The Experts below are selected from a list of 7428 Experts worldwide ranked by ideXlab platform
Chee Kai Chua - One of the best experts on this subject based on the ideXlab platform.
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layer by layer ultraviolet assisted extrusion based uae bioprinting of hydrogel constructs with high aspect ratio for soft tissue engineering applications
PLOS ONE, 2019Co-Authors: Pei Zhuang, Jia A, Chee Kai ChuaAbstract:One of the major challenges in the field of soft tissue engineering using bioprinting is fabricating complex tissue constructs with desired structure integrity and mechanical property. To accomplish such requirements, most of the reported works incorporated reinforcement materials such as poly(ϵ-caprolactone) (PCL) polymer within the 3D bioprinted constructs. Although this approach has made some progress in constructing soft tissue-engineered scaffolds, the mechanical compliance mismatch and long degradation period are not ideal for soft tissue engineering. Herein, we present a facile bioprinting strategy that combines the rapid extrusion-based bioprinting technique with an in-built ultraviolet (UV) Curing system to facilitate the layer-by-layer UV Curing of bioprinted photo-curable GelMA-based hydrogels to achieve soft yet stable cell-laden constructs with high aspect ratio for soft tissue engineering. GelMA is supplemented with a viscosity enhancer (gellan gum) to improve the bio-ink printability and shape fidelity while maintaining the biocompatibility before crosslinking via a layer-by-layer UV Curing process. This approach could eventually fabricate soft tissue constructs with high aspect ratio (length to diameter) of ≥ 5. The effects of UV source on printing resolution and cell viability were also studied. As a proof-of-concept, small building units (3D lattice and tubular constructs) with high aspect ratio are fabricated. Furthermore, we have also demonstrated the ability to perform multi-material printing of tissue constructs with high aspect ratio along both the longitudinal and transverse directions for potential applications in tissue engineering of soft tissues. This layer-by-layer ultraviolet assisted extrusion-based (UAE) Bioprinting may provide a novel strategy to develop soft tissue constructs with desirable structure integrity.
Tobias Robert - One of the best experts on this subject based on the ideXlab platform.
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straightforward synthetic protocol to bio basedunsaturated poly ester amide s from itaconic acidwith thixotropic behavior
Polymers, 2020Co-Authors: Lazaros Papadopoulos, Marcel Kluge, Dimitrios N Bikiaris, Tobias RobertAbstract:In the field of polymer chemistry, tremendous efforts have been made over the last decade to replace petrochemical monomers with building blocks from renewable resources. In this respect, itaconic acid has been used as an alternative to acrylic acid or maleic acid in unsaturated polyesters for thermal or UV-Curing applications. However, examples of poly(ester amide)s from itaconic acid are scarce. Under standard polycondensation reactions, the presence of free amines leads to aza-Michael addition reactions at the α,β-unsaturated double bond of the itaconic acid and isomerization reactions to mesaconic acid. Both reactions make the resulting materials useless as UV-Curing polymer resins. To avoid these undesired side reactions, we herein report the use of preformed, well-defined diols containing internal amide bonds. The resulting unsaturated poly(ester amide) resins were analyzed before and after UV-induced crosslinking. Viscosity measurements revealed a strong thixotropic behavior induced by the amide groups, which is usually not detected in structurally similar polyester resins.
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Optimized synthesis of highly reactive UV-curable hyperbranched polyester acrylates
Journal of Coatings Technology and Research, 2019Co-Authors: Sacha Pérocheau Arnaud, Payam Hashemi, Petra Mischnick, Tobias RobertAbstract:Highly reactive radical polyester acrylates are widely used as UV-Curing binder resins for printing inks, coatings, and materials for additive manufacturing. Especially for the latter, polyesters with low viscosities are of high interest, as they allow for UV-Curing materials with reduced amounts of reactive diluents to adjust the viscosity. One possibility to obtain polyester acrylates with low viscosities is the synthesis of hyperbranched structures, as the interactions of the polymer chains are reduced in comparison to their linear counterparts. In this study, an optimized synthetic protocol is described to obtain a set of highly branched polyester acrylates with a high degree of acrylation, without the use of activated reagents like anhydrides or acid chlorides that are usually employed to synthesize these products. Different cores and number of pseudo-generations of 2,2-bis(hydroxymethyl)propionic (bisMPA) are utilized to study the structure–property relationship of this class of polyesters. Comprehensive characterization of the synthesized resins and cured materials revealed high reactivities and good mechanical properties compared to similar materials reported in the literature. The design of the structure significantly influences the properties, allowing for the synthesis of specific resins with a wide range of potential applications.
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Bio-based polyester itaconates as binder resins for UV-Curing offset printing inks
Journal of Coatings Technology and Research, 2019Co-Authors: Tobias Robert, Steven Eschig, Toine Biemans, Frank ScheiflerAbstract:UV-Curing inks have several economic and environmental advantages compared with standard printing inks, such as high printing velocities, low VOC emissions and good adhesion to nonabsorbing substrates. However, there are also some drawbacks, such as residual monomers, pungent odor and allergic potential of monomers and prepolymers derived from acrylic acid. In addition, only few examples of UV-Curing inks derived from renewable resources are known. Herein, acrylate-free UV-Curing polyester itaconates with a renewable content up to 100% and their application as binder resins in UV-Curing offset ink formulations are presented. In order to obtain a high renewable content in the polyester resins, Zn(OAc)_2 had to be used as polycondensation catalyst, as standard Brønsted acid catalyst led to undesired side reactions. The resins obtained with this synthetic protocol were tested on their reactivity, which was slightly lower than a commercial polyester acrylate. Printing inks formulated from these polyester itaconates showed interesting properties despite the fact that no acrylic acid was incorporated in the resins.
Marco Sangermano - One of the best experts on this subject based on the ideXlab platform.
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cationic UV Curing technology and applications
Macromolecular Materials and Engineering, 2014Co-Authors: Marco Sangermano, Nicolo Razza, James V CrivelloAbstract:This paper reviews the field of cationic UV-Curing and reports recent progress made in understanding the fundamental chemistry and in technology applications. Radiation Curing technologies are expanding rapidly on an industrial scale and interest in cationic photopolymerizations has advanced rapidly. In particular, the cationic UV-Curing process presents additional benefits, including: the absence of air inhibition, a “dark-Curing” reaction, low levels of toxicity and irritation, and a lower volume shrinkage during photopolymerization. In this review, a large number of papers and patents are reviewed and critically discussed specifically with respect to the application of cationic UV-Curing technology in the field of coatings, composites, adhesives, and inks.
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UV Curing of organic inorganic hybrid coatings containing polyhedral oligomeric silsesquioxane blocks
Macromolecular Materials and Engineering, 2008Co-Authors: Ezio Amerio, Marco Sangermano, Giulio Malucelli, Giovanna Colucci, Massimo Messori, Rosa Taurino, Paola FabbriAbstract:Hybrid nanocomposite coatings were prepared by the UV-Curing technique with a methacrylic oligomer and multifunctional methacrylic polyhedral oligomeric silsesquioxane blocks (POSS®). The results obtained from the polyhedral compounds were compared with those of a disordered framework obtained by the condensation of a silica precursor (MEMO). The inorganic domains generated during synthesis created constraints in movement of polymer segments, which reflected in an increase in Tg of the hybrid nanocomposite coatings. The films were transparent. The random structure obtained by the condensation of the MEMO showed a stronger effect on T g than that observed by introducing POSS®. The effect of inorganic domains reflected on thermal stability, surface hardness and mechanical properties of the hybrid nano-composite coatings.
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UV-cured interpenetrating acrylic-epoxy polymer networks: Preparation and characterization
Macromolecular Materials and Engineering, 2008Co-Authors: Marco Sangermano, William Carbonaro, Giulio Malucelli, Aldo PriolaAbstract:Acrylic-epoxy interpenetrating polymer networks were prepared by means of UV Curing. The photopolymerization process was investigated via real-time FTIR spectroscopy. The hybrid, cured films showed a broad tan d peak in DMTA demonstrating the high damping properties of the hybrid, cured formulations. A decrease on shrinkage was achieved by increasing the epoxy-resin content in the photocurable formu lation, with a consequent increase in adhesion properties.
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Synthesis of an epoxy functionalized spiroorthocarbonate used as low shrinkage additive in cationic UV Curing of an epoxy resin
European Polymer Journal, 2008Co-Authors: Marco Sangermano, Ricardo Acosta Ortiz, Bertha A. Puente Urbina, Lydia Berlanga Duarte, Aida E. Garcia Valdez, Ramiro Guerrero SantosAbstract:The synthesis of an epoxy functionalized spiroorthocarbonate (SOC) is reported. The obtained monomer has been used a slow shrinkable additive in cationic UV Curing of a commercially available dicycloepoxy resin. A polymer network flexibilization was evidenced by increasing the SOC content in the photocurable formulation. It has been demonstrated that SOC acts as shrinkage reduction additive reaching expansion on volume after polymerization in the presence of 10 wt% of the functionalized spiroorthocarbonate.
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UV Curing and characterization of polymer clay nanocoatings by dispersion of acrylate funtionalized organoclays
Progress in Organic Coatings, 2008Co-Authors: Marco Sangermano, Giulio Malucelli, N Lak, A Samakande, R D SandersonAbstract:Nanocoatings have been prepared by dispersing two different surfmer-modified nanosilicate platelets into acrylic resins. UV-induced polymerization gave rise to highly crosslinked networks. The UV-Curing kinetics was not affected by the presence of the nanofiller. XRD and TEM investigations showed that, during the dispersion of the organoclays in the UV-curable resins, the surfmer treatment promotes an important lamellae intercalation which is maintained after UV Curing. An increase of the Tg values and of the thermal stability was achieved in the samples containing 5 wt% of modified clay.
Pei Zhuang - One of the best experts on this subject based on the ideXlab platform.
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layer by layer ultraviolet assisted extrusion based uae bioprinting of hydrogel constructs with high aspect ratio for soft tissue engineering applications
PLOS ONE, 2019Co-Authors: Pei Zhuang, Jia A, Chee Kai ChuaAbstract:One of the major challenges in the field of soft tissue engineering using bioprinting is fabricating complex tissue constructs with desired structure integrity and mechanical property. To accomplish such requirements, most of the reported works incorporated reinforcement materials such as poly(ϵ-caprolactone) (PCL) polymer within the 3D bioprinted constructs. Although this approach has made some progress in constructing soft tissue-engineered scaffolds, the mechanical compliance mismatch and long degradation period are not ideal for soft tissue engineering. Herein, we present a facile bioprinting strategy that combines the rapid extrusion-based bioprinting technique with an in-built ultraviolet (UV) Curing system to facilitate the layer-by-layer UV Curing of bioprinted photo-curable GelMA-based hydrogels to achieve soft yet stable cell-laden constructs with high aspect ratio for soft tissue engineering. GelMA is supplemented with a viscosity enhancer (gellan gum) to improve the bio-ink printability and shape fidelity while maintaining the biocompatibility before crosslinking via a layer-by-layer UV Curing process. This approach could eventually fabricate soft tissue constructs with high aspect ratio (length to diameter) of ≥ 5. The effects of UV source on printing resolution and cell viability were also studied. As a proof-of-concept, small building units (3D lattice and tubular constructs) with high aspect ratio are fabricated. Furthermore, we have also demonstrated the ability to perform multi-material printing of tissue constructs with high aspect ratio along both the longitudinal and transverse directions for potential applications in tissue engineering of soft tissues. This layer-by-layer ultraviolet assisted extrusion-based (UAE) Bioprinting may provide a novel strategy to develop soft tissue constructs with desirable structure integrity.
Marcel Kluge - One of the best experts on this subject based on the ideXlab platform.
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straightforward synthetic protocol to bio basedunsaturated poly ester amide s from itaconic acidwith thixotropic behavior
Polymers, 2020Co-Authors: Lazaros Papadopoulos, Marcel Kluge, Dimitrios N Bikiaris, Tobias RobertAbstract:In the field of polymer chemistry, tremendous efforts have been made over the last decade to replace petrochemical monomers with building blocks from renewable resources. In this respect, itaconic acid has been used as an alternative to acrylic acid or maleic acid in unsaturated polyesters for thermal or UV-Curing applications. However, examples of poly(ester amide)s from itaconic acid are scarce. Under standard polycondensation reactions, the presence of free amines leads to aza-Michael addition reactions at the α,β-unsaturated double bond of the itaconic acid and isomerization reactions to mesaconic acid. Both reactions make the resulting materials useless as UV-Curing polymer resins. To avoid these undesired side reactions, we herein report the use of preformed, well-defined diols containing internal amide bonds. The resulting unsaturated poly(ester amide) resins were analyzed before and after UV-induced crosslinking. Viscosity measurements revealed a strong thixotropic behavior induced by the amide groups, which is usually not detected in structurally similar polyester resins.
