With the continuous development of the electronics industry, the energy density of modern electronic devices increases constantly, thus releasing a lot of heat during operation. Modern electronic devices take higher and higher request to the thermal interface materials. Achieving high thermal conductivity needs to establish an interconnecting thermal conductivity network in the matrix. For this purpose, the suspension of Al₂O₃ and curdlan was first foamed to construct a bubble-templated continuous ceramic framework. Owing to the rapid gelation property of curdlan, we can easily remove moisture by hot air drying. Finally, the high thermally conductive composites are prepared by vacuum impregnation of silicone rubber. The result showed that composites prepared by our method have higher thermal conductivity than the samples obtained by traditional method. The thermal conductivity of the prepared composite material reached 1.253 W·m^–1·K^–1 when the alumina content was 69.6 wt%. This facile method is expected to be applied to the preparation of high-performance thermal interface materials.

Solvents have an essential association with polymer solution behavior. However, few researches have been deeply done on this respect. In recent years, our research group focus on the study on effect of solvent properties on solution behavior and film condensed state structure for semi-rigid conjugated polymer up till to apply for optoelectronic device. Herein, influence of solvent properties including solubility of solvent, aromaticity, polarity and hydrogen bonds on semi-rigid polymer chain solution behavior, i.e., single chain conformation, chain shape, size and chains aggregated density were studied by means of static/dynamic laser light scattering (DLS/SLS) and exponential law etc. Effect of solvent properties on condensed state structure of the semi-rigid conjugated polymer film was studied by UV absorption spectroscopy, PL spectroscopy and electron microscopy etc. The essential reasons for the influence were discovered and the mechanism was revealed. It was found that solution behavior with different solvent properties had an essential physical relationship with chains condensed state structure of the semi-rigid conjugated polymers. More importantly, there was a quantitative structure-activity relationship between solution and film. The key to this relationship depended on the interaction between solvent molecules and the semi-rigid conjugated polymer chains. This interaction could also affect optoelectronic devices performance. This study is of great significance to effectively control the condensed state structure of the semi-rigid conjugated polymers in the process of dynamic evolution from solutions to films. It not only enriches the knowledge and understanding of both semi-rigid conjugated polymer solution behaviors and film condensed state physics based on polymer physics, but also is meaningful to practical application for conjugated polymer and other traditional polymer systems.

The surfaces and interfaces of biomaterials interact with the biological systems in multi-scale levels, and thereby influence the biological functions and comprehensive performance in vitro and in vivo. In particular, a surface promoting the selective adhesion and directional migration of desired types of cells in complex environment is extremely important in the repair and regeneration of tissues such as peripheral nerve and blood vessel, and long-term application of intracorporal devices such as intravascular implants. Therefore, surface modification of biomaterials is a facile and effective method to achieve the desired cell-biomaterials interactions. In this short review, recent advances on the surface modification of biomaterials to regulate selective cell adhesion and migration are briefly summarized. In particular, the surface properties of biomaterials are manipulated via the convenient introduction of amino groups to the ester-based polymers, the formation of polyelectrolyte multilayers, and the fabrication of topology and gradient cues, etc., followed by the association of chemical and biological signals such as collagen, heparin, hyaluronic acid, peptides and cell growth factors. The selective adhesion and directional migration of various types of cells such as endothelial cells (ECs), smooth muscle cells (SMCs), hepatocytes and Schwann cells (SCs) are achieved over the competitive counterpart cells by the use of cell-resisting substances and cell-selective motifs on gradient substrates in most cases. Recent advances on cell behaviors in three-dimensional (3D) cell-extracellular matrix (ECM)-mimicking substrates are also reviewed.

A type of novel electrospun supramolecular hybrid microfibers comprising poly(9-(4-(octyloxy)-phenyl)-2,7-fluoren-9-ol) (PPFOH) and poly(N-vinylcarbazole) (PVK) are successfully prepared for intriguing multi-color emission properties. The supramolecular tunable PPFOH aggregation in PVK matrix endows the complex with a smart energy transfer behavior to obtain the multi-color emissions. In stark contrast to PVK fibers, the emission color of PPFOH/PVK fibers with an efficient dispersion of PPFOH fluorophores at a proper dope ratio can be tuned in a wide spectrum of blue (0.1%), sky blue (0.5%), nearly white (1%), cyan (2%), green (5%) and yellow (10%). Besides, conductive behaviors of the microfiber were demonstrated in accompany with the increment of the doping ratio of PPFOH to PVK. Successful fabrication of polymer light-emitting diode (PLED) based on the blended electrospun fiber provided a further evidence of its excellent electrical property for potential applications in optoelectronic devices.

A series of polymer photodetectors with device configuration of ITO/PEDOT:PSS/P₃HT:PC₆₁BM/C₆₀/Al were prepared by using P₃HT as the donor material and PC₆₁BM as the acceptor material. By regulating the content of 1,8-diiodooctane (DIO) (V/V: 1%, 3%, 5%) as a processing additive, the morphology of the active layer can be greatly improved. With C₆₀ as the hole blocking layer, the dark current density of the device can be reduced by about an order of magnitude. When employing 3% DIO (V/V) in the active layer processing, the photodetetcors present the best performance, and the detectivity of the device is 1.52×10¹² Jones at 540 nm under a bias of −0.1 V. Moreover, it also has a wider linear dynamic range of 60 dB as well as faster response speed (τ_r/τ_f=0.53/0.71 μs) than those of devices with other content of DIO additives.

A series of copolymers of thiazoloisoindigo (TzII) with different chalcogenophene trimers were synthesized to systematically investigate the chalcogen effect on their charge transport properties. When only the middle thiophene ring of terthiphene (T-T-T) is replaced by heavier chalcogenophenes, a preference (expressed by the ratio of μ_e/μ_h) towards electron transport was observed descending from T-T-T to T-Se-T then to T-Te-T (Se and Te stand for selenophene and tellurophene, respectively). On the other hand, with the increased number of heavier chalcogenophenes, a preference toward hole transport was observed descending from Se-T-Se to Se-Se-Se then to Se-Te-Se. This phenomenon is well-explained by the balance between the aromatic resonance energy of the chalcogenophenes and the electronegativity of the chalcogens. Specifically, P(TzII-T-Se-T) displayed relatively balanced ambipolar property (μ_h^max and μ_e^max of 3.77 and 1.59 cm²·V⁻¹·s⁻¹ with a μ_e/μ_h of 0.42), while P(TzII-Se-Te-Se) exhibited the best preference to hole transfer with a μ_e/μ_h of 0.09. P(TzII-T-Te-T) exhibited the best preference to electron transfer with a μ_e/μ_h of 16 and the μ_e^max of 0.64 cm²·V⁻¹·s⁻¹ which is the highest electron mobility among the known conjugated polymers containing tellurophenes.

Poly(3-hexylthiophene) (P3HT) thin films, obtained by normal spin-coating and solvent vapor assisted spin-coating (SVASP) before and after thermal annealing (TA), and the corresponding devices were prepared to unravel the microstructure-property relationship, which is of great importance for the development of organic electronics. When SVASP-TA films were used as the active layers of the organic field-effect transistors, a hole mobility up to 0.38 cm²·V^–1·s^–1 was achieved. This mobility was one of the highest values and one order of magnitude higher than that of the normal spin-coating films based transistors. The relationship between the microstructure and the device performance was fully investigated by UV-Vis absorption spectra, grazing incident X-ray diffraction (GIXD), and atomic force microscopy (AFM). The impressive mobility was attributed to the high crystallinity and ordered molecule packing, which stem from the synergistic effects of SVASP and thermal annealing.

Herein we present a new perspective showing that water-soluble liquids, when added to water, undergo transient emulsification before complete dissolution. Thus, non-amphiphilic macromolecules can self-assemble at the two-miscible-phase interface when cononsolvent effect appears. A representative case shown here is that when poly(N-isopropylacrylamide) (PNIPAm), prepared by aqueous radical polymerization, in methanol solution is added into water, the polymer chains rapidly self-assemble into hollow micro-vesicles based on the cononsolvency at water/methanol interface. This finding provides a subtle strategy to prepare hollow micro-vesicles by non-amphiphilic polymers without template participating. We proposed a new concept “interfacial cononsolvency” to describe the formation process. Due to the easy modification process, sugar-contained PNIPAm chains are synthesized by copolymerization. As an application example, it is shown that these sugar-contained PNIPAm chains can afford “sweet” micro-vesicles (containing glucose residues). And the “sweet” micro-vesicles can well mimick the protocells which are involved in the recognition of bacteria.

Poly(2-oxazoline) (POx) is a kind of polymeric amides that can be viewed as conformational isomers of polypeptides with excellent cyto- and hemo-compatibility, and is promising to be used as drug carriers. However, the drug loading capacity (DLC) of POx for many drugs is still low except several hydrophobic ones including paclitaxel (PTX). Herein, we prepared a series of amphiphilic POx block copolymers with various functional groups, and investigated the relationship between functional structures and the DLC. Functional POxs with benzyl, carboxyl, and amino groups in the side-chain were synthesized based on a poly(2-methyl-2-oxazoline)-block-poly(2-butyl-2-oxazoline-co-2-butenyl-2-oxazoline) (PMeOx-P(nBuOx-co-ButenOx), PMBEOx) precursor, followed by click reaction between vinyl and the 2-phenylethanethiol, thioglycolic acid and cysteamine. Using thin-film hydration method, eight commonly used drugs with various characteristics were encapsulated within these functional POx polymers. We found that amine-containing drugs were more easily encapsulated by POx with carboxyl groups, while amine functionalities in POx enhanced the loading capacity of drugs with carboxyl groups. In addition, π-π interactions resulted in enhanced DLC of most drugs, except several hydrophobic drugs with aromatic to total carbon ratios less than 0.5. In general, we could successfully encapsulate all the selected drugs with a DLC% over 10% using properly selected functional POxs. The above results confirm that the DLC of polymeric carriers can be adjusted by modifying the functional groups, and the prepared series of functional POxs provide an option for various drug loadings.

Poly(styrene-b-isobutylene-b-styrene) triblock copolymer (SIBS), a kind of thermoplastic elastomer with biocompatibility and biostability containing fully saturated soft segments, could be synthesized via living cationic copolymerization. A novel poly[(styrene-co-methylstyrene)-b-isobutylene-b-(styrene-co-methylstyrene)]-g-polytetrahydrofuran (M-SIBS-g-PTHF) block graft copolymer was prepared to increase the polarity and service temperature of SIBS by grafting polar PTHF segments onto SIBS. A series of the above block graft copolymers with average grafting numbers from 2 to 6 and molecular weights of PTHF branches ranging from 200 g·mol⁻¹ to 4200 g·mol⁻¹ were successfully synthesized via living cationic ring-opening polymerization of tetrahydrofuran (THF) coinitiated by AgClO₄. The introduction of PTHF branches led to an obvious microphase separation due to thermodynamic incompatibility among the three kinds of segments of polyisobutylene (PIB), polystyrene (PS) and PTHF. Moreover, the microphase separation promotes the rearrangement of PTHF branches to form the nanocrystallization-locked physically cross-linked network after storage at room temperature for 2 months, leading to insolubility of the copolymers even in good solvents. The melting temperature and enthalpy of PTHF nanocrystallization locked in hard domains of M-SIBS-g₅-PTHF-1.1k block graft copolymer increased remarkably up to 153 °C and 117.0 J·g⁻¹ by 23 °C and 11.6 J·g⁻¹ respectively after storage for long time. Storage modulus (G') is higher than loss modulus (G'') of M-SIBS-g-PTHF block graft copolymer at temperatures ranging from 100 °C to 180 °C, which is much higher than those of the SIBS triblock copolymer. To the best of our knowledge, this is the first example of high performance M-SIBS-g-PTHF block graft copolymers containing segments of PIB, PS and PTHF with nanocrystallization-locked architecture.

The reinforcement of rubbers by nanoparticles is always accompanied with enhanced dissipation of mechanical energy upon large deformations. Methods for solving the contradiction between improving reinforcement and reducing energy dissipation for rubber nanocomposites have not been well developed. Herein carbon black (CB) filled isoprene rubber (IR)/liquid isoprene rubber (LR) blend nanocomposites with similar crosslink density (ν_e) are prepared and influence of LR on the strain softening behaviors including Payne effect under large amplitude shear deformation and Mullins effect under cyclic uniaxial deformation is investigated. The introduction of LR could improve the frequency sensitivity of loss modulus and reduce critical strain amplitude for Payne effect and loss modulus at the low amplitudes. Meanwhile, tuning ν_e and LR content allows reducing mechanical hysteresis in Mullins effect without significant impact on the mechanical performances. The investigation is illuminating for manufacturing nanocomposite vulcanizates with balanced mechanical hysteresis and reinforcement effect.

In order to enhance the interfacial adhesion of carbon fiber (CF) and polymer matrix, a multiscale gradient modulus intermediate layer with rigid-flexible (GO-PA) hierarchical structure was designed and fabricated between CFs and matrix by a facile and businesslike strategy. The polarity, roughness and wettability of CFs surface as well as the thickness of intermediate layer in composite have been significantly increased after rigid-flexible hierarchical structure was constructed. The IFSS, ILSS, compression and impact toughness manifested that the hierarchical structure could bring about a fantastic improvement (76.8%, 46.4%, 40.7% and 37.8%) for the interfacial and mechanical properties than other previous reports. Consequently, the establishment of CF surface with gradient modulus rigid-flexible hierarchical structure via regulation of nanoparticles and polymer array would open a new, viable and promising route to obtaining high-performance composites.

Bulk amorphous polymers become stretched and parallel-aligned under loading stress, and their intermolecular cooperation slows down the subsequent stress relaxation process. By means of dynamic Monte Carlo simulations, we employed the linear viscoelastic Maxwell model for stress relaxation of single polymers and investigated their intermolecular cooperation in the stress relaxation process of stretched and parallel-aligned bulk amorphous polymers. We carried out thermal fluctuation analysis on the reproduced Debye relaxation and Arrhenius fluid behaviors of bulk polymers. We found a transient state with stretch-coil coexistence among polymers in the stress relaxation process. Further structure analysis revealed a scenario of local jamming at the transient state, resulting in an entropy barrier for stretch-coil transition of partial polymers. The microscopic mechanism of intermolecular cooperation appears as unique to polymer stress relaxation, which interprets the hydrodynamic interactions as one of essential factors raising a high viscosity in bulk amorphous polymers. Our simulations set up a platform of molecular modeling in the study of polymer stress relaxation, which brought new insights into polymer dynamics and the related mechanical/rheological properties.

Stretchable conductive fibers offer unparalleled advantages in the development of wearable strain sensors for smart textiles due to their excellent flexibility and weaveability. However, the practical applications of these fibers in wearable devices are hindered by either contradictory properties of conductive fibers (high stretchability versus high sensing stability), or lack of manufacturing scalability. Herein, we present a facile approach for highly stretchable self-crimping fiber strain sensors based on a polyether-ester (TPEE) elastomer matrix using a side-by-side bicomponent melt-spinning process involving two parallel but attached components with different shrinkage properties. The TPEE component serves as a highly elastic mechanical support layer within the bicomponent fibers, while the conductive component (E-TPEE) of carbon black (CB), multiwalled carbon nanotubes (MWCNTs) and TPEE works as a strain-sensitive layer. In addition to the intrinsic elasticity of the matrix, the TPEE/E-TPEE bicomponent fibers present an excellent form of elasticity due to self-crimping. The self-crimping elongation of the fibers can provide a large deformation, and after the crimp disappears, the intrinsic elastic deformation is responsible for monitoring the strain sensing. The reliable strain sensing range of the TPEE/E-TPEE composite fibers was 160%−270% and could be regulated by adjusting the crimp structure. More importantly, the TPEE/E-TPEE fibers had a diameter of 30−40 μm and tenacity of 40−50 MPa, showing the necessary practicality. This work introduces new possibilities for fiber strain sensors produced in standard industrial spinning machines.

Hybrid nanostructures possess a great potential for application in advanced nanotechnologies due to the anisotropic properties from different nanophases. Our previous work demonstrated that a linear A₁B₁A₂B₂ tetrablock copolymer of symmetric overall volume fraction can self-assemble into a hybrid lamella-sphere (LS) structure by tuning the relative length of the two A-blocks through self-consistent field theory (SCFT), where the spherical and the lamellar domains are mainly composed of the long A₁- and short A₂-blocks, respectively. However, the phase region of LS is limited. In order to expand the stable region of LS, we change the linear A₁B₁A₂B₂ copolymer to a branched A₁B₁A₂(B₂)_m copolymer resulting in an increase of the local spontaneous curvature between A₂- and B₂-blocks. We examine the impact of the branching number m of B₂-block on the stable region of LS in the phase diagram with respect to f_A1 and χN for fixed f_B=0.5 and f_B1=0.26, and find that m=2 expands the LS region significantly in contrast to the linear architecture. On the other hand, the stability window of LS does not change notably when m=2 is increased to 3 in our calculated parameter space.