Neat Copolymer Research Articles

Poly(vinyl benzoate)-b-poly(diallyldimethyl ammonium TFSI)-b-poly(vinyl benzoate) Triblock Copolymer Electrolytes for Sodium Batteries

Block copolymers (BCPs) as solid electrolytes for batteries are usually designed to have an ion-solvating block for ion conduction and an ionophobic block for providing mechanical strength. Here, we show a novel solid polymer electrolyte (SPE) for sodium batteries based on a poly(vinyl benzoate)-b-poly(diallyldimethyl ammonium bis(trifluoromethanesulfonyl)imide) PVBx-b-PDADMATFSIy-b-PVBx ABA triblock copolymer. The SPE triblock copolymer comprises a polymerized ionic liquid (PIL) ion-solvating block combined with NaFSI salt as an internal block and an ionophilic PVB as an external block. Four distinct compositions with varying chain lengths of the blocks were synthesized by reversible addition−fragmentation chain-transfer (RAFT) polymerization. The neat copolymers were subsequently mixed with NaFSI in a 2:1 mol ratio of Na to ionic monomer units. Through comprehensive analysis using differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR), it was revealed that the ion coordination within the polymer–salt mixtures undergoes changes based on the composition of the starting neat polymer. Electrochemical evaluations identified the optimal composition for practical application as PVB11.5K-b-PDADMATFSI33K-b-PVB11.5K, showing an ionic conductivity at 70 °C of 4.2 × 10−5 S cm−1. This polymer electrolyte formulation was investigated for sodium in Na|Na symmetrical cells, showing an overpotential of 200 mV at 70 °C at 0.1 mA cm−2. When applied in a sodium–air battery, the polymer electrolyte membrane achieved a discharge capacity of 1.59 mAh cm−2 at 50 °C.

Eliminating the Tg-confinement and fragility-confinement effects in poly(4-methylstyrene) films by incorporation of 3 mol % 2-ethylheyxl acrylate comonomer.

Nanoconfined poly(4-methylstyrene) [P(4-MS)] films exhibit reductions in glass transition temperature (Tg) relative to bulk Tg (Tg,bulk). Ellipsometry reveals that 15-nm-thick P(4-MS) films supported on silicon exhibit Tg - Tg,bulk = - 15 °C. P(4-MS) films also exhibit fragility-confinement effects; fragility decreases ∼60% in going from bulk to a 20-nm-thick film. Previous research found that incorporating 2-6 mol % 2-ethylhexyl acrylate (EHA) comonomer in styrene-based random copolymers eliminates Tg- and fragility-confinement effects in polystyrene. Here, we demonstrate that incorporating 3 mol % EHA in a 4-MS-based random copolymer, 97/3 P(4-MS/EHA), eliminates the Tg- and fragility-confinement effects. The invariance of fragility with nanoconfinement of 97/3 P(4-MS/EHA) films, hypothesized to originate from the interdigitation of ethylhexyl groups, indicates that the presence of EHA prevents the free surface from perturbing chain packing and the cooperative mobility associated with Tg. This method of eliminating confinement effects is advantageous as it relies on the simplest of polymerization methods and neat copolymer only slightly altered in composition from homopolymer. We also investigated whether we could eliminate the Tg-confinement effect with low levels of 2-ethylhexyl methacrylate (EHMA) in 4-MS-based or styrene-based copolymers. Although EHMA is structurally nearly identical to EHA, 4-MS-based and styrene-based copolymers incorporating 4 mol % EHMA exhibit Tg-confinement effects similar to P(4-MS) and polystyrene. These results support the special character of EHA in eliminating confinement effects originating at free surfaces.

Development of a magnified sunlight responsive shape memory bio-composite: effects of titanium nitride (TiN) nanoparticles on a bio-based benzoxazine/epoxy copolymer.

This study uniquely explored the effects of loading titanium nitride (TiN) nanoparticles in a bio-based benzoxazine/epoxy copolymer on the shape memory performance of the resulting composite using normal and magnified sunlight irradiation stimuli scenarios. Additionally, the effects of loading the TiN nanoparticles in the copolymer on light absorbance capacity, thermal stability, visco-elastic properties, and tensile properties of the composites were analysed. Results reveal that the different loading amounts (1 to 7 wt%) of TiN dispersed well within the copolymer matrix and produced excellent composite samples (TiN-1(wt%), TiN-3(wt%), TiN-5(wt%), and TiN-7(wt%)). Interestingly, the obtained samples were found to exhibit improved light absorbance in the wavelength range of 200-900 nm, giving the samples greater sunlight absorbing capacity. Moreover, the thermal stability of the composites increases with an increase in the loading amount; for instance, the initial degradation temperature increased from 316 °C to 324 °C. Meanwhile, visco-elastic and tensile properties increased and reached the optimum for TiN-5(wt%), where 3.1 GPa and 10.4 MPa were recorded as storage modulus and tensile stress, respectively. Consequent to these improvements in the properties of the composites, the shape memory performance of the composites was positively impacted. For instance, average shape fixity ratio, shape recovery ratio, and recovery time of 95%, 96%, and 38 seconds, respectively, were achieved with TiN-7(wt%), which represents 19%, 17%, and 38% improvements, respectively, compared to when the neat copolymer (TiN-0(wt%)) was used using magnified sunlight irradiation stimulus. Overall, this finding provides the basis for the utilization of magnified sunlight irradiation stimulus to achieve excellent shape memory performance with TiN-filled polymer composites.

Anionic starch-based hybrid cryogel-embedded ZnO nanoparticles: tuning the elasticity and pH-functionality of biocomposites with dicarboxylic acid units.

Weakly anionic semi-interpenetrating polymer network (semi-IPN) biocomposites based on starch (ST)-incorporated poly(acrylamide-co-itaconic acid)/ZnO (ST-PAI/ZnO) were synthesized by a simple one-pot method via free radical aqueous polymerization. Hybrid biocomposites exhibited lower equilibrium swelling compared with neat copolymer gel. For both hydrogels and cryogels, swelling followed a decreasing order as copolymer PAI > starch-free PAI/ZnO > ST-PAI/ZnO gels. With the addition of 9% ST and ZnO, the swelling ratio of gels decreased from 898 to 68.3, resulting in a significant increase in elastic modulus. Compared with a fixed amount of ST, biocomposite cryogels exhibited significantly higher modulus than hydrogels. With the addition of 9% ST, the elastic modulus of cryogels reached 22.2 kPa while it was 2.7 kPa for the hydrogels. An equation expressing the effective cross-linking density of semi-IPNs presented by a cubic polynomial as a function of starch was obtained. As pH increased with the presence of dicarboxylic acid units, a gradual increase in swelling occurred at two different pH values. A gradually reproducible swelling change of semi-IPNs was depicted with pH ranging from 2.1 to 11.2. Biocomposite cryogels showed rapid swelling in a buffer solution of pH 11.2 and rapid shrinking in pH 2.1. Salt-induced swelling testing showed that the ability to reduce the degree of swelling and solubility of starch was Br- > Cl- > NO3- > SO42- for anions consistent with the Hofmeister series. Adsorption efficiency for the removal of methyl violet (MV) dye was analyzed using Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. The results confirmed that the Langmuir isotherm and pseudo-second-order model are suitable for describing MV adsorption on semi-IPN biocomposites. The synthesized biocomposites with good swelling/deswelling kinetics in different pH-buffer solutions, high saline absorbency, desirable adsorption efficiency, and acceptable pH-dependent swelling reversibility can be considered as smart hybrid materials for the adsorption of the dye in water purification tasks.

Synthesis of Pyrrole-N-vinylcarbazole Neat Copolymer (Py-NVK) and ZnO Nanocomposite (Py-NVK_ZnO)

The present work focused on the synthesis of neat copolymer (Py-NVK) and ZnO Nanocomposite from their pyrrole (Py) and N-vinylcarbazole (NVK) host monomers and creating new conducting materials (Py-NVK & Py-NVK_ZnO). The choice of neat copolymer and ZnO Nanocomposite was motivated by the unique properties of their host monomers (Py & NVK). The neat and ZnO Nanocomposite copolymer was prepared by the sol-gel method using FeCl3 as an initiator. Structural analyses were performed using Field emission scanning electron microscopy (FESEM), High-resolution transmission electron microscopy (HRTEM), X-Ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR).

Rheological studies of nanocomposites based on hydrolyzed polyacrylamide with silica and alumina in saline media to enhance oil recovery

Many nanoparticles such as silicon dioxide (SiO2) and aluminum oxide (Al2O3) have been recently proposed to increase the performance of water-soluble polymers for use in oil recovery (EOR). However, nanoparticles in nanocomposites tend to precipitate, agglomerate, or even precipitate under harsh conditions such as high-temperature and high-salinity (HT-HS), which reduces their potential for field applications. In this work, silica and alumina nanoparticles were modified with 3-methoxysilyl-propyl-methacrylate (TMS) coupling agent containing a vinyl group to enhance better dispersibility in reaction media and much stronger adhesion with the polymer. Then, acrylamide (AM) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) monomers were copolymerized in the presence of modified NPs via radical polymerization and were covalently bound to the NPs. In this study, the effect of AM/AMPS ratio and alumina as well silica loading amount on thermal stability, rheological properties and aging of composite solution was investigated and compared with commercial HPAM used for EOR. Results depicted that used method of synthesis could improve the rheological properties and better dispersion of nanoparticles in the polymer. It was found that the modified nanoparticles reduced the thermal degradation of the polymer and protect its original structure when compared to the neat copolymer. After 30 days of aging, the loss of viscosity in PAMS and HPAM was approximately 46% and 75% while PAMS10-Silica2% and PAMS10-Alumina2% exhibited a viscosity loss of 27%.

POSS increased the toughness and mechanical modulus of acrylic copolymers by increasing the entanglement density

Polyhedral oligomeric silsesquioxane copolymerized with butyl acrylate (BA), methyl methacrylate (MMA), and acrylic acid (AA) induced ca. twofold increase of fracture energy Γ and of Young's modulus E of cast films at only 1 wt% content. The copolymer of composition BA:MMA:AA:POSS 56:41:2:1 mol% was synthesized in situ by seeded semi-batch emulsion polymerization. Films cast from the corresponding emulsions were optically transparent and transmission electron microscopy (TEM) showed that POSS was predominantly dispersed at nearly single unit in the acrylic matrix. Shear rheology and time-temperature superposition (TTS) analysis demonstrated an entangled state with the absence of terminal regime, and POSS increased the segmental relaxation time τe and the rubbery modulus Ge, hence the free volume and packing length p decreased, relative to the neat copolymer. The efficient dispersion of POSS and its size smaller than the virtual tube diameter suggests that POSS is intercalating the molecular mesh. Therefore, the entanglement density increased and induced an increase of tensile mechanical modulus. The mesh intercalation by POSS means that it did not act as stress concentrator and consequently the critical fracture strain ε* and the fracture energy Γ also increased. These results evidenced the topological constraints imposed by the bulky POSS to hinder chains past each other thus inducing an increase of entanglement density and this manifested in simultaneous mechanical reinforcement and resistance to fracture.

New nanocomposites based on poly(benzoxazine-co-epoxy) matrix reinforced by novel graphene single and mixed blend fillers

We report new nanocomposites with poly(benzoxazine-co-epoxy) matrix reinforced with 1 wt% graphene. Curabox 24-111, a benzoxazine resin was copolymerised with Epilok 60-566, a mixture of epoxy resins. Copolymerisation was also carried out in the presence of different graphene powders, namely, Nanene-001 and Nanene-002, used as single fillers and as mixture (relative weight ratio 70:30 or 30:70). DSC results showed the addition of either single filler caused a delay in polymerisation and an increase in the exothermic peak temperature of the curing reaction with a related reduction in ΔH Total. compared to the neat copolymer. Copolymerisation showed a 38% reduction and 24% increase in tensile modulus (E) compared to the neat polybenzoxazine and epoxy polymer, with a respective 18% and 30% reduction in tensile strength (TS). Nanocomposites with 0.7wt% Nanene-002 + 0.3 wt% Nanene-001 showed the highest increase of 35% in TS, a 1.6% reduction in E and 36% increase in elongation at break (EB) compared to the neat copolymer matrix. Samples with 1 wt% Nanene-001 showed the largest reduction of 21% in E, a 27% increase in TS and a 45% increase in EB. Additionally, TGA thermographs showed a 22°C increase in the onset of degradation (300°C–322°C) improving the materials thermal stability.

Magnetic- and light-responsive shape memory polymer nanocomposites from bio-based benzoxazine resin and iron oxide nanoparticles

Shape memory polymers (SMPs) are a class of smart materials that can be programmed to recover from temporary shape to permanent shape by applying external stimuli (temperature, magnetic field, light, electric field, and moisture, etc.). This unique property of SMPs makes them an appealing candidate in application for soft robotics, such as smart actuators, artificial muscles, and biomedical devices. In this contribution, we have developed multi-stimuli-responsive SMPs from bio-based benzoxazine resin and iron oxide nanoparticles (Fe3O4 NPs) that could be actuated by magnetic field and light. The nanocomposites were characterized by infrared spectroscopy, in which molecular interaction between benzoxazine/epoxy copolymers and Fe3O4 NPs was observed. Effects of nanoparticle content (0–5 wt%) on magnetic, mechanical, thermal, and thermo-mechanical properties of nanocomposites were investigated. Shape memory performance of nanocomposites was significantly improved with incorporation of Fe3O4 NPs. Shape fixity increased from 85% of neat copolymers to 93% of copolymers filled with 3 wt% Fe3O4 NPs, while shape recovery increased from 94% to 98%. Moreover, shape fixity could be done without external force contact by 808 nm-light actuation and magnetic attraction, due to photothermal and magnetic properties of nanocomposites. Shape recovery was tested under actuation by magnetic field. The highest shape recovery ratio was 99% within 26 s for copolymers filled with 5 wt% Fe3O4 NPs. Lastly, preliminary application of nanocomposites was demonstrated as they could push a 1 g-object within 10 s of actuation by magnetic field. In overall, these nanocomposites with multi-stimuli-responsive shape memory property had a good potential to be applied for soft robotics.

Structure-property relationships of Kaolin-nanocomposite beads decorated with tertiary amines: Influence of shape on network elasticity and multi-responsivity

Aluminosilicate mineral Kaolin-loaded nanocomposite beads containing cationic 2-(dimethylamino)ethyl methacrylate (DMAEMA) and thermoresponsive N-isopropylacrylamide (NIPA) have been successfully synthesized by combined method of dropwise freezing into cryogenic liquid and sedimentation cryogelation. Hertzian elasticity, thermal stability, and responsive-swelling properties were investigated. The nanocomposite gels exhibited better mechanical properties and thermal stability than neat copolymer gels. The stress and displacement distribution on surface of Kaolin-loaded nanocomposite beads were evaluated with classical Hertz theory, and the results were compared with the results obtained from Rubber elasticity theory. The scaling relationship for contact stress and surface displacement was obtained assuming Hertz's small contact area, and the compression force was scaled with displacement with an exponent of 1.34 ± 0.08. The elastic properties directly attributed to effective potential showed that Hertz potential is valid for small deformations and the elastic modulus decreased with the swollen bead diameter. Addition of Kaolin and NIPA to PDMAEMA-based network has opposite effect on the mechanical properties. The elastic modulus increased, but the swelling ratio decreased with addition of Kaolin. The opposite behavior was observed when NIPA was added, the swelling increased and the mechanical properties weakened. All gels showed significant temperature sensitivity as a result of combination of PDMAEMA and PNIPA, while the swelling was higher at acidic pH than alkaline pH. An overshooting effect attributed to the dynamic conformational changes of tertiary amine of DMAEMA was observed during swelling in pH 3.6. The increase in network density of nanocomposite gel with addition of Kaolin leads to slower relaxation of molecules, and water absorption tends to become relaxation-controlled. An increase in diffusion exponent is observed as diffusion changes from Fickian to non-Fickian. Influence of single salts; NaCl, KCl and K2CO3 on swelling of nanocomposites was investigated. The swelling of Kaolin-loaded nanocomposites decreased with increasing ionic strength, and a “salting-out” effect was observed. The use of naturally occurring nanoscale particles in such structural material design is an important method for biomedical applications and separation technology.

Stability of cubic single network phases in diblock copolymer melts

AbstractWe used self‐consistent field theory (SCFT) to examine the stability of three cubic single network structures, single gyroid, single diamond, and single primitive, in neat diblock copolymer melts. Arguments related to packing frustration, as measured by the standard deviation in the mean curvature of the interface relative to its mean, that explain the relative stability of double gyroid, double diamond and double primitive also extend to the relative stability of their single networks. However, this packing frustration measure fails to account for the relative stabilities of single and double networks, for example, single gyroid versus double gyroid, and arguments for a preferred curvature fail to explain the selection of double gyroid as the segregation strength increases. Rather, the larger interfacial areas per unit volume of single networks, arising from decreased domain sizes, are found to be a generic factor that leads to metastability of the cubic single networks relative to double gyroid in the network‐forming region of the morphology diagram. These results clarify the origins of the metastability of single cubic network phases in neat diblock copolymer melts.

Development of chopped glass fiber composites with difunctional benzoxazine and bio‐based phthalonitrile copolymer: A study of mechanical and thermomechanical properties

AbstractThe randomly‐oriented glass fibers (GF) reinforced composites with Bisphenol A–amine based benzoxazine (BA‐a) and bio‐based eugenol‐based phthalonitrile (EPN) copolymer were developed by an isothermal compression molding technique. The silane coupling agent‐treated GF (TGF) reinforced composites showed much better impact strength as compared to as‐received GF reinforced composites. A rise of 95.2 MPa, 5.5GPa, 69.1 MPa, and 2.5GPa in flexural strength, flexural modulus, tensile strength, and Young's modulus were observed, respectively. The DMA results confirmed that the storage modulus (E') and glass transition temperature (Tg) were gradually increased and the damping factor decreased as the TGF reinforcement was raised from 0 to 40 wt%. E' and Tg values were 3.09 GPa and 27°C, respectively, higher than the recorded values for the neat copolymer. The 40 wt% TGF reinforced poly(BA‐a/EPN) composite showed the maximum thermal stability values of 475.4, 507.3°C, and 75.43% for T5, T10, and Yc, respectively. The LOI values confirm that the TGF/copolymer composites have self‐extinguishing properties.

Poly[(vinyl benzyl trimethylammonium chloride)]-based nanoparticulate copolymer structures encapsulating insulin

We report on the synthesis and preparation of four double hydrophilic polyelectrolytes and their complexation with insulin (INS). Specifically, two cationic-neutral poly[oligo(ethylene glycol) methacrylate]-b-poly[(vinyl benzyl trimethylammonium chloride)] (POEGMA-b-PVBTMAC) and two poly[oligo(ethylene glycol) methacrylate-co-vinyl benzyl trimethylammonium chloride] (P(OEGMA-co-VBTMAC)) copolymers are successfully synthesized by reversible-addition fragmentation chain transfer (RAFT) polymerization with different compositions. Based on light scattering techniques (DLS, ELS), the POEGMA81-b-PVBTMAC19, POEGMA46-b-PVBTMAC54 P(OEGMA90-co-VBTMAC10), P(OEGMA75-co-VBTMAC25) (subscripts denote wt.% composition of the components) copolymers are present as single chains and aggregates in aqueous media. A significant aggregation tendency of bare copolymers into well-defined spherical-shape particles is also noticed in cryogenic transmission electron microscopy measurements (Cryo-TEM) measurements. The synthesized copolymers were utilized as nanocarriers for insulin (INS) encapsulation. Nanocarriers were formed via electrostatic co-assembly, and the effects of copolymer structure on the properties of the formed hybrid copolymer-INS nanostructures are studied. Physicochemical results on the copolymer/INS complexes corroborated the efficient complexation of INS with copolymers. The determined characteristics and the morphology of the copolymer/INS complexes were found to depend on (−)INS/(+)polymer charge ratio. The copolymer/INS complexes retain the initial spherical shape of neat copolymer aggregates after the electrostatic complexation with INS, according to Cryo-TEM measurements, also uncovering the presence of aggregates and threadlike structures. FBS interactions between bare copolymers and copolymer/INS complexes manifested a good stability of the hybrid copolymer/INS assemblies into a simulated biological environment. Moreover, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy shows physical interactions between INS and the respective polyelectrolytes. Fluorescence spectroscopy (FS) measurements indicated no significant changes on the conformation of complexed INS.

Field-Theoretic Simulations for Block Copolymer Melts Using the Partial Saddle-Point Approximation.

Field-theoretic simulations (FTS) provide an efficient technique for investigating fluctuation effects in block copolymer melts with numerous advantages over traditional particle-based simulations. For systems involving two components (i.e., A and B), the field-based Hamiltonian, , depends on a composition field, , that controls the segregation of the unlike components and a pressure field, , that enforces incompressibility. This review introduces researchers to a promising variant of FTS, in which fluctuates while tracks its mean-field value. The method is described in detail for melts of AB diblock copolymer, covering its theoretical foundation through to its numerical implementation. We then illustrate its application for neat AB diblock copolymer melts, as well as ternary blends of AB diblock copolymer with its A- and B-type parent homopolymers. The review concludes by discussing the future outlook. To help researchers adopt the method, open-source code is provided that can be run on either central processing units (CPUs) or graphics processing units (GPUs).

Preparation and enhanced electrical breakdown strength of PVDF-TrFE-CTFE/PVDF-HFP film composites

Poly(vinylidenefluoride-trifluoroethylenechlorotrifuoroethylene), PVDF-TrFE-CTFE composite films with addition poly(vinylidene fluoride-co-hexafluoropropylene), PVDF-HFP at different copolymer loading was prepared by using the tape casting solution method. Electrical breakdown strength (Eb) was measured by the dielectric breakdown test system and fitting the Eb by the Weibull model. The experimental results illustrated that the breakdown probability, P(E) of the neat terpolymer and copolymer film was 316 V/μm and 495 V/μm, respectively. In addition, the breakdown probability of composite films between terpolymer and copolymer is higher than the neat PVDF-TrFE-CTFE film, in which the value of Eb is almost double when compared with terpolymer film. We will discuss on their crystallinity, material homogeneity and crystalline size to provide the method to improve the electrical breakdown strength with addition copolymer for energy storage applications.

Dispersion at Single Unit TiO2 Nanoparticles Reduced Tg, Induced Chain Disentanglement and Reduced Tensile Modulus in Waterborne Acrylic Coatings

AbstractSpatially distributed TiO2 nanoparticles induced an order of magnitude decrease of glass transition temperature, Tg, and chain disentanglement in waterborne acrylic coatings. Acrylic/TiO2 coatings are synthesized in situ by batch emulsion polymerization. The copolymer is based on butyl acrylate (BA), methyl methacrylate (MMA), and acrylic acid (AA) with composition 56:42:2 mol%, and nano‐TiO2 (ca. 12 nm) is incorporated up to 3 wt% content. Transmission electron microscopy (TEM) showed that TiO2 is dispersed at nearly single unit throughout the acrylic matrix. The nanoparticle reduced Tg and broadened the temperature range of the glass transition, δTg. The considerable increase of δTg suggests gradients of dynamics. Shear rheometry demonstrated that TiO2 induced chain disentanglement, the rubbery modulus Ge decreased two orders of magnitude with only 1 wt% TiO2 content thus increasing the packing length p (and the reptation tube diameter as dt = kp, k > 1). Consequently, the tensile Young's modulus E decreased an order of magnitude, relative to the neat copolymer. The reduction of Tg, the slowdown of macromolecular dynamics, the chain disentanglement and the increase of dt suggests dynamics modification due to intercalation of the entangled web by the TiO2 nanoparticles, and these results may be ascribed to a nanoconfinement effect.

The impact of graphene nanofiller loading on the morphology and rheology behaviour of highly rigid polyurethane copolymer

This work attempts to study the effects of the addition of graphene nanoplatelets (xGNP) on the rheology properties of new version of polyurethane copolymer with 1,5 pentane diol as chain extender , containing a high amount of hard blocks. Two- step polymerisation was employed to synthesise this kind of polymer. The thermal and electrical conductivity of this copolymer was also investigated. Meanwhile, the rheology response has been analysed by measuring the viscosity It was found that the viscosity increases by 68% and 2 × 105% at loadings of 0.5 wt.% and 15 wt.% of xGNP, respectively, compared with that of neat polyurethane copolymer. This means that the melt viscoelastic behaviour of highly rigid polyurethane copolymer (HRPUC) is influenced by the presence of xGNP contents, transforming the behaviour of nanocomposite from liquid-like to solid-like. This result was attributed to the network formation and interaction between hard segments of the HRPUC structure and xGNP due to strong shear thinning behaviour. In addition, the thermal conductivity of HRPUC increases to 0.97 W m−1.k (410%), electricity conductivity rose to 102 s m−1 (1000%). SEM morphology images showed overall dispersion of xGNP in the HRPUC, implying a reduction in the interspacing of flakes with increasing xGNP concentration. Further investigation into HRPUC morphology and its nanocomposites was conducted using the TEM method, illustrating that the xGNP stacking resulted from poor ability to disperse at greater loadings of xGNP.

Comonomer Effect on the Thermal, Morphological and Mechanical Properties of Poly(ethylene-co-octene)/Poly(ethylene-co-vinyl acetate) Blends

The blends of ethylene-octene copolymers with octene content of 15 and 3 wt % and ethylene-vinyl acetate copolymer were studied by thermogravimetric analysis, differential scanning calorimetry, atomic force microscopy, and tensile experiments. Thermal behavior reveals that the addition of ethylene-octene copolymer improves the thermal stability of ethylene-vinyl acetate copolymer. Two single crystallization temperatures were detected. The surface morphology shows thin and elongated crystallites of neat ethylene-octene copolymer containing 3 wt % of octene and a bulky, random morphology for both the neat ethylene-octene copolymer containing 15 wt % of octane and ethylene-vinyl acetate copolymer, where a perfect mixture of aforementioned structures shows for 50/50 blend, with the immiscible domains of both ethylene-octene and ethylene-vinyl acetate copolymers. Additionally, the surface roughness of 50/50 blends is in between of the neat copolymers. All the experimental data confirms the immiscible nature of the blends. The mechanical properties of the binary blends were found to be between the values of the corresponding neat components.

Facile fabrication of graphene oxide/poly(styrene-co-methyl methacrylate) nanocomposite with high toughness and thermal stability

Graphene and related nanomaterial-based polymer composites have shown the potential to resolve the long-standing conflict between strength and toughness, the two vital mutually exclusive mechanical properties. The uniform dispersion of the nanofillers in polymer matrices to attain strong matrix-filler interfacial bonding, which is essential for effective load transfer between the polymer matrix and fillers, is the least investigated aspect and a major challenge in composite engineering. Copolymeric materials can be exploited to enhance the distribution of nanofillers. Herein the optimization of monomer ratios of the poly (styrene-co-methyl methacrylate) copolymer and a facile method to fabricate graphene oxide (GO) reinforced nanocomposites using in situ bulk copolymerization are reported. The ultimate tensile strength, failure strain, and storage modulus of the injection molded copolymer were increased by 14.6, 15, and 43%, respectively, by adding only 0.1 wt.% GO. Also, the thermogravimetric analysis revealed that the thermal stability of the nanocomposite is much better than the neat copolymer. Crack arresting mechanism and dispersion state of GO sheets in the copolymer matrix were also investigated using scanning and transmission electron microscopes. Thus, this paper provides a methodology for uniform dispersion of GO in copolymeric materials to attain high toughness and thermal stability.

Effect of Molecular Weight and Layer Thickness on the Dielectric Breakdown Strength of Neat and Homopolymer Swollen Lamellar Block Copolymer Films.

Designing next-generation lightweight pulsed power devices hinges on understanding the factors influencing the energy storage performance of dielectric materials. Polymer dielectric films have a quadratic dependence of energy storage on the voltage breakdown strength, and strategies to enhance the breakdown strength are expected to yield a path toward high energy storage densities. Highly stratified lamellar block copolymer (L-BCP) films of model polystyrene-b-polymethylmethacrylate (PS-b-PMMA) exhibited as much as ~50% enhancement in breakdown voltage ( ) (225% increase in stored energy density, ) compared to unordered as-cast L-BCP films. Such an energy density using amorphous polymer is on par with industry-standard semicrystalline biaxially oriented polypropylene (BOPP) and as such a notable development in the field. This work develops a deeper understanding of the molecular mechanisms of enhancement in L-BCP films, relating directly to molecular weight ( ), with interpretation to effects of chain-end density and distribution, interface formation, layer thickness, and their relative contributions. As-cast disordered L-BCP films show decreasing with decreasing similar to homopolymer studies because of the increase of homogeneously distributed chain ends in the film. increases significantly in parallel ordered L-BCP films because of the combination of interface formation and spatial isolation of the chain ends into segregated zones. We further confirm the role of chain ends in the breakdown process blending a low L-BCP with matched homopolymers to attain the same layer spacing as neat L-BCP of higher . shows a significant decrease at low homopolymer fractions because of increased net chain-end density within swollen ordered L-BCP domains in wet-brush regime, followed by increased because of layer thickness increase via segregated "interphase layer" formation by excess homopolymers. Notably, of homopolymer swollen L-BCPs is always lower than that of neat L-BCPs of the same domain spacing because of overall adverse chain-end contribution from homopolymers. These findings provide important selection rules for L-BCPs for designing next-generation flexible electronics with high energy density solid-state BCP film capacitors.