Copolymer Materials Research Articles

Influence of Carbon Black (CB) on Mechanical Behaviour and Microscopic Analysis of Poly-propylene (PP)/ Acrylonitrile-butadiene- styrene (ABS) Nanocomposites

Composite materials allow designing materials that may combination of mechanical properties similar to those high load bearing materials. For advance mechanical properties of material polypropylene (PP) as a polymer, acrylonitrile-butadiene styrene (ABS) as rubber phase copolymer and filler material as carbon black (CB) are used to prepare blending of PP/ABS and formation of nanocomposites. Nanocomposite is prepared using twin screw extruder via injection molding. For characterization of polymer nanocomposites, microscopic analysis and mechanical properties are studied. For microscopic analysis to understand the morphology, the scanning electron microscopy (SEM) is used. Further, for mechanical behaviour, tensile test and impact test are carried out. As carbon black has comparatively unique structure and properties became an important group of filler material which offered improvement mechanical properties. The existing polymer blend is modified with the nano filler material; which exhibits improved morphological and mechanical properties having cost efficient application. These mechanical and morphological results depicts PP/ABS (80/20) blends in presence of CB improves the results. It is found that 2.5 wt % of CB gives better tensile properties and 5wt % CB showing better improvement in Impact strength.

Continuum models for directed self-assembly

The computational description of directed self-assembly (DSA) of copolymer materials requires the prediction of large-scale structure formation of copolymer materials guided by chemical or topographical patterns. Continuum models provide the highest level of coarse-graining describing the system only by the local composition and allowing for a fast optimization of thermodynamic quantities.

Thermo-reversible self-healing in a fluorous crosslinked copolymer

Self-healing in a fluorous copolymer material enhances its safety index and extends its working lifetime.

Fabrication of Ellipsoidal Mesostructures in Block Copolymers via a Step-Shear Deformation

Ellipsoids have attracted abiding attention because of their shape-dependent, anisotropic properties. In some applications, e.g., photonic crystals, both positional and orientational order of the ellipsoidal packing are required. We propose a versatile, facile, and efficient strategy to fabricate positionally and orientationally ordered crystals of soft ellipsoids in block copolymers via a step-shear deformation. Starting from the thermodynamically stable, equilibrium spherical mesophase of the copolymer material, the step-shear deformation provides an instantaneous, anisotropic stimulus to deform the spherical domains into ellipsoids and simultaneously stretches the macromolecular conformations. Subsequently, at fixed strain, the molecular stress relaxes to an equilibrium where the shape and orientation of the obtained ellipsoids are dictated by the packing frustration. Since the residual molecular stress is minuscule, the lattice relaxation via slippage in the absence of external stress is protracted, i...

Effect of Counterions on the Self-Assembly of Polystyrene-Polyphosphonium Block Copolymers.

The ability to manipulate block copolymers on the nanoscale has led to many scientific and technological advances. These include nanoscale ordered bulk and thin films and also solution phase components; these are promising materials for making smaller ordered electronics, selective membranes, and also biomedical applications. The ability to manipulate block copolymer material architectures on such small scales has risen from thorough investigations into the properties that affect the architectures. Polyelectrolytes are an important class of polymers that are used to make amphiphilic block copolymers. In this context the authors synthesized polystyrene-b-polyphosphonium block copolymers with different anions coordinated to the polyphosphonium block in order to study the effect of the anion on the aqueous self-assembly of the polymers. The anions play an important role in the solubility of the monomeric materials which results in differences in the self-assembly observed through dynamic light scattering and transmission electron microscopy.

The effect of asymmetry of the coil block on self-assembly in ABC coil-rod-coil triblock copolymers

Using the self-consistent field approach, the effect of asymmetry of the coil block on the microphase separation is focused in ABC coil-rod-coil triblock copolymers. For different fractions of the rod block $f_{\text B}$, some stable structures are observed, i.e., lamellae, cylinders, gyroid, and core-shell hexagonal lattice, and the phase diagrams are constructed. The calculated results show that the effect of the coil block fraction $f_{\text A}$ is dependent on $f_{\text B}$. When $f_{\text B}=0.2$, the effect of asymmetry of the coil block is similar to that of the ABC flexible triblock copolymers; When $f_{\text B}=0.4$, the self-assembly of ABC coil-rod-coil triblock copolymers behaves like rod-coil diblock copolymers under some condition. When $f_{\text B}$ continues to increase, the effect of asymmetry of the coil block reduces. For $f_{\text B}=0.4$, under the symmetrical and rather asymmetrical conditions, an increase in the interaction parameter between different components leads to different transitions between cylinders and lamellae. The results indicate some remarkable effect of the chain architecture on self-assembly, and can provide the guidance for the design and synthesis of copolymer materials.

Dual stimuli-responsive Fe3O4 graft poly(acrylic acid)-block-poly(2-methacryloyloxyethyl ferrocenecarboxylate) copolymer micromicelles: surface RAFT synthesis, self-assembly and drug release applications

BackgroundStimuli-responsive polymer materials are a new kind of intelligent materials based on the concept of bionics, which exhibits more significant changes in physicochemical properties upon triggered by tiny environment stimuli, hence providing a good carrier platform for antitumor drug delivery.ResultsDual stimuli-responsive Fe3O4 graft poly(acrylic acid)-block-poly(2-methacryloyloxyethyl ferrocenecarboxylate) block copolymers (Fe3O4-g-PAA-b-PMAEFC) were engineered and synthesized through a two-step sequential reversible addition-fragmentation chain transfer polymerization route. The characterization was performed by FTIR, 1H NMR, SEC, XRD and TGA techniques. The self-assembly behavior in aqueous solution upon triggered by pH, magnetic and redox stimuli was investigated via zeta potentials, vibration sample magnetometer, cyclic voltammetry, fluorescent spectrometry, dynamic light scattering, XPS, TEM and SEM measurements. The experimental results indicated that the Fe3O4-g-PAA-b-PMAEFC copolymer materials could spontaneously assemble into hybrid magnetic copolymer micromicelles with core–shell structure, and exhibited superparamagnetism, redox and pH stimuli-responsive features. The hybrid copolymer micromicelles were stable and nontoxic, and could entrap hydrophobic anticancer drug, which was in turn swiftly and effectively delivered from the drug-loaded micromicelles at special microenvironments such as acidic pH and high reactive oxygen species.ConclusionThis class of stimuli-responsive copolymer materials is expected to find wide applications in medical science and biology, etc., especially in drug delivery system.

In vitro and in vivo degradation behavior of poly(trimethylene carbonate-co-d,l-lactic acid) copolymer

We present P(TMC-co-DLLA) copolymer with the molar ratio of TMC: DLLA = 15: 85 was used to systematic study of in vivo and in vitro degradation behaviors. Dense homogeneous copolymer specimens were prepared by compression molding method. The in vitro and in vivo degradation were, respectively, performed at simulative body condition and implanted into rat’s subcutaneous condition. Investigations were followed via physicochemical and histological analysis such as SEM, GPC, DSC, FTIR and H&E stain. The results demonstrate that copolymeric material can degrade in phosphate buffer solution (PBS) and in rat’s body, and the in vivo degradation rate is faster. Obvious decline of molecule weight and mass loss has been observed, which led to the attenuation of mechanical strength. Furthermore, apart from the hydrolysis, macrophagocytes took part in the phagocytosis in vivo, indicating that degradation rate could be regulated by the combinational mechanism. It is concluded that P(TMC-co-DLLA) copolymer is a promising candidate for tissue repair.

Depolarized Scattering from Block Copolymer Grains Using Circularly Polarized Light

The grain structure of ordered block copolymer materials affects their viscoelastic, adhesive, optical, and electrical properties. Depolarized light scattering has proven to be an important method for characterizing this grain structure. In this paper, we use both theory and experiments to demonstrate the relationship between grain structure and depolarized light scattering from ordered block copolymer samples performed with crossed circular polarizers. We model the sample assuming it comprises randomly oriented ellipsoidal grains with optic axes coincident with the ellipsoid axes. We show that the scattering pattern obtained using circularly polarized (CP) light is azimuthally symmetric, in contrast to that obtained using linearly polarized (LP) light which exhibits 4-fold angular modulation. The integrated scattered power in the CP case is twice as large as that in the LP case. By simultaneously fitting CP and LP light scattering data, we obtain robust measures of parameters that characterize grain stru...

New method of single liquid-phase reactor synthesis of high-impact polypropylene: Structure, morphology, and impact properties of copolymers

High-impact polypropylene (hiPP) copolymer is a very important material in the industry because of its various applications. It is obtained in an industrial process involving two consecutive reactions either in the same or different phases. Unlike industrial processes that yield materials with a fixed amount of ethylene without the possibility of modifying the operation variables, we are presenting a new method to synthesize hiPP materials on a laboratory scale using two sequential steps in only one reactor. This approach permits the study of the influence of variables such as H2 addition, reaction time, and composition during the second step on the formation of propylene-ethylene copolymer materials with different properties. In the first step, the polypropylene matrix is synthesized in a liquid phase with or without addition of H2, and, in the second step, the elastomeric phase is also obtained in a liquid phase.The influence of the addition of hydrogen and ethylene and other operation conditions on the polypropylene matrix and the elastomeric phase distribution was studied and correlated to the mechanical and thermal properties of the material. Obtained materials were characterized by analytical temperature rising elution fractionation (TREF), calorimetric methods (DSC), 13C nuclear magnetic resonance (13C NMR), gel permeation chromatography (GPC), melt flow index (MFI), and scanning electron microscopy (SEM).The hydrogen addition remarkably enhanced the propylene polymerization while causing a significant decline in the ethylene polymerization rate. Based on these results, it seems that hydrogen has a complex effect on the catalyst behavior beyond its role as chain transfer agent. Furthermore, the presence of hydrogen in the polymerization caused a significant isotactic polypropylene (iPP) matrix molecular weight decay, which induced a modification of the viscosity ratio between the matrix and the rubbery phase produced in the second step. This yielded ethylene-propylene rubber (EPR) domains with higher average sizes and affected the phases’ morphology, resulting in a remarkable copolymer impact strength decline.The addition of ethylene to the second step in the absence of hydrogen affords an ethylene-propylene copolymer with high resistance to impact, which ranks it as a hiPP copolymer. Fractionation of this sample and the analysis of the obtained fractions provided knowledge about the microstructure of the copolymer and proved adequate distribution of the elastomeric phase into the iPP matrix.

Synthesis and characterization of poly(siloxane–ether–urethane) copolymers

Poly(siloxane–ether–urethane) (PSEU) copolymer materials were successfully synthesized from 4,4-diphenylmethane diisocyanate (MDI), 2,2-dimethylol propionic acid (DMPA) chain extender, and poly(siloxane–ether) copolymer (PSE) soft segments formed by hydrosilation of hydride-terminated polydimethylsiloxane (PDMS) and polyalkyl glycol allyl epoxyl ethers (PAGAEEs). The morphology, structure, and surface wettability of PSEU copolymer materials were characterized by FT-IR, XPS, TG, SEM, GPC, and contact angle measurements. It was demonstrated that the introduction of hard (urethane) segments can improve the thermal stability of PSEU materials. Moreover, due to the existence of strong polar groups originating from MDI segment, PSEU copolymer materials was superhydrophilic with water contact angle of 2.1°, which was possibly useful for surfactants and coatings applications.

Laccase-mediated synthesis of lignin-core hyperbranched copolymers.

Lignin, one of the major chemical constituents of woody biomass, is the second most abundant biopolymer found in nature. The pulp and paper industry has long produced lignin on the scale of millions of tons annually as a by-product of the pulping process, and the dawn of cellulosic ethanol production has further contributed to this amount. Historically, lignin has been perceived as a waste material and burned as a fuel for the pulping process. However, recent research has been geared toward developing cost-effective technologies to convert lignin into valuable commodities. Attributing to the polyphenolic structure of lignin, enzymatic modification of its surface using laccases (benzenediol:oxygen oxidoreductases, EC 1.10.3.2) has demonstrated to be highly successful. The current study aims at developing lignin-core hyperbranched copolymers via the laccase-assisted copolymerization of kraft lignin with methylhydroquinone and a trithiol. Based on the physical properties of the resulting material, it is likely that crosslinking reactions have taken place during the drying process to produce a copolymeric network rather than discrete hyperbranched copolymers, with NMR data providing evidence of covalent bonding between monomers. Preliminary thermal analysis data reveals that the copolymeric material possesses a moderate glass transition temperature and exhibits good thermostability, thus may have potential application as a lignin-based thermoplastic. Scanning electron microscopy images confirm the smooth, glossy surface of the material and that it is densely packed. The presented results are a sustainable, ecofriendly, economic method to create an exciting novel biomaterial from a renewable feedstock while further enhancing lignin valorization.

Non-destructive and wireless monitoring of biodegradable polymers

A method for monitoring changes in biodegradable polymers during hydrolysis is proposed. This wireless and non-destructive method is based on inductively coupled passive resonance sensors embedded in the polymer shell. In this study, we prepared specimens using two poly(lactide-co-glycolide) copolymers possessing different degradation profiles. The copolymer embedded sensors were immersed in buffer solution and their resonance features were compared with periodically performed conventional polymer characterization methods. A clear difference was noticed in the wirelessly measured signals between the two tested copolymer materials. Also the reference methods showed clear differences between the degradation profiles of the copolymers. The wirelessly measured signals are likely to correlate to the structural changes in the materials during the hydrolysis. In the future, this technique could be used in the laboratory to provide easy-to-access in situ information about the polymers. Even the state of biodegradable polymer implants could be wirelessly monitored.

Synthesis and Characterization of Acrylic-Based Photopolymer as a Candidate for Denture Base Material

Denture base is a denture part that rests on the soft tissue covering the jawbone and becomes an anchor of a denture. The material that commonly used for this purpose is poly (methyl methacrylate). However, it lacks in mechanical properties due to high water absorption. The aim of this research was to improve the physical and mechanical properties of poly (methyl methacrylate) by making a copolymer with styrene via photopolymerization process. In this method was used the addition of styrene monomer at 10, 20, 30, 40, and 50 wt% into the acrylic resin to form copolymer materials via photopolymerization process. The amount of 1.5 wt% Irgacure 784’s photoinitiator was added as a photoinitiator. The results showed that the addition of 40% by weight of styrene copolymer is the best performance compare to the addition styrene of 10, 20, 30, and 50%. The samples with an addition styrene of 40 wt% showed excellent properties such as high water absorption value of 2.405 μg/mm3, the solubility of 0.434 μg/mm3, the flexural strength of 69.336 MPa, a flexural modulus of 1.236 GPa, and a hardness value of 82.583 HD. Poly (methyl methacrylate-co-styrene) copolymer with the addition of styrene 40 wt% has the closest value to the requirements for a denture base material.

A monolithic hydro/organo macro copolymer actuator synthesized via interfacial copolymerization

Synthetic polymer actuators have attracted increasing attention for their potential applications in artificial muscles, soft robotics and sensors. The majority of previous efforts have focused on smart hydrogels with bilayer structures that can change their shape in response to environmental stimuli, such as temperature, light and certain chemicals. However, the practical application of hydrogels is limited because of their low modulus and weak mechanical strength. Here we synthesized a robust monolithic actuator of a macro-scale hydro/organo binary cooperative Janus copolymer film. The process involves direct, one-step interfacial polymerization of immiscible hydrophilic and hydrophobic vinyl monomer solutions, and the resultant product exhibited binary cooperative shape transformation to multiple external stimuli. The Janus copolymer film can work in both aqueous solutions and organic solvents, with bidirectional and site-specific bending arising from cooperative asymmetric swelling/shrinking of the hydrogel and organogel networks. In addition, the as-prepared Janus copolymer film can act as a sensor element for solvent leakage detection. This binary cooperative strategy is applicable to most immiscible monomer systems and provides a general approach to developing novel functional copolymer materials.

Spectroelectrochemical study on the copolymerization of o-aminophenol and aminoterephthalic acid

The electrochemical copolymerization of aminoterephthalic acid (ATA) and o-aminophenol (OAP) was carried out on platinum electrodes in acidic medium. The obtained material, poly(ATA-co-OAP), can be deposited by cyclic scanning of the potential in a wide potential range and shows significant electroactivity. However, it was observed that a copolymer with less overoxidation defects is obtained at inversion potentials where only OAP monomer (and not ATA monomer) is oxidized. The successful incorporation of unoxidized ATA monomers to the growing copolymer chain was confirmed by in situ FTIR spectroscopy and XPS, which suggested a monomer ratio close to 1:2 (ATA:POAP) within the obtained copolymer material. The redox switching of poly(ATA-co-OAP) in acidic medium involves reversible benzenoid-quinoid and phenoxazine-phenoxazone conversions but carboxylic groups do not participate actively on these transformations.

Electrochemical Characteristics of Advanced Sulfur-Based Cathode Material for Lithium-Sulfur Batteries

The demands for high-energy density and low cost advanced batteries, which can replace currently used lithium-ion batteries, are increasing for their possible applications to electric vehicles and energy storage systems. Lithium-sulfur (Li-S) batteries are one of the most attractive candidates for next-generation batteries due to high theoretical capacity of sulfur of 1672 mAhg-1 and earth-abundance and low cost of sulfur. However, the commercialization of Li-S batteries is being hindered by several issues such as the insulating nature and structural instability of sulfur, polysulfides shuttle and electrode-electrolyte interfacial instability, and as a result, limited cycle life and performance. Recently, a new class of sulfur copolymer materials is appealing as cathode active materials for Li-S batteries, which can exhibit improved performance compared to elemental sulfur.1-2There is however little report on a basic understanding of electrochemical characteristics of sulfur copolymer cathode materials. In this presentation, we discuss the material’s electrochemical characteristics and the critical factors affecting cycling performance of lithium cells. Acknowledgements: This work was supported under the framework of international cooperation program managed by National Research Foundation of Korea (2015K2A5A3000068) and German Academic Exchange Service (57141898).

Development and validation of a physical model to investigate the biomechanics of infant head impact

Head injury in childhood is the single most common cause of death or permanent disability from injury. However, despite its frequency and significance, there is little understanding of the response of a child’s head to injurious loading. This is a significant limitation when making early diagnoses, informing clinical and/or forensic management or injury prevention strategies. With respect to impact vulnerability, current understanding is predominantly based on a few post-mortem-human-surrogate (PMHS) experiments. Researchers, out of experimental necessity, typically derive acceleration data, currently an established measure for head impact vulnerability, by calculation. Impact force is divided by the head mass, to produce a “global approximation”, a single-generalised head response acceleration value. A need exists for a new experimental methodology, which can provide specific regional or localised response data. A surrogate infant head, was created from high resolution computer tomography scans with properties closely matched to tissue response data and validated against PMHS head impact acceleration data. The skull was 3D-printed from co-polymer materials. The brain, represented as a lumped mass, comprised of an injected gelatin/water mix. High-Speed Digital-Image-Correlation optically measured linear and angular velocities and accelerations, strains and strain rates. The “global approximation” was challenged by comparison with regional and local acceleration data. During impacts, perpendicular (at 90°) to a surface, regional and local accelerations were up to three times greater than the concomitant “global” accelerations. Differential acceleration patterns were very sensitive to impact location. Suture and fontanelle regions demonstrated ten times more strain (103%/s) than bone, resulting in skull deformations similar in magnitude to those observed during child birth, but at much higher rates. Surprisingly, perpendicular impacts produced significantly greater rotational velocities and accelerations, which are closer to current published injury thresholds than expected, seemingly as a result of deformational changes to the complex skull geometry. The methodology has proven a significant new step in characterising and understanding infant head injury mechanics.

Is the use of hemostatic matrix (Floseal) and alkylene oxide copolymer (Ostene) safe in spinal laminectomies? Peridural fibrosis assessment

ObjectiveFailed Back Syndrome (FBS) is unacceptable relief of pain or recurrence of symptoms in patients after spinal surgery, such as laminectomy. One possible cause of FBS is peridural fibrosis (PF). PF is the overproduction of scar tissue adjacent to the dura mater. Bleeding can cause PF after laminectomy. Ostene is an alkylene oxide copolymer material used to stop bleeding from bony surfaces. Floseal is a gelatin thrombin matrix sealant used to assist fibrin formation and to promote coagulation. MethodsTotal of 32 female Sprague–Dawley rats were evenly allotted to 4 experimental groups: laminectomy only, laminectomy + Ostene (Baxter International, Inc., Deerfield, IL, USA), laminectomy + Floseal (Baxter International, Inc., Deerfield, IL, USA), and laminectomy + Adcon-L (aap Implantate AG, Berlin, Germany). After performing total laminectomy, agents were placed over dura mater. Spinal column of test subjects was harvested 6 weeks after laminectomy. Histopathological examination of samples was based on Masson's trichrome and hematoxylin and eosin staining. PF observed in the groups was graded using system previously described by He et al. Statistically significant p value was defined as p < 0.005. ResultsPresent study revealed that Adcon-L, Ostene, and Floseal groups had reduced PF compared with laminectomy only group (p = 0.001). Comparison of Ostene and Floseal groups with Adcon-L group yielded no significant difference. ConclusionReoperation as result of FBS has greater risk and often has poor outcome; surgeons must take precautions to avoid FBS, such as careful selection of appropriate patient and operation technique. Ostene and Floseal may be applied and left in the operation field safely during laminectomy to reduce occurrence of PF after procedure.

Polymeric Materials Based on Acrylates and Modified Lignosulphonates

The effect of the enzymatic treatment of technical-grade lignosulphonates with laccase on the kinetics of synthesis and on the properties of copolymeric materials based on methacrylic acid was investigated.