Aggregation behaviour below the gelation threshold for metal-olefin coordination in diene polymers |
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| Institution: | 1. Biology Department, Biological Sciences Institute, Federal University of Juiz de Fora, José Lourenço Kelmer, Campus Universitário, 36036-900 Juiz de Fora, Brazil;2. Laboratory of Nanotechnology, Brazilian Agricultural Research Corporation (EMBRAPA), 36038-330 Juiz de Fora, Brazil;3. CiPharma (EFAR/UFOP), Federal University of Ouro Preto, 35400-000 Ouro Preto, Brazil;4. Interfaces, Treatments, Organization and Dynamics of System (ITODYS), University of Paris Diderot, Sorbonne Paris Cité, 7086 Paris, France;5. Regulations Development Molecular Diversit (RDDM), French National Museum of Natural History, 75005 Paris, France;6. Nucleus of Analytical Identification and Quantification (NIQUA), Federal University of Juiz de Fora, 36036-900 Juiz de Fora, Brazil;7. National Nanotechnology Laboratory for Agriculture (LNNA), Brazilian Agricultural Research Corporation, 13560-970 São Carlos, Brazil;1. School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China;2. Composites Research Division, Korea Institute of Materials Science, Changwon 51508, Republic of Korea;3. Division of Fluid and Experimental Mechanics, Luleå University of Technology, Luleå 97187, Sweden;4. School of Mechanical and Aerospace Engineering, Gyeongsang National University, Jinju 52828, Republic of Korea;1. Department of Pharmaceutical Chemistry, Vignan Pharmacy College, Jawaharlal Nehru Technological University, Vadlamudi 522213, Andhra Pradesh, India;2. Department of Pharmaceutical Sciences, College of Pharmacy & Health Sciences, Ajman University, Ajman PO Box 346, United Arab Emirates;3. Montvale, New Jersey, NJ 07645, USA;4. Faculty of Pharmaceutical Sciences, UCSI University, Kuala Lumpur, Malaysia;5. Department of Pharmaceutical Chemistry, Victoria College of Pharmacy, Nallapadu-522001, Guntur District, Andhra Pradesh, India;6. Medicines Research Group, School of Health, Sports and Bioscience, University of East London, Stratford Campus, Water Lane, London E 15 4LZ, United Kingdom;7. Center of Medical and Bio-allied Health Sciences Research, Ajman University, Ajman, United Arab Emirates;1. Life Science College, Luoyang Normal University, Luoyang, Henan, China;2. Agricultural and Food College, Zhejiang A&F University, Hangzhou, 311300, China;3. Jujube Research and Application Center, Luoyang, Henan, China |
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| Abstract: | This study focuses on aggregation below the gelation threshold in ternary solutions containing diene polymers, atactic 1,2-polybutadiene (PBu) or 3,4-polyisoprene (PI), and an inorganic salt, bis(acetonitrile) dichloropalladium(II). Upon mixing, effective coordination crosslinks are formed because the acetonitrile ligands of the palladium salt are displaced by olefinic pendant groups of the polymers. In all cases, the aggregation kinetics correlate with PdCl2 concentration because the polymer concentration is 100 times greater than the salt concentration. Aggregation is the process that occurs prior to gelation as the transition-metal salt forms a coordination bridge between two different polymer chains. Differential analysis of the initial aggregation rate on the basis of light scattering data at 45° relative to the incident throughput beam reveals that the ‘true’ order of the coordination reaction is close to unity. This suggests that coordination crosslinking is diffusion-controlled in the early stages of aggregation. Half-life analysis of viscous solutions yields an overall reaction order of 1.6 for aggregation of polybutadiene and palladium chloride in tetrahydorfuran (THF). Scaling analysis of the weight-average molecular weight dependence of the root-mean-square size of isolated scattering particles yields an effective exponent of 0.7 for polymer/metal-salt complexes at infinite dilution. This experimental scaling law agrees with literature values for cross-linked polymer networks. In all cases, the size of the aggregates increases at higher PdCl2 concentration. For polybutadiene/PdCl2 mixtures in THF or toluene below the gelation threshold, the light-scattering-detected average aggregation number (AN = Mw, complex/Mw, pure polymer via Zimm-plot intercepts) for low-viscosity solutions is 2, while AN ～ 9 for viscous THF solutions. In contrast, low aggregation numbers (AN ～ 2) were calculated for viscous ternary mixtures of 3,4-polyisoprene and PdCl2 in THF. |
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