长期苯暴露会对人体造成伤害甚至导致白血病,而通过对苯生物标志物的生物监测可以更有效地判断个体的苯暴露水平。为研究苯暴露生物监测的国际发展态势,本文以Web of Science核心合集收录的发表于2000-2021年的文献为研究对象,借助软件...长期苯暴露会对人体造成伤害甚至导致白血病,而通过对苯生物标志物的生物监测可以更有效地判断个体的苯暴露水平。为研究苯暴露生物监测的国际发展态势,本文以Web of Science核心合集收录的发表于2000-2021年的文献为研究对象,借助软件从关键词、高被引论文、主要国家、主要研究机构、主要作者等角度对文献进行分析,揭示苯暴露生物监测的研究现状和演化趋势,有利于科研工作者了解该领域在全球发展的整体情况,明确未来的研究方向。展开更多
Crystallinity of bottlebrush polymers due to side chain crystallization has been considered to be related to the length of the side chains only under the assumption of complete participation of crystallization by all ...Crystallinity of bottlebrush polymers due to side chain crystallization has been considered to be related to the length of the side chains only under the assumption of complete participation of crystallization by all sidechains.Recent experimental results revealed that in poly(n-alkyl methacrylate)s a fraction of side chains could not crystallize due to constraints imposed by the trapped main chain entanglements and required expansi on of main chain-main chain distanee.This result renders the original simplified con sideration of the origin of crystallinity in bottlebrush polymers questionable.In this work,we introduce a new parameter f_(c),the fraction of crystallizable side chains,to better describe the crystallinity of bottlebrush polymers.A lin earrelati on ship between the meltingenthalpy and the number of alkyl groups in side chains for bottlebrush polymers reported repeatedly indicates that f_(c) remains essentially unchanged when bottlebrush polymers had the same main chain structure and grafting degree but different side chain lengths.The slope of the above-mentioned linear relationship is thus △H_(CH2)xf_(c),where △H_(CH2) stands for the melting enthalpy of one mole alkyl group packed into the crystal.With a known value of f_(c),it is possible to estimate the value of △H_(CH_(2)).In case of poly(n-alkyl methacrylate)s,we estimated △H_(CH_(2)) of hexagonal crystal being at most 5.74 kJ/mol with the knowledge of possibly smallest f_(c) of 0.67 obtained from small angle X-ray scattering data.Therefore,the crystallinity of bottlebrush polymer would be calculated based on the equati on X_(c)=f_(c)×N_(c)/N with N and N_(c) being the nu mber of alkyl groups in a side chain and those packed in the crystalline structure,respectively.Both chemical structure and grafting degree of bottlebrush polymers affect f_(c).展开更多
文摘长期苯暴露会对人体造成伤害甚至导致白血病,而通过对苯生物标志物的生物监测可以更有效地判断个体的苯暴露水平。为研究苯暴露生物监测的国际发展态势,本文以Web of Science核心合集收录的发表于2000-2021年的文献为研究对象,借助软件从关键词、高被引论文、主要国家、主要研究机构、主要作者等角度对文献进行分析,揭示苯暴露生物监测的研究现状和演化趋势,有利于科研工作者了解该领域在全球发展的整体情况,明确未来的研究方向。
基金This work was finandaily supported by the National Natural Science Foundation of China(No.51525305).
文摘Crystallinity of bottlebrush polymers due to side chain crystallization has been considered to be related to the length of the side chains only under the assumption of complete participation of crystallization by all sidechains.Recent experimental results revealed that in poly(n-alkyl methacrylate)s a fraction of side chains could not crystallize due to constraints imposed by the trapped main chain entanglements and required expansi on of main chain-main chain distanee.This result renders the original simplified con sideration of the origin of crystallinity in bottlebrush polymers questionable.In this work,we introduce a new parameter f_(c),the fraction of crystallizable side chains,to better describe the crystallinity of bottlebrush polymers.A lin earrelati on ship between the meltingenthalpy and the number of alkyl groups in side chains for bottlebrush polymers reported repeatedly indicates that f_(c) remains essentially unchanged when bottlebrush polymers had the same main chain structure and grafting degree but different side chain lengths.The slope of the above-mentioned linear relationship is thus △H_(CH2)xf_(c),where △H_(CH2) stands for the melting enthalpy of one mole alkyl group packed into the crystal.With a known value of f_(c),it is possible to estimate the value of △H_(CH_(2)).In case of poly(n-alkyl methacrylate)s,we estimated △H_(CH_(2)) of hexagonal crystal being at most 5.74 kJ/mol with the knowledge of possibly smallest f_(c) of 0.67 obtained from small angle X-ray scattering data.Therefore,the crystallinity of bottlebrush polymer would be calculated based on the equati on X_(c)=f_(c)×N_(c)/N with N and N_(c) being the nu mber of alkyl groups in a side chain and those packed in the crystalline structure,respectively.Both chemical structure and grafting degree of bottlebrush polymers affect f_(c).
