RESUMEN
Because of the different crystallization behaviors of semicrystalline supramolecular polymers (SMPs) from conventional polymers, investigation on the unique crystallization kinetics and crystalline structures of SMPs is of fundamental importance to tune their physical properties and functions in processing. Herein, we chose the multiple hydrogen-bonding 2-ureido-4[1H]-pyrimidinone (UPy) group as the supramolecular unit and poly(butylene adipate) (PBA) as the polymorphic polymer block, and synthesized UPy-functionalized PBAs (i.e., UPy-bonded supramolecular PBAs). The crystallization kinetics, polymorphic crystalline structure, phase transition, and lamellar morphology of the UPy-functionalized PBAs were investigated and compared with those of the pristine PBA. UPy end functionalization suppressed the crystallization rate and crystallinity of the linked PBA chains. Compared to the pristine PBA, the UPy-functionalized PBAs preferred to form the thermally-stable α crystals at the same temperature; this was more obvious for the samples with a high content of the UPy end group. The facilitated formation of α crystals in the UPy-functionalized PBAs was attributed to the decreased equilibrium melting temperature. UPy end functionalization also decreased the critical temperature and broadened the temperature range for the ß-to-α phase transition of PBA during heating. Due to the segregation of the UPy unit in the amorphous phase, the UPy-functionalized PBAs exhibited larger long periods than the pristine PBA, even though they had a lower degree of crystallinity.
RESUMEN
The rheology of carboxymethyl fenugreek gum (CFG) is characterized and applied it as a binder for the silicon anode of lithium-ion batteries (LIBs). First, a series of carboxymethyl fenugreek gum (namely CFG-1, CFG-2 and CFG-3) was prepared and characterized by Fourier transform infrared spectrophotometer and hydrogen nuclear magnetic resonance spectrometry studies. In rheological measurements, the CFG solutions show higher flowability, weaker viscoelastic behavior and better thixotropy than that of fenugreek gum (FG) solution. Furthermore, the higher degrees of substitution (DS) of CFG solutions lead to lower apparent viscosity and higher flow index, weaker elastic effect and smaller relaxation time, and higher viscosity recoverability than those obtained for lower DS of CFG solutions. In electrochemical measurements, the polar hydroxyl and carboxyl groups in the CFG skeleton chain provide bonding points between the CFG binders and the silicon electrode to produce binder-silicon bonds, which cause strong hydrogen bonding, and resulted in excellent electrochemical stability and specific capacity. The electrochemical performances were measured via the silicon electrodes with FG and CFG at 5â¯wt% content. As the DS is increased, the initial Coulombic efficiency can increase from 88.74% to 91.3%. When the electrode undergoes a volume change, the CFG binder with silicon electrodes can hold high capacity of above 1500â¯mAh/g after 200 charge-discharge cycles. Therefore, the carboxymethyl fenugreek gum as a binder may also be a novel extended binder-design, with applications for silicon anodes of LIBs.
