Solid-state Plastic Research Articles

Reversible TAD Chemistry as a Convenient Tool for the Design of (Re)processable PCL-Based Shape-Memory Materials.

A chemically cross-linked but remarkably (re)processable shape-memory polymer (SMP) is designed by cross-linking poly(ε-caprolactone) (PCL) stars via the efficient triazolinedione click chemistry, based on the very fast and reversible Alder-ene reaction of 1,2,4-triazoline-3,5-dione (TAD) with indole compounds. Typically, a six-arm star-shaped PCL functionalized by indole moieties at the chain ends is melt-blended with a bisfunctional TAD, directly resulting in a cross-linked PCL-based SMP without the need of post-curing treatment. As demonstrated by the stress relaxation measurement, the labile character of the TAD-indole adducts under stress allows for the solid-state plasticity reprocessing of the permanent shape at will by compression molding of the raw cross-linked material, while keeping excellent shape-memory properties.

Exploring Dynamic Equilibrium of Diels–Alder Reaction for Solid State Plasticity in Remoldable Shape Memory Polymer Network

The reversible and click nature of Diels-Alder (DA) reactions has made them ideal candidates to design materials with nonconventional properties. Most commonly, the reversibility of DA is utilized for designing thermosets that can be liquefied for reprocessing and self-healing, yet the dynamic equilibrium nature has been largely neglected. In this work, shape memory polymers (SMP) containing DA moieties in the networks were synthesized. In addition to its remoldability at the liquid state at sufficiently high temperatures (above 110 °C), we show uniquely and surprisingly that such a network can undergo plastic deformation in its solid state at intermediate temperatures (60-100 °C) by taking advantage of its dynamic equilibrium for network topological rearrangement. The liquid state remoldability and solid state plasticity represent two distinct yet complementary mechanisms to manipulate the permanent shape of an SMP, leading to unprecedented versatility that can benefit a variety of applications in the future.

ChemInform Abstract: New Insights into Ordering and Dynamics in Organic Ionic Plastic Crystal Electrolytes

AbstractReview: 39 refs.

New insights into ordering and dynamics in organic ionic plastic crystal electrolytes

Solid state phases of organic salts, whose chemistry is closely related to that of ionic liquids, often show interesting phase behavior and dynamics resulting in solid-state conductors that have potential application in electrochemical devices such as solid state batteries. The mechanism of conduction in these solid-state plastic crystal phases is still not entirely understood. We have recently shown using molecular dynamics (MD) simulations that the introduction of defects, such as vacancies, leads to heterogeneous dynamics in the OIPC arising from amorphous and mobile domains in these materials. Advanced magnetic resonance imaging (MRI) analysis indicates that these domains can exhibit distinct orientations, leading to anisotropic ionic conductivity with enhanced values in a particular direction. This paper will review this new understanding, drawing links between the molecular and macroscopic-level information provided by these two techniques.

222Rn Distribution Pattern in Dwellings of Copper Mineralized Area of East Singhbhum Region, Jharkhand, India

Seasonal variation of 222 Rn levels was studied in the dwellings in U-Cu mineralized area of East Singhbhum, Jharkhand, India. Copper mining and processing industry is operational in this area for the last hundred years. Copper minerals of this region contain a significant fraction of uranium and the decay products. To measure the activity concentration of 222 Rn, LR-115, type-II solid-state nuclear plastic track detector was used in an indigenously developed radon dosimeter cup. A higher value of 222 Rn activity concentration was recorded in some of the dwellings in the mineralized zone. The results at different locations adjoining the facilities show that the 222 Rn activity concentration varies to a great extent following an approximate log-normal distribution. The observed range varied from 29.1 and 314.6 Bq m -3 with an overall geometric mean of 72.3 Bq m -3 and geometric standard deviation 1.67. Further, in poorly ventilated dwellings 222 Rn levels were higher compared to the properly ventilated houses. The peak activity concentration of 222 Rn was recorded during winter (December-February). Appreciably lower activity concentration of radon was observed during summer and rainy seasons. The results reflect that the levels are higher than the global average indoor activity concentration of 40 Bq m -3 (UNSCEAR-1993) for 222 Rn, but are comparable to the studies carried out in similar types of geological formations.

Asteroidal processes recorded by polyphase deformation in a harzburgitic diogenite NWA 5480

Expectations regarding structural deformation of asteroidal meteorites have typically revolved around impact-induced shock metamorphism or the gravity-driven axial compression of cumulates at the base of magma chambers. Recent structural analyses, however, of several olivine-rich diogenites (harzburgites) reveal solid-state plastic deformation not attributable to either scenario and propose dynamic mantle movements in the parent body, assumed to be Vesta. In this study we examine the microstructures of pyroxene and olivine in the olivine-rich diogenite NWA 5480. Coarse-grained, poikilitic texture, exsolution lamellae and plastic deformation attest to polyphase deformation and a re-heating event, followed by relatively slow cooling. Observations suggest that impact events alone are insufficient to generate and sustain the thermal and deformation conditions required to achieve all of the observed features. The proposed dynamic mantle movements in the Vestan interior may offer a means of heat transport to the system to provide a thermal environment inducive to slow cooling as well as generate the incremental stress fields required for the polyphase plastic deformation observed in the olivine.

Terahertz Conductivity and Hindered Molecular Reorientation of Lithium Salt Doped Succinonitrile in its Plastic Crystal Phase

The terahertz complex permittivity of the molecular plastic crystal succinonitrile (SN) or 1,2 dicyanoethane (N≡C−CH2−CH2−C≡N), doped with the lithium salts LiBF4, LiPF6, LiTFSI, and LiClO4 to form solid-state plastic crystal electrolytes, is measured and compared using temperature-dependent terahertz time-domain spectroscopy (THz-TDS). In contrast to the trends at low frequency, SN’s terahertz conductivity decreases slightly when doped with Li-salts. This indicates that at high frequencies the dielectric response is not dominated by ionic charge transport, but instead by relaxational processes which are hindered by the presence of the ionic dopants. Assuming a single Cole-Cole distribution of Debye-like processes dominates the measured spectra, the average relaxation times τ and Arrhenius activation energies Ea are extracted for each electrolyte and are shown to increase significantly relative to undoped SN’s τ and Ea, indicating the relaxational processes are hindered by the presence of the ionic dopants.

EXPERIMENTAL STUDY ON ULTRASONIC WELDING OF ALUMINUM SHEET TO COPPER SHEET

Ultrasonic welding is devoted to weld thin sheet me tals of similar or dissimilar couples of non-ferrou s alloys like copper, aluminum and magnesium without addition of filler material rin high quality weld; it can count on a lo w energy consumption and on a joining mechanism based on a solid state plastic de formation which creates a very homogeneous metallic structure between the base materials, free from pores & characterized by refin ed grains and confined inclusions’ Ultrasonic metal welding can join also painted or covered sheet metals. Thin sheets of aluminium have been joined to thin copper sheets by means of Ultrasonic spot Welding. Results are particularly effective in order to eval uate the relevance of various phenomena influencing the lap joint technique obtained on thin aluminium and copper by the application of Ultrasonic Metal Spot Welding (USMSW). The Present study considers the experiments carried out on the aluminum and copper sheets joints at room temperature. The aim is to e valuate the relevance of various factors influencing the lap joining techniq ue, allowing a deep understanding of the phenomena and the possibility to keep them under control; in the meantime, the feasibilit y and relevance of the proposed hybrid joining tech nology is discussed..

Liquid scintillation counting of solid-state plastic pellets to distinguish bio-based polyethylene

Bio-based polyethylene (bio-PE) is chemically identical to conventional fossil-based PE. The only method to differentiate them is radiocarbon (14C) analysis. The purpose of this study was to evaluate the potential of liquid scintillation counting (LSC) as a screening method. The pellets of bio-PE and fossil-PE were soaked in a scintillation cocktail, and measured by LSC. The counting rate of bio-PE increased as a function of time and then saturated (35 ± 1.7 cpm) in 30 h. This counting rate was much higher than that of fossil-PE (3.3 ± 0.5 cpm). Pre-soaking of PE in toluene (the solvent of the scintillation cocktail) enhanced the counting rate of bio-PE. Bio-PE with higher crystallinity showed a lower counting rate. These results suggest that the solvent of the scintillation cocktail permeated into the non-crystalline regions, inducing scintillation of bio-PE in the solid state. LSC is a potential high-throughput screening method to detect bio-PE.

Controlled Radical Polymerization and Quantification of Solid State Electrical Conductivities of Macromolecules Bearing Pendant Stable Radical Groups

Macromolecules with aliphatic backbones that bear pendant stable radical groups (i.e., radical polymers) have attracted much attention in applications where a supporting electrolyte is capable of aiding charge transport in solution; however, the utilization of these materials in solid state applications has been limited. Here, we synthesize a model radical polymer, poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PTMA), through a controlled reversible addition-fragmentation chain transfer (RAFT) mediated polymerization mechanism to generate well-defined and easily-tunable functional polymers. These completely amorphous, electronically-active polymers demonstrate relatively high glass transition temperatures (Tg ∼170 °C) and, because of the aliphatic nature of the backbone of the radical polymers, are almost completely transparent in the visible region of the electromagnetic spectrum. Additionally, we quantify the conductivity of PTMA (∼1×10(-6) S cm(-1)) and find it to be on par with pristine π-conjugated polymers such as poly(phenylene vinylenes) (PPVs) and poly(3-alkylthiophenes) (P3ATs). Furthermore, we demonstrate that the addition of small molecules bearing stable radical groups provides for more solid state charge hopping sites without altering the chemical nature of radical polymers; this, in turn, allows for an increase in the conductivity of PTMA relative to neat PTMA thin films while still retaining the same high degree of optical transparency and device stability. Because of the synthetic flexibility and easily-controlled doping mechanisms (that do not alter the PTMA chemistry), radical polymers present themselves as promising and tunable materials for transparent solid-state plastic electronic applications.

Solid-state plastic deformation in the dynamic interior of a differentiated asteroid

Diogenite meteorites are thought to represent mantle rocks that formed as cumulates in magma chambers on 4 Vesta or a similar differentiated asteroid. Microstructural analysis of olivine grains from a diogenite meteorite show that the preferred orientation of their crystal lattice was formed through plastic deformation, indicating dynamic, planet-like processes in its parent body.

Anatomy of 2.57 - 2.52 Ga granitoid plutons in the eastern Dharwar craton, southern India: Implications for magma chamber processes and crustal evolution

We present results of field studies for magmatic processes of 2.57-2.52 Ga calc-alkaline plutonic bodies from three corridors in the eastern Dharwar craton (EDC) corresponding to different crustal levels. At deeper levels plutons are bounded by thick zone of migmatites with numerous melt filled shear bands which often overprinted by incipient charnockite. On the other hand in the mid-to-upper crustal levels plutons show relatively sharp contacts and truncates the adjoining basement. The plutons are composite which comprises voluminous intrusive monzodiorite, quartz-monzonite and porphyritic monzogranite in the central part and minor anatectic granites or diatexite at periphery. Numerous xenoliths, Mafic Magmatic Enclaves (MME), disrupted trains of synplutonic mafic dykes are found in both intrusive and anatectic facies. The plutons show magmatic as well as solid-state plastic fabrics defined by magmatic flow banding and C-S fabrics respectively. Crustal scale shear zone network comprising early melt filled NE trending hot ductile dextral shear bands and slightly later colder NW trending sinistral shear bands defined by rotation of mafic boudins, phenocrysts and C-S fabrics. The internal architecture of plutons is attributed to the crustal scale magma chamber processes where voluminous intrusive magmas emplaced into the crust caused reworking of surrounding basement resulting in production of anatectic magmas. Crystallization of voluminous intrusive magmas in the deep crust probably caused development of fractures to mantle depth causing decompression melting of mantle and resultant mafic magmas penetrated the crystallizing host in magma Archaean magmatic accretion, reworking and cratonization. chambers. Field evidences together with published ages and Nd isotope data reveal a spatial link between late Archaean magmatic accretion, reworking and cratonization.

Initiation of left-lateral deformation along the Ailao Shan–Red River shear zone: new microstructural, textural, and geochronological constraints from the Diancang Shan metamorphic massif, SW Yunnan, China

The Diancang Shan metamorphic massif, the northwestern extension of the Ailao Shan Massif, is a typical metamorphic complex situated along the NW–SE-trending Ailao Shan–Red River shear zone. Diancang Shan granitic and amphibolitic mylonites collected from sheared high-grade metamorphic rocks were studied using petrographic and electron-backscatter diffraction techniques. Sensitive high-resolution ion microprobe U–Pb dating of zircon grains from the granitic mylonites constrains the timing of shearing. Macro- and microstructural and textural analysis reveals intense plastic deformation of feldspar, quartz, and amphibole under amphibolite-facies conditions, all consistently document left-lateral shearing. Porphyritic monzogranitic mylonite within the shear zone possesses evidence supporting a sequential, progressive process from crystallization during magma emplacement, through submagmatic flow to solid-state plastic deformation. We suggest that the early-kinematic pluton subsequently underwent strong left-lateral strike–slip shearing. The development of complex textures of quartz, feldspar, and amphibole from the granitic and amphibolitic mylonites apparently records successive variation of conditions attending coherent, solid-state high-temperature ductile deformation during regional left-lateral shearing. All magmatic zircons from the mylonitized porphyritic monzogranite give U–Pb ages of 30.95 ± 0.61 million years for the crystallization of the granite. This age provides the timing of onset of left-lateral shearing along the Ailao Shan–Red River shear zone in the Diancang Shan high-grade metamorphic massif.

Citric acid as a solid-state plasticizer for Eudragit RS PO

The use of solid-state plasticizers for the hot-melt extrusion of pharmaceutical dosage forms has been shown to be beneficial compared with liquid plasticizers. The purpose of this study was to determine the suitability of citric acid (CA) as a solid plasticizer for the preparation of Eudragit RS PO extended-release matrix systems by a melt extrusion technique. The influence of increasing levels of CA monohydrate (CA MH) or anhydrous CA in the powder blend on the extrusion process parameters (screw speed and motor load) was determined as a function of temperature. The solubility of CA MH in extruded tablets was studied by means of modulated differential scanning calorimetry (MDSC) and powder X-ray diffraction (PXRD). Films were cast from organic solutions to demonstrate the plasticizing effect of CA MH as a change in physico-mechanical properties (tensile strength, elastic modulus and elongation). The CA release from extruded tablets was studied over 12 h. The monohydrate form was found to distinctly facilitate the extrusion of Eudragit RS PO, whereas the addition of anhydrous CA to the polymer powder was less effective. This divergent behaviour in plasticization of Eudragit RS PO was attributed to the higher solubility of the monohydrate in the acrylic polymer. The plasticizing effect of the CA MH reached a plateau at 25% during hot-melt extrusion, which coincided with the solubility limit of the organic acid in the polymer as shown by MDSC and PXRD results. The CA MH increased the flexibility of Eudragit RS PO films, as demonstrated by a decrease in tensile strength and elastic modulus and an increase in elongation as a function of CA MH concentration. The dissolution of CA from the matrix tablets followed an extended-release profile, with CA MH exhibiting a faster dissolution rate than the anhydrous form. In conclusion, CA MH was found to be an effective plasticizer for Eudragit RS PO that facilitates the production of controlled-release matrix systems by hot-melt extrusion.

The manufacture and characterisation of hot-melt extruded enteric tablets

The aim of this highly novel study was to use hot-melt extrusion technology as an alternative process to enteric coating. In so doing, oral dosage forms displaying enteric properties may be produced in a continuous, rapid process, providing significant advantages over traditional pharmaceutical coating technology. Eudragit L100-55, an enteric polymer, was pre-plasticized with triethyl citrate (TEC) and citric acid and subsequently dry-mixed with 5-aminosalicylic acid, a model active pharmaceutical ingredient (API), and an optional gelling agent (PVP K30 or Carbopol 971P). Powder blends were hot-melt extruded as cylinders, cut into tablets and characterised using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and dissolution testing conducted in both pH 1.2 and pH 6.8 buffers. Increasing the concentration of TEC significantly lowered the glass transition temperature (Tg) of Eudragit L100-55 and reduced temperatures necessary for extrusion as well as the die pressure. Moreover, citric acid (17% w/w) was shown to act as a solid-state plasticizer. HME tablets showed excellent gastro-resistance, whereas milled extrudates compressed into tablets released more than 10% w/w of the API in acidic media. Drug release from HME tablets was dependent upon the concentration of TEC, the presence of citric acid, PVP K30, and Carbopol 971P in the matrix, and pH of the dissolution media. The inclusion of an optional gelling agent significantly reduced the erosion of the matrix and drug release rate at pH 6.8; however, the enteric properties of the matrix were lost due to the formation of channels within the tablet. Consequently this work is both timely and highly innovative and identifies for the first time a method of producing an enteric matrix tablet using a continuous hot-melt extrusion process.

Natural examples of olivine lattice preferred orientation patterns with a flow-normal a-axis maximum.

Tectonic plate motion is thought to cause solid-state plastic flow within the underlying upper mantle and accordingly lead to the development of a lattice preferred orientation of the constituent olivine crystals. The mechanical anisotropy that results from such preferred orientation typically produces a direction of maximum seismic wave velocity parallel to the plate motion direction. This has been explained by the existence of an olivine preferred orientation with an 'a-axis' maximum parallel to the induced mantle flow direction. In subduction zones, however, the olivine a axes have been inferred to be arranged roughly perpendicular to plate motion, which has usually been ascribed to localized complex mantle flow patterns. Recent experimental work suggests an alternative explanation: under conditions of high water activity, a 'B-type' olivine preferred orientation may form, with the a-axis maximum perpendicular to the flow direction. Natural examples of such B-type preferred orientation are, however, almost entirely unknown. Here we document widespread B-type olivine preferred orientation patterns from a subduction-type metamorphic belt in southwest Japan and show that these patterns developed in the presence of water. Our discovery implies that mantle flow above subduction zones may be much simpler than has generally been thought.

Influence of methylparaben as a solid-state plasticizer on the physicochemical properties of Eudragit® RS PO hot-melt extrudates

The purpose of this study was to investigate the properties of methylparaben as a solid-state plasticizer for Eudragit® RS PO during a hot-melt extrusion process. Extruded matrices containing different levels of methylparaben and Eudragit® RS PO, were prepared by feeding the powder blend through a hot melt extruder. The melt viscosity of the polymer blends was assessed by torque rheometry using a Brabender Plasticorder. The physicochemical properties of the extruded methylparaben-containing polymer matrix were characterized by differential scanning calorimetry and X-ray diffraction. Solid state nuclear magnetic resonance spectroscopy (NMR) was used to study the possible interaction between methylparaben and Eudragit® RS PO polymer. The results demonstrated that the glass transition temperature of the Eudragit® RS PO decreased with increasing levels of methylparaben in the extrudate, due to an increase in the chain mobility of Eudragit® RS PO. The crystallinity of methylparaben was absent following hot-melt processing. At increasing levels of methylparaben in the extrudates, a decrease in the melt viscosity was seen due to a plasticization of the polymer. Rheological properties of the extrudates containing methylparaben were compared with the extrudates containing conventional plasticizers. It was found that methylparaben was as effective as triethyl citrate (TEC) in reducing torque during the extrusion process. Solid state NMR spectra indicated a change in the chemical shift of Eudragit® RS PO plasticized with methylparaben, which could be ascribed to an interaction between the hydroxyl group of the methylparaben and the ester group of the Eudragit® RS PO polymer. The results of this study demonstrated that methylparaben could be used as a solid-state plasticizer for the Eudragit® RS PO polymer when a hot melt extrusion technique was employed in the preparation of sustained release tablets.

Solid-state plasticization of an acrylic polymer with chlorpheniramine maleate and triethyl citrate

The influence of in situ plasticization of chlorpheniramine maleate (CPM) on Eudragit® RS PO from hot-melt extruded matrix tablets, and from compressed granules prepared by thermal processing was investigated. CPM was studied as both a model drug substance and as a solid-state plasticizer for the acrylic polymer. Triethyl citrate (TEC) was incorporated into the polymer blend as a liquid plasticizer for the polymer. The influence of TEC and CPM concentration on the dissolution properties of CPM tablets was investigated. The glass transition temperature ( T g) of the samples was determined by modulated differential scanning calorimetry (MDSC). The morphologies of the granules formed by hot-melt extrusion and hot-melt granulation processes were investigated by scanning electron microscopy. The addition of 12% TEC to the polymer reduced the T g by 32.5 °C, while the reduction in the T g for the same level of CPM was 16.4 °C. The effect of TEC levels on drug release was dependent on the tablet preparation method. At high TEC levels, the release rate of CPM decreased in tablets prepared by direct compression and tablets made from compressed granules that had been prepared by high shear hot-melt granulation. However, the CPM release rate increased from hot-melt extruded tablets with increasing blends of plasticizer in the extruded tablets. An increase in the CPM content in the tablets resulted in an increase in the drug release rate. During high shear hot-melt granulation, the model drug adhered to the polymer to form a porous discontinuous structure. Following hot-melt extrusion, the drug was distributed at a molecular level in the continuous polymeric structure. The influence of both CPM and TEC levels on the drug release rate from these polymeric drug delivery systems was shown to be a function of whether the granules or tablets were formed by either hot-melt granulation or hot-melt extrusion, as well as the plasticization effects of both TEC and CPM on the acrylic polymer.

PLASTICIZER EFFECT ON THE GLASS TRANSITION TEMPERATURE OF BETA–LACTOGLOBULIN FILMS

The effect of plasticizer on betalactoglobulin (.Lg) film glass transition temperature (Tg) was investigated toelucidate the plasticization mechanism. The Tg of film containing polyethylene glycol 400 (PEG 400) as a plasticizer couldnot be observed because an icemelting peak occurred during heating. Films plasticized by propylene glycol (PG), glycerol(Gly), and PEG 200 possessed similar film Tg values, related to the plasticizer waterbinding properties. However, sorbitol(Sor) and sucrose (Suc) produced higher film Tg values due to their larger MW and solidstate plasticizer behavior. Lubricationof .Lg molecules by plasticizer domains external to the .Lg is suggested as a film plasticization mechanism because noshift in film Tg was observed with increasing plasticizer content. The size, shape, and physical state of plasticizer were thekey factors affecting film properties, consistent with previous results on mechanical and oxygen permeability (OP) properties.

Influence of ibuprofen as a solid-state plasticizer in eudragit® RS 30 D on the physicochemical properties of coated beads

The purpose of this study was to investigate the physicochemical properties of nonpareil beads coated with Eudragit® RS 30 D containing ibuprofen as a multifunctional agent. The influence of the concentration of ibuprofen in the film coating and the effect of the coating level on drug release from coated beads was determined in pH 7.2 phosphate buffer solution. The influence of storage time at 23°C and 60°C on the release of ibuprofen from coated beads was also investigated. The thermal properties of the films were determined using a differential scanning calorimeter. Scanning electron microscopy was employed to image the surface morphology of the coated beads. Infrared spectroscopy was used to study the interaction of Eudragit RS 30 D and ibuprofen. Results from the dissolution studies demonstrated that increasing the amount of ibuprofen in the polymeric film reduced the rate of drug release, mainly because of a more complete coalescence of the polymeric particles of the latex dispersion. The glass transition temperature (Tg) of Eudragit RS 30 D films decreased and the surface of the coated beads became smoother as the concentration of ibuprofen was increased. Hydrogen bonding between the polymer and ibuprofen was demonstrated by Fourier transform infrared spectroscopy. No significant differences were found in drug dissolution between the coated beads stored at 23°C for 12 months and those stored at 60°C for 12 hours. The results of this study demonstrated that the ibuprofen plasticized the Eudragit RS 30 D. Furthermore, the dissolution rate of ibuprofen can be controlled and changes in the drug release rate can be minimized by using the drug-induced plasticization technique with this polymer.