Although stimuli-responsive polymers have appeared as promising materials for drug administration,the effectiveness of these materials on various bioinspired stimuli is still open for dispute.In this work,the stimuli-...Although stimuli-responsive polymers have appeared as promising materials for drug administration,the effectiveness of these materials on various bioinspired stimuli is still open for dispute.In this work,the stimuli-responsive behaviors of radical-containing nonamphiphilic copolymers were investigated using electron paramagnetic resonance(EPR)spectroscopy while altering the pH and reductant concentration.The concentration of radicals in the aqueous solution had a considerable impact on self-assembly.The nitroxide radicals(hydrophobic)were converted to hydroxylamine(hydrophilic)when ascorbic acid(Asc)was added as a reductant,and the assemblies were switched to dissolution with a rate control behavior.The behavior of morphological change was observed in the acidic pH due to the disproportionation reaction of nitroxide radicals forming cationic species.The acquired results give new insights into the colloidal nanoparticles of nonamphiphilic copolymers and encourage the development of comparable responsive nanoparticles with intriguing drug delivery applications.展开更多
The structure of polyolefin has an important influence on its performance and application.Ethylene/1-hexene copolymerization is one of the important ways to control the structure of the polyolefin.However,research on ...The structure of polyolefin has an important influence on its performance and application.Ethylene/1-hexene copolymerization is one of the important ways to control the structure of the polyolefin.However,research on the ethylene/1-hexene copolymerization catalyzed by nickel complexes with different steric ligands remains to be refined.Here,three α-dimine nickel catalysts are used to study the ligand effect on catalytic performance in the ethylene/1-hexene copolymerization.Reaction activity,molecular weight,phase-transition temperature and branching density of the resultant copolymer are measured to evaluate the catalytic performance.The results indicate that the steric ligands could exert great effect on the copolymerization.As for the chemical valence of Ni species,detailed EPR demonstrate that the presence of excess xo-catalyst can reduce Ni(Ⅱ)to the lower valence and affect the catalytic performance.展开更多
基金the Natural Science Foundation of Zhejiang Province(LHDMZ22H300003)is gratefully acknowledged.
文摘Although stimuli-responsive polymers have appeared as promising materials for drug administration,the effectiveness of these materials on various bioinspired stimuli is still open for dispute.In this work,the stimuli-responsive behaviors of radical-containing nonamphiphilic copolymers were investigated using electron paramagnetic resonance(EPR)spectroscopy while altering the pH and reductant concentration.The concentration of radicals in the aqueous solution had a considerable impact on self-assembly.The nitroxide radicals(hydrophobic)were converted to hydroxylamine(hydrophilic)when ascorbic acid(Asc)was added as a reductant,and the assemblies were switched to dissolution with a rate control behavior.The behavior of morphological change was observed in the acidic pH due to the disproportionation reaction of nitroxide radicals forming cationic species.The acquired results give new insights into the colloidal nanoparticles of nonamphiphilic copolymers and encourage the development of comparable responsive nanoparticles with intriguing drug delivery applications.
基金Financial support from the National Key Research and Development Program(2016YFB0302403)is gratefully acknowledged.
文摘The structure of polyolefin has an important influence on its performance and application.Ethylene/1-hexene copolymerization is one of the important ways to control the structure of the polyolefin.However,research on the ethylene/1-hexene copolymerization catalyzed by nickel complexes with different steric ligands remains to be refined.Here,three α-dimine nickel catalysts are used to study the ligand effect on catalytic performance in the ethylene/1-hexene copolymerization.Reaction activity,molecular weight,phase-transition temperature and branching density of the resultant copolymer are measured to evaluate the catalytic performance.The results indicate that the steric ligands could exert great effect on the copolymerization.As for the chemical valence of Ni species,detailed EPR demonstrate that the presence of excess xo-catalyst can reduce Ni(Ⅱ)to the lower valence and affect the catalytic performance.