Showing papers by "Christoph Weder published in 2014"

Comparison of the properties of cellulose nanocrystals and cellulose nanofibrils isolated from bacteria, tunicate, and wood processed using acid, enzymatic, mechanical, and oxidative methods

Abstract: This work describes the measurement and comparison of several important properties of native cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs), such as crystallinity, morphology, aspect ratio, and surface chemistry. Measurement of the fundamental properties of seven different CNCs/CNFs, from raw material sources (bacterial, tunicate, and wood) using typical hydrolysis conditions (acid, enzymatic, mechanical, and 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation), was accomplished using a variety of measurement methods. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and 13C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectroscopy were used to conclude that CNCs, which are rodlike in appearance, have a higher crystallinity than CNFs, which are fibrillar in appearance. CNC aspect ratio distributions were measured and ranged from 148 ± 147 for tunicate-CNCs to 23 ± 12 for wood-CNCs. Hydrophobic interactions, measured usin...

Mechanically-compliant intracortical implants reduce the neuroinflammatory response

Abstract: Objective. The mechanisms underlying intracortical microelectrode encapsulation and failure are not well understood. A leading hypothesis implicates the role of the mechanical mismatch between rigid implant materials and the much softer brain tissue. Previous work has established the benefits of compliant materials on reducing early neuroinflammatory events. However, recent studies established late onset of a disease-like neurodegenerative state. Approach. In this study, we implanted mechanically-adaptive materials, which are initially rigid but become compliant after implantation, to investigate the long-term chronic neuroinflammatory response to compliant intracortical microelectrodes. Main results. Three days after implantation, during the acute healing phase of the response, the tissue response to the compliant implants was statistically similar to that of chemically matched stiff implants with much higher rigidity. However, at two, eight, and sixteen weeks post-implantation in the rat cortex, the compliant implants demonstrated a significantly reduced neuroinflammatory response when compared to stiff reference materials. Chronically implanted compliant materials also exhibited a more stable blood-brain barrier than the stiff reference materials. Significance. Overall, the data show strikingly that mechanically-compliant intracortical implants can reduce the neuroinflammatory response in comparison to stiffer systems.

Mechanochemistry with metallosupramolecular polymers.

Abstract: The transduction of mechanical force into useful chemical reactions is an emerging design approach to impart soft materials with new functions. Here, we report that mechanochemical transductions can be achieved in metallosupramolecular polymers. We show that both reversible and irreversible reactions are possible and useful to create mechanically responsive materials that display new functions. The metallopolymer studied was a cross-linked network assembled from a europium salt and a telechelic poly(ethylene-co-butylene) with 2,6-bis(1′-methylbenzimidazolyl)pyridine (Mebip) ligands at the termini. The Eu3+ complexes serve both as mechanically responsive binding motifs and as built-in optical probes that can monitor the extent of (dis)assembly due to their characteristic photoluminescent properties. Indeed, dose-dependent and reversible metal–ligand dissociation occurs upon exposure to ultrasound in solution. The absence of ultrasound-induced dissociation of a low-molecular weight model complex and in-dept...

Light-Induced Bonding and Debonding with Supramolecular Adhesives

Abstract: Light-responsive supramolecular polymers were applied as reversible adhesives that permit bonding and debonding on demand features. A telechelic poly(ethylene-co-butylene) (PEB) was functionalized with either self-complementary hydrogen-bonding ureidopyrimidinone (UPy) motifs (UPy-PEB-UPy) or 2,6-bis(1′-methylbenzimidazolyl)-pyridine (Mebip) ligands (Mebip-PEB-Mebip), which can coordinate to metal ions (Zn(NTf2)2) and form a metallosupramolecular polymer with the sum formula [Znx(Mebip-PEB-Mebip)](NTf2)2x, with x ≈ 1. In the latter case, light-heat conversion is facilitated by the ultraviolet (UV) light-absorbing metal-ligand motifs, while in the case of UPy-PEB-UPy a UV absorber was added for this purpose. Single lap joints were prepared by sandwiching films of the supramolecular polymers of a thickness of 80–100 μm between two glass, quartz, or stainless steel substrates and bonded by exposure to either UV light (320–390 nm, 900 mW/cm2) or heat (80 or 200 °C for UPy-PEB-UPy and the metallopolymer, respe...

Water-Responsive Mechanically Adaptive Nanocomposites Based on Styrene–Butadiene Rubber and Cellulose Nanocrystals—Processing Matters

Abstract: Biomimetic, stimuli-responsive polymer nanocomposites based on a hydrophobic styrene–butadiene rubber (SBR) matrix and rigid, rod-like cellulose nanocrystals (CNCs) isolated from cotton were prepared by three different approaches, and their properties were studied and related to the composition, processing history, and exposure to water as a stimulus. The first processing approach involved mixing an aqueous SBR latex with aqueous CNC dispersions, and films were subsequently formed by solution-casting. The second method utilized the first protocol, but films were additionally compression-molded. The third method involved the formation of a CNC organogel via a solvent exchange with acetone, followed by infusing this gel, in which the CNCs form a percolating network with solutions of SBR in tetrahydrofuran. The thermomechanical properties of the materials were established by dynamic mechanical thermal analysis (DMTA). In the dry state, all nanocomposites show much higher tensile storage moduli, E′, than the ...

Biosensors Based on Porous Cellulose Nanocrystal–Poly(vinyl Alcohol) Scaffolds

Abstract: Cellulose nanocrystals (CNCs), which offer a high aspect ratio, large specific surface area, and large number of reactive surface groups, are well suited for the facile immobilization of high density biological probes. We here report functional high surface area scaffolds based on cellulose nanocrystals (CNCs) and poly(vinyl alcohol) (PVA) and demonstrate that this platform is useful for fluorescence-based sensing schemes. Porous CNC/PVA nanocomposite films with a thickness of 25-70 nm were deposited on glass substrates by dip-coating with an aqueous mixture of the CNCs and PVA, and the porous nanostructure was fixated by heat treatment. In a subsequent step, a portion of the scaffold's hydroxyl surface groups was reacted with 2-(acryloxy)ethyl (3-isocyanato-4-methylphenyl)carbamate to permit the immobilization of thiolated fluorescein-substituted lysine, which was used as a first sensing motif, via nucleophile-based thiol-ene Michael addition. The resulting sensor films exhibit a nearly instantaneous and pronounced change of their fluorescence emission intensity in response to changes in pH. The approach was further extended to the detection of protease activity by immobilizing a Forster-type resonance energy transfer chromophore pair via a labile peptide sequence to the scaffold. This sensing scheme is based on the degradation of the protein linker in the presence of appropriate enzymes, which separate the chromophores and causes a turn-on of the originally quenched fluorescence. Using a standard benchtop spectrometer to monitor the increase in fluorescence intensity, trypsin was detected at a concentration of 250 μg/mL, i.e., in a concentration that is typical for abnormal proteolytic activity in wound fluids.

Reinforcement of Optically Healable Supramolecular Polymers with Cellulose Nanocrystals

Abstract: We report the preparation and characterization of light-healable nanocomposites based on cellulose nanocrystals (CNCs) and a metallosupramolecular polymer (MSP) assembled from a telechelic poly(ethylene-co-butylene) that was end-functionalized with 2,6-bis(1′-methylbenzimidazolyl) pyridine (Mebip) ligands and Zn(NTf2)2. The polymer absorbs incident ultraviolet (UV) radiation and converts it into heat, which causes dissociation of the metal–ligand motifs. This process liquefies the material, and small defects are readily filled. When the UV light is switched off, the MSP reassembles and the original properties are restored. The introduction of CNCs into the MSP matrix leads to a significant increase of the stiffness and strength, from 52 and 1.7 MPa for the neat polymer to 135 and 5.6 MPa upon introduction of 10% w/w CNCs. The Zn2+ ions bind to the CNCs which means the metal:ligand ratio of the MSP must be adjusted accordingly. In nanocomposites thus made, deliberately introduced defects can be efficiently...

Isolation of cellulose nanocrystals from pseudostems of banana plants

Abstract: On account of their excellent mechanical properties, cellulose nanocrystals (CNCs) are attracting significant interest as a naturally sourced, renewable and inexpensive component of a broad range of nanomaterials. CNCs can be extracted from virtually any natural cellulosic material, but characteristic properties such as maximum aspect ratio, crystal structure, and crystallinity vary considerably between sources. In this work, the isolation of CNCs from the pseudostems of banana plants was explored. The dried stems from the species musa sapientum linn were first cleaned by Soxhlet extraction, alkali treatment and bleaching and subsequently hydrolyzed to CNCs using sulfuric acid. The hydrolysis time was systematically varied, with the objective to maximize the length (L = 375 ± 100 nm) and aspect ratio (A = 28) of the resulting CNCs. The surface charge density of the CNCs thus isolated was 168 mmol kg−1, the predominant crystal structure was that of cellulose I, and the crystallinity was 74%. In order to elucidate the reinforcing capability of the new CNCs, nanocomposites with an ethylene oxide–epichlorohydrin copolymer were prepared and their mechanical properties were investigated by dynamic mechanical analysis (DMA). A comparison with reference nanocomposites made with CNCs isolated from cotton shows that the new CNCs display a higher reinforcing capability.

An in vitro testing strategy towards mimicking the inhalation of high aspect ratio nanoparticles

Abstract: The challenge remains to reliably mimic human exposure to high aspect ratio nanoparticles (HARN) via inhalation. Sophisticated, multi-cellular in vitro models are a particular advantageous solution to this issue, especially when considering the need to provide realistic and efficient alternatives to invasive animal experimentation for HARN hazard assessment. By incorporating a systematic test-bed of material characterisation techniques, a specific air-liquid cell exposure system with real-time monitoring of the cell-delivered HARN dose in addition to key biochemical endpoints, here we demonstrate a successful approach towards investigation of the hazard of HARN aerosols in vitro. Cellulose nanocrystals (CNCs) derived from cotton and tunicates, with differing aspect ratios (~9 and ~80), were employed as model HARN samples. Specifically, well-dispersed and characterised CNC suspensions were aerosolised using an “Air Liquid Interface Cell Exposure System” (ALICE) at realistic, cell-delivered concentrations ranging from 0.14 to 1.57 μg/cm2. The biological impact (cytotoxicity, oxidative stress levels and pro-inflammatory effects) of each HARN sample was then assessed using a 3D multi-cellular in vitro model of the human epithelial airway barrier at the air liquid interface (ALI) 24 hours post-exposure. Additionally, the testing strategy was validated using both crystalline quartz (DQ12) as a positive particulate control in the ALICE system and long fibre amosite asbestos (LFA) to confirm the susceptibility of the in vitro model to a fibrous insult. A rapid (≤4 min), controlled nebulisation of CNC suspensions enabled a dose-controlled and spatially homogeneous CNC deposition onto cells cultured under ALI conditions. Real-time monitoring of the cell-delivered CNC dose with a quartz crystal microbalance was accomplished. Independent of CNC aspect ratio, no significant cytotoxicity (p > 0.05), induction of oxidative stress, or (pro)-inflammatory responses were observed up to the highest concentration of 1.57 μg/cm2. Both DQ12 and LFA elicited a significant (p < 0.05) pro-inflammatory response at sub-lethal concentrations in vitro. In summary, whilst the present study highlights the benign nature of CNCs, it is the advanced technological and mechanistic approach presented that allows for a state of the art testing strategy to realistically and efficiently determine the in vitro hazard concerning inhalation exposure of HARN.

Low-power photon upconversion in organic glasses

Abstract: Green-to-blue upconverting molecular glasses consisting of a metal octaethylporphyrin (MOEP, M = Pd, Pt) sensitizer and 9-(4-hydroxymethylphenyl)-10-phenyl anthracene (DPA-CH2OH) as an emitter are reported. In these materials, incident light is transformed into higher-energy radiation by way of triplet–triplet annihilation upconversion. The DPA-CH2OH–MOEP mixtures form transparent glasses when cooled from the thermally stable melt, even at rates as low as 1 °C min−1. In a systematic study, the PdOEP concentration was varied from 0.025 to 6.6 mol%. The normalized upconverted light intensity decreased with increasing sensitizer concentration by almost three orders of magnitude, as a result of sensitizer aggregation. The upconverted light intensity also decreased upon deliberate crystallization of the upconverting materials. Beyond demonstrating the first embodiment of upconversion in molecular glasses, the results highlight the importance of morphology control in solid-state upconverting materials.

Reinforcing Poly(ethylene) with Cellulose Nanocrystals

Abstract: The fabrication of nanocomposites of low-density polyethylene (LDPE), one of the world’s most widely used polymers, and cellulose nanocrystals (CNCs), which represent the world’s most abundant bio-based nanofi ller, is reported. While the hydrophobic polymer and the hydrophilic fi ller seem to be intrinsically incompatible, this article shows that it is possible to kinetically trap homogeneous nanocomposites by a templating approach. An organogel is fi rst prepared by exchanging the solvent of an aqueous CNC dispersion against acetone, impregnating the resulting organogel, in which the CNCs form a percolating network with a hot LDPE solution in toluene, and compression-molding the resulting materials into thin fi lms. At a fi ller content of 7.6% v/v, the resulting materials display a three- to four-fold increase in strength and stiffness compared with the neat LDPE, which confi rms that the CNC network could be largely maintained. It is also possible to reprocess these nanocomposites and dilute them with LDPE using conventional melt-processing techniques.

Influence of mechanical treatments on the properties of cellulose nanofibers isolated from microcrystalline cellulose

Abstract: The possibility of preparing cellulose whiskers-like materials by mechanical treatment of commercially available microcrystalline cellulose (MCC) was explored. High shear homogenization, grinding with a supermass colloider, and hammer-milling were the processes selected to disintegrate the MCC, which yielded F-MCC, G-MCC and H-MCC, respectively. Processing aqueous dispersions with high solid content allowed for the production of cellulose particles with greatly reduced dimensions. Morphological characterization revealed that homogenization and grinding reduced the particle size more effectively than hammer-milling, although the disintegration was incomplete in all cases. The reinforcing potential of the materials was evaluated against commercially available whiskers by using the various particles as fillers to mechanically reinforce hydroxypropylcellulose. Nanocomposite films containing 5, 10, or 20 wt.% of the filler were prepared and the mechanical properties were characterized. The results show that H-MCCs are just slightly better than the original MCC, whereas F-MCC and G-MCC performed similar to whiskers at 10 wt.% loading, despite the presence of a fraction of micrometer-sized particles. It is therefore reasonable to envision the use of the more easily produced F-MCC and G-MCC as replacement of cellulose whiskers in some applications.

Mechanical and shape‐memory properties of poly(mannitol sebacate)/cellulose nanocrystal nanocomposites

Abstract: "This is the peer reviewed version of the following article: Sonseca, A, Camarero‐Espinosa, S, Peponi, L, Weder, C, Foster, E J, Kenny, J M, & Gimenez, E (2014) Mechanical and shape‐memory properties of poly (mannitol sebacate)/cellulose nanocrystal nanocomposites Journal of Polymer Science Part A: Polymer Chemistry, 52(21), 3123-3133, which has been published in final form at https://doiorg/101002/pola27367 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving"

Thermoplastic shape-memory polyurethanes based on natural oils

Abstract: A new family of segmented thermoplastic polyurethanes with thermally activated shape-memory properties was synthesized and characterized. Polyols derived from castor oil with different molecular weights but similar chemical structures and a corn-sugar-based chain extender (propanediol) were used as starting materials in order to maximize the content of carbon from renewable resources in the new materials. The composition was systematically varied to establish a structure–property map and identify compositions with desirable shape-memory properties. The thermal characterization of the new polyurethanes revealed a microphase separated structure, where both the soft (by convention the high molecular weight diol) and the hard phases were highly crystalline. Cyclic thermo-mechanical tensile tests showed that these polymers are excellent candidates for use as thermally activated shape-memory polymers, in which the crystalline soft segments promote high shape fixity values (close to 100%) and the hard segment crystallites ensure high shape recovery values (80–100%, depending on the hard segment content). The high proportion of components from renewable resources used in the polyurethane formulation leads to the synthesis of bio-based polyurethanes with shape-memory properties.

Functional Iron Oxide Nanoparticles as Reversible Crosslinks for Magnetically Addressable Shape‐Memory Polymers

Abstract: hape-memory nanocomposites are reported, in which super-paramagnetic iron oxide nanoparticles (SPIONs) serve as both the crosslinks of a macromolecular network and inductive heating elements. SPIONs capped with polymerizable groups are synthesized in a one-step reaction by oxidation of Fe(acac)3 in the presence of 5-norbornene-2-carboxylic acid. Between 0.1 and 20 wt% of the resulting Fe3O4 nanoparticles are subsequently copolymerized with norbornene by ring-opening metathesis polymerization (ROMP) using Grubbs' 1st-generation catalyst. This affords a series of crosslinked polynorbornenes in which the Fe3O4 nanoparticles are very well dispersed. The reversible nature of the non-covalent binding of the polymerizable ligands to the Fe3O4 nanoparticles allows melting and processing of these materials at elevated temperature, with the shape-memory properties are only retained for high Fe3O4 content.

Supramolecular Polymers with Orthogonal Functionality

Abstract: Supramolecular polymers with orthogonal interactions are of broad interest, and reports on such materials with multifunctional stimuli-responsive behavior are rare. Polymer blends based on a poly(ethylene-co-butylene) core (PEB) terminated with either 2-ureido-4[1H]-pyrimidinone (UPy) hydrogen-bonding motifs (UPy-PEB-UPy) or 2,6-bis(1′-methylbenzimidazolyl)pyridine (Mebip) ligands coordinated to metal ions ([M(Mebip-PEB-Mebip)]2+ (M = Zn, Fe)) were prepared. The degree of orthogonality of the supramolecular polymer blends was explored by UV–vis spectroscopy, small-angle X-ray scattering, and dynamic mechanical thermal analysis (DMTA). Polymer blends of [Zn(Mebip-PEB-Mebip)](NTf2)2 and UPy-PEB-UPy resulted in a statistical mixture of noncovalent interactions, whereas blends with [Fe(Mebip-PEB-Mebip)](ClO4)2 and UPy-PEB-UPy assembled in an orthogonal fashion. Additionally, the DMTA showed two transitions for the disassembly of UPy (ca. 60 °C) and Fe2+-Mebip (ca. 180 °C) phases. The Fe2+-Mebip interactions w...

Isophthalic Acid–Pyridine H-Bonding: Simplicity in the Design of Mechanically Robust Phase-Segregated Supramolecular Polymers

Abstract: We report a new series of supramolecular polymeric networks based on the isophthalic acid–pyridine (IPA–Py) H-bonding motif. The IPA units were attached as end-groups to telechelic poly(ethylene-co-butylene) to create a tetrafunctional macromonomer, which was cross-linked by the addition of various bispyridines. Some of the supramolecular polymer networks thus made display surprisingly good mechanical characteristics. We show that their structure and properties are strongly influenced by the nature of the bispyridine motif and by the fact that some of the IPA–Py motifs aggregate into particularly well-defined hard phases.

Physiologically responsive, mechanically adaptive polymer optical fibers for optogenetics

Abstract: The capability to deliver light to specific locations within the brain using optogenetic tools has opened up new possibilities in the field of neural interfacing. In this context, optical fibers are commonly inserted into the brain to activate or mute neurons using photosensitive proteins. While chronic optogenetic stimulation studies are just beginning to emerge, knowledge gathered in connection with electrophysiological implants suggests that the mechanical mismatch of conventional optical fibers and the cortical tissue may be a significant contributor to neuroinflammatory response. Here, we present the design and fabrication of physiologically responsive, mechanically adaptive optical fibers made of poly(vinyl alcohol) (PVA) that may mitigate this problem. Produced by a one-step wet-spinning process, the fibers display a tensile storage modulus E′ of ∼7000 MPa in the dry state at 25°C and can thus readily be inserted into cortical tissue. Exposure to water causes a drastic reduction of E′ to ∼35 MPa on account of modest swelling with the water. The optical properties at 470 and 590 were comparable with losses of 0.7±0.04 dB/cm at 470 nm and 0.6±0.1 dB/cm at 590 nm in the dry state and 1.1±0.1 dB/cm at 470 nm and 0.9±0.3 dB/cm at 590 nm in the wet state. The dry end of a partially switched fiber with a length of 10 cm was coupled with a light-emitting diode with an output of 10.1 mW to deliver light with a power density of >500 mW/cm2 from the wet end, which is more than sufficient to stimulate neurons in vivo. Thus, even without a low-refractive index cladding, the physiologically responsive, mechanically adaptive optical fibers presented here appear to be a very useful new tool for future optogenetic studies.

Controlled fragrance release from galactose-based pro-fragrances

Abstract: The volatile nature of olfactory compounds has led to the development of pro-fragrances, which slowly release the active fragrance molecules upon cleavage of a chemical bond to a substrate. Based on the hypothesis that monosaccharide motifs could serve to effectively anchor pro-fragrances on cotton, which is an important requirement for use in laundry products, we investigated new galactose-based pro-fragrances. A retro 1,4-Michael-type reaction was employed as the release mechanism. Thus, δ-damascone was reacted in a 1,4-addition with mercaptoacetic acid, and the product was coupled with 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose. To explore the influence of the molecules' polarity on the deposition and release kinetics, both the isopropylidene-protected hydrophobic as well as the deprotected hydrophilic pro-fragrance were studied. The fragrance release was investigated in aqueous solution by 1H-NMR spectroscopy as a function of pH; the data show that both pro-fragrances are stable under acidic conditions, but release the δ-damascone under basic conditions. The release kinetics are well described by a first-order process, and observed to be much faster in the case of the isopropylidene-protected hydrophobic pro-fragrance. The fragrance release from washed and dried cotton tissue was investigated via dynamic headspace analysis followed by gas chromatography. The data show that the deposition from solution is much better for the hydrophobic pro-fragrance, that the δ-damascone is slowly released in both cases, and that the amount of δ-damascone that can be released is increased by over two orders of magnitude higher than in the case of tissue washed with the neat fragrance under identical conditions.

Synthesis of poly(sulfonate ester)s by ADMET polymerization

Abstract: Many hydrocarbon polymers containing heteroatom defects in the main chain have been investigated as degradable polyethylene-like materials, including aliphatic polyesters. Here, acyclic diene metathesis (ADMET) polymerization was used for the synthesis of aliphatic poly(sulfonate ester)s. The requisite sulfonate ester containing α,ω-diene monomers with varying numbers of methylene groups was synthesized, and their polymerization in the presence of ruthenium-N-heterocyclic (Ru-NHC) alkylidene catalysts was studied. A clear negative neighboring group effect (NNGE) was observed for shorter dienes, either inhibiting polymerization or resulting in low-molecular-weight oligomers. The effect was absent when undec-10-en-1-yl undec-10-ene-1-sulfonate was employed as the monomer, and its ADMET polymerization afforded polymers with appreciable number-average molecular weights of up to 37 000 g mol−1 and a dispersity Đ of 1.8. These polymers were hydrogenated to afford the desired polyethylene-like systems. The thermal and morphological properties of both saturated and unsaturated polymers were investigated. The incorporation of sulfonate ester groups in the polymer backbone offers an interesting alternative to other heteroatoms and helps further the understanding of the effects of these defects on the overall polymer properties.

Water-insoluble aerogels made from cellulose nanocrystals and poly(vinyl alcohol)

Abstract: Cellulose nanocrystal (CNC) aerogels are attractive low-density materials, although the brittleness and/or water dispersibility can limit the usefulness of these materials. The authors report here ...

Microscale characterization of a mechanically adaptive polymer nanocomposite with cotton-derived cellulose nanocrystals for implantable BioMEMS

Abstract: A mechanically adaptive polymer nanocomposite for use as a structural material for microelectromechanical system (MEMS)-based penetrating implantable biosensors, particularly for the brain, is presented as a solution to the limited clinical implementation of such sensors. Micromechanical testing of MEMS-scale test structures was used to determine the Young's moduli of the polymer nanocomposite in both its dry rigid state (E = 2414 MPa) and its wet compliant state (E = 4.9 MPa), as well as the rate of mechanical switching upon immersion in an aqueous solution. The softening of the composite materials after implantation in the cortex of a Sprague-Dawley rat was studied by ex vivo environmentally controlled microtensile testing. A microfabrication process for producing metallized neural probes for recording of electrical signals was also developed. The results support the mechanically adaptive nanocomposite as a viable option for MEMS-based penetrating implantable biosensors.

Conducting Polymers, Solution- and Gel-processing of

Abstract: Conducting polymers, been a key research area, have found the attention of various researchers and scientists. Since polymers, alone, are not the conductors of electricity or even heat. So, huge amount of research progress has been seen in last decade in the field of the conducting polymer. Polymer has taken place of various conducting materials in various applications. Now a day’s polymers are major area of concern from the research point view. Not only the polymer engineering researcher, but also researcher from various other fields are putting efforts on polymer processing, making polymer processing a very bright field. Some researcher had worked on making a conducting polymer by synthesizing the polymers with various techniques. Where, some had used various doping techniques and making polymer electronically or ionically conducting. In this article various research works will be discussed with conductance of polymer with special attention. This article solely focuses on the conducting polymer and their gel processing by chemically processing it to prepare the final product by using the filament wire and then using it on the 3D printer machine. Hence, process shows the amalgamation of the chemical and the FDM route to process the chemically treated the solution of the Graphene-ABS blend in known quantities to impart the thermal and electrical properties into it. A case study has been discussed to support the view, in which firstly, graphite has been procure and Graphene has been extracted to obtain the blended Graphene-ABS solution and gel, that was processed to form the filament wire and part has been made on the FDM and very promising results has been obtained.

Preparation of Cellulose Nanocrystal/Polymer Nanocomposites via Sol-Gel Processes

Abstract: As a result of high specific surface area and energy, cellulose nanocrystals (CNCs) usually have a strong tendency for aggregation This makes it difficult to produce nanocomposites with polymers in which these filler particles are homogeneously dispersed and form percolating networks This chapter summarizes recent efforts to create such nanomaterials by applying sol-gel processes One particularly useful method, dubbed the "template approach", relies on the formation of a three-dimensional network through self-assembly of originally well-individualized nanofibers, and subsequently filling the template with a polymer of choice The template is made by first forming a homogeneous aqueous CNC dispersion, followed by gelation through solvent exchange with a water-miscible solvent The resulting CNC organogel is subsequently imbibed with a matrix polymer by immersion into a polymer solution The process is broadly applicable and has allowed for the fabrication of several CNC-based nanocomposites It is particularly useful for the fabrication of otherwise inaccessible nanocomposites of immiscible components, such as the polar CNCs and hydrophobic matrix polymers