A novel positively thermo-sensitive hydrogel based on ethylenediaminetetraacetic dianhydride and piperazine:Design,synthesis and characterization

A new positively thermo-sensitive hydrogel was designed and synthesized by a condensation polymerization reaction of ethylenediaminetetraacetic dianhydride（EDTAD） and piperazine（PA） to give poly（ethylenediaminetetraacetic dianhydride-copiperazine） （PEP）.The obtained polymers＇ structure was characterized by FTIR and ^（13）C NMR.The backbone of the polymer linked by amide bond and abundant of carboxyl groups as pendant group could form strong intermolecular and intramolecular hydrogen bond at lower temperature and dissociate at higher temperature,resulting in the polymer with thermo-sensitivity.The aqueous solution of PEP at lower temperature（〈20℃） showed micro-gel formation and transformed to transparent solution at higher temperature（〉40℃）.Transition temperature shifted to higher value with the increasing of concentration.The hydrogel exhibited reversible phase transition and the transmittance change was not weakened by multiple temperature changes.

Design,synthesis and characterization of a novel pH-sensitive hydrogel

A novel degradable pH-sensitive hydrogel with pendent carboxyl groups was designed and synthesized from ethylenediaminetetraacetic dianhydride （EDTAh） and butanediamine （BDA） with dicyclohexylcarbodiimide （DCC） as a condensating agent and BDA as a crosslinking agent. The obtained polymers were characterized by ^13C NMR, ^1H NMR and FTIR. The swelling experiments of the hydrogel in pH 3, 7, and 12 media indicated much higher swelling ratio in pH 12 media than in pH 3 and pH 7 media, exhibiting sound pH sensitivity. The pH sensitivity of this type of hydrogel may be regulated through controlling the type and the dose of the crosslinking agent.

Imide-based covalent organic framework with excellent cyclability as an anode material for lithium-ion battery

Covalent organic frameworks(COFs)exhibiting reversible redox behaviors have been identified as promising candidates for constructing electrode materials in lithium-ion batteries(LIBs).However,their extensive application has been limited due to finite redox sites and poor structural stability.In this study,we design and synthesize a novel polyimide covalent organic framework(PI-COF)using the traditional solvothermal method and successfully apply it as an anode material for LIBs.The large conjugated structure of PI-COF accelerates charge transfer,while its large surface area provides more active sites,making PI-COF an attractive anode material for LIBs.Furthermore,the PI-COF anode material demonstrates high reversible specific capacity and excellent long-term cycling stability due to its COF characteristics.Specifically,the PI-COF electrodes deliver a specific capacity of 800 m Ah/g at a current density of 200 m A/g after 200 cycles,while a specific capacity of 450 m Ah/g at a current density of 1000 m A/g is sustained after 800 cycles.The outstanding lithium storage capacity,particularly the satisfactory long-term cycling stability,establishes PI-COF as a promising material for LIBs.