Studies In The Synthesis And Properties Of Poly Hydroxy Dithiols

Author : Daihui Zhang
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (14 download)

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Download or read book Synthesis and Characterization of 5-hydroxymethlfurfural Derivative Based Materials written by Daihui Zhang and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The thiol-Michael addition reaction offers high conversion, mild reaction conditions, and rapid reaction rate. However, there are few research works reporting on the synthesis of linear polymers using this reaction, probably due to the occurrence of side reactions. Therefore, the potential side reactions which occur when performing the thiol-Michael addition reaction were elucidated using a model reaction between furfural acrylate and 1-propanethiol (Chapter 3). Moreover, linear poly([beta]-thioether esters) were successfully synthesized from HMF derivative (2,5-furan diacrylate) and 1,6-hexanedithiol using a catalytic amount of dimethylphenylphosphine (DMPP) under mild reaction conditions (Mn=20000 g/mol). Three commercial dithiol monomers, including 1,4-benzenedithiol, 1,3-propanedithiol, and dithiothreitol, were used to synthesize 2,5-furan diacrylate (2,5-FDA) based polymers with varied structures and properties (Chapter 4). The synthesis of copolymers was investigated as well using 1,6-hexanedithiol and 1,4-benzendithiol as monomers. 1H NMR analysis of the synthesized copolymers revealed that the ratios of these two dithiol monomers present in the copolymers matched well the theoretical ratios. Several interesting phenomena, including multiple melting peaks and two-stage degradation behaviour observed by DSC and TGA, were elucidated by different techniques. Additionally, 2,5-FDA based linear polymers were dynamically crosslinked by the DA reaction using bismaleimide as the crosslinker to improve the thermal and mechanical properties. As the weight ratio of crosslinker to polymer increased from 1:10 to 1:2, the storage modulus at room temperature was significantly enhanced from 1.5 MPa to 1691 MPa. Despite the successful synthesis of TPEs reported in Chapter 4, their relatively poor solvent resistance and unsatisfactory elasticity could limit their applications. Hence, a thermoset elastomer was synthesized by the combination of the thiol-Michael addition reaction and the DA reaction (Chapter 5). When the weight ratio of polymer to crosslinker was 5:1, the Young's modulus, ultimate strength, and elongation at break were 4.3±0.6 MPa, 5.7±1.1 MPa, and 205.3±20.1%, respectively. Moreover, a high elastic recovery (98.9 %) and low residual strain (0.7 %) were observed after the third cycle during the cyclic tensile test. Additionally, the structure and functionality of elastomers were varied by the synthesis of linear copoly([beta]-thioether ester). The mechanical properties of the elastomers were adjusted by the incorporation of flexible polymeric chains. Although covalent bonds were formed to generate the networks, the reprocessability of thermosets elastomers was demonstrated due to the reversibility of the DA reaction. Due to the renewability, non-toxicity, biodegradability, and tunable crystallization behavior of polylactic acid (PLA), PLA was used as hard blocks in the synthesis of TPEs. Therefore, the last chapter reported the use of soft segments having thioether groups to synthesize PLA based elastomers (Chapter 6). The reaction was carried out in a one-pot reaction under mild reaction conditions due to the efficient macromolecular coupling between the thiol and the acrylate groups of polymers catalyzed by DMPP. In conclusion, this work has demonstrated the use of the thiol-Michael addition reaction to synthesize 2,5-FDA based linear polymers with varied structures and properties. The occurrence of the DA reaction between furan rings in the polymeric chains and maleimide groups provided an efficient approach to further adjust the thermal and mechanical properties. Due to the reversibility of the DA reaction, networks synthesized by the combination of the thiol-Michael addition and the DA reaction may be used as reversible adhesive, self-healing or recycled materials, and coating applications. " --