Synthesis and Characterization of Low-Melting-Point Polyamides with Trace Thermoreversible Cross-Linked Networks

In this study, we synthesized low-melting-point polyamides (LMPAs, Tm ≈ 145 °C), which were composed of ε-caprolactam, hexamethylenediamine, adipic acid, 1,10-decanedicarboxylic acid, and 2,5-furandicarboxylic acid. The LMPA materials with temperature-triggered reversible cross-linking were prepared by adding various bismaleimide (BMI) loadings (0, 0.1, 0.5, and 1.0 wt %), and their thermal and mechanical properties were obviously better than those of pure LMPA without BMI loading. According to rheological studies, the temperature-triggered reversible cross-linking (i.e., Diels–Alder reaction) described above occurs at a temperature range of 150–160 °C. In addition, the rheological activation energy of LMPAs with cross-linked networks was significantly higher than that of LMPA without cross-linked networks (298.6 vs 77.7 J kg–1 K–1, respectively). For mechanical properties, the yield strength of LMPAs with BMI loading (29.1–36.5 MPa) was higher than that of LMPA without BMI loading (19.1 MPa), which was improved by about 50%. As a method of developing LMPA materials with high performance, this is the first report of LMPA materials with temperature-triggered reversible cross-linking

In-Situ Template Synthesis of a Polymer/Semiconductor Nanohybrid Using Amphiphilic Conducting Block Copolymers

In this study, we synthesized organic/inorganic hybrid materials containing cadmium sulfide (CdS) nanoparticles using a novel amphiphilic conducting block copolymer as a synergistic structure-directing template and an efficient exciton quencher of the hybrid. The amphiphilic rod−coil block copolymer of polyphenylene-b-poly(2-vinyl pyridine) (PPH-PVP) was first prepared from its coil−coil precursor block copolymer of poly(1,3-cyclohexadiene)-b-poly(2-vinyl pyridine) (PCHD-PVP) by using sequential anionic polymerization followed by the aromatization reaction of converting the PCHD block to form conducting PPH. The synthesized PCHD-PVP block copolymers self-assembled into different bulk nanostructures of lamellae, cylinders, and spheres at a volume fraction similar to that of many coil−coil block copolymer systems. However, an enhanced chain-stiffness-induced morphological transformation was observed after the aromatization reaction. This is evidenced by the TEM observation in which both spherical and cylindrical structured PCHD-PVPs transform into lamellar structured PPH-PVPs after aromatization. In addition to the bulk-phase transformation, the rigid-rod characteristic of the conducting PPH block also affects the self-assembling property of the block copolymers in their solution state. CdS nanoparticles were synthesized in situ in a selective solvent of THF using PCHD-PVP and PPH-PVP micelles as nanoreactors. The PPH-PVP/Cd ion in THF exhibits a new ringlike structure of uniform size (∼50 nm) with PPH in the inner rim and complexed PVP/Cd ions in the outer rim as a result of the effects of strong intermolecular forces between PPH segments and the solvophobic interaction. CdS nanoclusters were subsequently synthesized in situ from the PPH-PVP/Cd2+ ring structure, forming a nanohybrid with intimate contact between the PPH domain and CdS nanoparticles. In particular, we found that there is an efficient energy/electron transfer between the conducting PPH domain and CdS nanoparticles in the hybrid, resulting in an enhanced PL quenching effect. The novel nanohybrid shows the potential to be used for optoelectronic applications

Self-Healing Nanocomposites with Carbon Nanotube/Graphene/Fe₃O₄ Nanoparticle Tricontinuous Networks for Electromagnetic Radiation Shielding

Recently, high-performance self-healing electromagnetic interference (EMI) shielding materials with superior electrical conductivity, excellent shielding efficiency, and effective self-repairing ability have gained great attention. However, the practical development of such systems still encounters considerable challenges. In this study, a highly efficient EMI shielding self-healing nanocomposite system composed of multiple components of multiwalled carbon nanotubes (MWCNTs), graphene nanosheets (GNSs), and Fe3O4 nanoparticles was developed by integrating a novel amphiphilic poly­(ethylene glycol)-block-poly­(caprolactone-co-furfuryl glycidyl ether) block copolymer (PEG-b-PCLF) with 1,1′-(methylenedi-4,1-phenylene)­bismaleimide and nanofillers via Diels–Alder (DA) chemistry and molecular affinity. Within this composite system, MWCNTs were distributed within the GNSs and served as connecting bridges across adjacent GNSs. Simultaneously, Fe3O4 nanoparticles were uniformly interspersed in the space around the MWCNT/GNS staggered framework due to good affinity with the hydrophilic PEG block, thereby forming MWCNT/GNS/Fe3O4 tricontinuous networks. Upon heating, the retro-DA mechanisms endowed the material system with excellent reprocessability and self-repairability. More importantly, the MWCNT/GNS/Fe3O4 tricontinuous networks not only provided efficient channels for charge transport but also served as an electromagnetic framework that synergistically endowed the material system with excellent EMI shielding properties. Accordingly, a favorable electrical conductivity of 18.5 S m–1 and an extremely high shielding effectiveness of 92.7 dB in the X-band were achieved. Additionally, the material system also possessed sufficient performances in the recovery of mechanical properties and shielding efficiency after repair, thereby leading to a prolonged service life. This study offers a promising strategy for the effective integration of multiple electromagnetic nanofillers into a self-healing polymeric system, which leads to highly efficient electrical and EMI shielding properties as well as remarkable self-repairability. We believe that these results can guide the development of advanced, durable EMI shielding applications

Synthesis and Self-Assembly of Poly(diethylhexyloxy-<i>p</i>-phenylenevinylene)-<i>b</i>-poly(methyl methacrylate) Rod−Coil Block Copolymers

A series of poly(diethylhexyloxy-p-phenylenevinylene-b-methyl methacrylate) (DEH-PPV-b-PMMA) polymers with narrow polydispersity (PDI 1H nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC). Transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) studies reveal the details of copolymer morphology. The DEH-PPV-b-PMMA system presented here has higher block segregation strength than many previously studied rod−coil block copolymers yet still shows experimentally accessible phase transitions with respect to temperature. As a result, this molecule offers new insight into the competition between rod−rod and rod−coil interactions that occurs in the system. The DEH-PPV rods are organized as a monolayer that is inclined with the lamellar normal (smectic C) for the copolymers containing low volume fraction of PMMA coil (<54%). However, as the coil fraction increases, the strips containing DEH-PPV pack into hexagonal lattice. In contrast to previous work which demonstrated similar morphologies, the sequence of reversible liquid crystalline and microphase phase transitions is altered as a result of the increased block segregation. Upon heating, the low coil fraction copolymers exhibit a series of clear transitions of smectic−lamellar to amorphous−lamellar to disordered structures. In high coil fraction copolymers, the transitions between smectic−hexagonal to amorphous−hexagonal and smectic−hexagonal to disorder structures could not be clearly differentiated. The order-to-disorder temperature (ODT) decreases slowly with increasing coil fraction while the smectic-to-isotropic transition (SI) temperature stays relatively unchanged. The steady SI temperature suggests that the strong rod−rod interaction keeps the liquid crystalline rod in the nanodomain structure regardless of the amount of coil segment in the copolymers

Facile Synthesis of Well-Defined Block Copolymers Containing Regioregular Poly(3-hexyl thiophene) via Anionic Macroinitiation Method and Their Self-Assembly Behavior

P3HT-P2VP block copolymers were synthesized using anionic macroinitiation of a vinyl end-functionalized P3HT. With different block ratio of P2VP to P3HT, the block copolymers exhibit sphere, cylinder, lamellae, and nanofiber nanostructures

Effect of TiO₂ Nanoparticles on Self-Assembly Behaviors and Optical and Photovoltaic Properties of the P3HT-<i>b</i>-P2VP Block Copolymer

An ordered nanostructure can be created from the hybrid materials of self-assembly poly(3-hexyl thiophene-b-2-vinyl pyridine) and nicotinic acid-modified titanium dioxide nanoparticles (P3HT-b-P2VP/TiO2). TEM and XRD analyses reveal that the TiO2 nanoparticles (NPs) are preferentially confined in the P2VP domain of P3HT-b-P2VP whereas TiO2 NPs interact with either pure P3HT or a blend of P3HT and P2VP to produce microsized phase segregation. The morphologies of lamellar and cylindrical structures are disturbed when the loading of TiO2 NPs is 40 wt % or higher. Cylindrical P3HT-b-P2VP/TiO2 exhibits a small blue shift in absorption and photoluminescence spectra with increasing TiO2 loading as compared to P3HT/TiO2. The NPs cause a slightly misaligned P3HT domain in the copolymer. Furthermore, the PL quenching of P3HT-b-P2VP/TiO2 becomes very large as a result of efficient charge separation in the ordered nanodomain at 16 nm. Solar cells fabricated from self-assembly P3HT-b-P2VP/TiO2 hybrid materials exhibit a >30 fold improvement in power conversion efficiency as compared to the corresponding 0.3P3HT-0.7P2VP/TiO2 polymer blend hybrid. This study paves the way for the further development of high-efficiency polymer−inorganic nanoparticle hybrid solar cells using a self-assembled block copolymer

In Situ Fabrication of Poly(3-hexylthiophene)/ZnO Hybrid Nanowires with D/A Parallel-Lane Structure and Their Application in Photovoltaic Devices

In this study, we demonstrate a facile in situ synthetic strategy to fabricate self-assembled organic/inorganic hybrid nanowires, wherein a “pre-crystallization” approach was first utilized to co-organize P3HT molecules and zinc precursors into highly elongated nanowires, followed by a thermal oxidation treatment to directly grow ZnO nanocrystals on the existing nanofibrillar template. By further thermal annealing the ZnO embossed hybrid nanowires, a unique superhighway-like architecture which composed of alternating parallel channels of P3HT nanofibrils and ZnO nanocrystals could be further obtained. This donor/acceptor (D/A) parallel-channel structure gave access to the improvements in the exciton dissociation and charge transport, thereby enhancing photoluminescence quenching, charge transport, and device performance. The photovoltaic devices with the D/A parallel-lane structure gave a high PCE of 0.61% as compared to only 0.07% from a conventional P3HT/ZnO bulk heterojuction solar cell. Our approach offers a versatile route to coassemble inorganic nanocrystals with π-conjugated polymer hosts, forming uniform one-dimensional hybrid nanochannels potentially useful in optoelectronic applications

Self-Assembled All-Conjugated Block Copolymer as an Effective Hole Conductor for Solid-State Dye-Sensitized Solar Cells

An all-conjugated diblock copolymer, poly(2,5-dihexyloxy-p-phenylene)-b-poly(3-hexylthiophene) (PPP-b-P3HT), was synthesized and applied as a hole transport material (HTM) for the fabrication of solid-state dye-sensitized solar cells (ss-DSCs). This copolymer is characterized by an enhanced crystallinity, enabling its P3HT component to self-organize into interpenetrated and long-range-ordered crystalline fibrils upon spin-drying and ultimately endowing itself to have a faster hole mobility than that of the parent P3HT homopolymer. Transient photovoltage measurements indicate that the photovoltaic cell based on PPP-b-P3HT as the HTM has a longer electron lifetime than that of the reference device based on P3HT homopolymer. Moreover, comparing the two ss-DSCs in terms of the electrochemical impedance spectra reveals that the electron density in the TiO2 conduction band is substantially higher in the PPP-b-P3HT device than in the P3HT cell. Above observations suggest that the PPP block facilitates an intimate contact between the copolymer and dye molecules absorbed on the nanoporous TiO2 layer, which significantly enhances the performance of the resulting device. Consequently, the PPP-b-P3HT ss-DSC exhibits a promising power conversion efficiency of 4.65%. This study demonstrates that conjugated block copolymers can function as superior HTMs of highly efficient ss-DSCs