for both SCLC polyethers. It is found that the polyether with a longer spacer exhibits a complex phase which is a mixture of a HexB phase and a frustrated HexB phase in analogy to smectic antiphase, whereas no such effect occurs for the polymer with a shorter spacer. Only HexB phase is observed for the low temperature phase of this polymer. The difference in phase structures is also revealed in the texture changes of PLM.

Rational design and successful synthesis of a novel double side-chain liquid crystalline (SCLC) diblock copolymer bearing a common flexible polyether backbone were achieved via sequential anionic polymerization. The distinct differences in transition temperatures as well as phase ranges of the constituting blocks counterparts merited the full exploration of complex phase structures of the diblock copolymer in a potential non-segregation state. It was clearly demonstrated that the presence of a comparably strong LC phase domain of one block could prohibit the formation of an LC phase of the adjacent block, despite that the size incommensurateness of phase structures across the interface is only ∼0.3 nm. Moreover, it was observed that the existing LC phase could be disrupted with the evolution of the dominating LC phase domain of the neighboring block. Release of constraint from the dominating LC phase domain allowed the development of the originally suppressed LC phase.

A self-complementary heteroditopic molecule composed of thymine and diamidopyridine end groups and a flexible aliphatic interconnecting chain has been synthesized. The glassy dynamics of this hydrogen-bonded supramolecule have been investigated by using dielectric and rheological measurements, in combination with infra-red spectroscopy and solid-state 13C NMR experiments. Decoupling of main dielectric relaxation from viscosity has been found in the vicinity of the glass transition and the temperature dependence of viscosity appears to be stronger than that of dielectric relaxation. The unusual dynamic decoupling phenomenon is ascribed to the chemical/dynamic heterogeneity and formation of hydrogen bonds in the supramolecules.

A model self-complementary supramolecular polymer based on thymine and diamidopyridine triple hydrogen-bonding motifs has been synthesized, and its dielectric and rheological behavior has been investigated. The formation of supramolecular polymers has been unequivocally demonstrated by nuclear magnetic resonance, electrospray ionization mass spectrometry with traveling wave ion mobility separation, dielectric spectroscopy, and rheology. The dynamical behaviors of this associating polymer generally conform to those of type-A polymers, with a low-frequency chain relaxation and a high-frequency α relaxation visible in both rheological and dielectric measurements. The dielectric chain relaxation shows the ideal symmetric Debye-like shape, resembling the peculiar features of hydrogen-bonding monoalcohols. Detailed analysis shows that there exists a weak decoupling between the mechanical terminal relaxation and dielectric Debye-like relaxation. The origin of the Debye-like dielectric relaxation is further discussed in the light of monoalcohols.