91970-02-4Relevant academic research and scientific papers
Facile catalyst-free synthesis, exchanging, and hydrolysis of an acetal motif for dynamic covalent networks
Li, Qiong,Ma, Songqi,Wang, Sheng,Yuan, Wangchao,Xu, Xiwei,Wang, Binbo,Huang, Kaifeng,Zhu, Jin
, p. 18039 - 18049 (2019/08/07)
Dynamic covalent networks offer the favorable features of cross-linked polymers as well as the functions of reprocessing, recycling, self-healing, reshaping, and welding; however, it is a challenge to design readily monomer-recovery, highly malleable, catalyst-free, dynamic materials. Here we report the first design of acetal dynamic networks to address this challenge. Acetal dynamic networks were built via the catalyst-free "click" addition of polyol and a commercial divinyl ether without releasing small molecules. Small-molecule model compounds demonstrated thermally-induced acetal exchange without a catalyst. There are two mechanisms for the dynamic exchange of acetal: one is the metathesis of acetal, another is transacetalization. Acetal dynamic covalent networks exhibited excellent malleability and recyclability. They presented rapid stress relaxation at high temperatures. Hot press recovery can be achieved in 10 min at 150 °C. Meanwhile, the starting material was recovered with 92% recovery in 1 h under hot water treatment at 100 °C, and could be recross-linked with a commercial divinyl ether to obtain an acetal network. The acetal networks recovered by the two methods maintained the original structure and performance. An acetal dynamic linkage will open up a new way for the development of catalyst-free dynamic covalent networks and enrich acetal chemistry.
Cyclopolymerization of α,ω-heterodifunctional monomers containing styrene and maleimide moieties
Zou, Lei,Liu, Jian'An,Zhang, Ke,Chen, Yongming,Xi, Fu
, p. 330 - 338 (2014/01/06)
A series of α,ω-heterodifunctional monomers with styrene (St) and maleimide moieties bridged by a varied length of oligo-ethylene glycol (OEG) linkers were synthesized. Cyclopolymerizations of these monomers through reversible addition-fragmentation chain transfer-mediated alternating radical copolymerization between intramolecular St and maleimide moieties were investigated. For the monomers with three or more ethylene glycol (EG) units, their cyclopolymerizations can be realized properly in low monomer feeding concentrations, affording well-defined cyclopolymers with crown ether encircled in their main chains. Importantly, the cyclopolymerizations of monomers with six or seven EG units in the presence of KPF6 could be enhanced by the supramolecular effects between the OEG linkers and the potassium metal ion. Thus, the monomer feeding concentration could be largely improved, which may benefit preparation of the cyclopolymers with high degrees of copolymerization. 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 330-338 The cyclopolymerizations of α,ω-heterodifunctional monomers with styrene and maleimide moieties bridged by oligo-ethylene glycol linkers can be realized in low monomer feeding concentrations. The cyclopolymerizations of monomers with six or seven ethylene glycol units in high concentrations could be enhanced by the supramolecular effects between the linkers and the potassium metal ion, both of which afford well-defined cyclopolymers with crown ether encircled in their main chains. Copyright
Structure and properties of polymer electrolyte membranes containing phosphonic acids for anhydrous fuel cells
Lee, Sung-Il,Yoon, Kyung-Hwan,Song, Myeongsoo,Peng, Huagen,Page, Kirt A.,Soles, Christopher L.,Yoon, Do Y.
experimental part, p. 115 - 122 (2012/05/20)
Recently, water-free, proton-conducting polymer electrolytes have been attracting attention because of their possible application as fuel cell membranes at intermediate temperatures (100 to 200 °C). Phosphonic acid groups are considered feasible anhydrous proton conducting moieties due to the high degree of proton self-dissociation arising from their intrinsic amphoteric character and high mobility of protonic charge carriers. In this work, we have synthesized and characterized model, phosphonic acid-functionalized proton-conducting polymers, poly(vinylbenzyloxy-alkyl-phosphonic acid)s, for the purpose of exploring the relationship between molecular design, nanostructure, and performance characteristics. These novel proton conducting materials were characterized for their thermal stability, nanostructure, and performance properties. Thermogravimetric analysis (TGA) indicates that the polymers are thermally stable up to 140 °C, where the condensation of phosphonic acid groups starts to occur. Results from small-angle X-ray scattering (SAXS) show a peak corresponding to a Bragg spacing of approximately 21-24 A, which is attributed to layerlike structure formation of the phosphonic acid containing conducting channels. The proton conductivity increases with temperature, reaching a value on the order of 3 × 10-4 S/cm at 140 °C under nominally anhydrous conditions.
Efficient biocatalytic cleavage and recovery of organic substrates supported on soluble polymers
Pasini, Dario,Filippini, Marco,Pianetti, Ilaria,Pregnolato, Massimo
, p. 971 - 978 (2008/03/28)
The applicability of novel solution-phase supports in combination with enzymes for biocatalytic transformations is reported. Ex novo designed styrene-based copolymers, bearing a phenylacetic residue in variable loadings and linked as a pendant group to the macromolecular backbone, through a spacer of variable length, have been synthesized and characterized. These derivatives are compatible and can be used as soluble supports in combination with immobilized penicillin G acylase (PGA - EC 3.5.1.11) for the biocatalytic cleavage of the covalently anchored organic substrate in quantitative yields, in water or water/dimethylformamide solvent mixtures, with recovery of the immobilized enzyme with negligible losses in activity.
