553 research outputs found
Structure Analysis of Poly(n-hexyl isocyanate)-Poly(e-caprolactone Miktoarm starpolymer in Thin film
No full textChemically Controlled Volatile and Nonvolatile Resistive Memory Characteristics of Novel Oxygen-Based Polymers
No full textRecent advancements in modern microelectronics continuously increase the data storage capacity of modern devices, but they require delicate and costly fabrication processes. As alternatives to conventional inorganic based semiconductors, semiconducting polymers are of academic and industrial interest for their cost-efficiency, power efficiency, and flexible processability. Here, we have synthesized a series of novel oxygen-based polymers through the postmodification reactions of poly(ethylene-alt-maleate) with various oxybenzyl alcohol derivatives. The oxygen-based polymers are thermally stable up to 180 degrees C, and their nanoscale film devices exhibit reliable, power efficient p-type unipolar volatile and nonvolatile resistive memory characteristics with high ON/OFF current ratios. Additionally, when given a higher number of oxygen atoms in oxyphenyl side groups, the thin film polymer devices demonstrate a wide operational film thickness range. The memory characteristics depend on the oxyphenyl moieties functioning as charge trap sites, where a combination of Schottky emission and trap-limited space charge limited conductions in OFF-state and hopping conduction in ON-state are observed. This study demonstrates the chemical incorporation of oxyphenyl derivatives into polymer dielectrics as a powerful development tool for p-type resistive memory materials
Polyether/Polythioether Synthesis via Ring-Opening Polymerization of Epoxides and Episulfides Catalyzed by Alkali Metal Carboxylates
No full textAlkali metal carboxylates were evaluated as simple and green catalysts for the ring-opening polymerization (ROP) of various epoxides (e.g., alkyl-substituted epoxides and glycidyl ethers) and episulfides (alkyl-substituted episulfides and thioglycidyl ethers). The thus-produced functional polyethers (end-functionalized polyethers, block copolyethers, polyether- polyester block copolymers, topologically unique polyethers, and isotactic-enriched polyethers) and polythioethers featured well-defined structures and controlled molecular weights (Mn,SEC = 1.0-32 kg mol-1). The most effective catalyst was identified as cesium pivalate, and the variation of carboxylate moieties and alkali metal cations enabled the tuning of acid/base character-istics and thus allowed one to control polymerization behavior and expand the scope of functional monomers and initiators. Kinetic analysis confirmed the controlled/living nature of the polymerization process, while mechanistic studies revealed that carboxylate moieties did not directly initiate the ring-opening of epoxide monomers via nucleophilic attack but rather activated the alcohol initiators/chain ends via H-bonding and thus rendered the corresponding OH groups sufficiently nucleophilic to attack the alkali metal cation-activated epoxides
A facile strategy for manipulating micellar size and morphology through intramolecular cross-linking of amphiphilic block copolymers
No full textThe effect of intramolecular cross-linking in an amphiphilic block copolymer (BCP) system was systematically investigated in terms of its thermal properties, critical micelle concentration (CMC), and aqueous self-assembly. A series of linear BCPs consisting of poly(ethylene glycol) (PEG) as a hydrophilic block and poly(epsilon-caprolactone-co-7-allyloxepan-2-one) (P(CL-co-ACL)) as a hydrophobic block were prepared by the ring-opening copolymerization of epsilon-caprolactone (CL) and 7-allyloxepan-2-one (ACL) using poly (ethylene glycol) monomethyl ether as an initiator. The intramolecular olefin metathesis reaction in the P(CL-co-ACL) block was subsequently carried out under various conditions to prepare the cross-linked BCPs with different degrees of cross-linking. The thermal analysis confirmed that the linear P(CL-co-ACL) block was found to crystallize, while the cross-linked one showed no crystallinity. In addition, glass transition temperature of the P(CL-co-ACL) block increased upon cross-linking. On the other hand, the intramolecular cross-linking had no significant influence on the CMC. The self-assembled micelles were prepared from the obtained BCPs and their size and morphology were investigated. For the BCPs with relatively short PEG chains, the micellar size decreased from 36.6 nm to 16.7 nm as the degree of cross-linking of the P(CL-co-ACL) block increased. On the other hand, the BCPs with relatively long PEG chains showed a change in the micellar morphology from spherical micelles to short worm and large compound micelles upon cross-linking
Bicyclic Topology Transforms Self-Assembled Nanostructures in Block Copolymer Thin Films
No full textOngoing efforts in materials science have resulted in linear block copolymer systems that generate nanostructures via the phase separation of immiscible blocks; however, such systems are limited with regard to their domain miniaturization and lack of orientation control. We overcome these limitations through the bicyclic topological alteration of a block copolymer system. Grazing incidence X-ray scattering analysis of nanoscale polymer films revealed that bicyclic topologies achieve 51.3-72.8% reductions in domain spacing when compared against their linear analogue, which is more effective than the theoretical predictions for conventional cyclic topologies. Moreover, bicyclic topologies achieve unidirectional orientation and a morphological transformation between lamellar and cylindrical domains with high structural integrity. When the near-equivalent volume fraction between the blocks is considered, the formation of hexagonally packed cylindrical domains is particularly noteworthy. Bicyclic topological alteration is therefore a powerful strategy for developing advanced nanostructured materials for microelectronics, displays, and membranes
Correlations of nanoscale film morphologies and topological confinement of three-armed cage block copolymers
No full textThe nanoscale film morphologies of three-armed cage block copolymers showing three different variations (Cage-A, -B, and -C) have been investigated for the first time via synchrotron grazing incidence X-ray scattering. For all cage block copolymers, the individual block components revealed amorphous characteristics. Nevertheless, they all exhibited either cylindrical or lamellar phase-separated nanostructures. Key structural parameters such as domain spacing (d-spacing), structural ordering, and orientation varied depending on the cage topologies. In particular, the d-spacing of nanostructures ranged from 6.50 to 10.85 nm. Compared to their linear block copolymer analogues, the cage block copolymers achieved a 54.8-74.5% d-spacing reduction. Overall, structural parameters such as d-spacing, structural ordering, and orientation were found to be correlated with the topological confinement which originated from the molecular cage topology
Organophosphate-catalyzed bulk ring-opening polymerization as an environmentally benign route leading to block copolyesters, end-functionalized polyesters, and polyester-based polyurethane
No full textThe ring-opening polymerizations (ROPs) of epsilon-caprolactone (epsilon-CL), delta-valerolactone, 1,5-dioxepan-2-one, trimethylene carbonate, and L-lactide were performed in the bulk using an organophosphate, such as diphenyl phosphate, bis(4-nitrophenyl)phosphate, and di(2,6-xylyl)phosphate, as the catalyst. The ROPs proceeded in a well-controlled manner even under the bulk conditions to afford well-defined aliphatic polyesters, polyester-ether, and polycarbonate with relatively low dispersities. Notably, the amount of the loaded catalyst was successfully reduced when compared to the conventional organophosphate-catalyzed ROP in solution. A kinetic study revealed the controlled/living nature of the present bulk ROP system, which allowed us to produce the block copolymers composed of polyesters, polyester-ether, and polycarbonate in one pot. Syntheses of the end-functionalized poly(epsilon-caprolactone)s (PCLs) and poly(trimethylene carbonate) were successfully demonstrated using alcohol initiators possessing highly reactive functional groups. Furthermore, the alpha,beta-dihydroxy telechelic PCL-diol as well as the three-and fourarmed star-shaped PCL-polyols were also easily obtained by using the polyols as an initiator. Finally, the one-pot synthesis of polyurethane via the ROP of epsilon-CL and a subsequent urethane forming reaction was demonstrated by taking advantage of the dual catalytic abilities of the organophosphate for both the ROP and polyurethane synthesis
Highly Ordered Nanoscale Film Morphologies of Block Copolymers Governed by Nonlinear Topologies
No full textAmong many properties of cyclic block copolymers, the notable domain spacing (d-spacing) reduction offers nonlinear topology as an effective tool for developing block copolymers for nanolithography. However, the current consensus regarding the topology-morphology correlation is ambiguous and in need of more studies. Here we present the morphological investigation on nanoscale films of cyclic and tadpole-shaped poly(n-decyl glycidyl ether-block-2-(2-(2-methoxyethoxy)ethoxy)-ethyl glycidyl ether)s and their linear counterpart via synchrotron grazing-incidence X-ray scattering. All copolymers form phase-separated nanostructures, in which only the nonlinear copolymers form highly ordered and unidirectional nanostructures. Additionally, d-spacings of cyclic and tadpole-shaped block copolymers are 49.3-53.7% and 25.0-32.5% shorter than that of their linear counterpart, respectively, exhibiting greater or comparable d-spacing reductions against the experimentally and theoretically achieved values from the literature. Overall, this study demonstrates that cyclic and tadpole topologies can be utilized in developing materials with miniaturized dimensions, high structural ordering, and unidirectional orientation for various nanotechnology applications
Influence of Topological Confinement on Nanoscale Film Morphologies of Tricyclic Block Copolymers
No full textThis study is the first quantitative synchrotron grazing incidence X-ray scattering investigation of nanoscale film morphologies of tricyclic block copolymers based on poly (n-decyl glycidyl ether) (PDGE) and poly (2-(2-(2-methoxyethoxy)-ethoxy)ethyl glycidyl ether) (PTEGGE) blocks in equivalent volume fractions. Both PDGE and PTEGGE blocks of the tricyclic block copolymers are amorphous, but copolymers exhibit phase-separated lamellar nanostructures due to block immiscibility. The lamellar structures vary in their structural parameters such as lamellar orientation and structural integrity stability depending on the degree of topological confinement effect taking effect. Interestingly, sub-10 nm domain spacings are established by all nanostructures, which are remarkably shorter than that of the linear analogue. These exceptionally short domain spacings are evident that the tricyclic block copolymer approach is highly efficient for developing high-performance nanolithographic materials for future advanced semiconductor applications
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