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Karpov SV, Iakunkov A, Chernyaev DA, Kurbatov VG, Malkov GV, Badamshina ER. A Theoretical Investigation of the Polyaddition of an AB 2+A 2+B 4 Monomer Mixture. Polymers (Basel) 2024; 16:426. [PMID: 38337315 DOI: 10.3390/polym16030426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 01/25/2024] [Accepted: 01/29/2024] [Indexed: 02/12/2024] Open
Abstract
Hyperbranched polymers (HBPs) are widely applied nowadays as functional materials for biomedicine needs, nonlinear optics, organic semiconductors, etc. One of the effective and promising ways to synthesize HBPs is a polyaddition of AB2+A2+B4 monomers that is generated in the A2+CB2, AA'+B3, A2+B'B2, and A2+C2+B3 systems or using other approaches. It is clear that all the foundational features of HBPs that are manufactured by a polyaddition reaction are defined by the component composition of the monomer mixture. For this reason, we have designed a structural kinetic model of AB2+A2+B4 monomer mixture polyaddition which makes it possible to predict the impact of the monomer mixture's composition on the molecular weight characteristics of hyperbranched polymers (number average (DPn) and weight average (DPw) degree of polymerization), as well as the degree of branching (DB) and gel point (pg). The suggested model also considers the possibility of a positive or negative substitution effect during polyaddition. The change in the macromolecule parameters of HBPs formed by polyaddition of AB2+A2+B4 monomers is described as an infinite system of kinetic equations. The solution for the equation system was found using the method of generating functions. The impact of both the component's composition and the substitution effect during the polyaddition of AB2+A2+B4 monomers on structural and molecular weight HBP characteristics was investigated. The suggested model is fairly versatile; it makes it possible to describe every possible case of polyaddition with various monomer combinations, such as A2+AB2, AB2+B4, AB2, or A2+B4. The influence of each monomer type on the main characteristics of hyperbranched polymers that are obtained by the polyaddition of AB2+A2+B4 monomers has been investigated. Based on the results obtained, an empirical formula was proposed to estimate the pg = pA during the polyaddition of an AB2+A2+B4 monomer mixture: pg = pA = (-0.53([B]0/[A]0)1/2 + 0.78)υAB2 + (1/3)1/2([B]0/[A]0)1/2, where (1/3)1/2([B]0/[A]0)1/2 is the Flory equation for the A2+B4 polyaddition, [A]0 and [B]0 are the A and B group concentration from A2 and B4, respectively, and υAB2 is the mole fraction of the AB2 monomer in the mixture. The equation obtained allows us to accurately predict the pg value, with an AB2 monomer content of up to 80%.
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Affiliation(s)
- Sergei V Karpov
- Department of Polymers and Composites, Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry of Russian Academy of Sciences, 1 Academician Semenov Avenue, Chernogolovka 142432, Russia
| | - Artem Iakunkov
- School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden
| | - Dmitry A Chernyaev
- Department of Polymers and Composites, Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry of Russian Academy of Sciences, 1 Academician Semenov Avenue, Chernogolovka 142432, Russia
| | - Vladimir G Kurbatov
- Department of Polymers and Composites, Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry of Russian Academy of Sciences, 1 Academician Semenov Avenue, Chernogolovka 142432, Russia
| | - Georgiy V Malkov
- Department of Polymers and Composites, Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry of Russian Academy of Sciences, 1 Academician Semenov Avenue, Chernogolovka 142432, Russia
| | - Elmira R Badamshina
- Department of Polymers and Composites, Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry of Russian Academy of Sciences, 1 Academician Semenov Avenue, Chernogolovka 142432, Russia
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Gazo Hanna E, Younes K, Amine S, Roufayel R. Exploring Gel-Point Identification in Epoxy Resin Using Rheology and Unsupervised Learning. Gels 2023; 9:828. [PMID: 37888401 PMCID: PMC10606702 DOI: 10.3390/gels9100828] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 10/03/2023] [Accepted: 10/17/2023] [Indexed: 10/28/2023] Open
Abstract
Any thermoset resin's processing properties and end-use performance are heavily influenced by the gel time. The complicated viscosity of resin as a function of temperature is investigated in this work, with a particular emphasis on identifying the gel point and comprehending polymerization. Rheology studies carried out using a plate-plate controlled stress rheometer under isothermal conditions were used to compare three experimental techniques for figuring out an epoxy resin's gel point. We also look at the basic modifications that take place during polymerization. We verify the reliability of the three strategies by including Principal Component Analysis (PCA), an unsupervised machine learning methodology. PCA assists in uncovering hidden connections between these methods and various affecting factors. PCA serves a dual role in our study, confirming method validity and identifying patterns. It sheds light on the intricate relationships between experimental techniques and material properties. This concise study expands our understanding of resin behavior and provides insights that are essential for optimizing resin-based processes in a variety of industrial applications.
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Affiliation(s)
- Eddie Gazo Hanna
- College of Engineering and Technology, American University of the Middle East, Egaila 54200, Kuwait; (K.Y.); (S.A.); (R.R.)
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Krieg D, Müller MT, Boldt R, Rennert M, Stommel M. Additive Free Crosslinking of Poly-3-hydroxybutyrate via Electron Beam Irradiation at Elevated Temperatures. Polymers (Basel) 2023; 15:4072. [PMID: 37896317 PMCID: PMC10610128 DOI: 10.3390/polym15204072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 10/05/2023] [Accepted: 10/09/2023] [Indexed: 10/29/2023] Open
Abstract
When applying electron or gamma irradiation to poly-3-hydroxybutyrate (P3HB), main chain scissions are the dominant material reactions. Though propositions have been made that crosslinking in the amorphous phase of P3HB occurs under irradiation, a conclusive method to achieve controlled additive free irradiation crosslinking has not been shown and no mechanism has been derived to the best of our knowledge. By applying irradiation in a molten state at 195 °C and doses above 200 kGy, we were able to initiate crosslink reactions and achieved gel formation of up to 16%. The gel dose Dgel was determined to be 200 kGy and a range of the G values, the number of scissions and crosslinks for 100 eV energy deposition, is given. Rheology measurements, as well as size exclusion chromatography (SEC), showed indications for branching at doses from 100 to 250 kGy. Thermal analysis showed the development of a bimodal peak with a decrease in the peak melt temperature and an increase in peak width. In combination with an increase in the thermal degradation temperature for a dose of 200 kGy compared to 100 kGy, thermal analysis also showed phenomena attributed to branching and crosslinking.
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Affiliation(s)
- David Krieg
- Institute for Circular Economy of Bio:Polymers at Hof University (ibp), 95028 Hof, Germany;
| | - Michael Thomas Müller
- Leibniz-Institut für Polymerforschung Dresden e.V., 01069 Dresden, Germany; (M.T.M.); (R.B.)
| | - Regine Boldt
- Leibniz-Institut für Polymerforschung Dresden e.V., 01069 Dresden, Germany; (M.T.M.); (R.B.)
| | - Mirko Rennert
- Institute for Circular Economy of Bio:Polymers at Hof University (ibp), 95028 Hof, Germany;
| | - Markus Stommel
- Leibniz-Institut für Polymerforschung Dresden e.V., 01069 Dresden, Germany; (M.T.M.); (R.B.)
- Institute of Material Science, Technical University Dresden, 01069 Dresden, Germany
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Bastida GA, Tarrés Q, Aguado R, Delgado-Aguilar M, Zanuttini MÁ, Galván MV. Flocculation of Cellulose Microfiber and Nanofiber Induced by Chitosan-Xylan Complexes. Nanomaterials (Basel) 2023; 13:2420. [PMID: 37686928 PMCID: PMC10489922 DOI: 10.3390/nano13172420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 08/23/2023] [Accepted: 08/23/2023] [Indexed: 09/10/2023]
Abstract
This study aims to provide a comprehensive understanding of the key factors influencing the rheological behavior and the mechanisms of natural polyelectrolyte complexes (PECs) as flocculation agents for cellulose microfibers (CMFs) and nanofibers (CNFs). PECs were formed by combining two polyelectrolytes: xylan (Xyl) and chitosan (Ch), at different Xyl/Ch mass ratios: 60/40, 70/30, and 80/20. First, Xyl, Ch, and PEC solutions were characterized by measuring viscosity, critical concentration (c*), rheological parameter, ζ-potential, and hydrodynamic size. Then, the flocculation mechanisms of CMF and CNF suspensions with PECs under dynamic conditions were studied by measuring viscosity, while the flocculation under static conditions was examined through gel point measurements, floc average size determination, and ζ-potential analysis. The findings reveal that PEC solutions formed with a lower xylan mass ratio showed higher intrinsic viscosity, higher hydrodynamic size, higher z-potential, and a lower c*. This is due to the high molecular weight, charge, and gel-forming ability. All the analyzed solutions behave as a typical non-Newtonian shear-thinning fluid. The flocculation mechanisms under dynamic conditions showed that a very low dosage of PEC (between 2 and 6 mg PEC/g of fiber) was sufficient to produce flocculation. Under dynamic conditions, an increase in viscosity indicates flocculation at this low PEC dosage. Finally, under static conditions, maximum floc sizes were observed at the same PEC dosage where minimum gel points were reached. Higher PEC doses were required for CNF suspensions than for CMF suspensions.
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Affiliation(s)
- Gabriela Adriana Bastida
- Institute of Cellulosic Technology, Faculty of Chemical Engineering (FIQ-CONICET), National University of the Litoral, Santiago del Estero 2654, Santa Fe S3000AOJ, Argentina; (G.A.B.); (M.Á.Z.); (M.V.G.)
- LEPAMAP-PRODIS Research Group, University of Girona, Maria Aurèlia Capmany 61, 17003 Girona, Spain; (R.A.); (M.D.-A.)
| | - Quim Tarrés
- LEPAMAP-PRODIS Research Group, University of Girona, Maria Aurèlia Capmany 61, 17003 Girona, Spain; (R.A.); (M.D.-A.)
| | - Roberto Aguado
- LEPAMAP-PRODIS Research Group, University of Girona, Maria Aurèlia Capmany 61, 17003 Girona, Spain; (R.A.); (M.D.-A.)
| | - Marc Delgado-Aguilar
- LEPAMAP-PRODIS Research Group, University of Girona, Maria Aurèlia Capmany 61, 17003 Girona, Spain; (R.A.); (M.D.-A.)
| | - Miguel Ángel Zanuttini
- Institute of Cellulosic Technology, Faculty of Chemical Engineering (FIQ-CONICET), National University of the Litoral, Santiago del Estero 2654, Santa Fe S3000AOJ, Argentina; (G.A.B.); (M.Á.Z.); (M.V.G.)
| | - María Verónica Galván
- Institute of Cellulosic Technology, Faculty of Chemical Engineering (FIQ-CONICET), National University of the Litoral, Santiago del Estero 2654, Santa Fe S3000AOJ, Argentina; (G.A.B.); (M.Á.Z.); (M.V.G.)
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Bastida GA, Schnell CN, Mocchiutti P, Solier YN, Inalbon MC, Zanuttini MÁ, Galván MV. Effect of Oxalic Acid Concentration and Different Mechanical Pre-Treatments on the Production of Cellulose Micro/Nanofibers. Nanomaterials (Basel) 2022; 12:2908. [PMID: 36079947 PMCID: PMC9457602 DOI: 10.3390/nano12172908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 08/19/2022] [Accepted: 08/22/2022] [Indexed: 06/15/2023]
Abstract
The present work analyzes the effect of process variables and the method of characterization of cellulose micro/nanofibers (CMNFs) obtained by different treatments. A chemical pre-treatment was performed using oxalic acid at 25 wt.% and 50 wt.%. Moreover, for mechanical pre-treatments, a rotary homogenizer or a PFI mill refiner were considered. For the mechanical fibrillation to obtain CMNFs, 5 and 15 passes through a pressurized homogenization were considered. The best results of nanofibrillation yield (76.5%), transmittance (72.1%) and surface charges (71.0 µeq/g CMNF) were obtained using the PFI mill refiner, 50 wt.% oxalic acid and 15 passes. Nevertheless, the highest aspect ratio (length/diameter) determined by Transmission Electron Microscopy (TEM) was found using the PFI mill refiner and 25 wt.% oxalic acid treatment. The aspect ratio was related to the gel point and intrinsic viscosity of CMNF suspensions. The values estimated for gel point agree with those determined by TEM. Moreover, a strong relationship between the intrinsic viscosity [η] of the CMNF dispersions and the corresponding aspect ratio (p) was found (ρ[η] = 0.014 p2.3, R2 = 0.99). Finally, the tensile strength of films obtained from CMNF suspensions was more influenced by the nanofibrillation yield than their aspect ratio.
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Brounstein Z, Zhao J, Geller D, Gupta N, Labouriau A. Long-Term Thermal Aging of Modified Sylgard 184 Formulations. Polymers (Basel) 2021; 13:polym13183125. [PMID: 34578026 PMCID: PMC8466950 DOI: 10.3390/polym13183125] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 09/10/2021] [Accepted: 09/14/2021] [Indexed: 11/28/2022] Open
Abstract
Primarily used as an encapsulant and soft adhesive, Sylgard 184 is an engineered, high-performance silicone polymer that has applications spanning microfluidics, microelectromechanical systems, mechanobiology, and protecting electronic and non-electronic devices and equipment. Despite its ubiquity, there are improvements to be considered, namely, decreasing its gel point at room temperature, understanding volatile gas products upon aging, and determining how material properties change over its lifespan. In this work, these aspects were investigated by incorporating well-defined compounds (the Ashby–Karstedt catalyst and tetrakis (dimethylsiloxy) silane) into Sylgard 184 to make modified formulations. As a result of these additions, the curing time at room temperature was accelerated, which allowed for Sylgard 184 to be useful within a much shorter time frame. Additionally, long-term thermal accelerated aging was performed on Sylgard 184 and its modifications in order to create predictive lifetime models for its volatile gas generation and material properties.
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Affiliation(s)
- Zachary Brounstein
- Los Alamos National Laboratory, Los Alamos, NM 87545, USA; (Z.B.); (D.G.); (N.G.)
- Department of Nanoscience and Microsystems Engineering, University of New Mexico, Albuquerque, NM 87131, USA
| | - Jianchao Zhao
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA;
| | - Drew Geller
- Los Alamos National Laboratory, Los Alamos, NM 87545, USA; (Z.B.); (D.G.); (N.G.)
| | - Nevin Gupta
- Los Alamos National Laboratory, Los Alamos, NM 87545, USA; (Z.B.); (D.G.); (N.G.)
| | - Andrea Labouriau
- Los Alamos National Laboratory, Los Alamos, NM 87545, USA; (Z.B.); (D.G.); (N.G.)
- Correspondence:
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7
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Sanchez-Salvador JL, Campano C, Lopez-Exposito P, Tarrés Q, Mutjé P, Delgado-Aguilar M, Monte MC, Blanco A. Enhanced Morphological Characterization of Cellulose Nano/Microfibers through Image Skeleton Analysis. Nanomaterials (Basel) 2021; 11:nano11082077. [PMID: 34443907 PMCID: PMC8398699 DOI: 10.3390/nano11082077] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 08/06/2021] [Accepted: 08/11/2021] [Indexed: 11/16/2022]
Abstract
The present paper proposes a novel approach for the morphological characterization of cellulose nano and microfibers suspensions (CMF/CNFs) based on the analysis of eroded CMF/CNF microscopy images. This approach offers a detailed morphological characterization and quantification of the micro and nanofibers networks present in the product, which allows the mode of fibrillation associated to the different CMF/CNF extraction conditions to be discerned. This information is needed to control CMF/CNF quality during industrial production. Five cellulose raw materials, from wood and non-wood sources, were subjected to mechanical, enzymatic, and (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO)-mediated oxidative pre-treatments followed by different homogenization sequences to obtain products of different morphologies. Skeleton analysis of microscopy images provided in-depth morphological information of CMF/CNFs that, complemented with aspect ratio information, estimated from gel point data, allowed the quantification of: (i) fibers peeling after mechanical pretreatment; (ii) fibers shortening induced by enzymes, and (iii) CMF/CNF entanglement from TEMPO-mediated oxidation. Being mostly based on optical microscopy and image analysis, the present method is easy to implement at industrial scale as a tool to monitor and control CMF/CNF quality and homogeneity.
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Affiliation(s)
- Jose Luis Sanchez-Salvador
- Department of Chemical Engineering and Materials, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense, 28040 Madrid, Spain; (J.L.S.-S.); (C.C.); (M.C.M.)
| | - Cristina Campano
- Department of Chemical Engineering and Materials, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense, 28040 Madrid, Spain; (J.L.S.-S.); (C.C.); (M.C.M.)
| | - Patricio Lopez-Exposito
- Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganés, Spain;
| | - Quim Tarrés
- Group LEPAMAP, Department of Chemical Engineering, University of Girona, C/M. Aurèlia Campmany 61, 17071 Girona, Spain; (Q.T.); (P.M.); (M.D.-A.)
| | - Pere Mutjé
- Group LEPAMAP, Department of Chemical Engineering, University of Girona, C/M. Aurèlia Campmany 61, 17071 Girona, Spain; (Q.T.); (P.M.); (M.D.-A.)
| | - Marc Delgado-Aguilar
- Group LEPAMAP, Department of Chemical Engineering, University of Girona, C/M. Aurèlia Campmany 61, 17071 Girona, Spain; (Q.T.); (P.M.); (M.D.-A.)
| | - M. Concepcion Monte
- Department of Chemical Engineering and Materials, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense, 28040 Madrid, Spain; (J.L.S.-S.); (C.C.); (M.C.M.)
| | - Angeles Blanco
- Department of Chemical Engineering and Materials, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Avenida Complutense, 28040 Madrid, Spain; (J.L.S.-S.); (C.C.); (M.C.M.)
- Correspondence: ; Tel.: +34-913-944-247
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Pillai S, Davies G, Lawrence M, Whitley J, Stephens J, Williams PR, Morris K, Evans PA. The effect of diabetic ketoacidosis (DKA) and its treatment on clot microstructure: Are they thrombogenic? Clin Hemorheol Microcirc 2021; 77:183-194. [PMID: 32925001 DOI: 10.3233/ch-200957] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Diabetic ketoacidosis (DKA) is a medical emergency with a high mortality rate and is associated with severe metabolic acidosis and dehydration. DKA patients have an increased risk of arterial and venous thromboembolism, however little is known about this metabolic derangement in the first 24 hours of admission and to assess its effect on coagulation. We therefore utilised a novel functional marker of clot microstructure (fractal dimension - df) to assess these changes within the first 24 hours. METHODS Prospective single centre observational study to demonstrate whether the tendency of blood clot formation differs in DKA patients. RESULTS 15 DKA patients and 15 healthy matched controls were recruited. Mean df in the healthy control group was 1.74±0.03. An elevated df of 1.78±0.07 was observed in patients with DKA on admission. The mean pH on admission was 7.14±0.13 and the lactate was 3.6±2.0. df changed significantly in response to standard treatment and was significantly reduced to 1.68±0.09 (2-6& h) and to 1.66±0.08 at 24& h (p < 0.01 One-way ANOVA). df also correlated significantly with lactate and pH (Pearson correlation coefficient 0.479 and -0.675 respectively, p < 0.05). CONCLUSIONS DKA patients at presentation have a densely organising less permeable thrombogenic clot microstructure as evidenced by high df. These structural changes are due to a combination of dehydration and a profound metabolic acidosis, which was reversed with treatment. These changes were not mirrored in standard clinical markers of thromboge-nicity.
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Affiliation(s)
- Suresh Pillai
- Welsh Centre for Emergency Medicine Research, Emergency Department, Morriston Hospital, Swansea, UK.,Morriston Hospital, Swansea, UK.,Swansea University, Swansea, UK
| | - Gareth Davies
- Welsh Centre for Emergency Medicine Research, Emergency Department, Morriston Hospital, Swansea, UK
| | - Matthew Lawrence
- Welsh Centre for Emergency Medicine Research, Emergency Department, Morriston Hospital, Swansea, UK.,Swansea University, Swansea, UK
| | - Janet Whitley
- Welsh Centre for Emergency Medicine Research, Emergency Department, Morriston Hospital, Swansea, UK.,Swansea University, Swansea, UK
| | - Jeffrey Stephens
- Morriston Hospital, Swansea, UK.,Swansea University, Swansea, UK
| | | | | | - Phillip Adrian Evans
- Welsh Centre for Emergency Medicine Research, Emergency Department, Morriston Hospital, Swansea, UK.,Morriston Hospital, Swansea, UK.,Swansea University, Swansea, UK
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Kohl K. Comparison of Dynamic Light Scattering and Rheometrical Methods to Determine the Gel Point of a Radically Polymerized Hydrogel under Mechanical Shear. Micromachines (Basel) 2020; 11:mi11050462. [PMID: 32354108 PMCID: PMC7281437 DOI: 10.3390/mi11050462] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 04/16/2020] [Accepted: 04/27/2020] [Indexed: 11/29/2022]
Abstract
The phase transition of nanocomposite hydrogels made of N-isopropylacrylamide (NIPAm) and clay (Laponite® XLS) was investigated under mechanical shear influencing the gelation. The hydrogels were synthesized by free radical polymerization. For the processing of cross-linked gels, the phase transition (liquid–solid) and its dependence on mechanical stress are of paramount importance. On the one hand, the determination of the gel point (tg) is possible with rheometry and, on the other hand, with dynamic light scattering (DLS). With rotational rheometry, by identifying the abrupt increase of viscosity, the gel point is evaluated. The DSL is an alternative method to rheometry, to investigate hydrogels under the action of the shear flow, to make results comparable to the rheometric investigations, with and without shear. Experimental parameters were chosen based on preparatory work to obtain comparable results regarding the determination of the gel point of a radically polymerized NIPAm hydrogel.
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Affiliation(s)
- Katinka Kohl
- Chair of Magnetofluiddynamics, Measuring and Automation Technology, Technische Universität Dresden, 01069 Dresden, Germany
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10
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Abstract
During the coagulation process, blood changes from a liquid to a solid gel phase. These changes are reflected by changes in blood viscosity; however, blood viscosity at different shear rates (SR) has not been previously explored during the coagulation process. In this study, we investigated the viscosity changes of whole blood in 10 subjects with a normal coagulation profile, using a cone-on-plate viscosimeter. For each subject, three consecutive measurements were performed, at a SR of 20, 40, 80 sec(-1). On the basis of the time-dependent changes in blood viscosity, we identified the gel point (GP), the time-to-gel point (TGP), the maximum clot viscosity (MCV), and the clot lysis half-time (CLH). The TGP significantly (P = 0.0023) shortened for increasing SR, and was significantly associated with the activated partial thromboplastin time at a SR of 20 sec(-1) (P = 0.038) and 80 sec(-1) (P = 0.019). The MCV was significantly lower at a SR of 80 sec(-1) versus 40 sec(-1) (P = 0.027) and the CLH significantly (P = 0.048) increased for increasing SR. These results demonstrate that measurement of blood viscosity during the coagulation process offers a number of potentially useful parameters. In particular, the association between the TGP and the activated partial thromboplastin time is an expression of the clotting time (intrinsic and common pathway), and its shortening for increasing SR may be interpreted the well-known activating effects of SR on platelet activation and thrombin generation. Further studies focused on the TGP under conditions of hypo- or hypercoagulability are required to confirm its role in the clinical practice.
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Affiliation(s)
- Marco Ranucci
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy
| | - Tommaso Laddomada
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy
| | - Matteo Ranucci
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy
| | - Ekaterina Baryshnikova
- Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy
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11
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Wood LA. Modulus of Natural Rubber Cross-Linked by Dicumyl Peroxide III. Some Molecular Interpretations, Possible Refinements of Theory, and Conclusions. J Res Natl Bur Stand A Phys Chem 1976; 80A:451-463. [PMID: 32196273 PMCID: PMC5293352 DOI: 10.6028/jres.080a.051] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The shear modulus G = 5.925 × 10 - 3(fp - 0.45)T+G* (Part I), its energy component G* = 0.0684 (fp - 0.45)+ 2.70 (Part II), and the number of effective suh-chains per unit volume ve = (G - G*)/RT are given detailed molecular consideration. G is given in Mdyn cm-2 for rubber cross-linked by adding p parts of dicumyl peroxide per hundred of rubber, and heating until a fraction f of the peroxide is decomposed. ve is found to be approximately twice the density of cross-links, after a correction for impurities and chain ends is made. It can not be computed as G/RT since only the entropy component of modulus is related to ve. The sub-chains for the most highly cross-linked rubbers studied had a molecular weight of about 575 g mol-1, corresponding to about 8 isoprene units. The modulus corresponding to no added cross-links is not zero. It is determined chiefiy by the energy component of the modulus; it does not arise from entanglements. The "front factor" is found to be unity. An extensive literature survey yields values of the quantity RTΨ(v 2), where Ψ (v 2) is the Flory- Rehner equation function of v 2, the equilibrium volume fraction obtained by swelling the cross-linked rubber. RTψ (v 2) is found to be greater than G - G* but not as large as G itself.
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Affiliation(s)
- Lawrence A Wood
- Institute for Materials Research, National Bureau of Standards, Washington, D.C. 20234
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Abstract
Thermodynamics and molecular considerations are applied to an examination of the equation G = S(fp + B)T + H(fp + B) + A = 5.925 × 10-3(fp - 0.45)T + 0.0684(fp - 0.45) + 2.70, found experimentally in Part I. G is the shear modulus in Mdyn cm-2 at a temperature T for natural rubber cross-linked by adding p parts of dicumyl peroxide per hundred of rubber (phr) and heating until a fraction f of the peroxide is decomposed. G*, the energy component of the modulus, is H(fp + B) + A. The ratio G*/G decreases from 1.00 at the gel point (fp = 0.45 phr) to 0.5 near 2 phr and to 0.09 at 23.8 phr. The modulus G is related to ν e , the number of moles of effective sub-chains per cm3, by the equation G - G* = v e RT where R is the gas constant. If each molecule of decomposed dicumyl peroxide of molecular weight M d produces one cross-link in the rubber of specific volumeυ ¯ r , then it is predicted that S = 2 R ( 100 M d υ ¯ r ) - 1 = 5.5535 × 10 - 3 Mdyn cm-2 phr-1 K-1, as compared with the experimental value 5.925 × 10-3. Theory gives no prediction of the values of A, or of H. The gel point may be located experimentally as the point where the slope of the modulus-temperature relation is zero. The value of G at the gel point is the energy component G*. The experimental value of fp at the gel point permits a calculation of the molecular weight of the rubber before cross-linking as 193,000. The results afford a very satisfactory confirmation of the essential validity of the statistical theory of rubber elasticity in its simplest form, if due regard is paid to G*, the energy component of the modulus.
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Affiliation(s)
- Lawrence A Wood
- Institute for Materials Research, National Bureau of Standards, Washington, D.C. 20234
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